Biomedical subjects

V J Choy

Publications and source records attributed to V J Choy.

22 records · Page 2Linked to original sources

PubMedDate not supplied

HPLC separation of vasopressin-like hormones in chicken neurohypophysial extracts.

HPLC techniques were used to identify peptides that possess vasopressin-like immunoreactivity in the chicken neurohypophysis. The presence of arginine vasotocin (AVT) was confirmed together with arginine vasopressin (AVP). That the presence of AVP may be confined to the chicken, and not other avian species, was concluded from the absence of the hormone in the neurohypophysis of the duck and turkey. The chicken thus resembles some members of the suiformes and metatheria in possessing two vasopressin-like peptides.

Animals↗

PubMedDate not supplied

Identification of neurohypophysial peptides in the ovaries of several mammalian and nonmammalian species.

Ovarian tissue from a variety of mammalian and nonmammalian species were extracted in acid. All extracts contained both oxytocin- and vasopressin-like immunoreactivites as determined by radioimmunoassay. Analysis by high performance liquid chromatography revealed the presence of oxytocin in all ovarian extracts examined. This was in contrast to the corresponding posterior pituitary gland which other workers have shown do not necessarily contain the oxytocin peptide. It is suggested that oxytocin may play an important role in ovarian function in species of differing phylogeny.

Animals↗

PubMedDate not supplied

Bulbospinal serotonin neurons and hypotensive effects of methyldopa in the spontaneously hypertensive rat.

Systemic methyldopa administration in genetically hypertensive rats evoked a hypotension which was attenuated after prior treatment with the neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) given either intracerebroventricularly, to produce a generalised ablation of serotonin nerves in brain and spinal cord, or by injection into the cervical spinal cord, to cause a selective destruction of descending serotonin pathways. Direct microinjection of methyldopa into the ventrolateral medulla in the area of the B1 and B3 serotonin cells was also effective in lowering arterial pressure. The hypotensive response to this medullary administration of methyldopa was again attenuated by 5,7-DHT given either intracerebroventricularly or by intraspinal injection. On the other hand, prior treatment intracerebroventricularly with 6-hydroxydopamine did not affect the hypotensive effect of methyldopa injected into the region of the ventrolateral B1 and B3 cells, supporting the suggestion that this effect of methyldopa is mediated by bulbospinal serotonin neurons and not by descending catecholamine nerves. The fact that methyldopa injection into the ventrolateral medulla in a region coinciding with the B1 and B3 cells lowers blood pressure is consistent with previous studies demonstrating that these neurons serve to maintain or elevate arterial pressure.

5,7-Dihydroxytryptamine↗

PubMedDate not supplied

Importance of central serotonin neurons in the hypotensive action of methyldopa in the rat.

Normotensive (WKY) and stroke prone spontaneously hypertensive (SHR-SP) rats were given methyldopa (200 mg/kg i.p.) daily for five days and their brains were then sectioned and processed with the Faglu method for catecholamine fluorescence. This treatment with methyldopa induced a green fluorescence not seen in control animals, in cells coinciding with the B1-B9 groups of serotonin neurons in the brainstem. Pretreatment with the neurotoxin 5,7-dihydroxytryptamine (5,7-DHT, i.c.v.), which is relatively specific for serotonin neurons, prevented the appearance of this green fluorescence in the serotonin cell groups of rats given methyldopa. Pretreatment with 5,7-DHT, i.c.v. approximately halved the magnitude of the hypotensive response to a single dose of methyldopa (80 mg/kg i.p.). We suggest that central serotonin nerves contribute to the hypotensive action of methyldopa. It is our hypothesis that methyldopa is taken up by these serotonin cells and that the green fluorescence reflects the production of alpha-methyldopamine, as a result of decarboxylation by the ubiquitous enzyme, L-aromatic amino acid decarboxylase.

5,7-Dihydroxytryptamine↗