Effect of acetylcholine on corticotropin-releasing factor gene expression in the hypothalamic paraventricular nucleus of conscious rats.

To examine the physiological role of cholinergic input in the regulation of CRF neurons in the paraventricular nucleus (PVN) of the hypothalamus, acetylcholine (ACh) was microinjected bilaterally into the dorsolateral border of the PVN of conscious rats. Changes in the levels of POMC messenger RNA (mRNA) in the anterior pituitary, CRF mRNA in hypothalamic tissue containing the PVN, and plasma ACTH were assessed. Plasma ACTH concentrations increased in a dose-dependent manner after ACh injection (1-100 pmol/side), reaching a peak 30 min after ACh injection and returning to baseline within 120 min. The POMC mRNA level in the anterior pituitary and the hypothalamic CRF mRNA level increased in a dose-dependent manner 120 min after ACh (0.1-10 pmol/side) injection. Intracerebroventricular pretreatment with atropine completely abolished the ACh-induced increase in plasma ACTH concentrations, whereas pretreatment with hexamethonium was without significant effect. The intracerebroventricular injection of ACh also...