The effects of opiate agonists: morphine, fentanyl, D-Met-Pro-enkephalinamide, U-50-488H, Met-enkephalin and beta-endorphin have been measured on plasma growth hormone level of male rats in the morning and in the afternoon. The p.m. increase in GH release induced only by Met-enkephalin and beta endorphin were significantly greater than the morning response. The increase of GH secretion when injecting morphine D-Met2-Pro5-enkephalinamide as well as the decrease following U-50-480H administration was similar at both periods of measurements. The diurnal changes in opiate sensitivity were decreased by 30 days, gonadectomy, while adrenalectomy was ineffective in this respect. Testosterone replacement in castrated rats reestablished the daily alteration of GH response to Met-enkephalin and beta endorphin.
|Number of pages||9|
|Publication status||Published - Jan 1 1991|
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Clinical Neurology
- Psychiatry and Mental health