Pregnancy-induced analgesia: effects of adrenalectomy and glucocorticoid replacement

During pregnancy, rats show a progressive increase in jump threshold which is followed by a precipitous decrease after delivery. Overall, this pattern of change in pain threshold was not affected by adrenalectomy, with or without corticosterone replacement. It appears, therefore, that the adrenal glands are not necessary for the manifestation of opioid analgesia during pregnancy.