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J D Vincent

Publications and source records attributed to J D Vincent.

214 records · Page 12Linked to original sources
PubMedDate not supplied

Solubilization and characterization of covalently labeled angiotensin II receptors in cultured mouse spinal cord cells.

To investigate the physicochemical characteristics of angiotensin II receptors in nervous tissue, [125I]-labeled AII was covalently linked to its binding sites in cultured mouse spinal cord cells, using the chemical crosslinking agent disuccinimidyl suberate. The liganded complexes were analyzed by SDS/polyacrylamide gel electrophoresis. Autoradiograms revealed a single band which corresponding to a component with a calculated Mr value of 68,000 +/- 5,000. The same radioactive band was observed under reducing or non-reducing conditions, although in the presence of beta-mercaptoethanol the band was less intense. This suggests that the AII binding unit may contain essential disulfide bonds close to the AII binding site. After solubilization with 1% Triton X-100, extracts were analyzed by HPLC gel filtration. Three radioactive species were identified with apparent molecular weights of 65,000; 115,000 and 185,000. Results obtained in the presence or absence of 10 nM unlabeled AII showed that these three units were common to both the high and the low affinity binding sites. The results also demonstrate that AII receptors in nervous tissue have similar physicochemical properties to those from other tissues, and that the 68,000 subunit probably contains the AII binding site.

Angiotensin II↗
PubMedDate not supplied

Electrophysiological effects of FLFQPQRF amide, an endogenous brain morphine modulating peptide, on cultured mouse spinal-cord neurons.

Intracellular recordings were made from dissociated fetal mouse spinal cord neurones in primary culture. Micropressure application of FLFQPQRFamide (10(-5) M in the delivery pipette), an endogenous mammalian brain morphine modulating peptide, onto the surface of spinal cord neurones induced, in a dose dependent manner, a transitory hyperpolarization followed by a long lasting depolarization of the membrane potential (n = 37). In contrast, no response was observed when the peptide was applied on dorsal root ganglia neurones (n = 30). The depolarizing phase of this response was underlied by an increase of the input resistance. Extrapolated reversal potential for the depolarizing phase was close to -80 mV while it was close to -40 mV for the hyperpolarizing phase. Increasing extracellular K+ concentration raised the reversal potential value of depolarizing phases to more positive values. The amplitude of the depolarizing phase was reduced by application of tetraethylammonium (50 mM) while it was enhanced by application of 4-aminopyridine (3 mM). CaCl2 application (3 mM) reversibly blocked the hyperpolarization and decreased the subsequent depolarization. In presence of Ba2+ the extrapollated reversal potential of the hyperpolarizing phase was dramatically shifted to a more positive value. Finally FLFQPQRFamide induced response can be partially mimicked by FMRFamide application. Our observations indicate that FLFQPQRFamide can have multiple effects on membrane conductance of mammalian spinal cord neurones by acting on a single class of receptor. These effects of FLFQPQRFamide were found to be mainly excitatory.

Animals↗
PubMedDate not supplied

Dopamine inhibition of action potentials in a prolactin secreting cell line is modulated by oestrogen.

Secretory activity of the anterior pituitary gland is regulated by the brain through stimulatory and inhibitory substances released from nerve endings in the median eminence of the hypothalamus and carried by the adenohypophysial portal blood system to their respective target cells. These hypothalamic influences are modulated by the feedback action of peripheral hormones. Prolactin (PRL) secreting cells are, at least partially, under the stimulatory influence of thyrotropin releasing hromone (TRH) and of oestrogens. However, they are mainly controlled by inhibitory substances among which dopamine (DA) is one of the most potent in vivo as well as in vitro. The inhibitory effect of DA is reversed by oestrogen in vitro. The mechanism by which these factors interact on their target cells is poorly understood. The recent discovery that anterior pituitary cells are excitable and that they are able to generate Ca2+-dependent action potentials has led to the suggestion that these effects are involved in a stimulus-secretion coupling at the membrane level. In this paper, we report that DA inhibits both the spontaneous and TRH-induced action potentials in clonal PRL pituitary cells. In addition, oestradiol-17 beta is able to reverse the inhibitory effect of DA.

Action Potentials↗
PubMedDate not supplied

Oxytocin induces morphological plasticity in the adult hypothalamo-neurohypophysial system.

The hypothalamo-neurohypophysial system offers a unique example in the adult mammalian central nervous system (CNS) of a functional and structural plasticity related to a physiological state. During lactation, oxytocin neurones evolve a synchronized electrical activation which permits pulsatile hormone release at milk ejection. At the same time, in the supraoptic (SON) and paraventricular nuclei, glial coverage of neurones diminishes, so that large portions of their surface membrane become directly juxtaposed; synaptic remodelling also associates pairs of neurones through the formation of common presynaptic terminals. These structural changes, reversible after weaning, affect exclusively oxytocinergic neurones and could facilitate their synchronized electrical activity. As several observations suggest that oxytocin itself is released centrally, we have examined the effect of prolonged intracerebroventricular infusions of oxytocin on the structure of the SON of non-lactating animals. We report here that the peptide indeed engenders the structural reorganization characteristic of the oxytocin system when it is physiologically activated. Similar infusion of vasopressin has no effect. Our observations thus demonstrate that a central neuropeptide can induce anatomical changes in the adult CNS, and suggest that oxytocin can regulate its own release by contributing to the dramatic restructuring of the nuclei containing the neurones responsible for its secretion.

Animals↗
PubMedDate not supplied

[Transcerebral electrostimulation in hypnotic drug withdrawal].

This preliminary study attempted to test the efficacy of electrosleep therapy on hypnotic drug withdrawal. Among 89 outpatients complaining of chronic insomnia and receiving a heavy hypnotic drug treatment, an efficient withdrawal associated with a marked improvement of self-reported sleep was observed in 78% of cases, especially when insomnia was not related to medical aetiologies or to major psychiatric disorders. These results suggest further controlled studies to determine the magnitude of the placebo component in the effect observed.

Adult↗