Histaminergic mediation of the stress-induced release of prolactin in male rats.

Histamine (HA) is likely to participate in the neuroendocrine regulation of prolactin (PRL) secretion. We, therefore, studied the possible involvement of HA in the stress-induced release of PRL in conscious male rats. HA (30 micrograms) infused intracerebroventricularly 15 min before decapitation elevated PRL plasma levels from 5 +/- 1 to 54 +/- 6 ng/ml (p less than 0.01). Intracerebroventricular infusion of the H2 receptor antagonists cimetidine (CIM: 100 micrograms) or ranitidine (RAN: 125 micrograms) abolished the PRL response to HA (p less than 0.01), while intracerebroventricular infusion of the H1 receptor antagonist mepyramine (MEP; 100 micrograms) inhibited the response only 40% (p less than 0.05). Intra-arterial infusion of CIM (2,000 micrograms) or RAN (2,500 micrograms) inhibited the HA-stimulated PRL secretion 52% (p less than 0.01) or 63% (p less than 0.01), respectively. The H1 receptor antagonists MEP (1,000 micrograms) and SKF-93944 (1,500 micrograms) had no effect following intra-arterial administration. Restraint stress increased the PRL level to 84 +/- 6 ng/ml (p less than 0.01 vs. control). This effect was prevented by intracerebroventricular infusion of CIM or RAN (p less than 0.01) and inhibited 75% by MEP (p less than 0.01). Intra-arterial infusion of CIM, MEP, and SKF-93944 inhibited the stress response about 50% (p less than 0.01), while RAN decreased the response only 25% (p less than 0.05). Ether stress elevated the plasma PRL concentration to 46 +/- 5 ng/ml (p less than 0.01 vs. control). When infused intracerebroventricularly CIM or RAN prevented the response (p less than 0.01), while MEP had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)