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Thomson AM. Circuits and Synapses: Hypothesis, Observation, Controversy and Serendipity - An Opinion Piece. Front Neural Circuits 2021; 15:732315. [PMID: 34602985 PMCID: PMC8482872 DOI: 10.3389/fncir.2021.732315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/11/2021] [Indexed: 11/29/2022] Open
Abstract
More than a century of dedicated research has resulted in what we now know, and what we think we know, about synapses and neural circuits. This piece asks to what extent some of the major advances - both theoretical and practical - have resulted from carefully considered theory, or experimental design: endeavors that aim to address a question, or to refute an existing hypothesis. It also, however, addresses the important part that serendipity and chance have played. There are cases where hypothesis driven research has resulted in important progress. There are also examples where a hypothesis, a model, or even an experimental approach - particularly one that seems to provide welcome simplification - has become so popular that it becomes dogma and stifles advance in other directions. The nervous system rejoices in complexity, which should neither be ignored, nor run from. The emergence of testable "rules" that can simplify our understanding of neuronal circuits has required the collection of large amounts of data that were difficult to obtain. And although those collecting these data have been criticized for not advancing hypotheses while they were "collecting butterflies," the beauty of the butterflies always enticed us toward further exploration.
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Affiliation(s)
- Alex M. Thomson
- Department of Pharmacology, UCL School of Pharmacy, London, United Kingdom
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Bloom FE. Mentored and inspired by Mimo: a tribute to Erminio Costa. Neuropharmacology 2012; 60:1003-6. [PMID: 20869374 DOI: 10.1016/j.neuropharm.2010.09.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 09/01/2010] [Accepted: 09/16/2010] [Indexed: 11/29/2022]
Abstract
Throughout his long productive scientific career, Erminio Costa demonstrated several scholarly traits that illustrate a pattern for paths of successful achievement that should guide young scientists. Not only did he seek excellent training, he got and gave good mentoring. That guidance allowed him to ask important questions and to develop the methods necessary to obtain definitive answers by pursuing those questions in depth. Without question, he blazed trails in neuropharmacology that have been an inspiration to many others and me. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.
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Affiliation(s)
- Floyd E Bloom
- Molecular and Integrative Neuroscience Department, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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Andrianov VV. Chemical sensitivity of visual cortical neurons at different stages of food behavior formation. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 1983; 13:351-6. [PMID: 6324022 DOI: 10.1007/bf01148715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Marco E, Mao CC, Revuelta A, Peralta E, Costa E. Turnover rates of gamma-aminobutyric acid in substantia nigra, N. caudatus, globus pallidus and N. accumbens of rats injected with cataleptogenic and non-cataleptogenic antipsychotics. Neuropharmacology 1978; 17:589-96. [PMID: 29254 DOI: 10.1016/0028-3908(78)90153-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Murai S, Ogura Y. Effects of atropine and vagotomy on vocalization of the rabbit. JAPANESE JOURNAL OF PHARMACOLOGY 1978; 28:331-4. [PMID: 691876 DOI: 10.1254/jjp.28.331] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Abstract
In order to determine whether or not a serotoninergic mechanism is involved in the secretion of the growth hormone (GH), a study was made of the effect of cyproheptadine, an antiserotonin agent, on plasma GH levels in normal children. The oral administration of cyproheptadine (12 mg daily) reduced GH responses to both L-dopa and glucagon; similarly, the mean GH response to oral glucose administration was significantly reduced after cyproheptadine administration. Plasma glucose values during the tests were not altered by cyproheptadine therapy. These results suggest that the serotoninergic mechanism might be involved in L-dopa-, glucagon-, and glucose-induced GH release.
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Cheney DL, Trabucchi M, Racagni G, Wang C, Costa E. Effects of acute and chronic morphine on regional rat brain acetylcholine turnover rate. Life Sci 1974; 15:1977-90. [PMID: 4621002 DOI: 10.1016/0024-3205(74)90048-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Trabucchi M, Cheney D, Racagni G, Costa E. Involvement of brain cholinergic mechanisms in the action of chlorpromazine. Nature 1974; 249:664-6. [PMID: 4833805 DOI: 10.1038/249664a0] [Citation(s) in RCA: 100] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Maillis AG. Interneuronal activity as a factor interfering with the interpretation of results from microiontophoretic studies. Neuropharmacology 1974; 13:487-94. [PMID: 4153994 DOI: 10.1016/0028-3908(74)90138-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Jouvet M. The role of monoamines and acetylcholine-containing neurons in the regulation of the sleep-waking cycle. ERGEBNISSE DER PHYSIOLOGIE, BIOLOGISCHEN CHEMIE UND EXPERIMENTELLEN PHARMAKOLOGIE 1972; 64:166-307. [PMID: 4403272 DOI: 10.1007/3-540-05462-6_2] [Citation(s) in RCA: 80] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Pradhan SN, Dutta SN. Central cholinergic mechanism and behavior. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1971; 14:173-231. [PMID: 4338902 DOI: 10.1016/s0074-7742(08)60186-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Smythies JR, Benington F, Morin RD. The mechanism of action of hallucinogenic drugs on a possible serotonin receptor in the brain. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1970; 12:207-33. [PMID: 4918144 DOI: 10.1016/s0074-7742(08)60062-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Abstract
Sinigle neurons in cat visual cortex were driven by afferent stimuli to determine the effects of drugs liberated from multibarreled micropipettes on synaptic transmission. Acetylcholine increased, and atropine decreased, the number of neuron discharges fired in response to stimulation of the mesencephalic reticular formation without necessarily affecting responses to other stimuli or affecting spontaneous firing.
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Chapter 24. Neurotransmitters Revisited. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1969. [DOI: 10.1016/s0065-7743(08)60664-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Chapter 25. Current Status of Neurotransmitters. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1968. [DOI: 10.1016/s0065-7743(08)61330-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Pradhan SN, Roth T. Comparative behavioral effects of several anticholinergic agents in rats. Psychopharmacology (Berl) 1968; 12:358-66. [PMID: 5652217 DOI: 10.1007/bf00401415] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Marczynski TJ. Topical application of drugs to subcortical brain structures and selected aspects of electrical stimulation. ERGEBNISSE DER PHYSIOLOGIE, BIOLOGISCHEN CHEMIE UND EXPERIMENTELLEN PHARMAKOLOGIE 1967; 59:86-159. [PMID: 4384246 DOI: 10.1007/bf02269142] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Abstract
1. 5-Hydroxytryptamine (5-HT) and various 5-HT antagonists have been applied micro-electrophoretically from multibarrelled micropipettes into the environment of single neurones in the post-sigmoid and suprasylvian gyri of the cat cerebral cortex.2. In unanaesthetized animals (encéphale isolé) a high proportion of neurones (30%) were excited by 5-HT. This excitation usually had a rapid onset and was seen both in spontaneously active neurones and in otherwise quiescent neurones in which firing was induced by L-glutamate. Some neurones were so sensitive that the uncontrolled diffusion from micropipettes was sufficient to excite them. More cells were excited by 5-HT applied as a cation from solutions of the bimaleate salt than when solutions of the creatinine sulphate salt were used.3. In a high proportion of cells (33%) spontaneous firing or amino acid excitation was depressed by 5-HT.4. A mixed effect was seen in a small proportion (6%) of the cells tested; usually 5-HT caused an excitation initially which was followed by a depression. In other cells, desensitization occurred, and the excitatory effect of 5-HT was diminished or lost.5. When glutamate was used to excite otherwise quiescent cells, there was a significant increase in the number of cells excited by 5-HT and a significant decrease in the number of cells unaffected compared with spontaneously active cells.6. The micro-electrophoretic application of D-lysergic diethylamide (LSD 25), 2-brom LSD (BOL 148), methysergide (UML 491), or 2'- (3-dimethylaminopropylthio)cinnamanilide (SQ 10643) temporarily prevented excitation by 5-HT in half the cells tested. LSD and SQ 10643 were particularly potent in this respect. This antagonism of 5-HT excitation could still be seen when excitation of the cell by L-glutamate or acetylcholine (ACh) was unaffected.7. The depression induced by 5-HT was not prevented by the application of known 5-HT antagonists in the majority of the cells tested (93%). In two cells, however, the depression was reversibly prevented by these antagonists.8. Some cells tested with 5-HT were also tested with ACh or (-)-noradrenaline. The response of a cell to ACh was not significantly related to its response to 5-HT. The degree of correlation between the responses to noradrenaline and 5-HT was large, but not statistically significant with the small number of cells studied.9. The effects of 5-HT on cells in animals anaesthetized with alpha-chloralose did not differ significantly from its effects in unanaesthetized preparations. It is suggested that the use of this anaesthetic may prove a useful alternative to unanaesthetized preparations.10. The systemic injection of small quantities of thiopentone sodium selectively and reversibly reduced the sensitivity of some units to excitation by 5-HT at a time when the response to glutamate was unaffected. On other occasions, the 5-HT excitation was unaffected, though the response to glutamate was reduced.11. These results are discussed in relation to the possible nature of the 5-HT receptors in the cerebral cortex, and the interfering effects of anaesthesia on the response of brain cells to potential transmitter substances.
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Abstract
1. Studies on the anatomical distribution of tryptophan 5-hydroxylase in dog brain show that the activity of this enzyme parallels the activity of 5-hydroxytryptophan decarboxylase and the concentration of 5-hydroxytryptamine in various areas of the brain. 2. Subcellular fractionation of homogenates of rabbit hind-brain has shown that at least 40% of the tryptophan 5-hydroxylase activity is associated with the crude mitochondrial fraction; equilibrium centrifugation in a discontinuous sucrose gradient suggests that this particulate tryptophan 5-hydroxylase is localized in the synaptosomes (nerve-ending particles). 3. Attempts to increase the activity of tryptophan 5-hydroxylase in iso-osmotic homogenates of brain by adding 5,6,7,8-tetrahydro-6,7-dimethylpteridine failed. 4. Procedures designed to rupture synaptosomes caused a fall in the activity of tryptophan 5-hydroxylase, which fall was reversed by adding 5,6,7,8-tetrahydro-6,7-dimethylpteridine. This suggested either that the intact synaptosome, in which the tryptophan 5-hydroxylase is localized, contained an optimum amount of the pteridine, or that the pteridine could not pass across the nerve-cell membrane. 5. Partial purification of tryptophan 5-hydroxylase from brain preparations by ammonium sulphate precipitation revealed that the enzyme was completely dependent on 5,6,7,8-tetrahydro-6,7-dimethylpteridine for activity.
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Salmoiraghi GC, Stefanis CN. A critique of iontophoretic studies of central nervous system neurons. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1967; 10:1-30. [PMID: 4384125 DOI: 10.1016/s0074-7742(08)60149-x] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Curtis DR, Ryall RW, Watkins JC. The action of cholinomimetics on spinal interneurones. Exp Brain Res 1966; 2:97-106. [PMID: 5921136 DOI: 10.1007/bf00234363] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Winteringham FP. Metabolism and significance of acetylcholine in the brain of the adult housefly, Musca domestica L. JOURNAL OF INSECT PHYSIOLOGY 1966; 12:909-924. [PMID: 6004917 DOI: 10.1016/0022-1910(66)90078-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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Bloom FE, Barrnett RJ. Fine structural localization of acetylcholinesterase in electroplaque of the electric eel. J Cell Biol 1966; 29:475-95. [PMID: 5962939 PMCID: PMC2106980 DOI: 10.1083/jcb.29.3.475] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The electroplaques composing the electric organ of the eel, Electrophorus electricus, have been utilized for the dual purpose of demonstrating the subcellular sites of acetylcholinesterase activity and as a model for comparison of the several cytochemical methods available. Fresh tissue and tissue fixed by immersion in formalin, hydroxyadipaldehyde, or glutaraldehyde was reacted with the Cu-thiocholine method, the Cu-ferrocyanide thiocholine method, or the thiolacetic acid (TAA) method using Pb, Ag, or Au as capture reagents. Controls were obtained by omission of substrate, or by addition to complete media of varying concentrations of different cholinesterase inhibitors. Reactions were run at 0-5 degrees C at a pH range of 5.0-7.1 for 0.25 to 120 min. Regardless of the capture metal, the localization obtained with TAA as substrate was identical with that observed with acetylthiocholine, the majority of precipitate being deposited on or near the external innervated surface of the plaque and within the tubulovesicular organelles opening onto the innervated surface. Both of the thiocholine methods and the Pb-TAA method showed reaction product in synaptic vesicles of the nerve endings innervating the plaque which was uninhibitable by 10(-4)M physostigmine. All methods also showed some inhibitor-sensitive deposition of reaction product in the mucoid material forming the immediate extracellular environment of the innervated surface.
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Grundfest H. Comparative electrobiology of excitable membranes. ADVANCES IN COMPARATIVE PHYSIOLOGY AND BIOCHEMISTRY 1966; 2:1-116. [PMID: 5330181 DOI: 10.1016/b978-0-12-395511-1.50006-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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