[Effects of intraventricular injection of anti-DSIP serum on sleep in rats]

Endogenous delta sleep-inducing peptide (DSIP) has not been demonstrated to be necessary for sleep, although the administration of DSIP has been reported to increase sleep in several mammalian species. The purpose of the present study is to examine whether the immunological neutralization of endogenous DSIP in the brain can modulate sleep in unanesthetized rats. A high titer of the rabbit antiserum specific for the C-terminal of DSIP was used. Sixteen male SD rats were chronically implanted with electrodes for EEG and EMG and with a cannula into the lateral ventricle. The rats were injected with anti-DSIP (ADS) or normal rabbit serum as a control at 10 microliter for 10 min immediately before the onset of the light or dark period, and thereafter the polygraphic recordings were performed for a 24-hr period. The records were scored in 30-sec epochs by visual inspection into 3 stages; wakefulness, slow wave sleep (SWS), and paradoxical sleep (PS). ADS exerted no significant effect on the latencies of SWS and PS after injection in the light or dark period. For SWS and PS, neither the distributions measured each 10 min for the first 4 hr nor the hourly distributions for 24 hr were affected by ADS. The first 12-hr amounts of SWS and PS were also unaffected by ADS. These results may suggest the possibility that endogenous DSIP in the cerebrospinal fluid and/or the periventricular tissues is not responsible for sleep.