Inhibitory effect of norepinephrine on immunoreactive corticotropin-releasing factor release from the rat hypothalamus in vitro.

Abstract Effects of catecholamines on immunoreactive corticotropin-releasing factor (I-CRF) release from the rat hypothalamus were examined using a rat hypothalamic perifusion system and a rat CRF RIA in vitro. Norepinephrine had a potent inhibitory effect on I-CRF release in a dose-dependent manner at 0.1 nM - 1 μM concentrations, but dopamine did not. This inhibitory effect of norepinephrine was completely blocked by propranolol, but only partially blocked by phentolamine. Isoproterenol also had a potent inhibitory effect at 0.01 – 100 nM concentrations, and a high dose of phenylephrine (10 nM) inhibited I-CRF release. Clonidine did not influence I-CRF release. These results suggest that norepinephrine inhibits I-CRF release mainly through the β-adrenergic receptor and partially through the α 1 -receptor.