Role of the medial amygdala projection to the ventrolateral part of the ventromedial nucleus of the hypothalamus in social defense

Abstract

Social relationships directly influence the survival and reproduction of species, with frequent disputes over resources in intraspecific contexts. In this sense, interactions between males often result in relationships of dominance and subordination, which can be studied using the resident-intruder paradigm. The model consists of placing an intruder in a box housing a conspecific, where offensive behavior predominates on the part of the resident in order to intimidate the intruder and defend his territory. On the other hand, the intruder's defensive behaviors, such as fleeing, fighting and freezing, are triggered by stimuli generated by the identification of the attack. In this context, chemical communication plays a significant role in this process, with pheromones released in the rodent's facial and anogenital secretions being picked up by the conspecific. These olfactory molecules are detected by sensory neurons in the vomeronasal organ responsible for routing signals to the accessory olfactory bulb, which directs them to the medial amygdala (MeA), where the information is processed and sent to the hypothalamic circuit responsive to the conspecific, which guarantees a proportional response to the situation. This project focuses on the projection of the MeA to the ventrolateral part of the ventromedial nucleus of the hypothalamus (VMHvl), a central region in the regulation of social behaviors, including social defense. We will explore, using optogenetics, whether inhibition of the MeA and the MeA projection to the VMHvl can influence social defense behavior. In doing so, we aim to understand some of the neural mechanisms behind social defense behavior, in order to provide insights into how sensory information from conspecifics is processed and translated into adaptive survival behaviors.