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Manchanda R, Appukuttan S, Padmakumar M. Electrophysiology of Syncytial Smooth Muscle. J Exp Neurosci 2019; 13:1179069518821917. [PMID: 30733629 PMCID: PMC6343439 DOI: 10.1177/1179069518821917] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 12/05/2018] [Indexed: 01/21/2023] Open
Abstract
As in other excitable tissues, two classes of electrical signals are of fundamental importance to the functioning of smooth muscles: junction potentials, which arise from neurotransmission and represent the initiation of excitation (or in some instances inhibition) of the tissue, and spikes or action potentials, which represent the accomplishment of excitation and lead on to contractile activity. Unlike the case in skeletal muscle and in neurons, junction potentials and spikes in smooth muscle have been poorly understood in relation to the electrical properties of the tissue and in terms of their spatiotemporal spread within it. This owes principally to the experimental difficulties involved in making precise electrical recordings from smooth muscles and also to two inherent features of this class of muscle, ie, the syncytial organization of its cells and the distributed innervation they receive, which renders their biophysical analysis problematic. In this review, we outline the development of hypotheses and knowledge on junction potentials and spikes in syncytial smooth muscle, showing how our concepts have frequently undergone radical changes and how recent developments hold promise in unraveling some of the many puzzles that remain. We focus especially on computational models and signal analysis approaches. We take as illustrative examples the smooth muscles of two organs with distinct functional characteristics, the vas deferens and urinary bladder, while also touching on features of electrical functioning in the smooth muscles of other organs.
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Affiliation(s)
- Rohit Manchanda
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Shailesh Appukuttan
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Mithun Padmakumar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
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Burnstock G. Purinergic signalling in the reproductive system in health and disease. Purinergic Signal 2014; 10:157-87. [PMID: 24271059 PMCID: PMC3944041 DOI: 10.1007/s11302-013-9399-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 10/24/2013] [Indexed: 12/16/2022] Open
Abstract
There are multiple roles for purinergic signalling in both male and female reproductive organs. ATP, released as a cotransmitter with noradrenaline from sympathetic nerves, contracts smooth muscle via P2X1 receptors in vas deferens, seminal vesicles, prostate and uterus, as well as in blood vessels. Male infertility occurs in P2X1 receptor knockout mice. Both short- and long-term trophic purinergic signalling occurs in reproductive organs. Purinergic signalling is involved in hormone secretion, penile erection, sperm motility and capacitation, and mucous production. Changes in purinoceptor expression occur in pathophysiological conditions, including pre-eclampsia, cancer and pain.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK,
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Release of dopamine beta-hydroxylase and chromogranin A upon stimulation of the splenic nerve. Tissue Cell 2012; 2:547-68. [PMID: 18631532 DOI: 10.1016/s0040-8166(70)80030-1] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/1970] [Indexed: 11/22/2022]
Abstract
Two proteins present in noradrenergic vesicles of the splenic nerve (dopamine beta-hydroxylase and chromogranin A) are released into the perfusate from the spleen when the splenic nerve is stimulated. Experiments in which drugs were added to the perfusion fluid showed that the proteins were released from terminals of the splenic nerve. There was a correlation between the amounts of the proteins released and the quantity of noradrenaline released; and the release process was dependent upon calcium. It is suggested that the proteins are released from the large dense-cored vesicles present in the terminals of the splenic nerve, and that secretion from these vesicles occurs by exocytosis.
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CHANG CC, SU CY. Effect of cold stress on the subcellular distribution of noradrenaline in the rat heart. J Pharm Pharmacol 2011. [DOI: 10.1111/j.2042-7158.1967.tb08040.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Abstract
Rats were exposed to cold (4°) for 2 hr to study the effect of increased sympathetic activities on the subcellular distribution of noradrenaline in the heart. Cold-exposure caused about 30% decrease of total noradrenaline contents in both auricles and ventricles of normal or adrenalectomized rats. This depletion of noradrenaline caused by cold was completely prevented by pretreatment of the rat with hexamethonium chloride. Measurement of the subcellular distribution of noradrenaline revealed that the percentage depletion in particle-bound amine in both auricles and ventricles was greater than in the supernatant noradrenaline. It is suggested that the noradrenaline in the particulate fraction is the functional pool of the amine available for release by nerve impulses.
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Affiliation(s)
- C C CHANG
- Pharmacological Institute, College of Medicine, National Taiwan University, Taipei, Taiwan, China
| | - C Y SU
- Pharmacological Institute, College of Medicine, National Taiwan University, Taipei, Taiwan, China
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Holman ME, Hirst GDS. Junctional Transmission in Smooth Muscle and the Autonomic Nervous System. Compr Physiol 2011. [DOI: 10.1002/cphy.cp010112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Boullin DJ. The action of extracellular cations on the release of the sympathetic transmitter from peripheral nerves. J Physiol 2010; 189:85-99. [PMID: 16992247 PMCID: PMC1396051 DOI: 10.1113/jphysiol.1967.sp008156] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The noradrenaline stores in the sympathetic nerve endings of the cat colon were labelled in vivo with (+/-)-[7-(3)H]noradrenaline (500 muc, 11.3 mug) injected 3 hr before killing.2. The colon was removed and immersed in an organ bath containing Krebs solution. The vascular bed was perfused from the inferior mesenteric artery to the colic vein.3. The effects of Ca(2+), Ba(2+) and Mg(2+) on the output of [(3)H]noradrenaline and [(3)H]metabolites in the venous effluent were measured before and after electrical stimulation of the post-ganglionic inferior mesenteric nerves at 10 impulses/sec.4. Nerve stimulation increased the efflux of [(3)H]noradrenaline when the perfusion fluid contained Ca(2+). Variations in Ca(2+) concentration (1.5-10 mM) did not affect this response.5. Removal of Ca(2+) from the fluid passing through the vascular bed (and therefore from the region of the sympathetic nerve terminals), abolished the output of [(3)H]noradrenaline in response to nerve stimulation. There was no change when phenoxybenzamine was added to prevent the binding of transmitter on to post-synaptic receptors on the effector organ.6. The output of transmitter was not changed when Ca(2+) was present in the blood vessels of the colon even though it was removed from the solution in contact with the remainder of the tissue.7. Nerve stimulation released [(3)H]noradrenaline when Ba(2+) was used as a substitute for Ca(2+); Mg(2+) was not an effective substitute for Ca(2+) as then nerve stimulation did not increase the output of radioactive noradrenaline or metabolites.8. Ba(2+) also increased the resting output of [(3)H]noradrenaline in the absence of nerve stimulation. Addition of Ca(2+) or Mg(2+) did not change this spontaneous release but it was augmented by removal of Ca(2+).9. It is concluded that Ca(2+) is essential for release of the sympathetic transmitter by nerve stimulation but not for the spontaneous output that occurs in the absence of nervous activity. The site of action of Ca(2+) is considered to be the terminals of adrenergic fibres.
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Abstract
1. The membrane polarization in response to intracellular stimulation and external stimulation, the junction potentials evoked by nerve and field stimulation and the spontaneous junction potentials were studied in the guinea-pig vas deferens.2. The responses to intracellular stimulation differed from those to external stimulation applied through a large electrode in the following ways: short time constant of the electrotonic potential; linearity of current-voltage relation; all-or-none spike only in a small proportion of the cells; high critical firing level; short latency; weak tendency for repetitive activity during depolarization; and sharp spatial decay of the response.3. The difference between intracellular and external stimulation could be explained by differences in current distribution in the tissue, if many muscle fibres were aggregated in functional bundles, with three-dimensional cell-to-cell connexions, so that the membrane near an intracellular stimulating electrode was shunted by a large area of surrounding membrane.4. The time course of the junction potentials depended on the manner by which they were produced. The junction potential evoked by hypogastric nerve stimulation was recorded in every cell with almost the same amplitude. The spontaneous junction potential decayed very sharply with distance and the time course of the falling phase was about 10 times faster than that of the evoked junction potential.The difference between the time course of the junction potentials was also explained by the difference in current distribution in the tissue.
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Manchanda R, Venkateswarlu K. Identification of the Components of Excitatory Junction Potentials in the Guinea Pig Vas Deferens. ACTA ACUST UNITED AC 2009. [DOI: 10.3109/15368379709015654] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Abstract
After defining truly "neurotrophic" influences, and giving examples from the many studies of such influences on the somatomotor system, current research concerning sympathetic neurotrophic effects on the vascular bed is discussed. Tissue-culture studies have made it clear that, particularly in early growth phases, local trophic influences are quite important and interdependent between adrenergic neurons and vascular smooth muscle cells. Most experiments aimed at illustrating neurotrophic effects on vascular beds in vivo, however, seem to suggest the dominance of long-term adaptation processes inherent in the effector cells themselves which, particularly on sustained extrinsic activation however achieved, become increasingly mobilised. This is not to dispute the fact that truly neurotrophic influences seem to be superimposed, facilitating and modulating these essentially intrinsic mechanisms for long-term effector cell adaptation, but their relative importance is difficult to judge.
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Brain KL. Neuroeffector Ca2+ transients for the direct measurement of purine release and indirect measurement of cotransmitters in rodents. Exp Physiol 2008; 94:25-30. [PMID: 18805863 DOI: 10.1113/expphysiol.2008.043679] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Determining whether ATP and noradrenaline are released from the same vesicle at mature autonomic neuroeffector junctions is challenging because of the difficulty of simultaneously detecting the packeted release of these neurotransmitters. Contraction, overflow and electrophysiology experiments all show that both ATP and noradrenaline are released following field stimulation (although the ratio might vary) from autonomic nerves in tissues including the vas deferens, rat tail artery and mesenteric artery. The occurrence of purinergic neuroeffector Ca(2+) transients (NCTs) has been used to detect the packeted release of the neurotransmitter ATP acting on postjunctional P2X receptors to cause Ca(2+) influx. Neuroeffector Ca(2+) transients can also be used to detect the local effects of noradrenaline through its alpha(2)-adrenoceptor-mediated prejunctional autoinhibitory effects on nerve terminal Ca(2+) concentration and the probability of exocytosis (measured by counting NCTs). Evidence is presented that exocytosis from sympathetic varicosities does not occur in a manner independent of the history of that varicosity, but rather that the release of a packet of ATP transiently suppresses (or predicts the transient suppression of) subsequent release. This could arise by autoinhibition (by the prejunctional action of noradrenaline or purines) or due to a transient shortage of vesicles readily available for release. In summary, two high-resolution approaches are proposed to measure the intermittent release of packets of neurotransmitter: (1) local transient suppression of nerve terminal Ca(2+) transients; and (2) the local and transient inhibition of NCTs to infer local autoinhibition, hence transmitter release. Such approaches may allow the packeted corelease of ATP and noradrenaline to be investigated without the need to measure both neurotransmitters directly.
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Affiliation(s)
- K L Brain
- University Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
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Meng E, Young JS, Brading AF. Spontaneous activity of mouse detrusor smooth muscle and the effects of the urothelium. Neurourol Urodyn 2007; 27:79-87. [PMID: 17487871 DOI: 10.1002/nau.20456] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AIMS To characterize the detrusor muscle of the mouse urinary bladder in order to understand more precisely spontaneous contractile behavior of this organ. This study examined the spontaneous electrical activity and Ca(2+) dynamics of the detrusor smooth muscle and investigated the role of the urothelium. MATERIALS AND METHODS Detrusor smooth muscle strips were isolated from mouse bladders. The urothelium was either kept intact or removed. Changes in membrane potential were recorded using sharp electrode intracellular recording. To image Ca(2+) dynamics, tissue strips were exposed to 10 microM Oregon Green 488 BAPTA-1 AM for 70 min, and then image series were acquired with a laser-scanning confocal microscope. RESULTS (1) Mouse detrusor smooth muscle cells (SMCs) generate nifedipine-sensitive spontaneous action potentials (sAPs) at a low frequency (1.3 +/- 0.9 min(-1), n = 11) in preparations with intact urothelium. This frequency increased when the urothelium was removed (7 +/- 8.3 min(-1), n = 17) (P < 0.05, Student's t test). (2) Frequent ATP-mediated spontaneous depolarizations were recorded in all cells. (3) The frequency of whole cell Ca(2+) flashes of detrusor smooth muscle cells was higher in preparations with the urothelium removed (median 1.2 min(-1), n = 7) than in urothelium denuded preparations (median 0.6 min(-1), n = 7) (P < 0.01, Mann-Whitney U-test). CONCLUSIONS Spontaneous activity of the mouse detrusor smooth muscles was characterized enabling future comparative work on gene knock-out strains. Evidence suggesting release of an inhibitory factor by the urothelium was apparent.
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Affiliation(s)
- En Meng
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom.
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Ghildyal P, Palani D, Manchanda R. Post- and prejunctional consequences of ecto-ATPase inhibition: electrical and contractile studies in guinea-pig vas deferens. J Physiol 2006; 575:469-80. [PMID: 16675493 PMCID: PMC1819469 DOI: 10.1113/jphysiol.2006.109678] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
At sites of purinergic neurotransmission, synaptic ecto-ATPase is believed to limit the actions of ATP following its neural release. However, details of the modulation by this enzyme of the ATP-mediated conductance change and the possible mechanisms mediating this modulation remain unelucidated. We have addressed these issues by studying the effect of ARL 67156, a selective ecto-ATPase inhibitor, on ATP-mediated electrical and contractile activity in the sympathetically innervated guinea-pig vas deferens. ARL 67156 at 100 mum significantly potentiated the amplitude of spontaneous excitatory junction potentials (SEJPs) by 81.1% (P < 0.01) and prolonged their time courses (rise time by 49.7%, decay time constant by 38.2%; P < 0.01). Moreover, the frequency of occurrence of SEJPs was strikingly increased (from 0.28 +/- 0.13 to 0.90 +/- 0.26 Hz; P < 0.01), indicating an additional, primarily presynaptic, effect of ecto-ATPase inhibition. The frequency of occurrence of discrete events (DEs), which represent nerve stimulation-evoked quantal release of neurotransmitter, was also increased ( approximately 6-fold; P < 0.01), along with the appearance of DEs at previously 'silent' latencies. Purinergic contractions of the vas deferens were potentiated significantly (P < 0.01) by ARL 67156; these potentiated contractions were suppressed by the A1 agonist adenosine (P < 0.01) but left unaffected by the A1 antagonist 8-phenyltheophylline (8-PT). Our results indicate (i) that ecto-ATPase activity, in addition to modulating the ATP-mediated postjunctional conductance change, may regulate transmitter release prejunctionally under physiological conditions, and (ii) that the prejunctional regulation may be mediated primarily via presynaptic P2X, rather than A1, receptors.
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Affiliation(s)
- P Ghildyal
- Biomedical Engineering Group, School of Biosciences and Bioengineering, Indian Institute of Technology--Bombay, Mumbai 400076, India
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Stjärne L. Basic mechanisms and local modulation of nerve impulse-induced secretion of neurotransmitters from individual sympathetic nerve varicosities. Rev Physiol Biochem Pharmacol 2005; 112:1-137. [PMID: 2479077 DOI: 10.1007/bfb0027496] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Christ GJ, Venkateswarlu K, Day NS, Valcic M, Santizo C, Zhao W, Wang HZ, Persson K, Andersson KE. Intercellular communication and bladder function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 539:239-54. [PMID: 15088908 DOI: 10.1007/978-1-4419-8889-8_17] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
There is now considerable experimental and clinical evidence supporting the supposition that overactivity of the bladder is associated with detectable alterations in the electrical properties of the detrusor smooth muscle cells. The preliminary data described in this report indicates that intercellular communication through gap junctions might play an important role in this process. Moreover, alterations in Cx43 mRNA expression may represent a tissue response to a physiologic insult (i.e., increased after load) in an attempt to further increase the syncytial nature and force of detrusor contractility to compensate for an increased pressure load. Finally, this report elucidates the rationale for suspecting that intercellular communication through gap junctions may play a role in normal bladder physiology and the pathophysiology of urinary incontinence caused by partial outlet obstruction.
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Affiliation(s)
- George J Christ
- Department of Urology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Spencer NJ, Hennig GW, Smith TK. Spatial and temporal coordination of junction potentials in circular muscle of guinea-pig distal colon. J Physiol 2001; 535:565-78. [PMID: 11533145 PMCID: PMC2278784 DOI: 10.1111/j.1469-7793.2001.00565.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. In isolated, stretched, flat-sheet preparations of guinea-pig distal colon, simultaneous intracellular recordings were made from pairs of circular muscle (CM) cells to map the region of smooth muscle at which spontaneous junction potentials (sJPs) were coordinated in both space and time. 2. Spontaneous inhibitory junction potentials (sIJPs) and excitatory junction potentials (sEJPs) were recorded from all animals with varying frequencies and amplitudes (up to 25 mV). 3. Large amplitude (> or = 9 mV) sIJPs or sEJPs with near-identical amplitudes and time courses were recorded synchronously from two CM cells, even when the two electrodes were separated by up to 11 mm in the circumferential axis and < or = 4 mm in the longitudinal axis. However, smaller (< 9 mV) sIJPs or sEJPs were less coordinated and exhibited greater variability in their times to peak. 4. The standard deviation (S.D.) for the time difference between the peaks of sJPs was related to the amplitude of the events and the distance between the electrodes. The S.D. for large amplitude JPs (approximately 30 ms), which was less than that for small JPs (approximately 150 ms), remained constant across the circumferential axis (at least up to 6 mm), but declined rapidly for distances > or = 2 mm in the longitudinal axis. 5. Current injection (up to 8 nA) into a single CM cell elicited electrotonic potentials in neighbouring CM cells, only when the two electrodes were separated by less than 100 microm circumferentially. Beyond 50 microm electronic potentials were rarely detected. 6. Tetrodotoxin (TTX; 1 microM) abolished all sJPs, whereas hexamethonium (300 microM) either abolished, or substantially reduced all sJPs. 7. Nitro-L-arginine (L-NA; 100 microM) abolished the slow repolarisation phase of sIJPs without any apparent effect on the amplitude of sIJPs. Apamin abolished the fast, initial component of sIJPs, suggesting synchronous release of two inhibitory neurotransmitters during the sIJP. Atropine (1 microM) abolished sEJPs. 8. No sJPs were recorded from the CM layer when it was separated from the myenteric plexus. 9. In conclusion, sIJPs and sEJPs in colonic CM occur synchronously over large regions of the smooth muscle syncitium. The results are discussed in relation to the idea that spontaneous junction potentials in colonic CM are not monoquantal events, but are generated by the simultaneous release of transmitter from many release sites, due to the synchronous activation of many enteric motor neurons.
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Affiliation(s)
- N J Spencer
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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Jackson VM, Cunnane TC. Neurotransmitter release mechanisms in sympathetic neurons: past, present, and future perspectives. Neurochem Res 2001; 26:875-89. [PMID: 11699939 DOI: 10.1023/a:1012320130988] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In 1969, Paton and Vizi described the inhibitory actions of noradrenaline on acetylcholine release from the innervation of the guinea-pig ileum longitudinal muscle. They concluded "that acetylcholine output by the nervous networks of the longitudinal strip is under the normal control of the sympathetic by a species of presynaptic inhibition mediated by <==> receptors". This work was carried out in the Pharmacology Department at Oxford University. Clearly, a period in the 'Dreaming Spires' of Oxford sufficiently inspired Sylvester to take up a life long career in scientific research. He has published more than 300 papers on a wide range of topics but clearly has a strong interest in neurotransmitter release mechanisms and recently, non-synaptic interactions between neurons. It seems fitting therefore to write a brief review on the continuing studies on neurotransmitter release mechanisms in sympathetic neurons in a volume honoring the now distinguished Professor Vizi.
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Stjärne L. Do sympathetic nerves release noradrenaline in "quanta"? JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 2000; 81:236-43. [PMID: 10869727 DOI: 10.1016/s0165-1838(00)00119-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The discovery of excitatory junction potentials (EJPs) in guinea-pig vas deferens by Burnstock and Holman (1960) showed for the first time that a sympathetic transmitter, now known to be ATP, is secreted in "quanta". As it was assumed at the time that EJPS are triggered by noradrenaline, this discovery led to attempts to use the fractional overflow of noradrenaline from sympathetically innervated tissues to assess, indirectly, the number of noradrenaline molecules in the average "quantum". The basic finding was that each pulse released 1/50000 of the tissue content of noradrenaline, when reuptake was blocked and prejunctional alpha(2)-adrenoceptors were intact. This provided the constraints, two extreme alternatives: (i) each pulse releases 0.2-3% of the content of a vesicle from all varicosities, or (ii) each pulse releases the whole content of a vesicle from 0.2 to 3% of the varicosities. New techniques have made it possible to address questions about the release probability in individual sites, or the "quantal" size, more directly. Results by optical (comparison of the labelling of SV2 and synaptotagmin, proteins in the membrane of transmitter vesicles), electrophysiological (excitatory junction currents, EJCs, at single visualized varicosities) and amperometric (the noradrenaline oxidation current at a carbon fibre electrode) methods reveal that transmitter exocytosis in varicosities is intermittent. The EJC and noradrenaline oxidation current responses (in rat arteries) to a train of single pulses were observed to be similar in intermittency and amplitude fluctuation. This suggests that they are caused by exocytosis of single or very few "quanta" of ATP and noradrenaline, respectively, equal to the contents of single vesicles, from a small population of release sites. These findings support, but do not conclusively prove the validity of the "intermittent" model of noradrenaline release. The question if noradrenaline is always secreted in packets of preset size ("quanta") and if the "quantum" is a subfraction or the whole content of single synaptic vesicles, still remains open.
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Affiliation(s)
- L Stjärne
- Department of Physiology and Pharmacology, Karolinska Institutet, S-17177, Stockholm, Sweden.
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Manchanda R, Venkateswarlu K. Quantal evoked depolarizations underlying the excitatory junction potential of the guinea-pig isolated vas deferens. J Physiol 1999; 520 Pt 2:527-37. [PMID: 10523420 PMCID: PMC2269600 DOI: 10.1111/j.1469-7793.1999.00527.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. The effects of a putative gap junction uncoupling agent, heptanol, on the intracellularly recorded junction potentials of the guinea-pig isolated vas deferens have been investigated. 2. After the stimulation-evoked excitatory junction potentials (EJPs) had been suppressed by heptanol (2.0 mM) to undetectable levels, a different pattern of evoked activity ensued. This consisted of transient depolarizations that were similar to EJPs in being stimulus locked and in occurring at a fixed latency, but differed from EJPs in that they occurred intermittently and had considerably briefer time courses. 3. Analysis of the amplitudes and temporal parameters of the rapid residual depolarizations revealed a close similarity with spontaneous EJPs (SEJPs). There was no statistically significant difference between the rise times, time constants of decay and durations of the rapid residual depolarizations and of SEJPs. 4. Selected evoked depolarizations were virtually identical to SEJPs occurring in the same cell. Evoked depolarizations of closely similar amplitude and time course also occurred, usually within a few stimuli of each other. 5. These depolarizations appear to represent the individual quantal depolarizations that normally underlie the EJP and are therefore termed 'quantal excitatory junction potentials' (QEJPs) to distinguish them from both EJPs and SEJPs. 6. We examined the possibility that heptanol revealed QEJPs by disrupting electrical coupling between cells in the smooth muscle syncytium. Heptanol (2.0 mM) had no effect on the amplitude distribution, time courses, or the frequency of occurrence of SEJPs. Intracellular input impedance (Rin) of smooth muscle cells was left unaltered by heptanol. 7. 'Cable' potentials of the vas deferens, recorded using the partition stimulation method, also remained unchanged in the presence of heptanol. Thus, heptanol appeared not to modify syncytial electrical properties of the smooth muscle in any significant way. 8. Our observations show directly that the quantal depolarizations underlying the EJP in syncytial smooth muscle are SEJP-like events. However, no unequivocal statement can be made about the mechanism by which heptanol unmasks QEJPs from EJPs.
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Affiliation(s)
- R Manchanda
- School of Biomedical Engineering, Indian Institute of Technology-Bombay, Powai, Mumbai 400 076, India.
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BURNSTOCK G, HOLMAN ME. Effect of denervation and of reserpine treatment on transmission at sympathetic nerve endings. J Physiol 1998; 160:461-9. [PMID: 13875000 PMCID: PMC1359557 DOI: 10.1113/jphysiol.1962.sp006859] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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BENTLEY GA. Studies on sympathetic mechanisms in isolated intestinal and vas deferens preparations. BRITISH JOURNAL OF PHARMACOLOGY AND CHEMOTHERAPY 1998; 19:85-98. [PMID: 13867378 PMCID: PMC1482230 DOI: 10.1111/j.1476-5381.1962.tb01429.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The effects of various drugs which block sympathetic nerves have been studied in Finkleman preparations of rabbit and cat ileum. Contractile responses could be produced in many cases after the normal inhibitory responses to periarterial nerve stimulation had been blocked. In almost all cases this contractile response was abolished by ganglion-blocking drugs. The normal rabbit ileum Finkleman preparation was found to behave differently towards bretylium than do preparations taken from animals treated with reserpine. The block of the guinea-pig isolated hypogastric vas deferens preparation caused by hemicholinium HC-3 was found to be reversed in the presence of noradrenaline, histamine, or 5-hydroxytryptamine, as was the block caused by guanethidine and bretylium. The results are discussed in relation to the Burn-Rand theory of sympathetic nerve mechanism.
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OHLIN P, STROMBLAD BC. Observations on the isolated vas deferens. BRITISH JOURNAL OF PHARMACOLOGY AND CHEMOTHERAPY 1998; 20:299-306. [PMID: 13939659 PMCID: PMC1703632 DOI: 10.1111/j.1476-5381.1963.tb01469.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Experiments on the isolated vas deferens of guinea-pig and rat had unexpected results in several ways. The effect of stimulation of the hypogastric nerve was not abolished, but increased, by parasympathetic blocking agents or by sympathetic blocking agents such as dihydroergotamine and phenoxybenzamine. The sensitization is considered not due to anticholinesterase activity of the drugs. Prolonged contact with a stimulating agent evoked rhythmic contractions. Addition as well as removal of a drug from the bath caused a response. The results of experiments involving chronic denervation, addition of hexamethonium and histological examination tally with the assumption of a distribution of ganglionic cells along the nerve just outside the organ.
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Henery R, Gibson WG, Bennett MR. Quantal currents and potential in the three-dimensional anisotropic bidomain model of smooth muscle. Bull Math Biol 1997; 59:1047-75. [PMID: 9358735 DOI: 10.1007/bf02460101] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The potential generated in the smooth muscle of the vas deferens on release of a quantum of transmitter from a varicosity was analyzed using a three-dimensional bidomain continuum model. Current was injected at the origin of the bidomain; this current had the temporal characteristics of the junctional current. The membrane potential, intracellular potential, and extracellular potential, as well as the extracellular current, were then calculated throughout the bidomain at different times. Calculations were performed to show the effect of changing the anisotropy ratios of the intracellular and extracellular conductivities on the spread of current and potential in each of the three dimensions. These results provide a theoretical framework for ascertaining the time course of transmitter interaction at a varicosity following the secretion of a quantum of transmitter.
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Affiliation(s)
- R Henery
- Neurobiology Laboratory, Sydney Institute for Biomedical Research, University of Sydney, New South Wales, Australia
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The Croonian Lecture, 1964 The release and fate of the transmitter liberated by adrenergic nerves. ACTA ACUST UNITED AC 1997. [DOI: 10.1098/rspb.1965.0023] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
It is customary for Croonian lecturers, after expressing their thanks to the President and Council for the honour that they have received in being asked to give this lecture, to devote some time to a justification of their subject in terms of Mrs Croone’s suggestion that the lecture should deal with the advancement of natural knowledge on local motion. The first of these tasks, Mr President, I perform humbly and with deep gratitude, but at the same time with some surprise that Council in its wisdom should have chosen one so ill-fitted for the honour you have laid upon him. The second task is easier since my lecture will deal with the nerves which control the muscles surrounding the hollow organs of the body, blood vessels and bowels, and further justification as a theme dealing with local motion the most captious critic could not desire. Three years ago my former colleague Bernard Katz gave the Croonian Lecture on ‘ Transmission of impulses from nerve to muscle’ in which he described our present knowledge of the mechanism of the chemical mediation interposed between nerve and skeletal muscle and summarized his own brilliant contributions to this, to me, fascinating subject. Today I am dealing again with transmission from nerve to muscle, but in a different system and, I am afraid, at a quite different and lower intellectual level than that of Katz. The idea of chemical transmission from nerve to effector cell came first to T. R. Elliott in 1904 as a result of his observation, in an extensive comparative study, of the close similarities between the actions of adrenaline injected intravenously and the effects of stimulating nerves belonging to the sympathetic system. These nerves we should now call in Dale’s (1933) terminology the adrenergic nerves, those transmitting their effects whether excitatory or inhibitory by the liberation at their endings of a ‘minute charge’ of the catecholamine adrenaline or one of its analogues. The cells upon which these nerves exert their action are the smooth muscle cells controlling the movements of the hollow viscera, intestines, reproductive tract and so on, and of the muscle cells of the vascular system that regulate the diameter of the blood vessels. These are processes that do not demand high precision of timing nor do they apparently require the instant turning on and off of transmitter action with which we have grown familiar in the junction between nerve and skeletal muscle. At this junction, as Katz showed, liberation and action of acetylcholine and its inactivation by the specific enzyme cholinesterase are over in a few milliseconds, and there is no reason to believe that the liberated transmitter in the untreated junction can ever diffuse more than a few microus from its site of action. It is hemmed in by barriers of specific cholinesterase, and these are reinforced by barriers of the non-specific enzyme in blood and tissue fluids. This narrow coarctation of the transmitter acetylcholine in space and time seems, however, to be confined to places where precise timing is required, such as at the neuromuscular junction and in the ganglionic and central nervous synapse. When it is liberated as the transmitter from nerves to blood vessels, or to secretory glands, it can escape some way from its site of liberation and persist long enough to be detected by skeletal muscles sensitized by denervation, as is seen in the Sherrington, Rogowitz and Vulpian-Heidenhain phenomena. I have laboured a little this question of diffusion and action at a distance of transmitter because it constitutes
prima facie
one of the most striking differences between the adrenergic and the cholinergic transmitters in at least the mammalian body. It was indeed because the liberated adrenergic transmitter escaped into the blood stream and could be detected by another tissue or organ, sometimes, but not necessarily, specially sensitized, that W. B. Cannon and his colleagues in the 30’s were able to add so much to our knowledge of sympathetic innervation. Nevertheless, in spite of the relative stability of the adrenergic transmitter and its ready detection in the blood stream, little had been discovered about the quantitative aspects of its liberation and metabolism some 50 years after its existence had been postulated, whereas we now have, and have had for 30 years, quite reasonably complete information about the liberation, storage and metabolism of the unstable and ephemeral acetylcholine.
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BURNSTOCK G, HOLMAN ME, KURIYAMA H. FACILITATION OF TRANSMISSION FROM AUTONOMIC NERVE TO SMOOTH MUSCLE OF GUINEA-PIG VAS DEFERENS. J Physiol 1996; 172:31-49. [PMID: 14195692 PMCID: PMC1368901 DOI: 10.1113/jphysiol.1964.sp007401] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Abstract
This review attempts to clarify the definition of what constitutes an autonomic neuromuscular function formed by a varicosity. Ultrastructural studies of serial sections through varicosities, partly or wholly bare of Schwann cell covering, show that areas of close apposition occur between varicosities and muscle cell membrane that vary between 20 and 150 nm, depending on the muscle considered. Consideration of the diffusion of purine transmitters and their receptor kinetics after secretion in a packet show that the number of purinergic receptor channels opened at a site of 150 nm apposition by a varicosity is about 15% of that at a site of 50 nm apposition. These results, together with the analysis of the stochastic fast component and the deterministic slow components of the rising phase of the EJP suggest that the stochastic fast component is due to varicosities that form especially close appositions (20-50 nm), whereas the deterministic slow component is due to the large number of varicosities at distances up to about 150 nm. Varicosities forming appositions of 20-150 nm with muscle cells several hundred micrometers long possess junctional receptor types distinct from extrajunctional receptors. According to this argument, then, there are two different classes of varicosities: one that gives rise to a relatively large junctional current and another that is responsible for a very small junctional current. Present evidence suggests that two subclasses of varicosities can be discerned amongst the varicosities that generate large junctional currents. One of these subclasses of varicosity possesses relatively few post-junctional receptors compared with the amount of transmitter reaching the receptors from the varicosity, so that the junctional current generated is determined by the size of the receptor population; in this case, the size of the transmitter packages released from these varicosities is unknown and the size of the junctional current is relatively constant. The other subclass of varicosity possesses large receptor patches, sufficient to accommodate the largest amounts of transmitter released from the varicosities: in this case, the size of the transmitter packages is shown to be highly non-uniform. These speculations await confirmation by direct labelling of the receptor patches beneath varicosities, a possibility that is likely to be realized in the near future.
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Affiliation(s)
- M R Bennett
- Department of Physiology, University of Sydney, NSW, Australia
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KURIYAMA H. ELECTROPHYSIOLOGICAL OBSERVATIONS ON THE MOTOR INNERVATION OF THE SMOOTH MUSCLE CELLS IN THE GUINEA-PIG VAS DEFERENS. J Physiol 1996; 169:213-28. [PMID: 14078060 PMCID: PMC1368712 DOI: 10.1113/jphysiol.1963.sp007251] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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30
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KURIYAMA H. THE EFFECT OF TEMPERATURE ON NEUROMUSCULAR TRANSMISSION IN THE VAS DEFERENS OF THE GUINEA-PIG. J Physiol 1996; 170:561-70. [PMID: 14165695 PMCID: PMC1368690 DOI: 10.1113/jphysiol.1964.sp007349] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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31
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MCGREGOR DD. THE EFFECT OF SYMPATHETIC NERVE STIMULATION OF VASOCONSTRICTOR RESPONSES IN PERFUSED MESENTERIC BLOOD VESSELS OF THE RAT. J Physiol 1996; 177:21-30. [PMID: 14296957 PMCID: PMC1357221 DOI: 10.1113/jphysiol.1965.sp007572] [Citation(s) in RCA: 538] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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32
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KOPIN IJ, FISCHER JE, MUSACCHIO J, HORST WD. EVIDENCE FOR A FALSE NEUROCHEMICAL TRANSMITTER AS A MECHANISM FOR THE HYPOTENSIVE EFFECT OF MONOAMINE OXIDASE INHIBITORS. Proc Natl Acad Sci U S A 1996; 52:716-21. [PMID: 14212547 PMCID: PMC300335 DOI: 10.1073/pnas.52.3.716] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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33
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BURNSTOCK G, HOLMAN ME. AN ELECTROPHYSIOLOGICAL INVESTIGATION OF THE ACTIONS OF SOME AUTONOMIC BLOCKING DRUGS ON TRANSMISSION IN THE GUINEA-PIG VAS DEFERENS. BRITISH JOURNAL OF PHARMACOLOGY AND CHEMOTHERAPY 1996; 23:600-12. [PMID: 14256817 PMCID: PMC1704004 DOI: 10.1111/j.1476-5381.1964.tb01613.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Membrane potentials have been recorded from the guinea-pig isolated vas deferens with intracellular and sucrose-gap electrodes during stimulation of the hypogastric nerve and of intramural nerve fibres. Atropine had no detectable effect on the excitatory junction potentials in response to nerve stimulation or on the spontaneous discharge of small potentials. High concentrations of adrenolytic drugs, acting on alpha-receptors were needed to block the response to nerve stimulation and the spontaneous discharge. During the onset and recovery from yohimbine blockade, junction potentials in response to repetitive stimulation were not sustained. Bretylium initially reduced both the junction potentials and the spontaneous discharge. However, after 30 min exposure, the spontaneous discharge increased in frequency although the response to nerve stimulation was abolished. Block of the junction potentials by procaine was rapid in onset compared with that by bretylium and guanethidine, but the spontaneous discharge was not abolished. These results are discussed in relation to the mechanism of transmission from sympathetic nerve to smooth muscle.
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KURIYAMA H. EFFECT OF CALCIUM AND MAGNESIUM ON NEUROMUSCULAR TRANSMISSION IN THE HYPOGASTRIC NERVE-VAS DEFERENS PREPARATION OF THE GUINEA-PIG. J Physiol 1996; 175:211-30. [PMID: 14241164 PMCID: PMC1357114 DOI: 10.1113/jphysiol.1964.sp007513] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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35
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MERRILLEES NC, BURNSTOCK G, HOLMAN ME. CORRELATION OF FINE STRUCTURE AND PHYSIOLOGY OF THE INNERVATION OF SMOOTH MUSCLE IN THE GUINEA PIG VAS DEFERENS. ACTA ACUST UNITED AC 1996; 19:529-50. [PMID: 14086135 PMCID: PMC2106328 DOI: 10.1083/jcb.19.3.529] [Citation(s) in RCA: 189] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
An electron microscope study of the innervation of smooth muscle of the guinea pig vas deferens was undertaken in order to find a structural basis for recent electrophysiological observations. The external longitudinal muscle coat was examined in transverse section. Large areas of the surfaces of adjacent muscle cells were 500 to 800 A apart. Closer contacts were rare. A special type of close contact suggested cytoplasmic transfer between neighbouring cells. Groups of non-myelinated axons from ganglia at the distal end of the hypogastric nerve ramified throughout the muscle. Some small axon bundles and single axons lay in narrow fissures within closely packed muscle masses. Many axons contained "synaptic vesicles." About 25 per cent of the muscle fibres in the plane of section were within 0.25 µ of a partly naked axon; of these 15 per cent were within 500 A of the axon, and about 1 per cent made close contact (200 A) with a naked axon. It is unlikely that every muscle fibre is in close contact with an axon, and it is not possible for every fibre to have many such contacts. Muscle fibres are probably activated by both diffusion of transmitter from naked portions of axons a fraction of a micron distant, and electrotonic spread of activity from neighbouring cells.
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36
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Hirst GD, Choate JK, Cousins HM, Edwards FR, Klemm MF. Transmission by post-ganglionic axons of the autonomic nervous system: the importance of the specialized neuroeffector junction. Neuroscience 1996; 73:7-23. [PMID: 8783226 DOI: 10.1016/0306-4522(96)00031-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- G D Hirst
- Department of Zoology, University of Melbourne, Parkville, Victoria, Australia
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37
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Ziogas J, O'Farrell M, Slaughter M. Caffeine enhances sympathetic purinergic and noradrenergic transmission in the guinea-pig isolated vas deferens. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1995; 352:497-505. [PMID: 8751078 DOI: 10.1007/bf00169383] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Intracellular recording techniques were used to monitor the resting membrane potential of smooth muscle cells and the excitatory junction potentials (EJPs) evoked by stimulation of the hypogastric nerve. Stimulation with trains of 15 pulses at 1 Hz or 0.33 Hz evoked individual EJPs which increased in amplitude from the first pulse and reached a plateau after 6-8 pulses. Stimulation at 1 Hz resulted in EJPs facilitating to a plateau level of approximately 25 mV, whereas with stimulation at 0.33 Hz the EJPs only facilitated to a plateau level of about 12 mV. With stimulation at 1 Hz, caffeine (3 mM and 10 mM), increased the amplitude of the first few EJPs in each train and decreased the extent of facilitation and reduced the amplitude of fully facilitated EJPs. In comparison, the amplitude of all EJPs evoked by stimulation at 0.33 Hz was increased by caffeine (3 mM and 10 mM). With 0.33 Hz stimulation, facilitation of the first few EJPs was observed in the presence of 3 mM caffeine but not in the presence of 10 mM caffeine. In the presence of the alpha 2-adrenoceptor antagonist idazoxan, caffeine (3 mM and 10 mM) still enhanced the amplitude of EJPs early in trains of stimulation but there was no depression of EJPs later in the trains. Similarly, in reserpine-treated vasa deferentia, caffeine (3 mM) enhanced EJPs early in the train of stimulation at 1 Hz and there was no depression of EJPs at the end of the train. In addition to electrophysiological experiments, the effect of caffeine (0.1-30 mM) on the resting and stimulation-induced (S-I) efflux of radioactivity was investigated in guinea-pig isolated vasa deferentia previously incubated with [3H]-noradrenaline. Caffeine (10 mM) did not affect the resting efflux of [3H]-noradrenaline but significantly enhanced the S-I efflux by 150-160%. The present findings suggest that caffeine enhances sympathetic purinergic and noradrenergic transmission at the sympathetic neuroeffector junction in the guinea-pig vas deferens. Moreover, the increased release of transmitter noradrenaline can modulate purinergic transmission by activation of alpha 2-adrenoceptors located at sympathetic neuroeffector sites.
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Affiliation(s)
- J Ziogas
- Department of Pharmacology, University of Melbourne, Parkville Victoria, Australia
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38
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Abstract
Spontaneous synaptic potentials were identified at the motor endplate 40 years ago. These were shown to possess amplitudes that could be described by a Gaussian distribution as could the amplitudes of evoked synaptic potentials under conditions of very low probability for secretion. As these Gaussians were identical, the idea of a unit or quantum of transmission was conceived. The failure to obtain similar Gaussian distributions for both spontaneous and low-probability evoked potentials during development of endplates indicated that a unit of transmission was not operating. However both the spontaneous and very low-probability evoked potentials could each be described by mixtures of Gaussians indicating a subunit of transmission might be operative. There are no ganglionic or central synapses at which comparisons have been made between spontaneous and low-probability evoked potentials that show each can be described by a Gaussian distribution, let alone that these are the same indicating a unit of transmission as originally conceived. There is some evidence that mixtures of Gaussians can be used to describe both spontaneous and very low-probability evoked synaptic potential amplitudes, opening up the possibility for a subunit of transmission at these synapses. The vesicle hypothesis, that the quantum of transmission at the endplate is due to the exocytosis of the contents of a synaptic vesicle, was also enunciated nearly 40 years ago. The existence of subunits of transmission has required reconsideration of this hypothesis. Three alternatives are considered: in one, the calcium-transient hypothesis, the subunit of secretion is due to the release of calcium from one of several calcium stores in the nerve terminal, so that several subunits are released when a number of these calcium stores are engaged in a regenerative response to the terminal action potential; a second alternative, the mediatophore hypothesis, is that a subunit of secretion occurs when a single transmitter transport protein channels transmitter across the terminal membrane, several such mediatophore proteins acting in concert then give multiple subunit release; finally, there is the vesicle fusion-pore hypothesis, in which individual transient openings of a fusion-pore channel joining a synaptic vesicle to the terminal membrane are responsible for secretion of a transmitter subunit, with multiple transients giving several subunits. Perhaps we will have distinguished between these possibilities before the quantal hypothesis is 50 years old.
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Affiliation(s)
- M R Bennett
- Department of Physiology F13, University of Sydney, N.S.W., Australia
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Cunnane TC, Searl TJ. Neurotransmitter release mechanisms in autonomic nerve terminals. ADVANCES IN SECOND MESSENGER AND PHOSPHOPROTEIN RESEARCH 1994; 29:425-59. [PMID: 7848725 DOI: 10.1016/s1040-7952(06)80029-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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40
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Abstract
Sensory afferent nerves relay impulses from the airways to the central nervous system so that appropriate changes in bronchomotor tone and breathing patterns may occur. The dominant efferent control of airways smooth muscle is exerted via bronchoconstrictor parasympathetic cholinergic nerves. In some species this is opposed by bronchodilator sympathetic noradrenergic nerves. In addition, there exist both excitatory bronchoconstrictor and inhibitory bronchodilator non-adrenergic, non-cholinergic pathways. This review examines the role of the different branches of the autonomic nervous system in the control of airways smooth muscle tone with particular reference to modulation of these branches and the interactions which may exist between them.
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Affiliation(s)
- Y D Pendry
- Department of Cardiovascular and Respiratory Pharmacology, Glaxo Group Research, Ware, Hertfordshire, U.K
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Brock JA, Cunnane TC. Transmitter release from sympathetic nerve terminals on an impulse-by-impulse basis and presynaptic receptors. Ann N Y Acad Sci 1990; 604:176-87. [PMID: 1977347 DOI: 10.1111/j.1749-6632.1990.tb31992.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- J A Brock
- University Department of Pharmacology, Oxford, United Kingdom
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43
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Kreulen DL, Keef KD. Electrophysiological and neuromuscular relationships in extramural blood vessels. Compr Physiol 1989. [DOI: 10.1002/cphy.cp060144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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44
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Msghina M, Stjärne E, Stjärne L. Potassium channel blocking agents induce occasional spontaneous action potentials and multiquantal ATP release in sympathetic nerve terminals. ACTA PHYSIOLOGICA SCANDINAVICA 1989; 135:593-4. [PMID: 2544080 DOI: 10.1111/j.1748-1716.1989.tb08622.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- M Msghina
- Department of Physiology, Karolinska Institutet, Stockholm, Sweden
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45
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Cunnane TC, Manchanda R. Simultaneous intracellular and focal extracellular recording of junction potentials and currents, and the time course of quantal transmitter action in rodent vas deferens. Neuroscience 1989; 30:563-75. [PMID: 2549444 DOI: 10.1016/0306-4522(89)90151-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Simultaneous recordings were made of spontaneous excitatory junction potentials and the underlying spontaneous excitatory junction currents in guinea-pig and mouse vas deferens using adjacent intracellular and focal extracellular electrodes. Concurrent spontaneous excitatory junction potentials and spontaneous excitatory junction currents were observed in a small proportion of smooth muscle cells penetrated intracellularly within 50-200 microns of the extracellular electrode. These simultaneous events had identical variations in time course, indicating that they were caused by the same transmitter release event. Their amplitudes were not related. Concurrent spontaneous excitatory junction potentials and currents had identical durations, rise times and time constants of decay, showing that the spontaneous excitatory junction potential reflects the time course of quantal transmitter action. In contrast, spontaneous "discrete events" obtained by differentiating the rising phases of spontaneous excitatory junction potentials with respect to time were brief compared with the underlying currents. Excitatory junction potentials evoked by electrical stimulation of the hypogastric nerve were prolonged compared to the underlying excitatory junction currents. The peaks in the first time differential of individual excitatory junction potentials (evoked discrete events) were brief compared to corresponding excitatory junction currents. It is concluded that at the neuroeffector junction of the rodent vas deferens the membrane potential response to a quantum of spontaneously released transmitter is a good estimate of the duration of transmitter action, in accordance with some of the predictions for three-dimensional syncytial tissues. The first time differential of the membrane potential, the "discrete event", does not reflect the time course of spontaneous or evoked quantal transmitter action in these syncytial tissues.
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Affiliation(s)
- T C Cunnane
- University Department of Pharmacology, Oxford, U.K
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46
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Cunnane TC, Manchanda R. Electrophysiological analysis of the inactivation of sympathetic transmitter in the guinea-pig vas deferens. J Physiol 1988; 404:349-64. [PMID: 2908123 PMCID: PMC1190829 DOI: 10.1113/jphysiol.1988.sp017293] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
1. The properties of junction potentials evoked by nerve stimulation and by local application of drugs, and currents evoked by nerve stimulation, in the smooth muscle cells of the guinea-pig vas deferens have been investigated. The effects of temperature on these responses have been studied using intracellular and extracellular recording. 2. Local, brief (5-15 ms) application of 10(-4) M-adenosine-5'-triphosphate (ATP) from glass micropipettes onto the surface of the vas deferens, using pressure pulses (103-206 kPa), elicited a depolarization of the smooth muscle cell membranes which closely resembled the nerve stimulation-evoked excitatory junction potential (EJP). 3. Local application of 10(-4) M-noradrenaline (NA) failed to produce any detectable membrane potential response. Junction potentials elicited by a mixture of 10(-4) M-ATP and 10(-4) M-NA (ratio by volume 1:50) in the drug ejection micropipette were similar in shape to those evoked by ATP alone. 4. Cooling the tissue from 35 to 25 degrees C did not significantly alter resting membrane potentials but resulted in a significant prolongation of the rising and decaying phases of the EJPs. Fifty per cent decay times for EJPs at 35 and 25 degrees C were (mean +/- S.D.) 236 +/- 20 and 434 +/- 30 ms respectively (P less than 0.01). 5. Extracellularly recorded excitatory junction currents (EJCs) elicited by nerve stimulation, believed to reflect the transmembrane current underlying the EJPs, were prolonged in parallel at low temperatures (50% decay times of EJCs at 35 and 25 degrees C: 11.73 +/- 3.94 and 26.15 +/- 8.4 ms, respectively, P less than 0.01). 6. Junction potentials evoked by locally applied, exogenous ATP were also significantly prolonged by cooling (50% decay times: 663 +/- 88 ms at 35 degrees C and 1955 +/- 79 ms at 25 degrees C, P less than 0.01). 7. Bath application of 10(-6) M-alpha,beta-methylene ATP, the enzymatically stable, desensitizing analogue of ATP, reversibly abolished nerve-evoked EJPs. Local application of 10(-6) M-alpha,beta-methylene ATP led to a prolonged depolarization of the smooth muscle cells lasting between 20 and 60 s. 8. Junction potentials elicited by locally applied alpha,beta-methylene ATP were not prolonged or otherwise significantly altered on cooling. The durations of the depolarizations were 46.0 +/- 12.1 s at 35 degrees C and 43.4 +/- 10.6 s at 25 degrees C (P greater than 0.1).(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- T C Cunnane
- University Department of Pharmacology, Oxford
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Astrand P, Brock JA, Cunnane TC. Time course of transmitter action at the sympathetic neuroeffector junction in rodent vascular and non-vascular smooth muscle. J Physiol 1988; 401:657-70. [PMID: 2902221 PMCID: PMC1191872 DOI: 10.1113/jphysiol.1988.sp017185] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
1. Transmitter release from sympathetic postganglionic nerve terminals innervating the guinea-pig and mouse vas deferens and the rat tail artery has been studied in vitro by focal extracellular recording with particular emphasis on the time course of transmitter action underlying the intracellular potential changes. 2. In the absence of stimulation, spontaneous excitatory junction currents (SEJCs) were recorded with amplitudes up to 500 microV and durations between 40 and 100 ms. SEJCs were unaffected by the competitive alpha-adrenoceptor antagonist prazosin but blocked by alpha, beta-methylene ATP which desensitizes P2-purinoceptors. 3. During trains of supramaximal stimuli at 0.1-4 Hz stimulus locked excitatory junction currents (EJCs) were evoked intermittently from the population of varicosities located under the suction electrode. 4. SEJCs were similar in amplitude and time course to EJCs evoked by low-frequency stimulation in the same attachment in all three tissues. 5. SEJCs recorded using either a conventional AC amplifier or a patch clamp amplifier had the same time course. 6. These studies show that the time course of the current underlying the excitatory junction potential is brief and essentially the same in three different tissues. The prolonged time course of the excitatory junction potential in different tissues can be accounted for by the passive membrane properties.
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Affiliation(s)
- P Astrand
- University Department of Pharmacology, Oxford
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Brock JA, Cunnane TC. Electrical activity at the sympathetic neuroeffector junction in the guinea-pig vas deferens. J Physiol 1988; 399:607-32. [PMID: 2900334 PMCID: PMC1191683 DOI: 10.1113/jphysiol.1988.sp017099] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
1. The relationship between the nerve terminal action potential and transmitter release from sympathetic postganglionic nerve terminals has been studied in vitro by focal extracellular recording. 2. In the absence of stimulation, 'spontaneous excitatory junction currents' (SEJCs) were recorded with amplitudes up to 500 microV, durations of 50-80 ms and frequencies of occurrence of 0.3-0.05 Hz; SEJCs of unusually long time course were also observed. The SEJCs were not recorded in tissues pre-treated with 6-hydroxydopamine to destroy sympathetic nerves, were unaffected by tetrodotoxin (TTX), the competitive alpha-adrenoceptor antagonists, prazosin and phentolamine, the irreversible alpha-adrenoceptor antagonist benextramine but were blocked by alpha,beta-methylene ATP which desensitizes P2-purinoceptors. 3. During trains of supramaximal stimuli at 0.1-4 Hz stimulus locked 'excitatory junction currents' (EJCs) were evoked intermittently from the population of varicosities located under the suction electrode with a probability of occurrence of 0.005-0.8. Although EJCs occurred intermittently, they were always preceded by an associated, non-intermittent, nerve impulse (delay less than or equal to 3 ms). 4. The EJCs reflect transmitter release from nerves because they were abolished by TTX, removal of calcium from the bathing medium, exposure to alpha-beta-methylene ATP and exhibited frequency-dependent facilitation. 5. Amplitude distributions of SEJCs and EJCs recorded in the same attachment were similar and skewed towards low-amplitude events. Individual SEJCs and EJCs could be found which were identical in amplitude and time course. 6. Locally applied TTX blocked impulse propagation and transmitter release in the terminal region; electrotonic invasion of the terminals from the point of block did not activate the transmitter release process. 7. These studies indicate that (1) intermittence of transmitter release is caused by a low probability of release in the invaded varicosity and is not caused by conduction failure in the terminal regions, (2) only a single quantum is normally secreted when the release mechanism of a varicosity is activated by the nerve impulse and (3) active invasion of the terminals is necessary for transmitter release to occur.
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Affiliation(s)
- J A Brock
- University Department of Pharmacology, Oxford
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Smith PG, Bruckert JW, Mills E. Reinnervation of Müller's smooth muscle by atypical sympathetic pathways following neonatal ganglionectomy in the rat: structural and functional investigations of enhanced neuroplasticity. Neuroscience 1987; 23:781-93. [PMID: 3437987 DOI: 10.1016/0306-4522(87)90095-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Müller's extraocular smooth muscle is reinnervated by sympathetic nerves following denervation by ipsilateral superior cervical ganglionectomy in neonates but not in older animals. Experiments were performed to determine: (1) the source and extent of reinnervation, (2) the role of impulse activity in sympathetic outgrowth and (3) the effects of reinnervation on smooth muscle maturation. Müller's muscles were evaluated structurally (muscle volume, catecholamine histochemistry, retrograde labeling of sympathetic neurons) and functionally (contractile responses to electrical stimulation of postganglionic innervation and adrenoceptor agonist) in control preparations and in muscles following neonatal ipsilateral superior ganglionectomy, ipsilateral decentralization, ipsilateral superior ganglionectomy combined with contralateral decentralization of chemical (guanethidine) sympathectomy. Fluorescent tracer injections of muscles in adult control rats labeled cells in the ipsilateral superior (98%) and middle cervical ganglia. Acute ipsilateral superior ganglionectomy produced complete degeneration of sympathetic innervation of Müller's muscle in neonatal and adult rats. In preparations denervated neonatally and maintained chronically, muscles were reinnervated by neurons in both the contralateral superior and ipsilateral middle cervical ganglia. The total number of neurons reinnervating the muscle was one half that of controls. Sectional density of innervation was 45% of control. Electrical stimulation of postganglionic axons in the contralateral pathway produced muscle contractions with a prolonged time course. Reinnervation alleviated, in part, deficits in muscle volume and contraction which occurred following sustained denervation by chemical sympathectomy. Decentralization decreased ipsilateral muscle volume but did not affect numbers of neurons projecting to or nerve density within the muscle. Stimulation frequencies required to produce a 50% maximum contraction were reduced in these preparations. Decentralization of the contralateral ganglion did not impede sprouting into the denervated muscle, as nerve density and number of labeled cells were comparable to muscles reinnervated by contralateral ganglia with intact preganglionic innervation. However, maximum contraction to electrical stimulation was reduced. Comparisons with ipsilaterally decentralized muscles revealed that increased stimulation frequencies were required for 50% maximum contraction.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- P G Smith
- Department of Physiology, University of Kansas Medical Center, Kansas City 66103
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Markus RP, Ferreira AT, Lapa AJ. Influence of castration on the membrane reactivity of the guinea-pig vas deferens. Pflugers Arch 1987; 409:528-32. [PMID: 3627967 DOI: 10.1007/bf00583811] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The guinea-pig vas deferens is a quiescent muscle which after castration undergoes atrophy and shows spontaneous contractions preceded by membrane spike activity. The influence of castration on the spontaneous release of neurotransmitters and on the internal concentration of sodium and potassium ions was studied. Utilizing the microelectrode technique it was shown that castration induces a partial depolarization (10 mV) of the cell membrane, but did not change the frequency of spontaneous excitatory junction potentials (SEJPs) of guinea-pig vas deferens. However, the time-course and the amplitude of the SEJPs were increased after castration, probably because of changes in membrane properties related to organ atrophy. Castration probably promotes a change in the ionic permeability of the smooth muscle fibre, since the ratio pNa/pK was twice that of control muscles.
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