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M. C. ARAKELIAN, C. LIBERTUN, HI and H2 Histamine Receptor Participation in the Brain Control of Prolactin Secretion in Lactating Rats, Endocrinology, Volume 100, Issue 3, 1 March 1977, Pages 890–895, https://doi.org/10.1210/endo-100-3-890
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The aim of the present research was to evaluate the histaminergic regulation of prolactin secretion in the lactating rat and the possible involvement of HI and H2 histamine receptors in this control. Prolactin was measured by radioimmunoassay in blood samples withdrawnthrough an intrajugular silastic catheter from undisturbed lactating mothers 10 to 15 days after delivery. In some of those rats a stainless steel cannula was placed in the third ventricle. The tested drugs, HI and H2 receptor agonists and antagonists, were injected either by the intrasilastic route or intraventricularly immediately before the onset of suckling and after abasal sample was taken. New samples were withdrawn 10, 20, 30 and 60 min thereafter.
Suckling caused a 12- to 18-fold increase in serum prolactin by 10 min in control saline-injected mothers. In non-suckled mothers (NSM) injected with saline, prolactin levels were low at all times. Systemic or intraventricular diphenydramine and mepyramine, HI receptor antagonists, suppressed the increment in prolactin observed in suckledmothers (SM). Intraventricular metiamide, an H2 receptor antagonist, did not modify prolactin secretion in SM but drastically increased serum prolactin in NSM.
A small but significant increase in prolactin titers was observed in NSM injected intraventricularly with histamine. 4-Methylhistamine, an H2 agonist, was ineffective when used intraventricularly in NSM, but clearly suppressed prolactin enhancement in SM.
It is postulated that in lactating mothers, brain histamine has a dual control on prolactinsecretion. H2 receptors mediate events related to inhibition of prolactin release, since the agonist 4-methylhistamine blocked the prolactin rise in SM, while the antagonist metiamide promoted release of the hormone in NSM. HI receptors seem to be related to a facilitatory mechani m since classical antihistamines suppress the serum prolactin increase that follows the onset of suckling, while histamine itself is able to release prolactin in NSM. (Endocrinology100: 890, 1977)
