ADMINISTRATION OF HUMAN CHORIONIC-GONADOTROPIN AFFECTS SLEEP-WAKE PHASES AND OTHER ASSOCIATED BEHAVIORS IN CYCLING FEMALE RATS

We investigated the possible effects of human chorionic gonadotropin ( hCG) on sleep-wake phases and other associated behaviors controlled by the medial preoptic area, cerebral cortex and hippocampus. Chronic ep idural electroencephalographic (EEG) and temporal muscle electromyogra phic (EMG) electrodes were placed in cycling female rats. After a week of recovery, rats were injected intraperitoneally at 3.00 pm on the d ay of proestrus with either saline or highly purified hCG or indometha cin or hCG plus indomethacin. Three hours after injection, EEG, EMG an d behavioral activities were recorded for 3.5 h. The administration of hCG increased high and low amplitude sleep, resting phase and decreas ed active awake phase, walking, sniffing and chewing as compared to th e controls. While the administration of indomethacin alone had no effe ct, coadministration inhibited hCG effects. Medial preoptic area, cere bral cortex and hippocampus contain immunostaining for LH/hCG receptor s. The administration of hCG resulted in an increase of immunoreactive PGD(2) and a decrease of PGE(2) in median preoptic area, cerebral cor tex and hippocampus as compared to the controls. In summary, hCG admin istration affects sleep-wake phases and other associated behaviors in rats which can collectively be described as decreased activity. These effects are probably mediated by increasing PGD(2) and decreasing PGE( 2) in areas of brain which control these activities. The above finding s may be relevant to pregnant women who experience decreased activity when hCG is present in the circulation and cerebrospinal fluid.