EFFECTS OF PINEAL INDOLES AND PARACHLOROPHENYLALANINE ON SEASONAL REPRODUCTION IN THE PIGEON

The effect of melatonin, methoxytryptophol (ML), methoxytryptamine (MT ) and parachlorophenylalanine (p-CPA) on the mass and histology of the testes and the adrenal and thyroid glands and on serum thyroid hormon e levels have been studied in the recrudescent phase of the feral pige on Columba livia. All the pineal indoles showed a common anti-gonadal effect, resulting in the arrest of spermatogenesis and the degeneratio n of germ cells. Treatment with melatonin resulted in adreno-cortical enlargement and medullary hypertrophy, whereas ML, MT and p-CPA induce d medullary enlargement and hypertrophy without having much influence on the cortex. Treatment with melatonin and ML brought about colloid r etention in the thyroid follicles, while MT and p-CPA induced colloid depletion and hypertrophy of the follicular epithelium. From the prese nt study, it can be concluded that both pineal indoles and p-CPA induc e testicular regression in the breeding phase but do so by different m echanisms.