The REM sleep-inducing action of a naturally occurring organic bromine compound in the encéphale isolé cat

The acute effects on the sleep-wakefulness cycle of 2-octyl--bromo-acetoacetate (-Br), an organic bromine compound which occurs naturally in the brain and cerebrospinal fluid (CSF) of mammals, were studied in the encéphale isolé cat preparation under artificial respiration without fixation.In unmedicated preparations, the percentage of the three states, wakefulness, NREM sleep and REM sleep during the 3 h recording period was 32.8±15.59, 62.9±16.81 and 4.3±3.81, respectively.Various doses of synthetic -Br (0.1, 1.0 and 5.0 mg/kg) were injected intravenously. No central depressant effect was seen after injection of -Br up to 5 mg/kg. The effect of -Br on the sleep-wakefulness cycle was to increase REM sleep and to slightly decrease wakefulness or NREM sleep. Increase in REM sleep was significant (p<0.05) and its effective dose was 0.1 mg/kg. REM sleep-increasing effect appeared 5 to 15 min after injection. This coincided closely with the time of appearance of -Br in the CSF after intravenous injection.The relationship between -Br and short chain fatty acids as well as the possible mechanism related to REM sleep induction by -Br are discussed.This study was supported in part by a grant from the Ministry of Education of Japan. A preliminary report of this research was presented at the meeting of the Association for the Psychophysiological Study of Sleep in Santa Monica, California, U.S.A., April 6–9, 1967.