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Inhibiting the rabbit caudal ventrolateral medulla prevents baroreceptor‐initiated secretion of vasopressin.
Author(s) -
Blessing W W,
Willoughby J O
Publication year - 1985
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1985.sp015823
Subject(s) - vasopressin , baroreceptor , medulla , muscimol , medicine , endocrinology , hypothalamus , rostral ventrolateral medulla , medulla oblongata , inferior vena cava , chemistry , biology , agonist , central nervous system , receptor , blood pressure , heart rate
The A 1 noradrenergic neurones are known to project from the caudal ventrolateral medulla to the vasopressin‐secreting neuroendocrine cells in the hypothalamus. They therefore represent a possible central pathway from the medulla to the hypothalamus for baroreceptor‐initiated secretion of vasopressin. We tested this hypothesis in the anaesthetized rabbit. Muscimol, a gamma‐aminobutyric‐acid‐receptor agonist, was injected into the caudal ventrolateral medulla to inhibit the A 1 noradrenergic neurones. Secretion of vasopressin, measured by radioimmunoassay, was initiated either by arterial haemorrhage or by constriction of the inferior vena cava. After injection of vehicle into the caudal ventrolateral medulla, or after injection of muscimol into nearby control areas, both haemorrhage and constriction of the inferior vena cava produced the expected elevation in plasma vasopressin. After injection of muscimol into the caudal ventrolateral medulla, secretion of vasopressin in response to haemorrhage and to constriction of the inferior vena cava, was completely abolished. The A 1 noradrenergic neurones may be the sole pathway transmitting the reflex for baroreceptor‐initiated secretion of vasopressin from the medulla to the hypothalamus.