Short-term fasting enhances food seeking behaviour and increases hypothalamic neuropeptide Y mRNA expression in Japanese quail (Coturnix japonica) chicks

The regulation of feeding is a complex interaction between central and peripheral signalling governed centrally by the melanocortin system comprising specific neuronal populations and circuits in the hypothalamus and brainstem. Little is known about the central mechanisms regulating the onset of appetite in birds in early life and here we investigated how changes in nutritional status and food availability effect the hypothalamic pathways modulating appetite in young Japanese quail (Coturnix japonica). Nine-day old female and male chicks housed on 19L:5D, were randomly assigned to FED (control, ad libitum feeding) or FASTED (food removed at lights off and 4 hour fast from lights on) groups. FASTED chicks exhibited significantly lower body and gut weights as well as lower blood glucose levels compared to FED controls and no sex differences were observed. FASTED chicks also displayed more depolarised resting membrane potentials resulting in higher rates of spontaneous action potential firing in arcuate nucleus neurones using patch clamp electrophysiology. RFID PIT tag data and behavioural analysis of video recordings showed that FED and FASTED chicks rested and rarely fed or drank during darkness. Following lights on all chicks immediately exhibited food-seeking behaviour and the feeding station was visited with increased frequency during the first 2h of lights on; FASTED chicks showed more food seeking behaviour compared to FED chicks. RT-qPCR analysis showed increased hypothalamic mRNA expression for neuropeptideY (NPY), but not its receptor (NPYR1 or NPYR2), agouti-related peptide (AgRP), proopiomelanocortin (POMC), cocaine-and-amphetamine-regulated transcript (CART), gonadotrophin inhibitory hormone (GnIH) or its receptor (GnIHR, GPR147) in FASTED chicks. Despite conserved peptide signalling among vertebrates, these findings suggest that there are some functional differences in the neuropeptide mechanisms regulating food intake in birds compared to mammals