Neural mechanisms of predatory aggression in rats—Implications for abnormal intraspecific aggression

Abstract

Our recent studies showed that brain areas that are activated in a model of escalated aggression overlap with those that promote predatory aggression in cats. This finding raised the interesting possibility that the brain mechanisms that control certain types of abnormal aggression include those involved in predation. However, the mechanisms of predatory aggression are poorly known in rats, a species that is in many respects different from cats. To get more insights into such mechanisms, here we studied the brain activation patterns associated with spontaneous muricide in rats. Subjects not exposed to mice, and those which did not show muricide were used as controls. We found that muricide increased the activation of the central and basolateral amygdala, and lateral hypothalamus as compared to both controls; in addition, a ventral shift in periaqueductal gray activation was observed.Interestingly, these are the brain regions from where predatory aggression can be elicited, or enhanced by electrical stimulation in cats. The analysis of more than 10 other brain regions showed that brain areas that inhibited (or were neutral to) cat predatory aggression were not affected by muricide. Brain activation patterns partly overlapped with those seen earlier in the cockroach hunting model of rat predatory aggression, and were highly similar with those observed in the glucocorticoid dysfunction model of escalated aggression. These findings show that the brain mechanisms underlying predation are evolutionarily conservative, and indirectly support our earlier assumption regarding the involvement of predation-related brain mechanisms in certain forms of escalated social aggression in rats.

Nucleus Accumbens Dopamine Receptor 1 Expressing Neurons Are Instrumental in Appetitive Aggression

“…Finally, Golden et al (2019) indicate that the NAc shell may be more important than the NAc core in the mediation of appetitive aggression. This aligns with previous literature showing that the NAc shell receives inputs from the VTA and projects to the lateral hypothalamus (LH), a region commonly implicated in aggression (Tulogdi et al, 2015). The differential activation between the NAc shell and core is of particular interest because the NAc shell has been previously shown to have a role in formulating the value of reward, whereas the NAc core was associated with motivation to overcome response costs (West and Carelli, 2016).…”

“…The LH has been previously associated with predatory aggression in rats and cats, and the VMH has been identified as key in the generation of attack behavior. (Tulogdi et al, 2015). The LH receives axon projections from multiple nuclei that have roles relating to appetitive aggression including the arcuate nucleus and the central amygdala.…”

Two types of aggression in human evolution

“…Tulogdi et al (59) found that both feeding attacks and proactive aggression were associated with innervation of the central and basolateral amygdala, the lateral hypothalamus, and the ventrolateral periaqueductal gray. By contrast, reactive aggression among rats was associated with the medial amygdala, the mediobasal hypothalamus, and the dorsal periaqueductal gray (59,60,62). These differences in rat innervation between proactive and reactive aggression were the same as those found in cats between quiet biting attacks and affective defensive behavior.…”

“…The results of Tulogdi et al (59,60) indicate the existence of two different pathways in a key neural circuit underlying aggression. They thereby conform to much other evidence of differential innervation for the two types of aggression in humans.…”

“…A key finding was that feeding attacks and within-species aggression were not only ethologically similar but were also controlled by overlapping neural mechanisms, distinct from those supporting reactive aggression (59,60). In rats, as in other mammals, aggression is importantly modulated by a neural circuit that links the amygdala, hypothalamus, and periaqueductal gray (61).…”