Influence of gonadotropic releasing hormone, luteinizing hormone and pineal extracts on testes of immature cockerels.

Two, seven, and ten-day-old S.C.W.L. cockerels were injected with pineal extract (PE), gonadotropic releasing hormone (GnRH) and luteinizing hormone (LH), alone or in combination, to determine the effect of PE on the action of exogenous GnRH and LH on the testis in immature cockerels. Radioactive phosphorus (P-32) uptake by the testis was used as an assay for gonadotropic activity. GnRH had no effects on cockerels aged two days. However, LH caused increased P-32 uptake compared to the saline control at this age. In seven- and ten-day-old cockerels, PE in combination with GnRH resulted in lower P-32 c.p.m./g. of testis compared to the non-PE treated birds at the same doses of GnRH. On the other hand, PE did not cause any decrease in testis response to LH. These results indicate that PE is acting to inhibit release of gonadotropins by GnRH.