Release of prolactin and luteinizing hormone by histamine agonists in ovariectomized, steroid-treated rats under ether anesthesia

Abstract

Responses to histamine agonists administered intraventricularly under ether anesthesia were analyzed to evaluate receptor mediation in histamine stimulation of prolactin and LH release in ovariectomized, estradiol-progesterone-treated rats (OVX-E2P-treated rats). Prolactin release was markedly increased by the H2-histamine agonists, 4-methyl histamine and Dimaprit. These effects were antagonized by metiamide, an H2-blocking agent. The H1-histamine agonist, 2-(2-pyridyl)ethylamine (PEA) in high doses released prolactin and its effect was partially prevented by metiamide. Mepyramine, and H1-antagonist, did not exert any effect on the release of prolactin enhanced by the histamine agonists. LH release was significantly increased after 4-methyl histamine administration. Its effect was weak and was blocked by metiamide. Neither Dimaprit nor PEA exhibited action on plasma LH levels. The results obtained with histamine agonists suggest that histamine evokes prolactin release in OVX,E2P-treated rats through H2-receptors. At present, conclusions on H2-receptor mediation in LH release induced by histamine cannot be drawn from these results. The above-mentioned data, however, conclusively discard a significant participation of H1-receptors.

Involvement of H₁ Histamine Receptor in Basal and Estrogen-Stimulated Luteinizing Hormone-Releasing Hormone Secretion in Rats in vitro

“…The present results taken together with these findings suggest that histamine H i receptors are involved more closely than H: receptors in the control of gonadotropin secretion in female rats. This con clusion is not consistent w ith the report of Donoso and Za rate [8] that LH release was increased by 4-methylhistamine, and H; agonist, and that this increase was blocked by metiamide. an H; receptor antagonist, in ovariectomized.…”

“…Endroczi and Hilliard [9] and Libertun and McCann [13] observed that intracerebroventricular administration of histamine in creased the LH-releasing activity in plasma of female rab bits and dogs, and the plasma LH level in female rats, but that intrapituitary or intravenous injection of histamine had no effect on gonadotropin secretion in these animals. Many investigators have confirmed that intracerebroventricular histamine raises the plasma gonadotropin levels in female experimental animals [5,8,21], Charli et al [4], however, reported that histamine at concentration of KL5 M did not induce LH-RH release from the MBH isolated from male rats in vitro. Our findings are not consistent with those of Charli et al [4], This difference in the effects of histamine on LH-RH release may depend on the sex of the rats used.…”

“…There have been a few studies on the nature of the hista mine receptors involved in gonadotropin secretion [6,8,13]. Libertun and McCann [13] found that intravenous injection of diphenhydramine, an Hi receptor antagonist, blocked the decreases in LH and follicle-stimulating hormone in duced by restraint stress in ovariectomized rats.…”

“…There are reports that histamine induces release of thyr otropin-releasing hormone (TRH) from the hypothalamus [1,3], and that the content of histamine in the hypothalamus varies with change in the hormonal state [2,14]. Several studies have suggested that histamine is involved in the control of gonadotropin secretion in rats and rabbits [5,8,9,13,21], Intracerebroventricular or intrahypothalamic injec tion of histamine induces an increase in the plasma luteiniz- …”

The Immunology of Prolactin

“…Histamine evoked PRL release in ovariectomized, estradiol-and progesteronetreated rats through H 2 receptors. 161 The vasoactive substance, bradykinin, which is involved in pain, inflammation, and edema, stimu lated the release of PRL from rat anterior pituitary cells in culture. Bradykinin was as effective as TRH in stimulating PRL release in vitro.…”