摘要:

AbstractPrevious studies indicated that 5‐HT reduced the number of spontaneous excitatory junctional potentials (ejp's) that occurred in leech body wall muscle cells. The present study confirms these findings and shows that the ejp's arise from impulses in motoneuron L. This study further shows that 5‐HT acts by hyperpolarizing and reducing the membrane resistance of neuron L, thus inhibiting the motoneuron and reducing the frequency of spontaneous ejp's on body wall muscle cells. These effects of 5‐HT are not seen when the ganglion is bathed in a high magnesium solution, a finding that suggests that 5‐HT does not act directly on the membrane of motoneuron L. This study demonstrates that 5‐HT can have a central inhibitory effect on body wall muscle contractions. Previous studies provide evidence that 5‐HT may act as a direct neuromuscular inhibitory transmitter and may also take part in peripheral presynaptic inhibition. Thus, if further studies confirm these suggestions, the well‐known inhibitory effect of 5‐HT on leech body wall muscle is a more complex process than was pre

ISSN:0022-3034    

DOI:10.1002/neu.480070602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractA combined electron microscopic and electrophysiological study of the superior laryngeal nerve (SLN) was undertaken in postnatal kittens ranging in age from 1–63 days. The superior laryngeal nerve is predominantly a sensory nerve innervating the upper respiratory tract, and could play a potential role in the modulation of respiration, particularly in the infant animal. Distribution of fibers in the developing SLN indicates that within the first postnatal month, 75% of the fibers are unmyelinated, and by 42 days, the myelinated fibers increase in number to approximately 50%. Of the myelinated fibers present in the one day old kitten, 3–4% of those exceeded 4 μm in total diameter, which is the minimum diameter for normal conduction velocity of action potentials. The distribution of the diameter sizes of the myelinated fibers is bell‐shaped within the first 45 days after which the curve becomes skewed to the right (43–61 days; mean 2.6 μm, range 0.5–8.0 μm) to resemble the adult distribution of myelinated fibers (mean 4.2 μm, range 1.6–13.0 μm). Two variable plots of myelin width to axon diameter suggest a steeper slope for developing fibers as compared to that of the adult fibers. Electrical stimulation of the sectioned SLN indicates that evoked potentials could be recorded from the recurrent laryngeal nerve innervating the laryngeal intrinsic muscles and from the hypoglossal nerve to the tongue musculature in the youngest kittens tested (i.e., age 9 days). Stimulation at selected frequencies of 3 and 30/sec readily evoked apnea in the youngest kitten studied (i.e., age 5 days), while swallowing was more readily evoked at 28–30 days when using elec

ISSN:0022-3034    

DOI:10.1002/neu.480070603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractNeurons and gla from the central nervous system of the adult teleostCarassius auratushave been grown as explant cultures of minced brain tissue and as trypsin dissociated cells. These cultures exhibit extensive neurite growth from two neuronal types, have organotypic ultrastructure, and contain electrically active cells.Autoradiographic data indicate that these neurons do not divide in culture, and histological evidence suggests that some mature neurons survive explantation and regenerate processes. However, explantation of brain fragments not containing undifferentiated cells, localized in the ventricular and subventricular zones in the brains of fish, resulted in mesenchymal and glial cell cultures only. Therefore, a contribution to the population of cells in culture by undifferentiated cells must be considered.The cultured neurons remained viable for at least 19 weeks and ultrastructural and electrophysiological data indicate synaptic interaction between cells in explant cultures.

ISSN:0022-3034    

DOI:10.1002/neu.480070604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractIntramuscular injection of alpha‐bungarotoxin (αBGT) into rat extensor digitorum longus muscles produced pharmacological blockade of neuromuscular transmission and resulted in denervation‐like changes (Berg, D. and Hall, Z. (1975),J. Physiol. (London)244:659–676). More than 80% of fibers from αBGT‐injected muscles produced action potentials (ap's) in the presence of tetrodotoxin (TTX, 1 × 10−6M). Chronic electrical stimulation of these muscles, below the level necessary to elicit a contraction, resulted in a marked return toward normal of sarcolemmal sensitivity to TTX. After 4 days of submechanical threshold stimulation, less than 45% of αBGT‐injected fibers produced ap' in the presence of TTX, whereas more than 80% of unstimulated fibers from contralateral control muscles exhibited resistance to TTX. These findings indicate that in addition to sarcolemmal sensitivity to acetylcholine, sensitivity of the sodium conductance mechanism to TTX is also directly influenced by muscle activity independent

ISSN:0022-3034    

DOI:10.1002/neu.480070605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractExplants of 18‐ or 19‐day fetal mouse olfactory bulb have been maintained in culture for periods up to 5 weeks. Compound action potentials can be evoked in the bulb explants by 1 dayin vitro, and by 3–4 days, synaptically mediated slow wave discharges can be demonstrated in bicuculline (10−5M). The capability of the bulb explants to generate these slow‐wave discharges has also been revealed by the introduction of picrotoxin (10−5M),d‐tubocurarine (10−4M) and chloride‐free medium, but not of strychnine (up to 3 × 10−5M). The data indicate early functional development of inhibitory, as well as excitatory, synaptic systems. In addition, the selective and reversible depression of these slow wave potentials by GABA (1–5 × 10−4M), but not by glycine (up to 3 × 10−3M), indicates a GABA‐ergic component in the inhibitory network. Single unit extracellular recordings have been obtained from the presumptive mitral cells which, in culture, are spontaneously active even as early as 1–2 days after explantation. Correlative Bodian silver‐impregnations demonstrate the presence of neurons in these explants which resemble typical mitral cells. Studies of mitral cells using paired stimuli suggest the developmentin vitroof an inhibitory system analogous to that known to suppress the excitability of theirin situcounterparts following orthodromic or antidromic activation. These data, as well as the pharmacological sensitivities of the mitral cells in culture to GABA (5 × 10−4M) and bicuculline (10−5M), indicate that granule‐to‐mitral synapses may develop characte

ISSN:0022-3034    

DOI:10.1002/neu.480070606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe electrophysiological properties of a tissue culture muscle line, L6, and a K+resistant mutant (MK1) derived from L6were determined to elucidate certain aspects of membrane differentiation and function. MK1was selected as a clone of myoblasts resistant to the toxic effects of 55 mMK+. The resting potentials of L6and MK1myoblasts and myotubes were K+dependent and equal. The amplitudes of the action potentials were equal in normal medium, but 27.7 mMK+interfered with or eliminated the ability of L6myotubes to produce action potentials. MK1myotubes produced nearly normal action potentials under these conditions. Thus, the K+resistant myoblasts differentiate into myotubes which have an action potential generating mechanism much less sensitive to K+than the normal mechanism. Also, bothd‐tubocurarine and α‐bungarotoxin enhance the amplitude of the action potentials produced by L6myotubes in the presence of 27.7 mMK+; these compounds do not enhance the amplitude of the action potentials produced by MK1myotubes under the same conditions. It is proposed that as a consequence of differentiation a type of ionophore present in myoblasts becomes a voltage‐dependent ionophore in myotubes. Furthermore, these voltage‐dependent ionophores can be chemically s

ISSN:0022-3034    

DOI:10.1002/neu.480070607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe statistical characteristics of the spontaneous spike activity of rat hippocampal neurons in fields CA1−2were comparedin situand in tissue culture. Statistical analyses have shown strong similarities in estimators of basic numerical characteristics of interspike interval (ISI) distributions.These similarities may serve as evidence of maintenance of normal functional properties and an “organotypic arrangement” of neurons in tissue culture, and they are also indicative of an intrahippocampal origin of the spontaneous impulse activity in the hippocampus.On the other hand, some differences are noted in the tests of firing patterns. Interpretation of these results leads to some assumptions about mechanisms of the phenomenon under

ISSN:0022-3034    

DOI:10.1002/neu.480070608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractClimbing fiber (CF)–‐Purkinje cell (PC) relationships were studied electrophysiologically on the cerebellum of 8 to 15 day old rats. Some animals were rendered agranular by x‐irradiation from birth; some others were treated with 3‐acetyl pyridine 3 days before study to selectively destroy the CF. Unitary extracellular recordings in 8–9 day old normal rats revealed that more than 50μ of the PC units each exhibited either two types of all‐or‐none climbing fiber responses (CFR) or stepwise graded CFRs. The other PC units only presented one type of all‐or‐none CFR. These activities were entirely mediated via CF since they persisted at the same age in x‐irradiated rats, but were absent in animals treated with 3‐acetyl pyridine. Interaction experiments were performed between juxtafastigial and Inferior Olive stimulations on 49 PC units in 8–9 day old normal rats. Collisions between impulses set up in CFs were disclosed in 21 out of the 24 PCs which exhibited only one type of CFR. In the three others and in each of the 25 PCs that displayed two types of all‐or‐none CFRs, or CFRs graded by steps, no collision was detected. Moreover intracellular recordings of epsp's mediated via CFs in PCs of 8–9 day old normal rats revealed that they frequently fluctuated in stepwise fashion. These results demonstrate that in the immature rat more than 50μ of PCs are each innervated by at least two distinct CFs; later on, the disappearance of the supernumerary synapses between CF and PC leads, as early as day 15, to the one‐to

ISSN:0022-3034    

DOI:10.1002/neu.480070609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480070610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480070601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY