ABSTRACT
The less purified Sleep-Promoting Substance (SPS)-B clearly exhibited a bell-shaped dose response curve for slow-wave sleep, but not for paradoxical sleep and locomotor activity in our 10-h nocturnal intracerebroventricular infusion assay in freely behaving rats. Although a crude preparation of SPS was effective by i.p. administration, it is of interest to investigate the optimal dose of peripherally administered uridine. Inokuchi and Oomura examined the effects of electrophoretically applied uridine (derived from SPS and from commercial products) on neuronal activity in the preoptic area and the posterior hypothalamic area in urethane-anesthetized rats. Nagasaki et al. and Uchizono et al. developed a sensitive method of estimating the potency of SPS by quantifying the inhibitory activity on unit discharges of isolated abdominal ganglion of crayfish in vitro. The crude SPS extracted from the brainstems of 24-h sleep-deprived rats elicited a marked inhibitory effect on the firing activity at a minimal dose of 0.0002 brainstem equivalent units/ml.
