INFLUENCE OF SUBSTANCE P ON HYPOTHALAMO-PITUITARY-ADRENOCORTICAL ACTIVITY IN THE RAT

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Abstract
Substance P is present in the hypothalamus in relatively high concentrations. Its release is K+-evoked and Ca2+-dependent and it may be a neurotransmitter substance in the hypothalamus. Its effect was tested on secretion of corticotropin releasing factor (CRF) by the hypothalamus in vitro and on production of ACTH by the anterior pituitary gland of the rat both in vivo and in vitro. Substance P appears to inhibit ACTH secretion by the adenohypophysis but does not affect hypothalamic CRF production. If it enters the hypophysial portal vessels, from nerve endings in the median eminence or from the third ventricle via ependymal cells, it may play an inhibitory role in the control of ACTH synthesis and release.