Roles of hypothalamus and midbrain on the respiratory response during acute psychological stress

Abstract

Acute psychological stress evokes various vital reactions, including autonomic and endocrine responses. The autonomic response is thought to be originated from the defensive reaction and it has been classically reported that the centers for the defensive reaction are located in the lateral hypothalamic area (LHA) and the midbrain periaqueductal gray (PAG). The LHA is further divided into few areas including dorsomedial nucleus (DMN) and perifornical area (PeF) and artificial stimulations of these 2 areas evoke enhancement of respiratory function accompanying with pressor and tachycardic responses. In addition, there are subpopulation neuron groups participating in the autonomic functions in the DMN so that it has been shown that neurons in the DMN are not "command neuron". In contrast, stimulation of neurons in the dorsolateral PAG also increased the phrenic nerve activity and the sympathetic nerve activity (SNA) simultaneously. Furthermore, the increases in the phrenic burst and the SNA evoked by the PAG stimulation are mediated via neurons in the DMN. Thus, it is possible that neurons in the dorsolateral PAG are "command neurons" for the autonomic response evoked by the acute psychological stress.