[Effects of monoamine-related compounds on the sleep-awake cycle in rabbits].

The role of 5HT and NA in the regulation of the sleep-awake cycle, especially in the triggering mechanisms of paradoxical sleep (PT), was studied in rabbits using reserpine, parachlorophenylalanine (PCPA), alpha-methyl-p-tyrosine (alpha-MT) and alpha-methyl -m-tyrosine (alpha-MMT). 1) Reserpine (0.5 mg/kg, i.v.) caused a diphasic action on the brain electrical activity in rabbits: an initial activation pattern in the EEG which continued to 2approximately3 hr, was followed gradually by a slow wave. Forty to sixty min after reserpine administration, spike waves resembling the PGO waves in cats appeared from the medial nucleus Trapezoides (Trap. m.) in rabbits. From the electrophysiological point of view, these spike waves (reserpine spike waves) were in many respects similar to those recorded during PS (TR spike waves). Later reserpine spike waves appeared almost continuously for about 8approximately12 hr during arousal and slow wave sleep stages. When the amplitude and grouping of spike waves became prominent, severe myoclonic jerky movements resembling "pseudo hallucinatory" behavior were observed. Polygrams of these periods were similar to those of PS except for abrupt arousal and orienting reactions. The onset of the typical PS episode was delayed by more than 8approximately9 hr. 2). Repeated doses of PCPA (500 mg/kg/day for 3 consecutive days, i.p.) caused only slight suppressive effect on slow wave sleep (SS), but spike waves similar to TR spike and/or reserpine spike waves developed throughout SS. When the amplitude and grouping of these spike waves were progressively increased, SS was often followed by PS. Abrupt enhancement of these spike waves as associated with "pseudo hallucinatory" behavior and aroused the animal. Usually these spike waves were not seen during arousal phase. When reserpine (0.5 mg/kg) was given i.v. to PCPA-treated rabbits, the latent period of appearance of reserpine spike waves was markedly shortened. 3) alpha-MMT, at a dose which had no effect on SS, markedly suppressed PS for a long period. These findings suggest that 5HT and NA in the lower brainstem play inhibitory roles on the triggering mechanism of PS.