DSIP-INDUCED CHANGES IN THE CONTENT OF SU BSTANCE-P, BETA-ENDORPHIN, AND CORTICOSTERON IN RATS SUBJECTED TO EMOTIONAL-STRESS

The aim of this study was to investigate time-related changes in subst ance P (SP) beta-endorphin (BE), and corticosteron (CORT) levels induc ed by DSIP administration in;rats subjected to emotional stress. Exper iments 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 im munoreactivity in the hypothalamus and plasma and blood CORT level wer e determined radioimmunologically. Six groups of animals were formed: 1. control animals; 2. stressed animals; 3. rats which received DSIP i n 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 wh ich DSIP was injected one hour before decapitation during the 5th expo sure to stress; 6. stressed rats to which DSIP was injected 12 hours b efore 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 opigopeptides and hormon es. Evidently, DSIP triggers these processes inducing a cascade of int errelated molecular reactions which are different in Wistar and August rats. It seems likelly that DSIP administration stimulates the mechan isms of resistance in August rats to a lesser extent than in Wistar ra ts.