[The histaminergic mechanisms in the regulation of prolactin secretion in urethan-anesthetized rats (author's transl)].
In an attempt to detect the existence of histaminergic mechanisms in the regulation of prolactin secretion in rats, the effects of histidine and histamine-receptor antagonists (chlorpheniramine and metiamide) on plasma prolactin levels in urethan-anesthetized rats were investigated in relation to other aminergic mechanisms. Chlorpheniramine was used as an H1-receptor antagonist and metiamide as an H2-receptor antagonist. Wistar male rats were used under urethan anesthesia and blood was obtained by cardiac puncture. Rat plasma prolactin was measured by radioimmunoassay. As already reported, L-DOPA and diethyldithiocarbamate markedly decreased plasma prolactin levels in rats. Dihydroxyphenylserine increased prolactin levels. Brocresine phosphate, a histidine decarboxylase inhibitor, markedly stimulated prolactin secretion in urethan-anesthetized rats. This stimulation was not blocked by pretreatment with histidine or L-DOPA. Histidine alone did not affect plasma levels of prolactin or methyldopamine-induced increase in plasma prolactin levels. On the other hand, histidine significantly stimulated prolactin secretion in chlorpheniramine-treated rats. In contrast, histidine depressed plasma prolactin levels in metiamide-treated rats. These findings indicate that a dopaminergic component is inhibitory and a noradrenergic one is stimulatory in prolactin secretion in rats and further that there exist the histaminergic mechanisms, relatively independent from other aminergic mechanisms, which might also play an important role in the regulation of prolactin secretion in rats. Furthermore, it is suggested that H1-receptor is stimulatory and H2-receptor is inhibitory in prolactin secretion in rats.
[The histaminergic mechanisms in the regulation of prolactin secretion in urethan-anesthetized rats (author's transl)]. In an attempt to detect the existence of histaminergic mechanisms in the regulation of prolactin secretion in rats, the effects of histidine and histamine-receptor antagonists (chlorpheniramine and metiamide) on plasma prolactin levels in urethan-anesthetized rats were investigated in relation to other aminergic mechanisms. Chlorpheniramine was used as an H1-receptor antagonist and metiamide as an H2-receptor antagonist. Wistar male rats were used under urethan anesthesia and blood was obtained by cardiac puncture. Rat plasma prolactin was measured by radioimmunoassay. As already reported, L-DOPA and diethyldithiocarbamate markedly decreased plasma prolactin levels in rats. Dihydroxyphenylserine increased prolactin levels. Brocresine phosphate, a histidine decarboxylase inhibitor, markedly stimulated prolactin secretion in urethan-anesthetized rats. This stimulation was not blocked by pretreatment with histidine or L-DOPA. Histidine alone did not affect plasma levels of prolactin or methyldopamine-induced increase in plasma prolactin levels. On the other hand, histidine significantly stimulated prolactin secretion in chlorpheniramine-treated rats. In contrast, histidine depressed plasma prolactin levels in metiamide-treated rats. These findings indicate that a dopaminergic component is inhibitory and a noradrenergic one is stimulatory in prolactin secretion in rats and further that there exist the histaminergic mechanisms, relatively independent from other aminergic mechanisms, which might also play an important role in the regulation of prolactin secretion in rats. Furthermore, it is suggested that H1-receptor is stimulatory and H2-receptor is inhibitory in prolactin secretion in rats.