Role of preoptic and anterior hypothalamic cholinergic input on water intake and body temperature

To elucidate the role played by cholinergic mechanism in the preoptic area (POA) and anterior hypothalamus (AH) in the control of body temperature and water intake of rats, we used microdialysis without disturbing the behavio r of unanesthetized animals. After microdialysis, we also investigated immu noreactivity for c-Fos protein in the hypothalamus. Stimulation with neosti gmine, an acetylcholine esterase inhibitor, through microdialysis probe inc reased extracellular concentration of acetylcholine (ACh) in the POA and AH , and was accompanied by a dose-dependent fall in body temperature and incr eased water intake. Addition of atropine, a muscarinic receptor antagonist, to the dialysis medium containing neostigmine suppressed the neostigmine-i nduced changes in rectal temperature and water intake. Neostignime markedly increased c-Fos-like immunoreactivity (Fos-IR) in certain hypothalamic are as, including the paraventricular nucleus, supraoptic nucleus and median pr eoptic nucleus. This increase was also attenuated by atropine. These result s suggest that cholinergic inputs and activation of muscarinic processes in POA and AH induced a decline in body temperature and increased water intak e. (C) 2001 Elsevier Science B.V. All rights reserved.