Pineal-adrenal interactions in domestic male pigeon exposed to variable circadian light regimes and exogenous melatonin.

OBJECTIVE

This study was aimed to see the histophysiological changes of the pineal and adrenal glands under altered photoperiodic conditions due to the administration of melatonin in the male domestic pigeon, Columba livia Gmelin.

METHODS

Young adult male domestic pigeons were exposed to long photoperiod (LP; 20 hr light: 4 hr dark), short photoperiod (SP; 4 hr light: 20 hr dark) exogenous melatonin (MEL; 20 microg/100 g body weight/day) was administered for 60 days in the primary breeding and regressive phase. At the end of experiment, adrenal and pineal glands were quickly dissected and processed for histology, ultrastructure study, biochemical, histochemical and immunohistochemical analysis.

RESULTS

In the primary breeding phase, the number of mitochondria and rough endoplasmic reticulum were increased in the adrenal gland in MEL-LP group, while lipid granules were also increased in the subcapsular zone. In MEL-SP treated group, however, the number of mitochondria decreased. Pinealocytes were increased in size and well-developed Golgi complexes were present near the cell nucleus after induction with MEL-LP treatment during the primary breeding phase. No remarkable changes were noticed in the number of mitochondria. In the regressive phase-I, the adrenocortical cytoplasm showed similar morphological features both in MEL-LP treatment and control groups. In pinealocytes, few rough endoplasmic reticulum and lipid droplets and moderate number of mitochondria were present. In MEL-SP treatment, increased number of mitochondria in the adrenocortical cells and decreased nuclear diameter of the pinealocytes were noticed. Few mitochondria were observed within the pinealocyte cytoplasm. Side chain cleavage enzyme (immunocytochemical) activity was increased in the subcapsular zone in MEL-LP treated group.

CONCLUSIONS

The present data indicates that the changes in pineal and adrenocortical tissue histophysiology might be due to melatonin rhythm and light/dark regime which act as a modulator in the male domestic pigeon.