EFFECT OF ALPHA-2-ADRENERGIC DRUGS ON REM-SLEEP DEPRIVATION-INDUCED INCREASE IN SWIMMING ACTIVITY

Effects of alpha2-adrenergic agents on rapid eye movement sleep (REMs) deprivation-induced anti-immobility effect in the forced swimming tes t (FST) were investigated. Mice were deprived of REMs for 24-72 h by a small pedestal method. Animals that were either group housed or socia lly isolated during the same period as REMs deprivation were used as t he control groups. REMs deprivation for 48 and 72 but not 24 h signifi cantly increased swimming activity without increasing locomotor activi ty. Clonidine HCl (30-300 mug/kg, IP), an alpha2-adrenoceptor agonist, dose-dependently increased swimming activity in group-housed, isolate d, and REMs-deprived mice, but the effective doses of clonidine in REM s-deprived mice were lower than those in group-housed or isolated anim als. Yohimbine HCl (5 mg/kg, IP), an alpha2-adrenoceptor antagonist, b locked the clonidine (300 mug/kg)- but not the REMs deprivation-induce d increase in swimming activity. These results suggest that REMs depri vation enhances the sensitivity of the alpha2-adrenoceptor and that th e increase in swimming activity by REMs deprivation may be mediated by other neuronal mechanisms rather than the alpha2-adrenoceptor.