Abstracts

Rationale: Electroconvulsive seizure (ECS) is an animal model to investigate the therapeutic mechanism of depressive disorder. Both acute and chronic ECS have been reported to change the expression of transcription factors, neurotropic factors, and receptors important for synaptic function. Here, we examined protein expression of two major glutamate receptors, NMDA and AMPA receptors, as well as striatal enriched protein tyrosine phosphatase (STEP61) in hippocampus following acute and chronic ECS. Methods: Electroconvulsive seizures (ECS) Whole Brain Lysate Preparation Western Blot Analysis Statistical Analyses Results: To determine whether acute ECS induces the protein expression of NMDAR and AMPAR subunits, rats received a single electric shock (0.5 sec, 100 pulse/sec, 55 mA) and their hippocampal membrane fractions (P2) were collected for western blotting (Figure.1A). The protein expression of GluN2A and GluN2B significantly decreased at 3 to 24h following acute ECS compared to NS group (Figure.1B- C). We also observed a marked reduction of GluA1 and GluA2 protein levels at 3 to 48h following acute ECS (Insert values, p values) (Figure.1D-E). These results demonstrate that acute ECS leads to a significant but temporary decrease in the protein level of NMDAR and AMPAR subunits. We executed a single electric shock to rats for seven consecutive days and performed western blotting (Figure.2A). In contrast to a robust effect of acute ECS on NMDAR and AMPAR subunits expression (Figure.1) , there were no significant changes in the protein expression of GluN2A, GluN2B, GluA1, and GluA2 up to 72 hr following chronic ECS compared to NS group (Figure.2B-E). Taken together, these results indicate that the hippocampal expression of NMDAR and AMPAR subunits is differently modulated by acute and chronic ECS. Conclusions: We observed a significant decrease in the protein expression in NMDA receptor subunits, GluN2A and GluN2B, and AMPA receptor subunits, GluA1 and GluA2, at 3-48 hr following acute ECS. In contrast, the expression of STEP61 increased at 24h and 48h following acute ECS. Phosphorylation state of STEP61 substrate, GluN2B at tyrosine residue 1472, was reduced at 8-48h following acute ECS, whereas the phosphorylation state of tyrosine-rich motif within the intracellular GluA2 C-terminal region was unaltered. Chronic ECS did not induce significant changes in the protein level of GluN2A, GluN2B, GluA1, GluA2, and STEP61 nor tyrosine phosphorylation states of GluN2B and GluA2. In summary, we found that acute ECS but not chronic ECS induces inverse changes in the expression of NMDA and AMPA receptor subunits and STEP61, and differentially modulates STEP61-regulated tyrosine phosphorylation of GluN2B and GluA2 in hippocampus. Considering that STEP61 induces synaptic weakening by dephosphorylating GluN2B and GluA2, these results suggest the observed changes in the expression and phosphorylation of NMDA and AMPA receptors and STEP61 may reflect homeostatic anticonvulsant adaptations to acute ECS.