How REM sleep deprivation and amantadine affects male rat sexual behavior

There are conflicting findings about the sexual effects of REM sleep depriv ation (REMd). Otherwise, several studies show a dopaminergic hypersensitivi ty after REMd. The effect of REMd and amantadine (AMA) was studied for stan dard measures and temporal patterning in the first experiment, in four grou ps: normal with vehicle, normal with AMA (5.0 and 10 mg/kg), REMd with vehi cle and REMd with AMA (5.0 and 10.0 mg/kg). REMd reduced mount latency (ML) , intromission latency (IL) and mount number (MN) and increased copulatory efficiency (CE) and hit rate factor. REMd also reduced the mount bout numbe r (MBN) and increased the sexual interaction (mount bout time, MBT) among m ale and female during copula. AMA stimulates initiation and hit rate factor s and accelerates the temporal patterning of sexual behavior, evoking fewer and quicker mount bouts. In the experiments with combination of REMd and A MA administration, AMA did not increase behavior effects evoked by REM depr ivation, probably due to a top or a bottom effect, depending on the measure s considered. A second experiment studied the effects of AMA (1.25 to 5.0 m g/kg) and REMd on the sexual reflexes of nonimmobilized male rats. REMd enh anced the AMA effects upon the seminal emission reflex, but inhibited the p enile erection reflex elicited by 1.25 mg/kg of AMA. Curiously, our results showed that REMd, like AMA, a dopaminergic agonist, causes similar effects of sexual behavior in the male rat, particularly those related to arousal mechanism and hit rate factor. The results are discussed and the effects of REMd probably involve dopaminergic hypersensitivity and increased sexual m otivational response. (C) 2001 Elsevier Science Inc. All rights reserved.