The neuroendocrine control of avian parental behaviour (#95)
Nest building and incubation in birds is a complex, exquisite parental behaviour that is characterised by regression of the ovary, cessation of egg laying and increased maternal defence of the nest and chicks. The neuroendocrine system plays a major role in regulating maternal behaviour in birds and changes in hormones such as prolactin and sex steroids are associated with this behaviour. For example incubation onset may be associated by increased prolactin secretion induced by tactile contact with the eggs and nest and a reduced activity of the hypothalamic- pituitary-adrenal (HPA) axis. However there are complex interactions between neuropeptides, environmental cues and neurotransmitters. Surprisingly the links between the environment, genes responsible for avian parental behaviour and role of the neuroendocrine and central nervous system has still to be elucidated. We have known for centuries, that broodiness in chickens is under genetic control, as different bird breeds display different levels of incubation tenacity. In a recent study using cDNA chip analysis, 11 known genes were shown to be up-regulated in the hen’s brain when she displays maternal behaviour. Excitingly, the mesotocin gene was one of those; mesotocin is a nonapeptide and the avian homologue of the hormone oxytocin. Oxytocin, and the related neuropeptide vasopressin and their receptors have been shown in mammals (e.g. rodents) to be vital for controlling social behaviours including maternal behaviour and expression of these nonapeptides is regulated by gonadal steroids. Here I will review our latest findings highlighting the neuroendocrine mechanisms associated with reproductive behaviours in birds. I will discuss the importance of nonapeptides in relation to nest building in the zebra finch (Taeniopygia guttata) and the relationship of nonapeptide binding in the brain and changes in the HPA axis in relation to incubation and parental behaviour in free-living birds such as the white crowned sparrow (Zonotrichia leucophrys).
Research Supported by BBSRC Strategic Roslin Institute funding to SLM.