Repeated electroconvulsive shock increases tachykinin and cholecystokinin mRNA expression in ventral periaqueductal gray

The effect of repeated electroconvulsive shock (five shocks during 10 days) on preprocholecystokinin and preprotachykinin-A messenger RNA expression was studied in the mesencephalic periaqueductal gray and adjacent areas of rat using in situ hybridization histochemistry with specific oligonucleotide probes. An increased number of preprocholecystokinin and preprotachykinin-A messenger RNA hybridization positive neurons (+ 30% and +47%, respectively) in the Edinger-Westphal nucleus was observed following repeated electroconvulsive shock. In addition, both preprocholecystokinin and preprotachykinin-A messenger RNA expression, measured as grain density over single neurons, was significantly increased (+37% and +45%, respectively). The results indicate that cholecystokimn- and substance P-contaimng neurons in the Edinger-Westphal nucleus are activated by repeated electroconvulsive shock, which may be related to the antidepressant and analgesic effects of electroconvulsive shock treatment.