The analysis revealed that there was no significant change in the morphology of the visual nuclei in the three seasons. However, the activity of the NPY-ir cells was increased significantly in the breeding season in the three nuclei viz, HA, HP and RoT. During the breeding season, there was a significantly higher number of cells expressing NPY in all three nuclei than in pre-breeding and post-breeding phases. In addition, the area of NPY-ir cell fibers, most noticeably in the Glv, was significantly higher during the breeding season. Moreover, photoperiods have a significant effect on the expression of NPY in birds; interestingly, the area of NPY-ir cell fibers was greater during the breeding season away from day length. Since the breeding and post-breeding phases are characterized by visual activity, NPY may aid the activity in the visual centers. During the breeding season, the expression of NPY in the ROT, Glv, and TeO was significantly greater than in the post-breeding season and regressed phase. This indicates the importance of NPY in visual processes during mating season in birds such as Spotted Munias.
This work is the first ever report of the distribution of NPY in Spotted Munias. NPY is a peptide hormone which affects a variety of physiological processes. In birds, NPY is mainly produced in the telencephalon (Fig. 1), and produces anxiolysis and arousal, and to a lesser extent appetite, feeding, and circadian rhythm regulation. NPY is also known to modulate the development of feeding behavior. NPY is also needed to prevent seasonality disorders and to promote reproductive development. NPY is known to regulate firing rates of hypothalamic brain areas, and loss of NPY upregulation in humans causes hyperphagia and obesity. Because of the observed decrease in NPY levels in the brain in winter, it is possible that there is a decline in appetite and food intake. However, it does not affect reproduction or development significantly in Spotted Munias. This decline might be caused by the decline of NPY production or the inability of hypothalamic nuclei to respond, though it is still unknown whether this occurs due to the decline in the NPY levels or the inability of the hypothalamus to synthesize NPY. d2c66b5586