Effects of indole-pyruvic acid on sleep and food intake in the rat

Indole-pyruvic acid was studied for its short- and long-term effects on electro-encephalographic sleep and on food intake in rats implanted with cortical and muscular electrodes. Following a single injection, indole-pyruvic acid (10–50 mg kg-1 i.p.) reduced by 16–23 min (range) the latency of the first slow-wave episode in a dose-related fashion and produced a significant increase in slow-wave sleep time (12–40%) in doses of 10–30 mg kg-1. Rapid eye movement sleep latency and rapid eye movement sleep time were increased (by 23–37 min) and reduced (57–71%) respectively. The effects of indole-pyruvic acid on slow-wave sleep time were still present after 3, 7 and 14 days of chronic administration (10 mg kg-1 day-1), whereas tolerance to the effect of indole-pyruvic acid on rapid eye movement sleep was observed. Daily food consumption was reduced (20–28%) by acute administration of indole-pyruvic acid (15–30 mg kg-1 i.p.), but tolerance developed after 5 days of repeated injections. These findings are in accordance with previous evidence suggesting that indole-pyruvic acid effects may be related to the activation of central serotonin neurons, which are involved in the inhibitory control of sleep and food intake.