Norepinephrine but not epinephrine stimulates the release of corticotropin‐releasing factor from in vitro superfused rat hypothalamus

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Abstract
To clarify the controversy concerning the role of catecholaminergic systems in regulating hypothalamic corticotropin‐releasing factor (CRF) secretion, we assessed the direct effects of norepinephrine and epinephrine, alone and in association with mixed α and β antagonists on hypothalamic CRF secretion. An in vitro rat mediobasal hypothalamus perifusion system was used, in which CRF secretion from a single explant was evaluated by a specific radioimmunoassay. We found that norepinephrine stimulated CRF secretion, with peak effects at 10‐8 M concentration, whereas epinephrine had no effect on CRF secretion. The effect of norepinephrine was antagonised by the mixed a antagonist phentolamine and by the mixed β antagonist propranolol. We conclude that norepinephrine, but not epinephrine, stimulate hypothamic CRF secretion via a and β receptors. The data support the idea that the central noradrenergic systems are excitatory upon CRF‐41 secretion when acting directly at the hypothalamic level.