The role of corticosteroids in analgesic effect caused by stimulation of the periaqueductal gray matter of the midbrain in rats

: The effects of stimulation of periaqueductal gray matter on pain threshold and blood corticosterone level were studied in anesthetized rats. The stimulation resulted in a alteration of analgesia and corticosterone level. Stimuli-induced analgesia was decreased by adrenalectomy. Corticosterone implantation (50 micrograms) in periaqueductal gray matter resulted in the increase of analgesia. Pretreatment with naloxone (1 mg/kg) failed to modify the effect of stimulation of periaqueductal gray matter on analgesia and corticosterone level. Our results indicate the involvement of corticosterone in the analgesia induced the stimulation of periaqueductal gray matter.