Spermatogenesis in photostimulated Red-winged Blackbirds (Agelaius phoeniceus) chronically treated with a potent gonadotropin releasing hormone analogue

Abstract

To study the effect of a gonadotropin releasing hormone analogue (GnRH-A) on male Red-winged Blackbirds, birds received 13 (experiment 1) or 14 (experiment 2) consecutive daily injections of saline (control group) or GnRH-A during photoperiodically induced testicular growth. GnRH-A did not modify the diameter of the seminiferous tubules in treated groups compared with saline-injected controls. However, the thickness of the germinal epithelium was significantly reduced in groups receiving 0.1, 1.0, 10.0, or 20.0 μg of GnRH-A. Redwings showing disturbed spermatogenesis were significantly more frequent in the GnRH-A treated groups than in the control group. Moreover, there was a dose–response effect, since the proportion of redwings showing disturbed spermatogenesis increased with increasing doses of GnRH-A. Hyperplasia of the interstitial cells was frequent in GnRH-A treated birds compared with control birds, except for the group which received 0.01 μg of GnRH-A. These experiments show that chronic treatment with GnRH-A impairs spermatogenesis in Red-winged Blackbirds treated during testicular growth.