BETA-ADRENERGIC RECEPTORS ARE INVOLVED IN HISTAMINE-INDUCED SECRETIONOF PROOPIOMELANOCORTIN-DERIVED PEPTIDES AND PROLACTIN IN RATS

The neurotransmitter histamine (HA) is involved in central regulation of secretion of prolactin (PRL) and the proopiomelanocortin (POMC)-der ived peptides adrenocorticotropin (ACTH), beta-endorphin (beta-END) an d alpha-melanocyte-stimulating hormone (alpha-MSH). The effect of HA o n POMC-derived peptides and PRL release is, at least in part, indirect and may involve activation of catecholaminergic systems. Therefore, w e investigated the effect of beta-adrenergic receptor blockade on HA o r HA agonist-induced release of ACTH, beta-END, alpha-MSH and PRL. Cen tral administration of HA, the H-1-receptor agonist 2-thiazolylethylam ine (2-TEA) or the H-2-receptor agonist 4-methylhistamine (4-MeKA) sti mulated the secretion of ACTH, beta-END, alpha-MSH and PRL. Pretreatme nt with the beta-adrenergic antagonist propranolol inhibited secretion of the POMC peptides in response to HA, 2-TEA or 4-MeHA. Propranonol only inhibited the PRL response to HA or 2-TEA, but had no effect on t he PRL response to 4-MeHA. Administration of the beta-receptor agonist isoproterenol stimulated ACTH, beta-END, alpha-MSH and PRL two to fiv e-fold. This effect was totally blocked by pretreatment with propranol ol. We conclude that HA-induced secretion of POMC-derived peptides fro m the anterior and intermediate lobe of the pituitary gland and of PRL from the anterior lobe is, at least in part, mediated via catecholami nes. beta-Adrenergic receptors are involved in the mediation of the PO MC response to H-1- as well as H-2-receptor activation, whereas beta-r eceptors are involved only in the mediation of the PRL response to H-1 -receptor activation.