Neuropeptide AF differentially affects anorexia in lines of chickens selected for high or low body weight

The recently discovered anorectic effect of neuropeptide AF (NPAF) has not been studied in hypo-and hyperphagia animal models. The present study was designed to examine possible differences in appetite-related effects after central NPAF administration in lines of chickens that had undergone long-term divergent selection for low (LWS) or high (HWS) body weight and exhibit hypo- and hyperphagia, respectively. LWS chicks responded at a similar magnitude of food intake reduction to all doses of NPAF tested at all observation times. HWS chicks had an increased latency (150 min versus 30 min post injection) and an increased dose threshold of response (8 nmol versus 2 nmol) than LWS chicks. Water intake of LWS chicks was reduced in all doses tested at all observation times, whereas HWS chicks responded to the three doses of NPAF tested up to 60 min post injection, after which the decrease was sustained only at a dose of 8 nmol. In a comprehensive behaviour analysis, exploratory pecks, food pecks and locomotion were significantly reduced in both lines by NPAF, whereas sit time was increased in both lines. Other behaviours, including stand time, deep rest time and escape attempts, were not affected. These data suggest that the threshold of NPAF-induced anorexia is lower in LWS than HWS chicks and that NPAF-induced anorexia is a primary effect in both lines, and also support the hypothesis that differences exist in the central NPAF system between hypo- and hyperphagic individuals.