Changes in Gene Expression in the Locus Coeruleus-AmygdalaCircuitry in Inhibitory Avoidance PTSD Model

Abstract The locus coeruleus (LC)-amygdala circuit isimplicated in playing a key role in responses to emotionallyarousing stimuli and in the manifestation of post-traumaticstress disorder (PTSD). Here, we examined changes ingene expression of a number of important mediators of theLC-amygdala circuitry in the inhibition avoidance modelof PTSD. After testing for basal acoustic startle response(ASR), rats were exposed to a severe footshock (1.5 mAfor 10 s) in the inhibitory avoidance apparatus. They weregiven contextual situational reminders every 5 day for25 days. Controls were treated identically but with thefootshock inactivated. Animals were re-tested on secondASR and decapitated 1 h later. The shock group hadenhanced hyperarousal and several changes in geneexpression compared to controls. In the LC, mRNA levelsof norepinephrine (NE) biosynthetic enzymes (TH, DBH),NE transporter (NET), NPY receptors (Y1R, Y2R), andCB1 receptor of endocannabinoid system were elevated. Inthe basolateral amygdala (BLA), there were markedreductions in gene expression for CB1, and especially Y1R,with rise for corticotropin-releasing hormone (CRH) system(CRH, CRH receptor 1), and no significant changes inthe central amygdala. Our results suggest a fast forwardmechanism in the LC-amygdala circuitry in the shockgroup.Keywords Cannabinoid receptor Corticotropin-releasinghormone Neuropeptide Y Neuropeptide Y1 and Y2receptors Norepinephrine transporter Tyrosinehydroxylas