CHOLINERGIC SPROUTING IS BLOCKED BY REPEATED INDUCTION OF ELECTROCONVULSIVE SEIZURES, A MANIPULATION THAT INDUCES A PERSISTENT REACTIVE STATE IN ASTROCYTES

Previous studies have demonstrated that some of the molecular and morp hological changes that are characteristic of reactive astrocytes are i nduced following seizures. This discovery provides the means to experi mentally modify the time course and extent of reactive changes in astr ocytes following injury and so explore how these reactive changes modu late other events in the injured nervous system. The present study eva luates whether superinduction of a reactive state in astrocytes alters one form of postlesion synaptic reorganization (the sprouting of chol inergic projections in the dentate gyrus after destruction of the ento rhinal cortex). Cholinergic sprouting after entorhinal cortex lesions was evaluated in control mice and in mice that experienced electroconv ulsive seizures (ECS) from the day of surgery until 12 days postlesion . Animals were prepared for acetylcholinesterase (AChE) histochemistry at 2,4,6,8,10,12, 14, and 30+ days postlesion. Quantitative densitome tic analyses revealed that the increase in AChE staining that is indic ative of cholinergic sprouting was essentially eliminated in the anima ls that experienced daily ECS. These results indicate that the inducti on of electroconvulsive seizures during the postinjury period disrupts at least one form of postlesion synaptic reorganization that would ot herwise occur. This disruption of synaptic reorganization may be a con sequence of the induction of a persistent reactive state in astrocytes . (C) 1994 Academic Press, Inc.