Neuropeptide Y at the crossroads of male reproductive functions in a seasonally breeding reptile, Hemidactylus flaviviridis

Abstract

Neuropeptide Y (NPY) is known to be a key regulator of reproductive functions across vertebrates. Its role in the modulation of gonadotropin releasing hormone (GnRH) has been extensively explored in mammals and fishes. However, no such report exists in aves, amphibians, or reptiles. Hence, the present study aimed to develop an insight into reproductive phase-dependent expression and role of NPY in the diencephalon region of male wall lizards. Expression of ligand, npy, and its receptor, npyr varied across the annual reproductive cycle of Hemidactylus flaviviridis with the highest expression of both observed during recrudescence. Further, the diencephalon region of recrudescent wall lizards treated with NPY demonstrated an increased mRNA level of gnrh and its receptor, gnrhr. In addition, the current study also elucidates hormonal regulation of diencephalonic npy and npyr wherein neuropeptides like kisspeptin and substance P, the gonadotropin, FSH, as well as sex steroids, dihydrotestosterone (DHT) and 17β-estradiol (E₂) inhibited npy and npyr expression in the diencephalon region of wall lizards. With regard to adipokines, leptin stimulated while nesfatin-1 inhibited diencephalonic npy and npyr expression. In conclusion, the current study is the first to present a comprehensive picture of reproductive phase-specific expression pattern, role, and hormonal regulation of neuropeptide Y in the diencephalon region of the male wall lizard, H. flaviviridis.