Effects of remoxipride, a dopamine D-2 antagonist antipsychotic, on sleep-waking patterns and EEG activity in rats and rabbits.

The antipsychotic remoxipride, a selective dopamine D-2 receptor antagonist, was studied for its effects on sleep-waking patterns in the rat and electroencephalographic (EEG) activity in the rabbit. Haloperidol, which has lesser selectivity for D-2 receptors, was used for comparison. In the rat, remoxipride (1-10 mg/kg SC) did not affect either total sleep or non-rapid eye movement (non-REM) sleep. Only REM was slightly reduced by the high dose of 10 mg/kg. Haloperidol (0.1-1 mg/kg PO) enhanced duration of both total sleep and non-REM sleep. In the rabbit, remoxipride (3 and 10 mg/kg IV) induced no significant changes of the EEG power spectrum over 0.1-38.5 Hz or individual frequency bands. In both cortex and hippocampus the drug did not alter the arousal response to acoustic sensory stimuli. Plasma concentration of remoxipride 10 mg/kg IV in rabbits declined biexponentially and was 4 and 2 mumol/l at 30 min and 1 h, respectively. Haloperidol (0.3 and 1 mg/kg) slowed down the EEG activity, enhanced the power spectrum of the cortical and hippocampal activity, and significantly reduced the duration of arousal induced by sensory stimuli. The results indicate that, unlike haloperidol, remoxipride has weak or no sedative effects. The data also provide support to the notion that D-2 receptors are not involved in the regulation of states of sleep and sedation.