Platelet α2-adrenergic receptor coupling efficiency to Gi protein in subjects with post-traumatic stress disorder and normal controls

Low platelet membrane α2-adrenergic receptor (α2AR) density and low basal and forskolin-stimulated cyclic adenosine monophosphate responses, which have been reported in post-traumatic stress disorder (PTSD), suggest either abnormal α2AR coupling to Gi protein or dysregulation in post-receptor signal transduction mechanisms. α2AR density in the high- and low-conformational states, agonist affinity in both states and coupling to Gi protein were investigated in 23 drug-free combat PTSD patients and 25 normal controls. α2AR coupling measures were not different between PTSD patients and controls. Total α2AR density was higher in PTSD patients than controls, due to a higher density of the receptor in the high-conformational state. There were no differences in agonist affinity to the receptor in either conformational state. Results rule out dysregulation in α2AR coupling to Gi protein. Studies of post-receptor signal transduction mechanisms are warranted.