The effects of exogenous androgen on the testicular cycle of the weaver-finch Quelea quelea

Abstract

Adult male weaver-finches ( Quelea quelea) subjected to a stimulatory 17-hour daylength when in full breeding condition, are driven through their breeding phase into the regeneration period with its accompanying testicular regression. But daily injections of 1 mg testosterone propionate prevent testicular collapse and gonads are maintained in full breeding condition for as long as the androgens are administered. Withdrawal of the hormone is followed by a very rapid decrease in testis size and a depression of spermatogenetic activity. This consequence occurs whether the injections are terminated during the regeneration or during the acceleration phase. Androgen administration to birds already in the regeneration phase results in a marked gonadotropic effect and there is a rapid build up of spermatogenetic activity, whereas uninjected controls display regressed testes with only inactive spermatogonia. Injections given to birds in the early stages of the acceleration phase produce a depressive effect and suggest an antagonism between androgen and gonadotropin during this period. Prolonged treatment with exogenous androgens produces no apparent atrophic effects on the interstitial tissue of weaver-finches, but there is no way of determining whether its secretory function is in any way affected.