Biomedical subjects

S Charpak

Publications and source records attributed to S Charpak.

23 records · Page 2Linked to original sources

PubMed1988

A role of central oxytocin in autonomic functions: its action in the motor nucleus of the vagus nerve.

Neurones located in the dorsal motor nucleus of the vagus nerve were shown, in slices from the rat brainstem, to respond to oxytocin by a concentration-dependent increase in rate of firing. A newly available oxytocin antagonist suppressed the excitatory effect of oxytocin on single neurones; this antagonism was partially reversible. Further evidence that neurones located in the dorsal motor nucleus of the vagus nerve possess oxytocin receptors was obtained from in vitro light microscopical autoradiography using [125I]-labelled oxytocin antagonist. In conjunction with data by others which showed that oxytocin antagonist microinjected into the dorsal motor nucleus of the vagus nerve blocks gastric and cardiac effects caused by stimulation of the hypothalamic paraventricular nucleus, our results suggest a role for central oxytocin in autonomic efferent activity.

Animals↗

PubMed1988

Electrophysiological evidence for oxytocin receptors on neurones located in the dorsal motor nucleus of the vagus nerve in the rat brainstem.

Intracellular recordings were obtained from vagal neurones and their response to oxytocin was investigated in slices from the rat brainstem. Following recording, Lucifer Yellow was injected into the cells in order to verify their localization within the dorsal motor nucleus of the vagus nerve. Virtually all neurones throughout the rostro-caudal extent of the nucleus increased their rate of firing in the presence of 10-1000 nM oxytocin and their membrane depolarized in a reversible, concentration-dependent manner. This excitation was probably exerted directly on the impaled cells rather than being synaptically mediated, since it persisted in a low calcium-high magnesium medium or in the presence of tetrodotoxin. These data provide evidence for a direct membrane effect of oxytocin on a defined population of neurones in the rat brain.

Action Potentials↗

PubMed1987

Neurons in the dorsal motor nucleus of the vagus nerve are excited by oxytocin in the rat but not in the guinea pig.

Intracellular recordings were obtained from vagal neurons and their response to oxytocin was investigated in slices from the rat and the guinea pig brainstem. After recording, Lucifer yellow was injected into the cells to verify their localization within the dorsal motor nucleus of the vagus nerve (dmnX). In the rat, virtually all neurons throughout the rostrocaudal extent of the dmnX increased their rate of firing in the presence of 10-1000 nM oxytocin and their membrane depolarized in a reversible concentration-dependent manner. This excitation was probably exerted directly on the impaled cells rather than being synaptically mediated, since it persisted in a low calcium/high magnesium medium or in the presence of tetrodotoxin. These data provide evidence for a direct membrane effect of oxytocin on a defined population of neurons in the rat brain. In the guinea pig, vagal neurons were fired by glutamate but were not excited by oxytocin, even though we detected many more oxytocin-immunoreactive structures in the guinea pig dmnX than in the rat dmnX. Therefore, homologous nuclei in the brains of two closely related mammals differ markedly in the density of oxytocinergic axons they contain. Unexpectedly, the magnitude of the electrophysiological effects of oxytocin on vagal neurons appeared inversely related to the amount of oxytocin-like immunoreactivity present in dmnX.

Animals↗

PubMed1984

Contrasting effects of neurohypophysial peptides on pyramidal and non-pyramidal neurones in the rat hippocampus.

Oxytocin and vasopressin increased the rate of firing of a class of presumed non-pyramidal neurones located in the CA1 area of rat hippocampal slices. This excitatory effect persisted in conditions of synaptic uncoupling. In contrast, pyramidal neurones were either unaffected by neurohypophysial peptides or showed one or several of the following effects: a decrease in firing rate in cells which were spontaneously active; a slight membrane hyperpolarization; and an increase in the rate of occurrence of spontaneous inhibitory postsynaptic potentials. We therefore propose that oxytocin and vasopressin excite directly a class of non-pyramidal inhibitory interneurones, whereas their observed effect on pyramidal neurones is indirect and inhibitory.

Action Potentials↗

PubMed1984

Stimulatory action of oxytocin on neurones of the dorsal motor nucleus of the vagus nerve.

Extracellular recordings were obtained from spontaneously active neurones located in the dorsal motor nucleus of vagus nerve ( DMX ) in slices of the rat brainstem. Oxytocin applied to the bath at concentrations of 10(-7) M or 10(-6) M excited 79% of these cells in a concentration-dependent, reversible manner. The remaining cells were unaffected. The stimulatory effect of oxytocin was reversibly antagonized by a synthetic structural analogue known to block the peripheral, endocrine effects of neurohypophysial peptides. A selective oxytocic agonist was as potent as oxytocin, whereas vasopressin exerted a much weaker effect. We therefore suggest that neurones located in DMX are endowed with receptors for oxytocin.

Animals↗