Acute and chronic morphine effects on plasma corticosteroids and growth hormone in the cat

(1) Low doses of intravenous morphine in the cat caused an elevation of both corticosteroid and growth hormone in plasma. (2) Corticosteroid levels did not continue to increase in concert with the dose of morphine but the level of growth hormone did. (3) Tolerance developed to the effects of morphine on corticosteroids but not to the effect on growth hormone. (4) Naloxone precipitated withdrawal was associated with an increase in plasma corticosteroid but not growth hormone.