OPPOSITE EFFECTS OF [LEU(13),PRO(34)]NPY AND NPY(13-36) ON HYPNOTIC RESPONSE TO ALPHA(2)-ADRENOCEPTOR AGONIST DEXMEDETOMIDINE MICROINJECTEDINTO RAT LOCUS-COERULEUS

Neuropeptide Y is colocalised with noradrenaline in the locus coeruleu s (LC). This study evaluated the effects of neuropeptide Y (NPY) Y-1 a nd Y-2 receptor agonists on the hypnotic response to alpha(2)-agonist dexmedetomidine following the unilateral microinjection of these drugs into the vicinity of the locus coeruleus (LC). Dexmedetomidine alone (1 mu g) induced a loss of righting reflex and sleep in all animals. [ Leu(31),Pro(34)]NPY (10 pmol) lengthened, whereas NPY13-36 (100 pmol) shortened the time of latency to sleep. The duration of sleep was shor tened in rats pretreated with [Leu(31),Pro(34)]NPY. These data demonst rate that the hypnotic effect to dexmedetomidine in the LC can be modu lated differentially by Y-1 and Y-2 receptor-selective agonists and pr ovide additional evidence for NPY/alpha(2)-adrenoceptor interaction in this brain area.