Sleep suppressant action of quipazine: relation to central serotonergic stimulation

Administration of quipazine maleate (1-10 mg/kg, IP), a proposed 5-hydroxytryptamine (5-HT) receptor stimulant to rats produced a dose-related suppression of both slow-wave sleep (SWS) and rapid-eye-movement sleep (REMS) accompanied by an increase in head-shaking behavior. These effects were observed during the first 6 hr of a 12-hr EEG recording session. The latencies to the sleep states were markedly prolonged and correlated with the duration of head-shaking behavior induced by the drug. A significant inverse relationship was found between the amount of SWS or REMS and the number of head-shakes occurring during the first 6-hr period. Since head-shaking behavior in rodents has been proposed as a quantitative, behavioral model of central 5-HT activation, the data suggest a causal relationship between enhanced 5-HT activity and sleep suppression. This assumption is further supported by the observation that pretreatment with metergoline (2.5 mg/kg, IP) a 5-HT receptor blocker, reduced quipazine's effects on both SWS and head-shaking behavior.