[Changes in the content of substance P, beta-endorphin and corticosterone in the hypothalamus and blood of rats with emotional stress after the administration of the delta sleep-inducing peptide]

Abstract

The aim of this study was to investigate time-related changes in substance P (SP) beta-endorphin (BE), and corticosteron (CORT) levels induced by DSIP administration in rats subjected to emotional stress. Experiments were carried out in male Wistar and August rats with different resistance to emotional stress. At night rats were tied by their tails to the backside of the special cages. These stress-inducing procedure was repeated for 12 hours daily in the course of 5 days. SP and BE immunoreactivity in the hypothalamus and plasma and blood CORT level were determined radioimmunologically. Six groups of animals were formed: 1. control animals; 2. stressed animals; 3. rats which received DSIP in a dose of 60 nmol/kg one hour before decapitation; 3. rats to which DSIP was injected 24 hours before decapitation; 5. stressed rats to which DSIP was injected one hour before decapitation during the 5th exposure to stress; 6. stressed rats to which DSIP was injected 12 hours before the 5th exposure to stress, i.e. 24 hours before decapitation. Our experiments showed that DSIP administration induced marked changes in SP, BE, and CORT levels in the hypothalamus and blood plasma. This suggests that long-term stress-coping effects of DSIP in underlied by considerable changes in the content of other oligopeptides and hormones. Evidently, DSIP triggers these processes inducing a cascade of interrelated molecular reactions which are different in Wistar and August rats. It seems likely that DSIP administration stimulates the mechanisms of resistance in August rats to a lesser extent than in Wistar rats.