[Histamine and prolactin liberation in the rhesus monkey]

The effect of intra venous (i.v.) or intra cerebroventriculaire (i.c.v.) administration of histamine (HA) on plasma prolactin (PRL) levels was investigated in ovariectomized Rhesus Monkeys. Intra venous injection of 50 micrograms/kg HA increased the plasma PRL concentration but icv administration of 10 and 50 micrograms decreased PRL plasma levels. Intra venous injection of 2-thiazolyl-éthylamine, a H1 receptor agonist, rapidly stimulated PRL release (peak PRL concentration at 5 min) suggesting a direct effect on the pituitary. In contrast intra venous administration of the H2 receptor agonist, impromidine, inhibited PRL release at low doses. High doses of impromidine increased PRL concentrations but this effect was delayed (PRL peak values were reached at 20 minutes). Our results show that HA may influence PRL release in the primate via H1 and H2 receptors located at both pituitary and central levels.