Abstract
Secretion of corticotropin releasing factor (CRF) from the hypothalamic paraventricular nuclei into the hypophysial-portal circulation is modulated by a variety of neuronal afferents. Effects of intracerebroventricular acetylcholine (ACH), γ-aminobutyric acid (GABA) and epinephrine (EPI) on immunoreactive (ir) CRF concentration in portal plasma were directly evaluated in urethanized male rats. ACH (0.1–10 nmole) administration was associated with a dose-dependent elevation of portal irCRF which was attenuated by pretreatment with either muscarinic or nicotinic receptor antagonists. GABA (0.1–10 nmole) also caused inhibition of irCRF concentration in the portal plasma which was prevented by bicuculline pretreatment. Finally, EPI (0.1–10 nmole) facilitated irCRF secretion via α1- and β-adrenergic mechanisms. These observations provide the first direct information on possible neurotransmitter actions on hypothalamic CRF secretion.
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