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Seasonal Plasticity in the Peptide Neuronal Systems: Potential Roles of Gonadotrophin‐Releasing Hormone, Gonadotrophin‐Inhibiting Hormone, Neuropeptide Y and Vasoactive Intestinal Peptide in the Regulation of the Reproductive Axis in Subtropical Indian Weaver Birds
Author(s) -
Rastogi A.,
Rani S.,
Kumar V.
Publication year - 2015
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/jne.12274
Subject(s) - vasoactive intestinal peptide , medicine , endocrinology , hypothalamus , neuropeptide y receptor , biology , neuropeptide , gonadotropin releasing hormone , hormone , luteinizing hormone , receptor
Two experiments examined the expression of gonadotrophin‐releasing and inhibiting hormones (Gn RH ‐I, Gn RH ‐ II and Gn IH ), neuropeptide Y ( NPY ) and vasoactive intestinal peptide ( VIP ) in subtropical Indian weaver birds, which demonstrate relative photorefractoriness. Experiment 1 measured peptide expression levels in the form of immunoreactive (‐IR) cells, percentage cell area and cell optical density in the preoptic area (Gn RH ‐I), midbrain (Gn RH ‐ II ), paraventricular nucleus (Gn IH ), mediobasal hypothalamus [dorsomedial hypothalamus ( DMH) , infundibular complex ( IN c), NPY and VIP ] and lateral septal organ ( VIP ) during the progressive, breeding, regressive and nonbreeding phases of the annual reproductive cycle. Gn RH ‐I was decreased in the nonbreeding and VIP was increased in IN c in the breeding and regressive states. Gn RH ‐ II and NPY levels did not differ between the testicular phases. Double‐labelled immunohistochemistry (IHC) revealed a close association between the Gn RH /Gn IH , Gn RH / NPY , Gn RH / VIP and Gn IH / NPY peptide systems, implicating them interacting and playing roles in the reproductive regulation in weaver birds. Experiment 2 further measured these peptide levels in the middle of day and night in weaver birds that were maintained under short days (8 : 16 h light /dark cycle; photosensitive), exposed to ten long days (16 : 8 h light /dark cycle; photostimulated) or maintained for approximately 2 years on a 16 : 8 h light /dark cycle (photorefractory). Reproductively immature testes in these groups precluded the possible effect of an enhanced gonadal feedback on the hypothalamic peptide expression. There were group differences in the Gn RH ‐I (not Gn RH ‐ II ), Gn IH , NPY and VIP immunoreactivity, albeit with variations in immunoreactivity measures in the present study. These results, which are consistent with those reported in birds with relative photorefractoriness, show the distribution and possibly a complex interaction of key neuropeptides in the regulation of the annual reproductive cycle in Indian weaver birds.