We previously reported behavioral and electrophysiological evidence indicating that superior cervical ganglia (SCG) from rats that developed hypertension as a result of chronic psychosocial stress expressed ganglionic long-term potentiation (gLTP) in vivo. In the present study, we present additional supportive evidence by measuring changes in protein levels of essential signaling molecules in ganglia from chronically stressed rats. We compared protein levels of essential, LTP-related signaling molecules in ganglia isolated from chronic stress-hypertensive rats, known to have expressed gLTP, with those of the same molecules in normal ganglia 1h after eliciting gLTP by high frequency stimulation (HFS) in vitro. Immunoblot analysis showed a significant increase in the levels of phosphorylated CaMKII, total CaMKII, nitric oxide synthase (NOS-1), and calmodulin in SCG from both chronically stressed rats and from normal rat ganglia in which gLTP was expressed by HFS in vitro. Additionally, there was a parallel reduction in calcineurin protein levels in ganglia from both groups. The present results confirm that ganglia from stressed rats have expressed gLTP in vivo and that synaptic plasticity in sympathetic ganglia may involve a molecular cascade largely similar to that of LTP in the hippocampal CA1 region.