The effect of air puff stress on c-Fos expression in rat hypothalamus and brainstem: central circuitry mediating sympathoexcitation and baroreflex resetting

Teri M. Furlong, Lachlan M. McDowall, Jouji Horiuchi, Jaimie W. Polson and Roger A. L. Dampney European Journal of Neuroscience, pp. 1–10, 2014 doi:10.1111/ejn.12521 In response to psychological stress there is an increase in sympathetic nerve activity (SNA). The purpose of this article is to determine if this increase in SNA is because of activation of the RVLM in response to psychological stress. They looked at c-fos expression in the brain along with a retrograde tracer injection into NTS in order to determine if there are other areas projecting to NTS that may be involved in the psychological stress response. So rats were exposed to air puffs this is considered an unconditioned stressor. The control group did not receive the air puff exposure. The results showed that that there was a significant increase in c-fos in PVN, DMH, PeF, LH, MeA, BLA, dorsomedial, dorsolateral and ventrolateral PAG, LC, the VLM, and the medial portion of the NTS when compared to controls. They also looked at TH immunoreactivity and found that there were very few TH positive and c-fos neurons in the RVLM. They did see a significant amount of C-fos and TH positive neurons in the CVLM in the stressed group when compared to controls. They also looked at serotonin and found that there was a significant increase in c-fos and 5-HT labelled cells in the lateral portion of the mid line raphe in stressed rats compared to controls. They looked at the retorgradely labelled cells and found that CTB labelled cells in th PVN,DMH, PeF LH, CeA lateral PAG, PB there was only a significant number of CTB and c-fos found in PVN PeF and vlPAG when compared to controls. These data suggests that there are several regions that play role in sympathetic activation in response to psychological stress however the RVLM is not a major player.-MD