Vasopressin and the anterior olfactory nucleus

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Most mammals recognise other individuals by smell. Sometimes, some of these individuals are accorded a special status, such as when a bond is formed between a mother and offspring or between sexual partners in monogamous species, and in these cases an olfactory memory is forged in the olfactory bulb. Neuropeptides - a class of messenger molecules that mediate prolonged interactions between neurones, play a very important part in the formation of such memories. For example, oxytocin released in the mother's brain during parturition helps to establish the olfactory signatures of the offspring as memorable. The converse of social attachment is rejection of, or aggression towards, individuals who are recognized as intruders or competitors. For this, another neuropeptide, vasopressin, is important. Vasopressin is involved in the processing and/or integration of olfactory stimuli, and in particular it seems to couple socially relevant olfactory cues to an appropriate behavioural response. The anterior olfactory nucleus is the key part of the brain involved in processing odour information and sending that information to brain areas involved with behaviour and memory. Our work is focused on newly discovered nerve cells within this nucleus that make and release vasopressin. The aim of this proposal is to understand vasopressin's role in social recognition and how it can trigger a change in aggressive behaviour; we will study how vasopressin affects the olfactory system and how it is involved in forming olfactory memories there. In this proposal we will be studying how the activity of the vasopressin neurons in the olfactory system is affected by socially relevant olfactory stimuli, how vasopressin influences the processing of information in the olfactory system, and how blocking the actions of vasopressin in this system affects social behaviour. These studies will all be performed in rats, and will use a range of tests devised to study social behaviours.In the elderly, progressively increasing social dysfunction is a major aspect impairing quality of life. At present it is hard to judge the contribution of neural and cognitive degradation to this, as we have only a fragmentary understanding of the neurobiology of social behaviour. By studies of the neurobiology of social behaviour in the simpler system of rats, we expect to contribute to the foundations of an understanding that will inform a more sophisticated understanding of the neurobiology of social behaviour in humans. Other nerve cells release many different neuropeptides, and these have very diverse and powerful effects on other emotions and behaviours, including stress-related behaviours and appetite. Understanding how neuropeptides act is important because drugs that mimic them may be valuable therapeutically for particular behavioural disorders.