Noradrenergic regulation of prolactin secretion at the level of the paraventricular nucleus of the hypothalamus: functional significance of the alpha-1b and beta-adrenergic receptor subtypes.
Previous research has demonstrated that in the Siberian hamster, both photoperiod and estrous cyclicity alter the profile of noradrenergic activity with the paraventricular nucleus of the hypothalamus (PVN), and that noradrenergic activity is correlated with changes in circulating levels of prolactin. Work from our laboratory has demonstrated an inhibitory role for norepinephrine (NE) acting at the alpha-2 receptor subtype within the PVN on serum prolactin levels; however, the functional significance of other adrenergic receptor subtypes on this system is unknown. The purpose of this study was to investigate the functional significance of the alpha-1b and beta-adrenergic receptor subtypes at the level of the PVN on circulating levels of prolactin. These experiments were performed in male Siberian hamsters using reverse microdialysis coupled with serial blood sampling. In Experiment 1, infusion of l-phenylephrine hydrochloride (alpha-1b agonist) initiated a dose-dependent increase in circulating prolactin, whereas infusion of chloroethylclonidine (alpha-1b antagonist) induced a significant dose-dependent decline in prolactin. In Experiment 2, intraparaventricular administration of propranolol (beta antagonist) initiated a significant increase in prolactin levels in a dose-dependent manner, whereas isoproterenol (beta agonist) induced a dose-dependent decline in prolactin. The results of this study indicate that both the alpha-1b and beta-adrenergic receptor subtypes have a significant role in regulating circulating levels of prolactin at the level of the PVN in the Siberian hamster.
Dodge
James C
JC
Behavioral Neuroscience Program, Psychology Department, SUNY at Buffalo, USA. jim.dodge@genzyme.com
Badura
Lori L
LL
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D018340:Receptors, Adrenergic, alpha-1; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; C051731:chlorethylclonidine; D011388:Prolactin; D011433:Propranolol; D007545:Isoproterenol; D003000:Clonidine; D009638:Norepinephrine