Calmodulin and guanylyl cyclase inhibitors block the in vivo expression of gLTP in sympathetic ganglia from chronically stressed rats

Previous work from this laboratory indicated that superior cervical ganglia from rats exposed to chronic psychosocial stress expressed ganglionic long-term potentiation (gLTP) in vivo. In the present study, we report additional pharmacological evidence indicating involvement of calmodulin and guanylyl cyclase in gLTP, and supporting the in vivo gLTP expression in ganglia from chronically stressed rats. Pretreatment with the calmodulin inhibitors W-7 (5 μM) or calmidazolium (5 μM) or with guanylyl cyclase inhibitor LY-83583 (5 μM) completely blocked HFS (20 Hz/20 s)-induced gLTP in superior cervical ganglia isolated from normal rats. Along with that, inhibition of apparent basal ganglionic transmission by W-7 (5 μM), calmidazolium (5 μM) or LY-83583 (5 μM) is observed in ganglia isolated from chronically stressed rats, but not in those from control rats, indicating in vivo expression of gLTP in ganglia isolated from stressed rats. The present results confirm the involvement of both calmodulin and GC activities in gLTP, and indicate that ganglia from stressed rats may have expressed gLTP in vivo, which is known to precipitate hypertension in these animals.