Relevance of dorsomedial hypothalamus, dorsomedial division of the ventromedial hypothalamus and the dorsal periaqueductal gray matter in the organization of freezing or oriented and non-oriented escape emotional behaviors.

Electrical stimulation of the periaqueductal gray matter and ventromedial hypothalamus in humans showed the involvement of both these structures in panic attacks. The aim of this work was to make clear the role of dorsal periaqueductal gray (dPAG) matter, dorsomedial hypothalamus (DMH) and the dorsomedial part of the ventromedial hypothalamus (dmVMH) in panic attack-like behaviors. DMH, dmVMH and dPAG of Wistar rats were treated with N-methyl- d-aspartic acid (NMDA) at different doses. The rodents were then kept in a polygonal arena with a burrow to record panic attack-like responses and oriented defensive behaviors. In dmVMH, 6nmol of NMDA elicited alertness, freezing and oriented escape. The same set of behaviors was elicited by DMH neurons when stimulated by 9nmol of NMDA. Treatment of dmVMH with 9nmol of NMDA elicited typical explosive behaviors followed by freezing and oriented behaviors. The stimulation of the dPAG with NMDA at different doses provoked alertness and freezing (1nmol) or alertness, freezing, tail twitching, explosive behavior and oriented escape (3nmol), and explosive behavior followed by long-lasting freezing (6nmol). These data suggest that mainly dPAG plays a role in panic attack-like behaviors that resemble panic syndrome in humans. However, hypothalamic nuclei like dmVMH that mainly elicits oriented escape, can also produce explosive reaction when stimulated with 9nmol NMDA, whereas, DMH plays a role in coordinating defensive behaviors.