Effects of a new stressful manipulation, forced shaking stress at low temperature (4 degrees C) (FSLT stress), on sleeping induced by pentobarbital were investigated 70 min following its application. 2. Repeated application (7 times) decreased the duration of sleep induced by pentobarbital-Na (45 mg/kg, i.p.) in mice without affecting that induced by ketamine-HCl and chloral hydrate. This effect of FSLT stress disappeared 3 days after termination of application. 3. The latency of nociceptive response in hot-plate test increased in a naloxone-sensitive manner by single and repeated FSLT stress when tested immediately (2 min) after but not 70 min after the last stress application. 4. Diazepam (0.3 mg/kg, i.p.) significantly prolonged the duration of sleep induced by pentobarbital (45 mg/kg, i.p.) in stressed animals without changing that in unstressed animals. The effect of diazepam was blocked by Ro 15-1788 (10 mg/kg, i.p.), a specific benzodiazepine receptor antagonist. 5. Repeated FSLT stress thus appears to decrease pentobarbital sleep by inducing functional changes in the central nervous system and the GABAergic system may partially participate in FSLT stress-induced decrease in pentobarbital sleep.
