Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Neural Conduction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources
PubMed1979

Enhancement of GABA-mediated postsynaptic inhibition in cultured mammalian spinal cord neurons: a common mode of anticonvulsant action.

Murine spinal cord neurons grown in dissociated cell culture were used to study the effects of barbiturate (phenobarbital, mephobarbital) and benzodiazepine (diazepam, chlordiazepoxide( anticonvulsants on amino acid responses. Both types of anticonvulsant augmented GABA-mediated postsynaptic inhibition without augmenting beta-alanine or glycine-mediated postsynaptic inhibition. Barbiturates, but not benzodiazepines, antagonized glutamate-mediated postsynaptic excitation. Augmentation of GABA-mediated inhibition by the anticonvulsants should contribute to their anticonvulsant action; antagonism of glutamate-mediated excitation by barbiturates should also contribute to their anticonvulsant action and could be at least in part responsible for their sedative actions.

Animals↗
PubMed1980

An electrophysiological study of inputs to neurons of the ventral tegmental area from the nucleus accumbens and medial preoptic-anterior hypothalamic areas.

Extracellular recordings were obtained from neurons in the ventral tegmental area (VTA) of urethane-anesthetized rats. Neurons were divided into two types based on the latencies of antidromic activation following electrical stimulation of the nucleus accumbens (NAcc), and on the durations of action potentials. Type A neurons had longer latencies for antidromic activation (mean 15.9 msec) and longer durations of action potentials (> 2.6 msec), while type B neurons had shorter latencies (mean 4.5 msec) and shorter duration of action potentials (< 2.6 msec). Electrical stimulation of the medial preoptic-anterior hypothalamic areas (mPOA-AHA) and NAcc produced the following effects on the two types of VTA neurons: (i) the majority of both type A and B neurons were suppressed by mPOA-AHA stimulation with onset latencies of less than 10 msec; (ii) 42% of type B neurons were also suppressed by NAcc stimulation, with onset latencies of less than 10 msec; (iii) type A neurons were suppressed (33%) or activated (43% by NAcc stimulation, the onset latencies usually being longer than 10 msec; (iv) 71% of type A neurons tested had convergent inputs from the mPOA-AHA and NAcc, usually suppressed-suppressed or suppressed-activated, while 45% of type B neurons had convergent inputs from these two areas, usually suppressed-suppressed.

Animals↗
PubMed1981

Norepinephrine reduces excitability of single cutaneous primary afferent C-fibers in the cat spinal cord.

An excitability testing procedure of single afferent C-fibers was used to study possible presynaptic actions of norepinephrine (NE) applied to locally at the intraspinal sites of minimal threshold for their antidromic activation in spinalized cats. NE, applied by iontophoresis and/or pressure microinjection, produced dose-related increases in threshold for antidromic activation in 44 of 65 C-fibers. It was concluded that in addition to previously shown postsynaptic depressant action, NE reduces excitability of intraspinal cutaneous C-fibers.

Afferent Pathways↗
PubMed1983

Peripheral organization of the vestibular efferent system in the frog: an electrophysiological study.

The distribution and the properties of efferent fibers in vestibular nerve were studied in the isolated frog labyrinth. Electrical stimulation of the central stump of any vestibular nerve branchlet elicited compound action potentials in all the other eighth nerve branchlets, indicating the existence of neural links between the various vestibular organs. The same experimental paradigm, when repeated in frogs with chronic section of the eighth nerve roots, demonstrated that these pathways are efferent collaterals extending to all vestibular organs. There are more collaterals linking the 3 semicircular canals than the otolith organs and the otoliths with the canal organs. Efferent connections in the eighth nerve were preserved in full after ablation of the ipsilateral hemi-cerebellum, suggesting that the efferent pathways probably originate in the brainstem. Intracellular recordings from single afferent fibers of both canal and otolith organs revealed that efferent fiber activation could elicit either inhibition or facilitation of the receptor discharge. It was concluded that the frog efferent vestibular system is endowed with non-selective control channels which allow single neurons to influence the receptor activity of different labyrinthine organs.

Animals↗
PubMed1984

Modulation of segmental mechanisms by activation of a dorsal column brainstem spinal loop.

In decerebrate-decerebellate cats, dorsal column stimulation (DCst) rostral to selective dorsal funicular cuts, to prevent antidromic activation of afferent DC fibers, produced primary afferent depolarization and modulated reflexes at the lower spinal level. These findings indicate the importance of a DC-brainstem-spinal loop in explaining the effects of DC stimulation in man and experimental animals.

Animals↗
PubMed1984

Suppression of C-fibre discharges upon repeated heat stimulation may explain characteristics of concomitant pain sensations.

Nociceptors with unmyelinated axons were recorded from the superficial radial nerves of 7 volunteers. A sequence of uniform radiant heat stimuli of 18 s duration, starting from an individually adjusted adapting temperature were used to raise the skin surface temperature by 6 degrees C to a painful level (41-43 degrees C). These stimuli followed each other at 3 different interstimulus intervals of 35 s, 70 s and 105 s, occurring in a random order. The subjects were asked to track the time course of the stimulus-evoked sensation by manipulating the length of a light bar. Adaptation and stimulus temperatures were chosen to induce sensations of heat and/or pain. All nociceptors studied responded to these stimuli with a phasic response of 3-5 s duration, often followed by a low frequency tonic discharge, lasting as long as the stimulus. No discharges were seen in interstimulus periods. Discharge rates during the phasic responses were linearly related to interval duration, whereas tonic discharges were not influenced by the preceding interval. In parallel readings of pain responses were lower up to the 10th second of the stimulus after short rather than after long intervals. These results indicate that the suppression of C-fibre nociceptor discharges during repetitive stimulation may explain concomitant reductions in the magnitude of human pain sensations.

Adult↗
PubMed1984

Excitatory projection of the rat subicular complex to the cingulate cortex and synaptic integration with thalamic afferents.

We studied the responses of rat cingulate cortex neurons to electrical stimulation of the subicular complex. Intracellular and 'quasi-intracellular' recordings from layer V posterior cingulate neurons showed that stimulation of the presubiculum or postsubiculum evoked EPSPs and action potentials. These were usually followed by shallow IPSPs averaging 122 ms in duration. Frequency potentiation of an EPSP was demonstrated in one case. Laminar analysis of field potentials provided evidence for a source of excitatory synaptic drive in layer II-III of the posterior cingulate cortex, where the subicular projections terminate, presumably on apical dendrites of layer V pyramids. Intracellular HRP injection of neurons showing EPSPs after subicular complex stimulation established that these responsive neurons were layer V pyramids. One cell with physiological properties characteristic of inhibitory interneurons was recorded in layer V. Stimulation of the thalamic nuclei lateralis and anterior ventralis also evoked EPSPs and action potentials in layer V cingulate neurons. In one cell it was possible to show that EPSPs evoked by presubicular stimulation and by nucleus anterior ventralis summed. These results indicate that subicular and thalamic afferents make excitatory synaptic contact onto dendrites of the same layer V cingulate neurons; that spatial summation can integrate the input from these two sources; and that inhibition from local interneurons limits the duration of this excitatory influence.

Afferent Pathways↗
PubMed1985

Motor unit recruitment and firing rates interaction in the control of human muscles.

Muscle contractions are modulated by the number of motor units recruited and their respective firing rates. The work described in this report documents an interplay between recruitment and firing rates of motor units. The recruitment of a new motor unit appears to have a disfacilitatory influence on the firing rates of previously activated motor units. It is speculated that this effect is likely to be mediated, at least partially, via the stretch reflex loop and possibly by the recurrent inhibition of the Renshaw circuit. Such a mechanism would be functionally useful in providing smooth control of muscle output via peripheral circuitry (consisting of proprioceptive reflexes and recurrent inhibition), thus lessening the amount of detailed supervision of the alpha-motoneuron pool required by the central nervous system.

Action Potentials↗
PubMed1985

The hypothalamohypophyseal system in vitro: electrophysiology of the pars intermedia and evidence for both excitatory and inhibitory inputs.

The purpose of this study was to better assess the function of catecholamine-containing nerve terminals in the pituitary pars intermedia lobe. Hypothalamohypophyseal explants, which included the intact mediobasal hypothalamus (MBH), median eminence, infundibular stalk and the neurointermediate lobe, were obtained from 2-3-week-old male and female albino rats. The tissue was placed in a perfusion chamber and maintained under physiological conditions for up to 12 h. A set of bipolar stimulating electrodes was positioned on the surface of the median eminence, infundibular stalk or the rostroventral arcuate nucleus of the MBH. A microelectrode recorded electrical activity in the pars intermedia gland. Two types of spontaneous action potentials were found; fast 2-4 ms duration neural fiber type spikes and slower 7-10 ms duration spikes probably derived from non-neural endocrine cells. Single-pulse electrical stimulation at all 3 sites evoked both kinds of potentials, while trains of stimuli (0.1-20 Hz) decreased or completely inhibited the basal firing rate of the slower ones. Application of the neuroleptic. L-sulpiride (0.01, 0.1 or 1.0 mumol), to the perfusion medium increased the spontaneous endocrine cell activity and blocked the stimulus-induced inhibition in the explants but had no effect on the activity in isolated pituitaries. Dopamine (0.1 mumol), which is known to inhibit the secretion of pro-opiomelanocortin peptides, reversibly suppressed the spontaneous endocrine cell potentials. These observations support a hypothesis for the presence of a functional tuberohypophyseal dopamine inhibitory system and a possible, but as yet unidentifiable, excitatory system in the pars intermedia. Thus, hypothalamohypophyseal explants can be used to elucidate specific information on this type of neuroendocrine axis.

Action Potentials↗
PubMed1985

Evaluation of neuronal connectivity: sensitivity of cross-correlation.

Cross-correlation analysis of separable multi-unit activity is one of the most commonly used methods to investigate connectivity in neural networks. In the course of development of new analysis techniques which go beyond the study of pairs or triplets of neurons, the need arose for a simple yet versatile simulator to generate spike trains from networks of specified structure. The present paper describes such a simulator and presents some examples of its performance as analyzed by cross-correlation. We noted a distinct asymmetry in the sensitivity of cross-correlation for the presence of excitatory vs inhibitory connections. A theoretical analysis is given from which quantitative criteria for detectability were derived. It appears that indeed the sensitivity of cross-correlation for excitation is larger to an order of magnitude than it is for inhibition. Possible consequences of this finding are indicated, and the relation to commonly used methods to measure strength of interaction are discussed.

Action Potentials↗