The concept of neuroglia as an omnipresent connective tissue in the brain and in the spinal cord was introduced by Rudolf Virchow in 1850 s [1,2,3]. The true explosion of glial research however begun after Camillo Golgi introduced the famous Reazione nera in which the tissue was fixed in potassium dichromate and impregnated in a solution of silver nitrate; this produced intense black staining of neurones and neuroglia in their entirety from soma to distal processes [4]. This technical breakthrough allowed detailed morphometric analyses of neural cells in situ in the nervous tissue. Golgi was very much interested in the neuroglia. In his first attempts to visualize neuroglial cells, involving osmic acid staining, Golgi described cells with large nuclei and long radial processes emerging in all directions [5, 6]. Subsequently (using his black staining) Golgi described many glial morphotypes, and probably he was the first to produce an image of oligodendrocytes as depicted in his Opera Omnia [7]. The star-shaped morphology of many glial cells revealed by Golgi staining inspired Michael von Lenhossék to introduce the term astrocyte (ἄστρον κύτος; astron, star, kytos, a hollow vessel, later cell i.e. star-like cell). It has to be noted that Lenhossék was cautious in applying this new terminology; he wrote “I would suggest that all supporting cells be named spongiocytes. And the most common form in vertebrates be named spider cells or astrocytes, and use the term neuroglia only cum grano salis (with a grain of salt), at least until we have a clearer view” [8]. Indeed, now we know that astrocytes in the nervous tissue do not have star-like appearance but rather present spongiform morphology [9].

Camillo Golgi, however, not only invented the staining technique that opened the brain to neuroanatomists, but he also reflected on the functions of neuroglia. He was the first to visualise the neuroglial-vascular interface – the astrocytic endfeet (Fig. 1A [7]), which as we know now provide comprehensive coverage of all blood vessels entering the brain and the spinal cord through the glia limitans perivascularis [10, 11]. Golgi envisioned that the function of this interface and of neuroglia is to link the circulation with the parenchyma of the central nervous system to feed neurones. He also was first to realise that neuroglia is much more than a connective tissue, being a fundamental cellular element of the nervous tissue. In 1885 he wrote (in the Chap. 8 of a fundamental work Sulla fina anatomia degli organi centrali del sistema nervoso [12]): “Credo conveniente notare che la parola connettivo, da me viene qualche volta usata per indicare il tessuto interstiziale dei centri e quale sinonimo di nevroglia, senza punto voler assimilare il tessuto medesimo col tessuto connettivo ordinario di origine mesodermica o parablastica. Dichiaro anzi che, dopo tutto, la parola nevroglia… mi sembra abbia titoli di preferenza, valendo ad indicare un tessuto, che sebbene sia connettivo, perchè connette elementi d’altra natura e alla sua volta serve alla distribuzione del materiale nutritizio, pure si differenzia dal connettivo comune per caratteri morfologici, chimici.”. “It is convenient to note that I usually use the word “connective tissue” to indicate the interstitial tissue as synonymous with neuroglia, without comparing this particular tissue with the usual connective tissue of mesodermal or parablastical origin. I declare that, however, the word neuroglia… indicates a tissue that although is a connective tissue, because connecting elements of another nature and in turn it serves for distributing the nutritive material, but it is different from the common connective tissue for morphological and chemical features.“.

Fig. 1

Astrocyte-vascular coupling. Left, Camillo Golgi drawing of astrocytes which contact blood vessels and form endfeet. Reproduced from Golgi, C. 1903. Opera Omnia. Milano: Hoepli. B. Right, direct stimulation of an individual astrocyte results in arteriole dilatation. Reproduced from [18]. (a, b) Fluorescent (Lucifer yellow) images of two perivascular astrocytes superimposed to DIC images of the nearby arterioles. Note the processes in contact with the arteriole. (c, d) Magnification of the arteriole sector delimited by the dashed line box in (b), before and after astrocyte stimulation. Black arrowheads delimit the analysed sector. Scale bars, 10 μm. (e) Kinetics of the diameter changes from the analysed sector. (f) Kinetics of the diameter changes from a different arteriole that showed the maximal dilation after seal formation in a nearby astrocyte. (g) Kinetics of diameter changes from an arteriole upon seal formation and delivery of depolarizing stimuli to a nearby neurone

The discoveries of Golgi profoundly influenced Santiago Ramon y Cajal, who performed many studies on neuroglial cells. In particular, he developed the gold and mercury chloride-sublimate staining method that specifically labelled astrocytes through binding to glial fibrillary acidic protein [13]. Ramon y Cajal confirmed earlier ideas of the origin of astrocytes from radial glia and demonstrated that astrocytes proliferate in post-natal or even in the adult brain [14]. Cajal also considered the role of endfeet and proposed an astrocyte-mediated mechanism for vasodilatation and vasoconstriction, in which retraction or expansion of astrocytic perivascular processes connected to the blood vessels with endfeet change the diameter of the latter [15]. Diameter changes in cerebral vessels actually regulate the local blood flow in the nervous tissue, reflecting local neuronal activity in different brain regions. This phenomenon of functional hyperaemia was discovered by Angelo Mosso in humans and by Charles Roy and Charles Sherrington in animals. Acccording to Mosso, “We must suppose a very delicate adjustment whereby the circulation follows the needs of the cerebral activity. Blood very likely may rush to each region of the cortex according as it is most active” [16]. Roy and Sherrington also suggested that certain “chemical products of cerebral metabolism… cause variations of caliber of the cerebral vessels“ [17].

The details of astrocyte-dependent regulation of functional hyperaemia remained enigmatic all the way up to 2003 when Giorgio Carmignoto, Micaela Zonta, Tullio Pozzan and their colleagues revealed one of the mechanisms by which astrocytes connect neuronal activity with local blood supply. This involved astrocytic Ca2+ signals triggered by glutamate release from neurones during periods of activity [18]. Astrocytes cannot generate action potentials, being thus electrically non-excitable cells; instead, astrocytes employ intracellular signalling mediated by changes in cytoplasmic concentration of major ions (Ca2+, Na+, Cl−) and second messengers (InsP3, cAMP), which are generated by concerted activity of membrane receptors an ion channels [19,20,21]. These intracellular signals regulate various astrocytic functions and in particular astrocytic secretion [22]. The seminal discovery of Giorgio, Micaela and Tullio was confirmed by multiple subsequent studies, which also identified the nature of astrocytic molecules causing vasodilatation and vasoconstriction, which include prostaglandins and their derivatives and eicosanoids [18, 23,24,25]. Astrocyte Ca2+ nonetheless holds the master key.

Giorgio Carmignoto: The Early Years (Stefano Vicini)

It is a great pleasure to write a brief essay about my dear friend and colleague doctor Giorgio Carmignoto. I have known Giorgio since the winter of 1980, when we were colleagues, at the beginning of our career, at the Fidia Research Laboratories in Abano Terme, near Padua. In a rare case for a pharmaceutical company, the visionary and dynamic CEO, the late Francesco Della Valle, believed that Basic Science was the foundation of drug discovery. He hired two scientists, Alfredo Gorio and Gino Toffano, to lead the physiology and biochemistry efforts of the laboratory.

Giorgio and I were together in the nerve muscle section studying, with animal models, the implications for gangliosides on neuronal growth and plasticity. Giorgio was trained in electrophysiology in the laboratory of Alexander Mauro at Rockefeller University in New York in 1978. When he returned to Italy, he lead a team including a superb technician, Mario Finesso, that led to several important publications demonstrating a role for glycolipids in muscle re-innervation after nerve crush injury and a corresponding restoration of synaptic release mechanism, through studying the neuromuscular junction with electrophysiological and anatomical approaches.

Those were heroic times - there were neither computers nor internet. Giorgio demonstrated his passion and enthusiasm for scientific discovery and unique leadership. He presented his results at several meetings. One meeting I particularly remember is when we went together to Strasbourg. We drove there across the Swiss Alps and the Alsace region where I discovered sharing Giorgio passions for the mountains and good food. In those years, the leadership realised that it is productive sending researchers to established labs to learn state of the art approaches and techniques as well as to broaden the research horizons. Giorgio began a lifelong collaboration with Prof. Lamberto Maffei and his team at the CNR and Scuola Normale in Pisa. Together with Silvia Bisti and Lucia Galli, they produced a seminal publication studying spatial frequency characteristics of visual cortical neurons in the cat, with in vivo electrophysiological recordings [26]. Giorgio also learned to induce monocular deprivation in kittens, which he applied in his laboratory in Abano, together with another excellent technician and friend Roberto Canella.

The Nobel Prize in Physiology or Medicine was awarded in 1986 to Rita Levi Montalcini and Stanley Cohen for the discovery of nerve growth factor (NGF) and epidermal growth factor (EGF). Following the award, the hypothesis of a possible interaction between neurotrophins and gangliosides was formulated and Giorgio lead a team that included Giovanna Ferrari, Paola Candeo, Cristina Comelli, Renata Siliprandi, Guido Vantini, Roberto Dal Toso and several other investigators to study the action of NGF on the survival of rat retinal ganglion cells following optic nerve section. Still with Lamberto Maffei and his collaborators, including Nicoletta Berardi, they went further to discover the role of Schwann cells in the action of NGF [27]. In December 1988, we were invited to two symposia, first to Moscow and later to Leningrad, to honour Rita Levi-Moltalcini. I will never forget seeing the last of the USSR, visiting the neuroscience labs in Moscow of Vladimir G. Skrebitsky at the Russian Academy of Sciences and the night train ride between the two cities. Giorgio, for sure, will also not forget being pickpocketed while catching the bus, in the snowy morning of Leningrad going to the Hermitage.

In 1987, Giorgio joined my laboratory for a few months and he convinced me of the importance of studying the critical period of visual synaptic plasticity with patch-clamp recording from neurones in rat brain slices. We began reading papers by McCormick and Connors in David Prince’s lab on the neurophysiology and cell types in visual cortex. At that time, with another Italian scientist guest in our group, the late Giampaolo Mereu, we troubleshot the recently developed application of the patch clamp technique to brain slices.

Giorgio returned to Italy in 1988, and became the head of the department of Visual System Research at Fidia Labs. We continued to collaborate and to plan experiments to test our hypothesis that a modification of the NMDA receptor gating properties may account for the age-dependent decline of visual cortical plasticity. He was also my best Man when I got married in Italy.

Giorgio came back to Washington in 1991. His stamina was pivotal to set up at Georgetown ‘the dark rearing protocol’ to prove that it delays the decrease in NMDA receptor-mediated excitatory synaptic current. As plasticity is delayed when the animals are reared in the dark, we proposed that the slow NMDA current underlies the prolonged developmental plasticity. However to ultimately prove the link between development, plasticity and the NMDA current, we had to totally inhibit the visual input to the cortex with tetrodotoxin (TTX). Giorgio’s determination was essential to perform the demanding daily intracortical injections to inhibit neural activity in the visual pathway to show that it prevents the developmental decrease of the NMDA current. This lead to our Science publication in 1992 [28].

In 1995, Fidia support for basic research ended both in the US and in Italy. Giorgio and I moved on. I was granted tenure at Georgetown and Giorgio begun a brilliant career at Padua University in the Dipartimento di Scienze Biomediche Sperimentali lead by the late Tullio Pozzan. Giorgio was able to stir the field to show that astrocytes are not just passive players in brain function. Through these years, we continue to see each another occasionally and passionately discuss science. Giorgio Carmignoto has made seminal contributions to the field, and I hope he will continue to contribute intellectually to the field and to continue to inspire the next generation of scientists with his passion for neuroscience.

As anticipated by Stefano Vicini, during his time in Fidia Giorgio had the opportunity to gain experience in various laboratories outside Abano Terme. Thus, he was hosted for two years (1982 and 1983) in Professor Lamberto Maffei’s lab in Pisa, diving into the study of the visual system while acquiring valuable knowledge and techniques. Above all, he appreciated the chance to learn from Professor Maffei, an exceptional scientific mentor, and to work in a stimulating environment with colleagues who soon became good friends.

Giorgio in Pisa (Lamberto Maffei and Nicoletta Berardi)

Giorgio came to Pisa in 1982, joining the Laboratorio di Neurofisiologia directed by Lamberto Maffei, to learn to work on the visual system. This signalled the beginning of an enduring, strong and warm friendship with both of us, which, Giorgio being the special person he is, still takes a special place in our life. Initially, he worked with Silvia Bisti and then with Silvia and Lucia Galli to provide the electrophysiological characterisation of visual cortical areas in the cat, particularly on area 18, merrily recording single cell activity in response to drifting gratings and showing the differences between primary and secondary visual cortex properties. His previous work on neuronal regeneration made him directly collaborate with Lamberto on the effects of Schwann cell transplant and NGF delivery on the survival of retinal ganglion cell and attempted axon growth after lesion of the optic nerve; it also made him interested in cortical plasticity, and he started to work on the effects of monocular deprivation, which he would become very acquainted with over the years [29].

In those early years, in addition to the published papers, Giorgio contributed to revive mushroom gathering in the free time, and with the catch of the day he cooked fantastic risotto with porcini at Lamberto’s house in Asciano. He also contributed to Nicoletta’s home décor with a small Ficus Benjamin, won at a local raffle, which is now a big tree still gracing her house! In Nicoletta’s house Giorgio took also part in long Risiko games. We also smile remembering the ravenous hunger Giorgio exhibited at the end of the very long work days: once, at an European Conference on Visual Perception (ECVP) organized by Adriana Fiorentini at Il Ciocco, we had worked all day collecting the fees of the participants and had finished the last controls well after dinner was terminated. Giorgio run to the kitchen and asked for something to eat, whereupon a waiter appeared and put on our dishes the standard dose of risotto, muttering that by then it would have been overcooked. Giorgio gulped in one big spoonful all the risotto, and said to the waiter: the test is passed, risotto is still good, you can serve it!

Towards the end of the 1980s, Lamberto, during an afternoon teatime laboratory meeting, proposed a novel idea that NGF, well known for being a neurotrophic factor crucial for survival of specific classes of neurones during development, could also be a factor crucial for synaptic survival, a factor neurones are fighting for, competing with each other using patterns of electrical activity as a tool to stabilise their synapses on a common postsynaptic target which is the source of the NGF, and designed an experiment to test this idea. Giorgio, Luciano Domenici and Nicoletta were chosen to perform the experiment, which consisted in testing whether the deleterious effects of monocular deprivation in the visual cortex of developing rats, namely the loss of inputs driven by the deprived eye onto cortical neurones, and the loss of visual acuity of the deprived eye, could be prevented by exogenous supply of NGF to the visual cortex. Giorgio brought NGF and we performed the intraventricular injections or focal applications of NGF during monocular deprivation. Together (Giorgio, Luciano and Nicoletta) we recorded the visual evoked potentials in treated and control rats, double blind, aware that we were performing a novel experiment, and we were thrilled when results did show that NGF prevented the amblyopic effects of monocular deprivation. Giorgio took care also of the biochemical part of the experiment, and was determinant, with his optimism and ready smile, to keep up the mood of the crew during the long months which passed before the paper [30] was accepted for publication. To work with him has always been so cheerful and merry.

Of the neurotrophin period we also remember Giorgio’s partiality for “fo’accina ‘on la Cecina” (pancake with chickpea tart), eaten blistering hot in the Pizzeria Bagni di Nerone in the brief pauses between experimental hours.

Every year it was a tradition to meet Giorgio in the US for the Society of Neuroscience meeting, we all stayed in the same hotel, which Nicoletta booked by long phone calls (no Expedia at the time), with such a budget-conscious attitude that sometimes Giorgio laughed at her. Following the end of the meeting, Lamberto and Giorgio often went for small trips, generally accompanied by Gimmi Ratto, Stefano Vicini and Tommaso Pizzorusso, going swimming or diving. Once, on a beautiful beach, they formed a circle pulling each other, hand in hands and, in the picture taken by Giorgio’s wife, it turned out to be like a famous Matisse painting (Fig. 2).

Fig. 2

Evolution from The Dance of Matisse. This picture was taken by Lucia Pasti during an enjoyable time in Baja California. From the left, clockwise, Tommaso Pizzorusso, Giorgio Carmignoto, Lamberto Maffei, Stefano Vicini and Gimmi Ratto

Giorgio continued to come to Pisa often over the years, long after he had become the astrocyte world leading expert he is now, to work with Gimmi Ratto or, simply, to see us and talk over dinner together, and we often went to Padova to visit him. He has recently involved Nicoletta in a collaboration in a project on calcium dynamics in astrocyte in an AD mouse model, which has resulted in engaging talks and hypothesis making, enthusiastic data gathering and analysing, dinner for paper publishing with all his young students, which somehow brought us back to the Pisa dinners. Giorgio is a friend who is deeply part of us. We love him so much and we are sure that the love is reciprocal.

The scientific production following the period in Pisa highlights the importance of this experience, which encouraged him to continue researching in the field of vision, studying the effects of optic nerve section and of monocular deprivation on visual brain circuits. It is noteworthy to underline that besides a natural scientific curiosity in circuit characterisation, Giorgio’s interest was driven by the search for a therapeutic perspective, leading to focus on the potential role of NGF in promoting retinal ganglion cells survival and preventing visual acuity and contrast sensitivity loss. The papers he contributed to, published on PNAS and Journal of Neuroscience, promoted the advancement of knowledge on how neurotrophins can be used to support and recover neuronal function.

Meeting Giorgio: Where Very Little Science has Led to the Mountains (Gian Michele Ratto)

“I have been told that tomorrow Giorgio Carmignoto will be here…” this sentence was pronounced in a room of an office of an Institute, commonly referred to as “Neuro” short for Institute of Neurophysiology, but Neuro in Italian is also short for Neuropsychiatry and this incidental observation possibly explains the low, conspiratorial voice used in spite of the tightly shut door of the afore-mentioned office.

I distinctly remember this because the fact that this guy, this completely unknown “Giorgio Carmignoto” (GC from now on), was discussed quietly instead with the usual tension was remarkable. An explanation is now required: around those years, Neuro was a hotbed of tribalism with different factions continuously competing for no clear reason and no clear endgame. Thus, friendship and relations were not easy for somebody at the bottom of the food pyramid as I was, since the founding principles ruling social life at Neuro were: “the friend of my enemy is my enemy” and also “you shall not befriend a friend of an enemy”. Given that GC was supposed to visit people of the opposite camp, it is remarkable that his arrival was discussed so quietly and even with an hint of pleasantness. Hopefully, this necessarily succinct background explains why the ushered sentence “…tomorrow GC will be here” triggered some curiosity and expectation for what would have come next.

Tomorrow always comes, and brought a ferret-like figure rarely seen still and more rarely heard to be silent and, being in the City of the Slanted Tower (CST for short), was obviously a kick for him. Eventually I understood that GC had a long story of collaboration and friendship with a Prominent Figure in a tribe that was opposite to the group I was affiliated. GC turned out to be an hilarious figure, awfully smart and with a deep understanding of pharmacology. He had an encyclopedic knowledge of all possible agonist, antagonists, modulators of anything and was able to pronounce scores of improbably long names of chemical compounds in six seconds. He had a molecule for every occasion, as he was happy to share. Another grain of his knowledge that shared with me was the “focaccina dei bagni di Nerone” and everybody that has known this specific delicacy (that is sadly no more) will understand. For all the others, a silent majority, I can only say that this is your loss and if you feel diminished by having missed the focaccine, well, you are absolutely right. Go, and mourn the lost focaccina.

Due to some ectopically attributed credentials as an electrophysiologist, during that first visit GC said “we should patch clamp the retina…” an unlikely plan if ever there was one, but as I was a soul in search of a purpose, and also being slightly hyperactive myself we kind of fraternized.

Seasons kept cycling and eventually the search for a purpose and a job brought me to Cambridge, in the land where people drive on the wrong side of the street. A few days before leaving GC visited again CST exuding the usual exuberance. “Perhaps he needs a way of releasing his capital of unspent energy?” I wondered silently, and as a way of saying goodbye I told him: “you really should go climbing, you know?”.

So patch clamp of the retina never became a thing for us, and there was not much science either: while GC gradually convinced himself that neurons were only the support cells for astrocytes, I remained in steadfast awe of the intricacies of electric signaling. So, not much science, but climbing yes, that was a thing. As we had different taste regarding Our Favorite Brain Cell Type, we had sharply divided climbing experience. I was deep in my heart a Lover of the occidental Alps, he was swearing that nothing was better than the Dolomites in his homeland in the laborious North East. The dichotomy between east and west was even stronger than the science dichotomy between neurons and astrocytes. After all neurons and astrocytes are tightly intertwined while one can spend an entire life either on the West or on the East side of the Alps. Being in the West basically meant that mountains are much higher, there is lots of snow and ice to contend with, and the rock is mostly granite. In my completely uninformed view, the East was mostly composed of quaint countryside with some limestone protuberances that, at the very top, only reached the altitude were REAL mountains in the West are just beginning to ramp up. After I came back from Cambridge, I resisted GC attempts at dragging me East, but if GC decides something he is relentless, it dumbs you down with words and resistance is futile. Eventually I gave up and after one of his trip to the CST we drove together back to the North-East, destination Passo del Falzarego in the Dolomites. In this day like no other, I also met GR, the third element of a climbing triad that shaped the following 25-plus years of my life. One climb later, I had to admit that the rock was ok and that the scenery was ok and that the climb was OK. Well, I expressed myself in much stronger terms, but here I will not admit that GC was somehow right. Suffice to say that that was not the last trip East….

A partnership of a sort was born and, as I agreed to come East, GC agreed to come West and that started a love affair with a certain area of the French Alps (Fig. 3). Shily at first and with ever growing enthusiasm, 25 years of climbing explorations started. Every year on the first week of January after exchanging wishes for the new year that “certainly cannot be worse with the one just passed by” and invariably was, every year in January GC and GR were asking something that sounded “ghai prenotà?” that, translated from the strange dialect spoken in a certain city in the North-East, that I am not going to mention by name, roughly means “have you got a reservation?” which indicated the need of reserving our rooms, and breakfast, and dinners in a particularly lovely hotel that we discovered during the first expedition West and we loved and still love immensely.

Fig. 3

Giorgio’s happiness while climbing. The picture was taken on an afternoon in August 2018, on a climbing route over La Berarde in the Dauphiné Alps, France

I am so happy to say, to declare, to publicly admit that we climbed far more steep faces, we descended from far more mountains, that we spent far more hours to attend aching feet and limbs, than discussing science in any form. And this points out to the often forgotten truth that as much as we are obsessed and lost in our work, in our silly little papers that reviewers (look and behold!) NEVER seem to understand, Science needs us much less than we need it and that some solace comes from days of happiness and fulfillment that we need almost painfully and that finally form a landscape of memories that let you say: “it was all truly worthwhile”. And I frankly do not care a bit if those memories of mountains, now far away, have been stabilized in our minds by BDNF released by astrocytes, or whatever other mechanistic underpinning that we can debate forever, I only deeply care that those moments actually happened, I only care that we will always remember the one evening when we got lost in the fog on a glacier far from the hut, and I don’t care what specific cellular ensemble nested in the hippocampus made us finding the way back home, I only care that those days happened, were shared, and will always be with us.

How Giorgio Met Calcium and Astrocytes (Micaela Zonta)

Up until 1994, the main experimental approaches of Giorgio were related to electrophysiology and, consequently, his primary interest was focused on neurones. When he moved to Padova University and joined the lab of Professor Tullio Pozzan – wisely defined “the king of calcium signalling” (Fig. 4) - Giorgio could not but meet Ca2+ imaging and hence expand his expertise. Working on cultured neurones loaded with fluorescent Ca2+ probes alongside his future wife, doctor Lucia Pasti, and Tullio, he noticed that neuronal signals were disturbed by “all those cells lying under neurons”, which also showed Ca2+ signals when neurons were stimulated. Yes, those nasty cells were astrocytes and these experiments marked the beginning of astrocytes’ story for Giorgio and all alumni populating his group during the years.

Fig. 4

Tullio Pozzan’s lab at the time of Giorgio’s arrival. A picture of Tullio’s lab taken in 1994. From the left: Carlo Bastianutto, Giorgio Carmignoto, Tullio Pozzan, Irene Bovo, Giovanni Ronconi, Mario Santato, Rosario Rizzuto, Marisa Brini, Marta Murgia, Lucia Pasti and Barbara Innocenti

Joining the emerging community of scientists that in those years were opening the path of astrocyte research, Giorgio’s work especially contributed to dissect the properties of glutamate-induced Ca2+ signalling in astrocytes. He started working on primary cultures and then extended the research to acute brain slices, revealing a peculiar form of memory in the response of astroglial cells, which can encode information about previous stimulation episodes into Ca2+ oscillation frequency [31, 32]. These studies further promoted the scientific community awareness of the specific language used by astrocytes in their reciprocal communication with neurones, fostering fruitful collaboration with other ‘astroscientists’ and leading to valuable insights into how astrocytes release glutamate and signal to neurones in situ [33].

In those years, Giorgio was also granted tenure as a Researcher in National Research Council (CNR) Institute of Neuroscience, strongly contributing to the development of the research on neuron-glia interactions in the prestigious Italian research institution. Inspired by the discovery of Ca2+ frequency code in astrocytes, Giorgio’s curiosity drove him to search for functional readouts of this coding language, focusing on the possible relationship between Ca2+ oscillations and the release of glutamate from active astrocytes. It was at that moment that I joined the group for my Master’s thesis internship, finding an enthusiastic and wonderfully weird environment shaped by Giorgio’s exceptional ability to be scientifically visionary and Lucia’s natural capacity for scientific rigor and organisational skills. Working together was an extraordinary experience boosting passion and dedication, with our experimental efforts resulting in the characterisation of the strict correlation between glutamate receptor-dependent Ca2+ oscillations and the pulsatile, quantal like glutamate release from cultured astrocytes [34]. Enjoyable – and countless - hours of experiments were carried out in the legendary confocal room, where images were still recorded in large, squared two-sided Optical Memory Disks, and signal traces were extracted from manually drawn ROIs upon real-time replay of recorded time series, followed by a never-ending process of file transfer between computers located in three different floors! And we cannot forget the uncountable trips driving Giorgio’s motorcycle to the photo lab on via Dante, searching for the perfect balance of contrast, luminosity and colours in printed confocal images – not to mention the patience required to assemble the final figure sets for reviewers using a set square, glue and clean white tissue gloves.

This study unlocked a side project, revealing a regulated release of prostaglandins from astrocytes. From there, Giorgio’s brilliant intuition about the potential functional outcomes of prostaglandin release opened a new direction of research about the role of astrocytes in bridging neuronal activity and local blood flow in activated cerebral regions [18]. I still remember the exact moment when he wondered - his eyes blinking - “Come on, prostaglandins are powerful dilators… what if this release is related to an increase in cerebral blood flow?”. Different experimental approaches contributed to build the strength of this work, which integrated astrocyte Ca2+ signalling, electrophysiological stimulation of neuronal activity, vasomotion analysis and pharmacological approaches. We first highlighted the potential of astrocytes to get involved, by describing how activation of metabotropic glutamate receptors (mGluRs) induced intracellular Ca2+ signals that can propagate to endfeet in contact with cerebral vessels, and how astrocyte activation by different stimuli increasing intracellular Ca2+ can induce arteriole dilation in acute brain slices. Then, we de facto reproduced the process of neurovascular coupling in cortical slices, by evoking local vasodilatation through extracellular electrical stimulation of neuronal activity and demonstrating the genuine involvement of astrocytes through a pharmacological approach acting on mGluRs to inhibit astrocyte recruitment. Giorgio himself went to the lab of Konstantin Hossmann in Cologne, Germany, to follow the in vivo experiments confirming the efficacy of mGluR inhibition in reducing functional hyperaemia. The project was developed with the strong commitment of the whole lab team, enriched by the lively PhD student Sara Gobbo and by the postdoctoral fellow Maria Cecilia Angulo, ultimately leading to the seminal paper that demonstrated a crucial role for astrocytes in the regulation of cerebral blood flow. This work represents one of the milestones of Giorgio’s career: we stand proud for how a review identified this manuscript as marking a clear division between eras in the field, pre- and post- Zonta and colleagues paper! This paper also holds significant personal meaning for me, as it represents a special scientific connection with Giorgio, who deeply inspired me with his passionate and ever-smiling enthusiasm for astrocyte research. I am deeply grateful for this inspiration, and also for the care and consideration he manifested when my presence in the lab was discontinued upon the birth of my children. While recognizing that full commitment, including the opportunity to work abroad, is often the best path for research scientists to broaden their expertise, he offered me a different approach to continue my research, proposing a part-time arrangement to allow balancing family and work. We could thus coordinate the project of the psychologist PhD student Debora Crippa, developed in collaboration with the team of Professor Michela Matteoli in Milan. With this work, Giorgio extended our previous studies on glutamate release by characterizing vesicle exocytosis from cultured astrocytes [35], thus ideally closing the period of studies on primary cultures.

Giorgio and the International Astrocyte School IAS (Paulo J. Magalhães)

The second decade of the 2000 s started in very promising terms. For the first time in history, a FIFA World Cup was held in Africa: South Africa, to be more precise, from 11 June to 11 July 2010. At the same time, attended by slightly fewer people, the FENS Forum took place almost 10,000 km away: Amsterdam, 3–7 July. Here, a satellite symposium attracted the attention of a small bunch of scientists interested in relatively obscure brain cells called astrocytes. Later, three of these people sat in idle conversation, with an eye on the ongoing semi-final game playing on the hotel bar’s television screen. They lamented the state of affairs characterising their favourite research area. Something had to be done. They had to change the world. Their revolutionary idea was a school: to disseminate knowledge about astrocytes, how they function and, most importantly, how they needed to be studied in rigorous and unbiased terms.

The world of academia is rife with such meetings, lofty ambitions, and noble plans — oftentimes quickly reshaped into ephemeral dreams. Not our friends, though! The wheels had been set in motion and Giorgio quickly ensured the transformation of an impossible timetable into the smooth opening of the first edition of the International Astrocyte School in the early spring of 2011. It was a resounding success. The School managed to generate an enviable synergy that infused all the scholars present: the rapport established between the (older) faculty and the (younger) students yielded rich and fruitful rewards, treasured long after the School closed its doors one week later.

Almost naturally, the initial trepidation turned into boundless enthusiasm, and plans soon began for a second edition — and then again and again, in what has become an annual landmark for all those interested in astrocytes and the glial world. Giorgio, Alfonso and Richard have engaged friends and colleagues in offering an educational continuum that has benefitted a vast number of people. As of 2025, the faculty body has come from 15 different countries, from Canada to China, from the US to Japan, as well as numerous European countries. Over the years, more than 60 high-profile researchers have generously agreed to share their time, knowledge, and didactic experience, mostly with a genuine passion for the younger generations that have flowed through the School. Many have returned (some repeatedly) and the success of this School is unquestionably their merit too.

Surely due also to the impressive array of top-level scientists who have enriched the programme over the years, the School’s formative success is represented by its alumni body. The selection procedure is always tough and we strive to ensure that accepted applicants are distributed along various parameters in an equitable manner. In its first fourteen editions, the IAS has welcomed young (and sometimes not-so-young) scientists from literally all over the world: roughly 400 students from 40 + countries (and an even larger number of nationalities). Quite a number of these have gone on to become established researchers — and it is always a source of joy for the organisers when their students apply to the IAS. It is also a special occasion when past alumni are invited back to the School as part of the faculty.

Today, the International Astrocyte School is almost inextricably linked to Bertinoro and its medieval castle perched on top of the hill. On a clear day, it offers splendid views over the plains below, as far as the eye can see, all the way to the sea. Half-hidden, waiting to be pointed out, the iconic silhouette of San Marino in the distance is always a surprise to many. That the School has remained in Bertinoro, however, is a story in itself. Initially there was the thought of making the IAS an itinerant school and organising it in different locations, perhaps even with some form of rotating mechanism. Inertia played a role, of course, but there was more. The atmosphere that participants breathe in Bertinoro is not just that directly associated with the formal lessons or lectures. The various social activities (at the University Residential Center itself, the official venue of the School, as well as in restaurants and bars peppered around the village) bring together faculty and students in an informal environment that fosters the exchange of ideas on many different levels. The social fabric formed over the course of a week owes much of its value to unique (and to some extent ineffable) characteristics that would be difficult to replicate elsewhere. Time and again, we have witnessed spontaneous community building involving not only the students but also faculty members, sowing the seeds for future networking that helps shape emerging careers. A special word is needed for the exceptional local staff who, year after year, continue to welcome all the School participants almost as if we were part of the family — perhaps we have, indeed, become that.

The School’s format has been fine-tuned over the years, also with the help of the constructive feedback from its many students. There were the inevitable early teething problems, and the odd bounce along the road. These have taught us much. Especially in the initial years, the School benefited from support awarded by some companies and international institutions. With time, the IAS evolved into a fully independent entity. Notwithstanding a funding situation always on the edge, the School prides itself on the assistance provided to many of its students, especially those coming fro