Intragastric administration of glutamate increases REM sleep in rats

•Effect of intragastric glutamate administration on sleep was studied in rats.•Sleep-wake parameters were studied for six hours after intragastric administration of glutamate or saline.•Intragastric glutamate administration showed significant increase in REM sleep without much effect on slow wave sleep.

Monosodium glutamate, a umami taste substance is commonly used flavor enhancer. The effect of intragastric administration of 1.5 ml of 0.12 M monosodium glutamate on sleep-wake was studied in 10 adult male Wistar rats. Sleep-wake parameters were recorded through chronically implanted electroencephalogram, electrooculogram and electromyogram electrodes using a digital recording system (BIOPAC system Inc. BSL PRO 36, USA). The sleep-wake was recorded for 6 h after the intragastric administration of either glutamate or saline. Sleep-wake stages were analyzed as wake, slow wave sleep and REM sleep. Compared to saline, intragastric administration of glutamate significantly increased REM sleep duration and episode frequency. REM sleep duration was increased in all the three 2 h bins, 10:00-12:00 h (p = 0.037), 12:00-14:00 h (p = 0.037) and 14:00-16:00 h (p = 0.007). The slow wave sleep and total sleep time were not affected. It is concluded that intragastric glutamate administration increases REM sleep.