Effects of a Superactive Analogue of LH- RH on the Hypothalamo-Pituitary-Testicular Axis in Male Rats Pretreated with Estrogens

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Abstract
The effect of a highly active agonistic analogue of LH-RH on testicular weight and pituitary gonadotropin levels was studied in male rats previously treated with estrogens. These steroids induced a considerable depression of testicular weight. In the first experiment the treatment with a high dose (4 μg daily) of D-Ala-6-des-Gly-10-LH-RH-ethylamide, the superactive analogue used, further depressed testicular weight and pituitary gonadotropins. In a second experiment, the treatment with lower doses (100 ng daily) of the analogue in estrogen-treated rats induced a slight but significant stimulatory effect on testicular weight and pituitary FSH content. In the third experiment none of the three doses of the analogue used (1, 10, or 100 ng daily) modified testicular weight when the treatment was started shortly after the administration of estrogens. It is concluded that, according to the dose of the analogue used, it is possible to observe inhibitory or stimulatory effect on testes and pituitary gonadotropin levels.