Norbert Hajos of Indiana University - Bloomington will present a lecture entitled: A midbrain - amygdala pathway controls defensive behavior.
Abstract: Choosing appropriate behavior in a dangerous situation is essential for animals’ survival. In spite of many studies, the neural circuits controlling defensive behavior are still not fully uncovered. Recently, we identified a midbrain – amygdala pathway that regulates animal behavior under aversive conditions. Midbrain neurons giving rise to this pathway are present in the ventral periaqueductal grey/dorsal raphe nucleus (vPAG/DR) and express vasoactive intestinal polypeptide (VIP). Tacing studies show that they specifically innervate the bed nucleus of stria terminalis (BNST) and the central amygdala, two regions of the extended amygdala, which are known to be parts of survival circuits. These midbrain VIP neurons release glutamate on their postsynaptic partners demonstrated by in vitro electrophysiology combined with optogenetics. Using monosynaptic rabies virus tracing, we found that these excitatory VIP neurons receive synaptic inputs mainly from the hypothalamus, the midbrain reticular formation and their target areas, the BNST and central amygdala. Selective expression of tetanus toxin light chain in vPAG/DR VIP neurons - an intervention that blocks neurotransmitter release from the axon terminals - resulted in reduced contextual fear memory and predatory odor aversion. Thus, our data revealed that this midbrain excitatory pathway controls a set of behavioral outcomes under challenging situations by impacting directly amygdalar circuits.