Functional magnetic resonance imaging and the neurobiology of vasopressin and oxytocin.

Functional magnetic resonance imaging is used to assess the roles of vasopressin (AVP) in aggressive motivation and oxytocin (OXT) in maternal behaviour. In the case of aggression, male rats are triggered to show the autonomic signs of impending attack behaviour by simulating a resident/intruder conflict in the bore of the magnet during the imaging session. Intraventricular injection of AVP alone causes robust changes in brain activity mirroring many areas selective for AVP receptor binding and overlapped with many of the same areas activated during aggression. Pretreatment with an orally active AVP V1a receptor antagonist blocks aggression in bench-top studies and suppressed the pattern of brain activation caused by the intruder or administration of AVP. These findings using imaging corroborate and extended our understanding of the neural circuitry of aggression and the role of AVP neurotransmission in agonistic motivation. In the case of maternal behaviour, primiparous dams are imaged during nursing with and without OXT receptor blockade. Suckling alone activates many cortical and subcortical areas. Intracerebroventricular injection of OXT stimulates brain activity in areas selective to OXT receptor binding and overlap with many of the same areas activated during pup suckling. Pretreatment with OXT receptor antagonist suppresses the pattern of brain activation caused by suckling or administration of OXT. The data suggest that OXT may strengthen mother-infant bond formation partly by acting through brain areas involved in regulating olfactory discrimination, emotions and reward.