ACTIVATION PATTERNS OF THE IEG ARC IN RATS FOLLOWING ELECTROCONVULSIVE SHOCK TREATMENTS.

Abstract

The immediate early gene Arc is rapidly expressed in hippocampal subregions following excitatory neuronal activity including electroconvulsive shock treatments. Arc has been shown to play a role in synaptic plasticity and gaining insight into its regulation and mechanisms is critical to understanding the intricacies of learning and memory. This study aims to see if reducing the current of the electroconvulsive shock treatments will reduce the number of Arc mRNA-positive cells in the dentate gyrus and CA1 to further understand Arc’s role in the hippocampus. Fischer 344 (F344) rats were assigned to six different treatments: 0 mA, 20 mA, 40 mA, 65 mA, 77 mA, and 85 mA. The brains were extracted five minutes after the treatment, quick frozen, sectioned, and thaw mounted onto super frost slides. The number of Arc mRNA-positive cells were counted using compartmental analysis of temporal activity by fluorescence in situ hybridization (catFISH) combined with confocal microscopy in the dentate gyrus and CA1. This revealed a sharp increase in the number of Arc mRNA-positive cells between the 65 mA counts and the 77 mA counts in the dentate gyrus (~2.8% of cells to ~85% of cells) and CA1 (distal ~27.4% of cells to ~70.1% of cells, medial ~26% of cells to 71% of cells, proximal ~17.4% of cells to 72.1% of cells) suggesting a threshold for activation.