Ricardo Miledi Research Articles

Ricardo Miledi. 15 September 1927—18 December 2017

For nearly five decades, Ricardo Miledi was among the foremost researchers in elucidating how nerves transmit signals across synapses. Born in Chihuahua, Mexico, he qualified as a medical doctor, obtained a PhD with Arturo Rosenblueth and then, while in Canberra with John Eccles FRS, was invited by Bernard Katz FRS to join the Biophysics department at University College London, where he stayed from 1958 to 1984. Both independently and with Katz, he demonstrated that influx of calcium into the presynaptic nerve terminal is the essential trigger for the release of the neurotransmitter that carries signals across to the postsynaptic cell. He found that cutting the nerve to a frog's muscle increased the number and distribution of its muscle acetylcholine (ACh) receptors, which he purified and established as membrane proteins. Together with Katz, he introduced the technique of membrane noise analysis to determine the properties of the individual ion channels opened by ACh, providing the first functional characterization of a single receptor with integral ion channel. With Eric Barnard (FRS 1981), he pioneered a new approach facilitating the study of neurotransmitter receptors and ion channels by ‘transplanting’ them from brain and other tissues into largeXenopusoocyte cells by injection of messenger RNA. After moving to the University of California, Irvine, in 1984, he helped to establish the Mexican Institute for Neurobiology at Querétaro. Working in Irvine and Mexico he extended this oocyte expression technique to incorporate transplanted brain membranes, particularly from patients with epilepsy or other neurological disorders. He received many honours for his work, including the Royal Medal (1998), but was happiest working in his lab applying his extraordinary technical skills and imagination to study synaptic transmission and inspiring a generation of neuroscientists.

Eric A. Barnard. 2 July 1927—23 May 2018

Eric Barnard was a protein biochemist who played a leading role in the delineation of the molecular components of neuromuscular transmission and the emergence of molecular neuroscience as a scientific discipline. He began his career at King's College London, moving to the State University of Buffalo, New York, in 1965 before returning to Imperial College, London, in 1975. In 1985 he became the Director of the Medical Research Council (MRC) Molecular Neurobiology Unit in Cambridge. Upon retirement from the MRC, he moved to the Royal Free Hospital in London where he continued as Director of Molecular Neurobiology, but in 1998 returned to the University of Cambridge (Department of Pharmacology) as Emeritus Professor. In 2014, at the age of 86, he finally retired from active research. Although Eric was elected FRS for his early pioneering work on the protein chemistry of enzymes and the nicotinic acetylcholine receptor, his seminal contribution, initiated during his time at Imperial, was the application of molecular biological methods to the study of many neurotransmitter receptors. With Ricardo Miledi FRS (and later David Brown FRS and colleagues), he developed the Xenopus oocyte system for the expression of receptors from total tissue mRNA. His was the first group to clone a neurotransmitter receptor subunit cDNA, the nicotinic acetylcholine receptor α subunit of Torpedo marmorata . This was followed by purification and subsequent cloning of inhibitory γ-aminobutyric acid (GABA) A receptor subunit cDNAs. This achievement, driven by Eric and aided by his collaborator Peter Seeburg, led to the discovery of the ligand-gated ion channel superfamily, the discovery of neurotransmitter receptor heterogeneity, and the development of concepts of receptor families and superfamilies. His pioneering work was pivotal for the foundation of modern central nervous system drug discovery.

CrossTalk proposal: Apical NKCC1 of choroid plexus epithelial cells works in the net inward flux mode under basal conditions, maintaining intracellular Cl- and cell volume.

CrossTalk proposal: Apical NKCC1 of choroid plexus epithelial cells works in the net inward flux mode under basal conditions, maintaining intracellular Cl- and cell volume.

John Newsom-Davis. 18 October 1932—24 August 2007

John Newsom-Davis (‘JND’) was a neurologist who played an important role in the discovery of the causes of, and treatments for, myasthenia gravis (MG), and of other diseases of the nerve–muscle junction. He started his career at the National Hospital in London, becoming director of the Batten Unit there, with an interest in respiratory physiology. He began to work on MG in collaboration with Ricardo Miledi (FRS 1970) at University College London and in 1978, after performing the first study on plasma exchange in that disease, he established an MG research group at the Royal Free Hospital, subsequently identifying the role of the thymus in this disease and demonstrating an autoimmune basis for the Lambert–Eaton myasthenic syndrome and ‘seronegative’ myasthenia. He was awarded the first Medical Research Council Clinical Research Professorship in 1979 but moved to Oxford in 1987 when he was elected Action Research Professor of Neurology. While at Oxford he continued to run a very successful multidisciplinary group, and began the molecular work that identified the genetic basis for many forms of congenital myasthenic syndrome. He also helped to establish the Functional Magnetic Resonance Imaging of the Brain (FMRIB) Centre. Meanwhile he was also involved in university and college governance and contributed widely to the Medical Research Council, government committees, and the Association of British Neurologists (ABN). Among many honours, he was appointed Commander of the Order of the British Empire in 1996 and made a Foreign Associate Member of the Institute of Medicine (now the National Academy of Medicine) in the USA in 2001. Following retirement from Oxford, he was President of the ABN and Editor ofBrain, and led a National Institutes of Health-funded international trial of thymectomy.

Introducing a mammalian nerve-muscle preparation ideal for physiology and microscopy, the transverse auricular muscle in the ear of the mouse

A new mammalian neuromuscular preparation is introduced for physiology and microscopy of all sorts: the intrinsic muscle of the mouse ear. The great utility of this preparation is demonstrated by illustrating how it has permitted us to develop a wholly new technique for staining muscle T-tubules, the critical conductive-elements in muscle. This involves sequential immersion in dilute solutions of osmium and ferrocyanide, then tannic acid, and then uranyl acetate, all of which totally blackens the T-tubules but leaves the muscle pale, thereby revealing that the T-tubules in mouse ear-muscles become severely distorted in several pathological conditions. These include certain mouse-models of muscular dystrophy (specifically, dysferlin-mutations), certain mutations of muscle cytoskeletal proteins (specifically, beta-tubulin mutations), and also in denervation-fibrillation, as observed in mouse ears maintained with in vitro tissue-culture conditions. These observations permit us to generate the hypothesis that T-tubules are the “Achilles' heel” in several adult-onset muscular dystrophies, due to their unique susceptibility to damage via muscle lattice-dislocations. These new observations strongly encourage further in-depth studies of ear-muscle architecture, in the many available mouse-models of various devastating human muscle-diseases. Finally, we demonstrate that the delicate and defined physical characteristics of this 'new' mammalian muscle are ideal for ultrastructural study, and thereby facilitate the imaging of synaptic vesicle membrane recycling in mammalian neuromuscular junctions, a topic that is critical to myasthenia gravis and related diseases, but which has, until now, completely eluded electron microscopic analysis. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Oligodendrocyte Differentiation and Myelination Is Potentiated via GABAB Receptor Activation

Differentiation of oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes (OLs) is a key event for axonal myelination in the central nervous system (CNS). Several growth factors and neurotransmitters like GABA are postulated as important regulators of that process, and different protein kinases may also participate in OL differentiation and myelination. However, the molecular mechanisms underlying the regulation of myelination by neurotransmitters are only partially known. In the present study, we provide evidence showing that GABA receptors (GABARs) play an important role in OL differentiation. First, we observed that OPCs and OLs synthesize GABA and expressed GABAR and transporters, both in vitro and in vivo and, in contrast to GABAARs, the subunits GABAB1R and GABAB2R are expressed in OLs over time. Then, we found that exogenous GABA increases the number of myelin segments and MBP expression in DRG-OPC cocultures, indicating that GABA regulates myelination when OLs are in contact with axons. Notably, in purified rat OPC cultures, chronic treatment with GABA and baclofen, specific GABABR agonist, accelerates OPC differentiation by enhancing the processes branching and myelin protein expression, effects that are reverted in presence of GABABR specific antagonist CGP55845. Exposure of OPCs to baclofen promotes the Src-phosphorylation, and the baclofen-induced maturation is attenuated in presence of the Src-family kinases inhibitor PP2. None of these effects are mediated by the GABAAR agonist muscimol. Together, these results highlight the relevance of the GABAergic system in OL differentiation, and indicate that this functional role is mediated through GABABR involving the participation of Src-family kinases.This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Tonic Calcium-Activated Chloride Current Sustained by ATP Release and Highly Desensitizing Human P2X1 Receptors

Extracellular adenosine triphosphate (ATP) participates in maintaining the vascular tone in the CNS, particularly in the retina, via the tonic activity of ligand gated activated P2X1 receptors. P2X1 receptors are characterized by their high affinity for ATP and their strong desensitization to concentrations of ATP that are 200-fold lower than their EC50. The mechanism behind P2X1 tonic activity remains unclear. In this study, we expressed human P2X1 (hP2X1) homomeric receptors in Xenopus oocytes to explore the relationship between ATP release from oocytes at rest, hP2X1, and Ca2+-activated Cl− channels. Our results indicate that Xenopus oocytes release ATP at rest via vesicular exocytosis, and this process is a constitutive phenomenon independent of extracellular Ca2+. Our results also indicate that hP2X1 receptors are able to sustain a tonic activity of Ca2+-activated Cl− channels. In the presence of extracellular Ca2+ the activity of hP2X1 receptors is greatly amplified by its coupling with Ca2+-activated Cl− channels. Future studies addressing the relationship between hP2X1 receptors and Ca2+-activated Cl− channels in vascular smooth muscle cells should provide information about additional mechanisms that regulate the vascular tone and their potential as pharmaceutical targets. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

CLARITY analysis of the Cl/pH sensor expression in the brain of transgenic mice

Genetically encoded biosensors are widely used in cell biology for the non-invasive imaging of concentrations of ions or the activity of enzymes, to evaluate the distribution of small molecules, proteins and organelles, and to image protein interactions in living cells. These fluorescent molecules can be used either by transient expression in cultured cells or in entire organisms or through stable expression by producing transgenic animals characterized by genetically encoded and heritable biosensors. Using the mouse Thy1 mini-promoter, we generated a line of transgenic mice expressing a genetically encoded sensor for the simultaneous measurements of intracellular Cl− and pH. This construct, called ClopHensor, consists of a H+- and Cl−-sensitive variant of the enhanced green fluorescent protein (E2GFP) fused with a red fluorescent protein (DsRedm). Stimulation of hippocampal Schaffer collaterals proved that the sensor is functionally active. To reveal the expression pattern of ClopHensor across the brain of Thy1::ClopHensor mice, we obtained transparent brain samples using the CLARITY method and imaged them with confocal and light-sheet microscopy. We then developed a semi-quantitative approach to identify brain structures with high intrinsic sensor fluorescence. This approach allowed us to assess cell morphology and track axonal projection, as well as to confirm E2GFP and DsRedm fluorescence colocalization. This analysis also provides a map of the brain areas suitable for non-invasive monitoring of intracellular Cl−/pH in normal and pathological conditions.This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Demyelination–Remyelination of the Rat Caudal Cerebellar Peduncle Evaluated with Magnetic Resonance Imaging

Remyelination is common under physiological conditions and usually occurs as a response to a pathological demyelinating event. Its potentiation is an important goal for the development of therapies against pathologies such as multiple sclerosis and white matter injury. Visualization and quantification in vivo of demyelination and remyelination processes are essential for longitudinal studies that will allow the testing and development of pro-myelinating strategies. In this study, ethidium bromide (EB) was stereotaxically injected into the caudal cerebellar peduncle (c.c.p.) in rats to produce demyelination; the resulting lesion was characterized (i) transversally through histology using Black-Gold II (BGII) staining, and (ii) longitudinally through diffusion-weighted magnetic resonance imaging (dMRI), by computing fractional anisotropy (FA) and diffusivity parameters to detect microstructural changes. Using this characterization, we evaluated, in the lesioned c.c.p., the effect of N-butyl-β-carboline-3-carboxylate (β-CCB), a potentiator of GABAergic signaling in oligodendrocytes. The dMRI analysis revealed significant changes in the anisotropic and diffusivity properties of the c.c.p. A decreased FA and increased radial diffusivity (λ⊥) were evident following c.c.p. lesioning. These changes correlated strongly with an apparent decrease in myelin content as evidenced by BGII. Daily systemic β-CCB administration for 2 weeks in lesioned animals increased FA and decreased λ⊥, suggesting an improvement in myelination, which was supported by histological analysis. This study shows that structural changes in the demyelination–remyelination of the caudal cerebellar peduncle (DRCCP) model can be monitored longitudinally by MRI, and it suggests that remyelination is enhanced by β-CCB treatment.This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Gambierol Potently Increases Evoked Quantal Transmitter Release and Reverses Pre- and Post-Synaptic Blockade at Vertebrate Neuromuscular Junctions

Gambierol is a marine polycyclic ether toxin, first isolated from cultured Gambierdiscus toxicus dinoflagellates collected in French Polynesia. The chemical synthesis of gambierol permitted the analyses of its mode of action which includes the selective inhibition of voltage-gated K+ (KV) channels. In the present study we investigated the action of synthetic gambierol at vertebrate neuromuscular junctions using conventional techniques. Gambierol was studied on neuromuscular junctions in which muscle nicotinic ACh receptors have been blocked with d-tubocurarine (postsynaptic block), or in junctions in which quantal ACh release has been greatly reduced by a low Ca2+–high Mg2+ medium or by botulinum neurotoxin type-A (BoNT/A) (presynaptic block). Results show that nanomolar concentrations of gambierol inhibited the fast K+ current and prolonged the duration of the presynaptic action potential in motor nerve terminals, as revealed by presynaptic focal current recordings, increased stimulus-evoked quantal content in junctions blocked by high Mg2+–low Ca2+ medium, and by BoNT/A, reversed the postsynaptic block produced by d-tubocurarine and increased the transient Ca2+ signals in response to nerve-stimulation (1–10 Hz) in nerve terminals loaded with fluo-3/AM. The results suggest that gambierol, which on equimolar basis is more potent than 3,4-diaminopyridine, can have potential application in pathologies in which it is necessary to antagonize pre- or post-synaptic neuromuscular block, or both.This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Rare Diseases of Neurodevelopment: Maintain the Mystery or Use a Dazzling Tool for Investigation? The Case of Rett Syndrome

The investigation on neurotransmission function during normal and pathologic development is a pivotal component needed to understand the basic mechanisms underlying neurodevelopmental pathologies. To study these diseases, many animal models have been generated which allowed to face the limited availability of human tissues and, as a consequence, most of the electrophysiology has been performed on these models of diseases. On the other hand, the technique of membrane microtransplantation in Xenopus oocytes allows the study of human functional neurotransmitter receptors thanks to the use of tissues from autopsies or surgeries, even in quantities that would not permit other kinds of functional studies. In this short article, we intend to underline how this technique is well-fit for the study of rare diseases by characterizing the electrophysiological properties of GABAA and AMPA receptors in Rett syndrome. For our purposes, we used both tissues from Rett syndrome patients and Mecp2-null mice, a well validated murine model of the same disease, in order to strengthen the solidity of our results through the comparison of the two. Our findings retrace previous results and, in the light of this, further argue in favor of Prof. Miledi's technique of membrane microtransplantation that proves itself a very useful tool of investigation in the field of neurophysiology.This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Mechanisms of Blockade of the Muscle-Type Nicotinic Receptor by Benzocaine, a Permanently Uncharged Local Anesthetic

Most local anesthetics (LAs) are amine compounds bearing one or several phenolic rings. Many of them are protonated at physiological pH, but benzocaine (Bzc) is permanently uncharged, which is relevant because the effects of LAs on nicotinic acetylcholine (ACh) receptors (nAChRs) depend on their presence as uncharged or protonated species. The aims of this study were to assess the effects of Bzc on nAChRs and to correlate them with its binding to putative interacting sites on this receptor. nAChRs from Torpedo electroplaques were microtransplanted to Xenopus oocytes and currents elicited by ACh (IAChs), either alone or together with Bzc, were recorded at different potentials. Co-application of ACh with increasing concentrations of Bzc showed that Bzc reversibly blocked nAChRs. IACh inhibition by Bzc was voltage-independent, but the IACh rebound elicited when rinsing Bzc suggests an open-channel blockade. Besides, ACh and Bzc co-application enhanced nAChR desensitization. When Bzc was just pre-applied it also inhibited IACh, by blocking closed (resting) nAChRs. This blockade slowed down the kinetics of both the IACh activation and the recovery from blockade. The electrophysiological results indicate that Bzc effects on nAChRs are similar to those of 2,6-dimethylaniline, an analogue of the hydrophobic moiety of lidocaine. Furthermore, docking assays on models of the nAChR revealed that Bzc and DMA binding sites on nAChRs overlap fairly well. These results demonstrate that Bzc inhibits nAChRs by multiple mechanisms and contribute to better understanding both the modulation of nAChRs and how LAs elicit some of their clinical side effects.This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Erythropoietin Increases GABAA Currents in Human Cortex from TLE Patients

Erythropoietin (EPO) is a hematopoietic growth factor that has an important role in the erythropoiesis. EPO and its receptor (EPO-R) are expressed all over in the mammalian brain. Furthermore, it has been reported that EPO may exert neuroprotective effect in animal models of brain disorders as ischemia and epilepsy. Here, we investigate whether EPO could modulate the GABA-evoked currents (IGABA) in both human epileptic and non-epileptic control brain tissues.Therefore, we transplanted in Xenopus oocytes cell membranes obtained from autoptic and surgical brain tissues (cortex) of seven temporal lope epilepsy (TLE) patients and of five control patients. Two microelectrodes voltage-clamp technique has been used to record IGABA. Moreover, qRT-PCR assay was performed in the same human tissues to quantify the relative gene expression levels of EPO/EPO-R. To further confirm experiments in oocytes, we performed additional experiments using patch-clamp recording in slices obtained from rat cerebellum.We show that exposure to EPO significantly increased the amplitude of the IGABA in all the patients analyzed. No differences in the expression of EPO and EPO-R in both TLE and control patients have been found. Notably, the increase of IGABA has been recorded also in rat cerebellar slices. Our findings show a new modulatory action of EPO on GABAA receptors (GABAA-Rs). This effect could be relevant to balance the GABAergic dysfunction in human TLE. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Modulation of acid sensing ion channel dependent protonergic neurotransmission at the mouse calyx of Held

Acid-sensing ion channels (ASICs) regulate synaptic activities and play important roles in neurodegenerative diseases. It has been reported that homomeric ASIC-1a channels are expressed in neurons of the medial nucleus of the trapezoid body (MNTB) of the auditory system in the CNS. During synaptic transmission, acidification of the synaptic cleft presumably due to the co-release of neurotransmitter and H+ from synaptic vesicles activates postsynaptic ASIC-1a channels in mice up to 3 weeks old. This generates synaptic currents (ASIC1a-SCs) that add to the glutamatergic excitatory postsynaptic currents (EPSCs). Here we report that neuromodulators like histamine and natural products like lactate and spermine potentiate ASIC1a-SCs in an additive form such that excitatory ASIC synaptic currents as well as the associated calcium influx become significantly large and physiologically relevant. We show that ASIC1a-SCs enhanced by endogenous neuromodulators are capable of supporting synaptic transmission in the absence of glutamatergic EPSCs. Furthermore, at high frequency stimulation (HFS), ASIC1a-SCs contribute to diminish short term depression (STD) and their contribution is even more relevant at early stages of development. Since ASIC channels are present in almost all types of neurons and synaptic vesicles content is acid, the participation of protons in synaptic transmission and its potentiation by endogenous substances could be a general phenomenon across the central nervous system. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Dopamine requires unique residues to signal via the serotonin 2A receptor

Serotonin is an important neurotransmitter and neuromodulator. Disruption of the serotonergic system has been implicated in various psychiatric disorders such as schizophrenia and bipolar disorder. Most of the drugs targeting these neurotransmitter systems are classified primarily as agonists or inverse agonists/antagonists, with their described function being limited to activating the canonical signaling pathway(s), or inhibiting the pathway(s) respectively.Previous work with the human 5-HT2A has shown the receptor to be activated by dopamine, also an endogenous ligand. Dopamine is the cognate ligand of the dopaminergic system, which significantly overlaps with the serotonergic system in the brain. The two systems innervate many of the same brain areas, and the central serotonergic systems also regulate dopamine functions. Our aim was to investigate the downstream signaling set up by the receptor on being activated by dopamine. We show that dopamine is a functionally selective ligand at 5-HT2A and have examined dopamine as a ligand with respect to some receptor-dependent phenotypes. Our results show that dopamine acts as an agonist at the human serotonin 2A receptor and brings about its activation and internalization. Using in vitro assays, we have established differences in the signaling pathways set up by dopamine as compared to serotonin. Using site-specific mutagenesis we have identified residues important for this functional selectivity, shown by dopamine at this receptor. Our identification of specific residues important in the functional selectivity of dopamine at 5-HT2A could have far reaching implications for the field of GPCR signaling and drug-design. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Ricardo Miledi - an outstanding neurophysiologist of 20th-21st centuries (1927-2017)

Ricardo Miledi (16.09.1927-18.12.2017) is an outstanding neurophysiologist and biophysicist who made a great contribution to the study of synaptic transmission functions. He proved the key role of сalcium ions in the release of neuromediators, developed methods of receptor expression and membrane fragments integration into large oocytes that provided huge possibilities for thousands of researchers to study subtle mechanisms of transmembrane proteins function in norm and pathology. Ricardo Miledi received his MD degree in the National Autonomous University of Mexico and in 1954 he defensed his dissertation on the study of electrical nature of cardiac fibrillation in the National Institute of Cardiology (Mexico). In 1956-1958 he underwent training in Canberra Health Research Institute (Australia) in the laboratory headed by John Eccles (Nobel Prize 1963). In 1958 R. Miledi was invited to the Department of biophysics of University College London where in cooperation with Bernard Katz (Nobel Prize 1970) made a number of important discoveries in the analysis of acetylcholine receptor expression in denervated mucle; determination of the role of calcium in neuromediators release; analysis of membrane noise on neuromediator application to neuromuscular synapses; study of the effect of antibodies from patients with myasthenia gravis on neuromuscular transmission. In the early 1980s Ricardo Miledi implemented the method of functional expression in Xenopus frog oocytes of receptors and ion channels from messenger ribonucleic acid (mRNA). His heritage running the gamut is presented in more than 500 articles.

John Newsom-Davis: clinician-scientist and so much more.

John Newsom-Davis was born in 1932 and died, aged 74, in 2007. After national service in the Royal Air Force, he read Natural Sciences at Cambridge. Following clinical studies at the Middlesex Hospital, he began research into respiratory neurophysiology with Tom Sears at the National Hospital, Queen Square, in London, and spent 1 year with Fred Plum at Cornell University in New York. After neurology specialist training at Queen Square, he became the director of the Batten Unit, continuing his interest in respiratory physiology. There he began to work on myasthenia gravis in collaboration with Ricardo Miledi at University College London and in 1978, after performing the first studies on plasma exchange in that disease, he established a myasthenia gravis research group at the Royal Free Hospital. There he investigated the role of the thymus in this disease and demonstrated an autoimmune basis for the Lambert Eaton myasthenic syndrome and ‘seronegative’ myasthenia. He was awarded the first Medical Research Council Clinical Research Professorship in 1979 but moved to Oxford in 1987 when he was elected Action Research Professor of Neurology. While at Oxford, he continued to run a very successful multidisciplinary group, researched further into the thymic abnormalities and cellular immunology of myasthenia, identified antibody-mediated mechanisms in acquired neuromyotonia, and began the molecular work that identified the genetic basis for many forms of congenital myasthenic syndrome. Meanwhile, he was also involved in university and college governance and contributed widely to the Medical Research Council, government committees, research charities and the Association of British Neurologists. Among many honours, he was elected Fellow of the Royal Society in 1991, appointed Commander of the British Empire in 1996 and made a Foreign Associate Member of the Institute of Medicine of the United States in 2001. Nearing and following retirement from Oxford, where he continued to see patients with myasthenia, he was the President of the Association of British Neurologists and Editor of Brain, and led a National Institutes of Health-funded international trial of thymectomy.

Transplanting Receptors Allows Study of Their Function

Back to table of contents Previous article Next article Clinical & Research NewsFull AccessTransplanting Receptors Allows Study of Their FunctionJoan Arehart-TreichelJoan Arehart-TreichelSearch for more papers by this authorPublished Online:19 Sep 2008https://doi.org/10.1176/pn.43.18.0024All the highly complicated functions of the human brain ultimately depend on the transmission of electric signals from one nerve cell to another—a sort of passing of the Olympic torch. Neurotransmitters serve as the torch bearers, protein receptors located on the membrane of the receiving nerve cell as their docking sites.Relatively little is known, however, about the function of these receptors, since there has been no way to study them in living persons.During the past few years, though, Ricardo Miledi, M.D., a professor of neurobiology at the University of California, Irvine, and colleagues have found a way to study neurotransmitter-receptor function outside the living human brain and in an artificial environment. It is called microtransplantation.What they do is isolate nerve-cell membranes containing neurotransmitter receptors from a postmortem human brain. They inject the membranes—carrying the original receptors together with any ancillary proteins—into a frog egg. The human nerve-cell membranes fuse with the egg membrane. The human receptors then become functional in their new“ home,” and neurobiologists can then study their properties just as though they were still functioning in a living human brain.Moreover, the technique works whether neurotransmitter-receptor material is taken from fresh or frozen postmortem brain tissue, Miledi and colleagues reported in the July 21 Early Edition of the Proceedings of the National Academy of Sciences.This is important, they explained, because “fresh human brain tissues are difficult to obtain [but] frozen postmortem brain tissues ... are available from brain banks all over the world.” Thus their technique opens vast opportunities for neurobiologists to “study the properties of human receptors present in diseased brains” and to learn crucial things about their complicity in various neurological or psychiatric illnesses.For example, they noted, Italian scientists have used the technique to study the function of neurotransmitter receptors harvested from fresh postmortem brain tissue taken from epilepsy patients. The Italian scientists found an abnormality in the function of GABA receptors taken from this tissue. Miledi's team is using the technique to study the functions of neurotransmitter receptors harvested from frozen postmortem brain tissue taken from persons with autism.They have already found, for instance, that the temporal lobes of brains of individuals with autism seem to contain a greater number of functional GABA and glutamate receptors than the temporal lobes of control brains do. This may be because the cerebral cortexes of autistic brains are known to contain more neurons than the cerebral cortexes of control brains. They have also found that the situation seems to be more complex in the cerebellum: some autistic cerebella seem to contain fewer functional GABA and glutamate receptors than control cerebella do, whereas others seem to contain more.“Because of the multiple origins and symptoms of the autism spectrum disorders, we are fully aware that it is necessary to study many more brains and tissues from many areas,” they pointed out. Nonetheless, they asserted, it is “already sufficiently clear” that their microtransplantation technique “will help to determine in great detail the type, number, and functional properties of autistic neurotransmitter receptors....”Miledi and his team likewise foresee that neurotransmitter receptors harvested from frozen, diseased brain tissue and reactivated with their microtransplantation technique can be used to “develop novel medicinal drugs.” In fact, the Italian group is using its discovery of a GABA-receptor abnormality in epilepsy to try to find new medications for epilepsy, Miledi told Psychiatric News.Anthony Phillips, Ph.D., director of the University of British Columbia Institute of Mental Health in Canada, and his colleagues are using neurotransmitter receptors to develop a new generation of psychotropic drugs that target much more selectively the regulation of neurotransmitter receptors in the brain than current psychotropic drugs do (Psychiatric News, January 6, 2006). In essence, one of their drugs would not block a receptor or activate a receptor, as current psychotropic medications do, but would influence the movement of receptors in and out of the membranes of nerve cells. Phillips told Psychiatric News that he does not foresee the microtransplantation technique developed by Miledi and his group having an immediate application to his group's work. Nonetheless, he considers the technique an “exciting new development.”The research conducted by Miledi and his colleagues was funded by the Harvard Brain Tissue Resource Center, National Institute of Child Health and Human Development Brain and Tissue Bank for Developmental Disorders, and American Health Assistance Foundation.An abstract of “Microtransplantation of Neurotransmitter Receptors From Postmortem Autistic Brains to Xenopus Occytes” is posted at<www.pnas.org/content/early/2008/07/18/0804386105>.▪ ISSUES NewArchived

Ricardo Miledi and the foundations of synaptic and extra‐synaptic neurotransmitter receptor physiology

Ricardo Miledi and the foundations of synaptic and extra‐synaptic neurotransmitter receptor physiology

Nobel Laureates at the Stazione Zoologica Anton Dohrn: Phenomenology and Paths to Discovery in Neuroscience

The practice of science usually involves more than a solitary genius in a solitary room, coping with the problem of her/his life. From the second half of the 19th century onwards, scientific research, especially in the field of the Natural Sciences, has grown into a more and more complex practice, which often entangles very special needs, in terms of research objects, techniques, sources, and perspectives. A few special places, such as the Stazione Zoologica di Napoli, have represented in this period the focal points of an ever growing international scientific network, promoting independent research, exchange and diffusion of novel practices and techniques and unrestricted confrontation. The so-called “Naples experience” has been cited by a large number of renowned scientists of the last two centuries as a key moment in their scientific life. Here we have tried to test it against the experience of three great scientists par excellence, i.e. three Nobel laureates (T. H. Morgan, Otto Warburg, J. D. Watson). The different experiences they have had at Naples represent, in our view, three different moments of the professional life of almost every scientist. Therefore, we have chosen to present them as a phenomenology. The final section is dedicated to a survey of the Zoological Station's contribution to neurosciences, especially to the Naples experience of the Nobel Prize winner Sir Bernard Katz and his assistant Ricardo Miledi, between 1965 and 1970. Their work on the squid at Naples allowed probing and quantitative refinement of results already obtained on different animals and contributed to reinforce the long lasting neurophysiological tradition of the institute.