EFFECTS OF HYPNORM(R) (FENTANYL) ON ACTH/BETA-ENDORPHIN LEVELS IN PLASMA, PITUITARY AND BRAIN OF 10-DAY OLD RATS

Administration of Hypnorm(R), an anaesthetic containing the known mu-opiate receptor agonist fentanyl, elicited dose- and time-related elevation of plasma ACTH, beta-endorphin and corticosterone levels in 10-day old rat pups. Pretreatment with specific antibodies (raised against CRH, AVP and ACTH resp.) revealed that Hypnorm(R) administration activated the ACTH-corticosterone system in the 10-day old rat and its effect is mediated by CRH and/or AVP. Hypnorm(R) anaesthesia was associated with significant decrease in the ACTH and beta-endorphin levels in the pituitary lobes as well as in beta-endorphin content of the hypothalamus and medulla oblongata. Latter results may indicate that the beta-endorphinergic system in the brain of the 10-day old rat is activated by Hypnorm(R), an effect most probably elicited by the opiate agonist fentanyl.