0131 EFFECTS OF CRF RECEPTOR-1 AGONIST AND ANTAGONIST ON SLEEP AND NEURONAL C-FOS EXPRESSION IN THE PREOPTIC HYPOTHALAMUS

Abstract

Corticotropin releasing factor (CRF) neurons in the hypothalamic paraventricular nucleus and extended amygdala regulate endocrine and behavioral responses to stress. Sleep suppression frequently accompanies the stress response. Wake-promoting effects of CRF are mediated, in part, by excitation of hypocretin neurons in the lateral hypothalamus and noradrenergic neurons in the locus coeruleus. The extent to which CRF acts on sleep-promoting neuronal systems is not clear. We examined the effects of subarachnoid infusion of a CRF agonist and antagonist on sleep and on GABAergic neuronal activity in sleep regulatory nuclei in the rat preoptic hypothalamus, the median preoptic nucleus (MnPO) and ventrolateral preoptic area (VLPO). Adult Sprague Dawley rats were chronically implanted for electrographic sleep-wake state recording and a guide cannula targeting the ventral subarachnoid space rostral to the optic chiasm. In experiment 1, groups of rats were administered either vehicle (n=7) or one of two doses of CRF-receptor1 (R1) antagonist, Antalarmin (ANT; 2 μg; n=7 or 6 μg; n=7) by subarachnoid infusion (0.2 μl/min over 3 hrs starting at ZT 8). In experiment 2, groups of rats were administered subarachnoid infusion of either vehicle (n=6) or one of two doses of CRF-R1 agonist, Stressin (STR; 0.3 μg; n=6 or 1μg; n=6; 0.2 μl/min over 3 hrs starting at ZT 2). Sections through the MnPO and VLPO were harvested and immunostained for c- Fos protein and glutamic acid decarboxylase (GAD). Infusion of 6µg ANT decreased waking and increased NREM and REM sleep compared to vehicle and, and increased in percentage of GAD+ neurons expressing Fos in the MnPO (10.6 ± 1.1% versus 18.0 ± 1.9%) and the VLPO (11.2 ± 1.6% versus 22.3 ± 1.9%). Infusion of 1 µg STR increased waking and decreased NREM and REM sleep compared to vehicle. High dose STR infusion also decreased the percentage of GAD+ neurons expressing Fos-IR in MnPO (18.1 ± 9.9 versus 9.9 ± 1.5%) and VLPO (22.1 ± 1.3% versus 12.1 ± 1.8%). Vigilance state changes occurring in response to increased CRF-R1 signaling may be mediated by suppression of preoptic sleep-promoting neuronal systems as well as by activation of arousal promoting neurons. Supported by the Department of Veterans Affairs (Grant BX00155605).