Journal of Endocrinology and Reproduction

Sanjeev Kumar Yadav ¹, Chandana Haldar ¹

Affiliations
1 Pineal Research Laboratory, Department of Zoology, Banaras Hindu University, Varanasi 221005, IN

Abstract

Avian immunology is a fascinating and growing field. Ecologists are now taking an interest in measuring immune-competence and determining its importance as a heritable trait for the survival of the wild species. Seasonally breeding animals encounter different environmental challenges throughout the year. In order to survive in specific environments these animals have developed various strategies that help them to find food, protect themselves from the tough environments, and also reproduce accordingly. Indeed, wild birds are continually challenged with different natural stressors such as shortage of food (during winter and rainy season), lack of water during summer, predator pressure in social system, sudden change in weather, season-bound diseases, infection (like avian influenza), etc. Only a few ecological studies have analyzed the stress and general immunity in wild birds that might have a link with the anti-stress hormone melatonin. Therefore, approaches improving our understanding of the stress-induced immune depression and their interrelationship in birds are most desirable. Unfortunately, our knowledge of the immune system has advanced at a much faster pace for mammals while immunology of wild birds received less attention. The purpose of this review is to bring together the current knowledge on the biological effects of melatonin on avian immune defense with special emphasis on new immerging area of neuro-immuno-endocrinology i.e., eco-immunology.

Keywords

Eco-Immunology, Stress, Immunity, Birds, Melatonin.

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Chandana Haldar ¹, Sanjeev Kumar Yadav ¹, Sweta Arora ¹

Affiliations
1 Pineal Research Lab, Department of Zoology, Banaras Hindu University, Varanasi – 221005, Uttar Pradesh, IN

Abstract

Photoperiod influences circulatory Melatonin (Mel) and hypothalamic functions via retino-hypothalamic tract. However, interrelation between Mel receptors and Arginine Vasotocin (AVT), a water-electrolyte balancing hormone receptor expression in hypothalamic regions of avian brain has never been explored. We noted the expression pattern of two Mel receptors (Mel1a & Mel1b) along with AVT, in terms of neuronal immuno-positivity, in hypothalamic region of Japanese quail under different photoperiodic conditions with/without melatonin treatment. This is interesting and equally important because both Mel and AVT levels are regulated by light/dark cycle. Confocal imaging revealed specific regional localization of Mel1a/Mel1b in Supra-Chiasmatic Nucleus (SCN), Supra-Optic Nucleus (SON) and Para-Ventricular Nucleus (PVN), the intensity of which was dependent on the photoperiodic condition (long day, LD or short day, SD) and melatonin treatment. Mel1a/Mel1b was mostly co-localized along with AVT. Mel1b was abundant in hypothalamic regions in contrast to the Mel1a as reported in mammals. Mel1a immune-positivity was detected in SCN and SON regions of brain. Compared to control birds, a high intensity of Mel1a immunoreactivity was found in hypothalamic regions of birds under short photoperiod (SD, 8h L: 16h D) after Mel treatment. Further, Mel1b immunopositivity was high only in birds exposed to long days (LD, 16h L: 8h D). In SCN, abundant Mel1a and AVT immunoreative cells were found in Mel pretreated and SDexposed birds compared to LD-exposed ones. Mel1a and AVT immunoreative cells were less in PVN of both SD and LD exposed birds. Our data of co-localization of Mel receptor(s) along with AVT in hypothalamic regions (exposed to short or long days with/without melatonin administration) strongly suggest a role for Mel along with AVT in water-electrolyte balance of birds which is important during long duration nuptial migration/flight.

Keywords

Co-Localization, Hypothalamus, Melatonin/AVT, Quail, Receptor, Water-Electrolyte Balance.

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