Distribution and variation of neuropeptide Y in the brain of native Thai chicken

Abstract

Neuropeptide Y (NPY) plays a pivotal role in food intake and body weight regulation in both birds and mammals. Unlike imported broilers and layers, native Thai chicken, a tropical non-seasonal breeding species, has lower body weight and exhibits strongly maternal behaviors which, in turn, affect feeding behavior during the reproductive cycle. The aim of this study was to investigate the role(s) of NPY that might be associated with the reproductive cycle of female native Thai chickens using immunohistochemistry technique. The distributions of NPY-immunoreactive (-ir) neurons and fibers in the brain of laying and fasted chickens was also elucidated. Changes in body weight and number of NPY-ir neurons in the nucleus paraventricularis magnocellularis (PVN) were compared across reproductive stages. The results revealed that NPY-ir neurons and fibers were distributed throughout the brain with the greatest density located in the PVN. Differences in the number of NPY-ir neurons in the PVN were found across reproductive stages. The numbers were lowest in non-egg laying and egg laying stages and significantly higher during egg-incubating and chick-rearing stages. Changes in body weight were inversely related to the number of NPY-ir neurons across reproductive stages. In addition, food restriction caused an increase in NPY immunoreactivity, confirming the role of NPY in response to food restriction. Taken together, the present findings suggest that the NPYergic system in the PVN plays an important role in the regulation of food intake during the reproductive cycle in this non-seasonal breeding tropical species.

Distribution of dopamine-immunoreactive neurons in the brain of the male native Thai chicken

“…In this study, the primary and secondary antibodies used for detecting TH immunoreactivity were primary mouse ImmunoResearch Laboratories, Inc., West Grove, PA, USA) at 1:500 dilution with PBS, respectively. TH immunoreactivity using these antibodies has been previously described [26][27][28]42].…”

“…It expresses strong maternal behaviors which are inherited from the ancestor, the wild jungle fowl in Southeast Asia [36][37][38][39]. It is well documented that the neuroendocrine regulation of reproductive cycle and maternal behaviors are associated with GnRH, VIP, DA, PRL, MT, and neuropeptide Y in the female native Thai chickens [5,29,[40][41][42][43]. Presently, the neuroendocrine regulation of reproductive behaviors has been extensively studied in female native Thai chickens.…”

Distribution of neuropeptide Y in the brain of the male native Thai chicken

“…Similarly, in the female native Thai chickens, NPY-ir neurons and fibers are extensively distributed throughout the brain. The numbers of NPY-ir neurons within the PVN are low in non-egg laying and egg-laying stages and then markedly increase during incubating eggs and rearing chick stages and changes in body weight are found in the opposite direction of changes in the numbers of NPY-ir neurons across the reproductive stages [28]. Moreover, it has been suggested that the numbers of NPY-ir neurons within the PVN play a pivotal role in the transition from incubating to rearing behavior in the female native Thai chickens [29].…”

“…In birds, NPY is one of the most potent orexigenic regulators of food intake [5,[19][20][21][22]. Food deprivation enhances expression of NPY mRNA [23], neuron activity [24], and NPY contents in the nucleus paraventricularis magnocellularis (paraventricular nucleus; PVN) [25][26][27] NPY is involved in the regulation of the reproductive cycle and maternal behaviors in female native Thai chickens [28,29].…”

“…The anatomical distributions of NPY-immunoreactive (-ir) neurons and fibers in the brain of several avian species have been investigated including chicken [13,14,30,31], quail [30,32], pigeon [33,34], blackcapped chickadee, blue tit, great tit, dark-eyed junco [35], collared dove [36], domestic duck [37], and female native Thai chicken [28,29]. The distributions of NPY neurons and fibers have been mapped in several avian species and were found located in several regions of the brain such as the septalis lateralis (SL), nucleus suprachiasmaticus, pars medialis (SCNm), nucleus periventricularis hypothalami (PHN), regio lateralis hypothalami (LHy), PVN, nucleus rotundus (ROT), nucleus inferioris hypothalami (IH), and nucleus infundibuli hypothalami (IN) [13,14,[31][32][33][34][35][36][37].…”