EFFECTS OF P-CHLOROPHENYLALANINE (P-CPA) ON SLEEP IN OLFACTORY BULB LESIONED RATS

Abstract

The effect of p-CPA [p-chlorophenylalanine] and 5-HTP [5-hydroxytryptamine] followed by p-CPA on sleep was studied in rats with olfactory bulb lesions (OB lesioned rats). In these rats electrodes were chronically implanted to record the EEG (frontal cortex and dorsal hippocampus), the cervical eleectromyogram and eye movements. The REM [rapid eye movement] sleep stage was selectively decreased from 24-32 h after 200 mg/kg of p-CPA in the sham lesioned rats; both the slow wave sleep and REM sleep stages were markedly decreased by the same dose of p-CPA in the OB lesioned rats. In both sham and OB lesioned groups the slow wave sleep and REM sleep stages decreased from 24-32 h after 400 mg/kg of p-CPA and the percentage of decrease in the slow wave sleep stage was much larger with 400 mg/kg of p-CPA than with 200 mg/kg of p-CPA. The REM sleep stage disappeared from 24-32 h after 200 mg/kg and 400 mg/kg of p-CPA. In the OB lesioned rats the insomnia produced by 200 mg/kg and 400 mg/kg of p-CPA disappeared with 5-HTP (5 mg/kg). The insomnia produced by 200 mg/kg of p-CPA did not recur with 5-HTP in the sham lesioned rats, but with 400 mg/kg there was a recurrence. The enhanced effect of p-CPA and 5-HTP followed by p-CPA in the OB lesioned rats appears to be due to changes in the sensitivity of the serotonergic system in the brain.