Behavioral/Systems/Cognitive Brain Oxytocin Correlates with Maternal Aggression: Link

The oxytocinergic system is critically involved in the regulation of maternal behavior, which includes maternal aggression. Because aggression has been linked to anxiety, we investigated the maternal aggression and the role of brain oxytocin in lactating Wistar rats selectively bred for high anxiety-related behavior (HAB) or low anxiety-related behavior (LAB) during the 10minmaternal defense test. HABdamsdisplayedmorematernal aggression against a virgin intruder comparedwith LABdams, resulting inmore defensive behavior and higher anxiety of HAB-defeated virgins. The different levels of aggression were accompanied by opposite oxytocin release patterns within the paraventricular nucleus (PVN; HAB, increase; LAB, decrease). Furthermore, oxytocin release was higher within the central nucleus of the amygdala (CeA) of HAB dams compared with LABs. A direct correlation between the offensive behavior displayed during the maternal defense test and local oxytocin release was found in both the PVN and CeA. Using retrodialysis, blockade of endogenous oxytocin actionby infusion of an oxytocin receptor antagonist (des-Gly-NH2,d(CH2)5[Tyr(Me) 2,Thr4]OVT) into thePVNorCeA reduced maternal aggressionofHABdams,whereas infusionof synthetic oxytocin into thePVNtended to increase aggression toward the intruder inLABdams.Therewereno significantdifferences inoxytocin receptormRNAexpressionoroxytocin receptorbindingbetween lactating HAB and LAB dams. Therefore, differences in intracerebral release patterns of oxytocin, rather than differences at the level of oxytocin receptors, are critical for the regulation of maternal aggressive behavior. Key words:microdialysis; stress; paraventricular nucleus; central nucleus of the amygdala; receptor; oxytoci