cFOS and pCREB activation and maternal aggression in mice

Lactating mice exhibit a dramatic increase in aggression, termed maternal aggression, only in association with the rearing and protection of their offspring. Previous work indicates that the neural mechanisms underlying maternal and male aggression are different in rodents. In this study, we sought to examine possible neural regions involved in the control of maternal aggression by combining behavioral testing with immunohistochemistry for both cFOS and pCREB, two indirect markers of neuronal activity. All lactating female mice were exposed to a male intruder for 20 min and those exhibiting maternal aggression were placed in one group and those that were non-aggressive were placed in a second group. Thus, the sensory stimuli were similar and the main difference between the two groups was the behavior. cFOS expression increased significantly in the claustrum, bed nucleus of the stria terminalis, medial preoptic nucleus, paraventricular nucleus, medial amygdala, and cortical amygdala in association with maternal aggression. In contrast, the number of pCREB-positive cells significantly increased only in the ventrolateral portion of the caudal periaqueductal gray and in the lateral septum in aggressive lactating mice. Due to large variance in the counts of pCREB-positive cells, the data were log transformed prior to statistical analysis. Thus, the sites of cFOS and pCREB increases do not overlap, but provide complementary indirect information on neural regions active during maternal aggression. These results complement previous studies of nitric oxide release during maternal aggression to create a possible map of the functional neural circuitry underlying maternal aggression.