Phenoxybenzamine and bromocriptine attenuate need for REM sleep in rats

Phenoxybenzamine (10 mg/kg, IP), an alpha-adrenoreceptor blocker, and bromocriptine (5 mg/kg, IP), a dopamine receptor stimulant, were administered to rats while the animals were being deprived of REM sleep by selective REM sleep deprivation method. We have shown recently that alpha-adrenoreceptor blockers and bromocriptine when administered to rats after the animals had been deprived of REM sleep were able to abolish REM sleep rebound and thus attenuate the need for REM sleep. The purpose of this study was to investigate whether these agents might also have the capacity to attenuate the need for REM sleep when given to animals in a situation when the need for REM sleep is being generated, i.e. during REM sleep deprivation. Our results show that administration of phenoxybenzamine or bromocriptine to rats immediately before or during the period of REM sleep deprivation also abolished appearance of subsequent REM sleep rebound. This suggests that administration of the two pharmacological agents prevented the generation of REM sleep pressure by fulfilling the need for REM sleep.