Effects of Repeated Morphine Administration on Copulation and on the Hypothalamic-Pituitary-Gonadal Axis of Male Rats

Abstract
Adult male rats were administered morphine twice a day for 45 days and the effects of morphine on the copulation rate, the weight of various organs, and on the hypothalamic-pituitary-gonadal axis were examined. Morphine administered rats showed a loss of weight, hypertrophy of the adrenals, decreased weight of accessory sex organs, low sperm count, and decreased copulation rate. The contents of the luteinizing hormone releasing hormone in the hypothalamus and the luteinizing hormone [LH] in the pituitary remained unchanged. LH and testosterone levels decreased, but serum follicle-stimulating hormone levels increased. Morphine probably inhibits the hypothalamic-pituitary-gonadal axis and causes a diminution in the number of fertilizations of the partner females.