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Original Article

Exp Neurobiol 2014; 23(3): 231-237

Published online September 30, 2014

https://doi.org/10.5607/en.2014.23.3.231

© The Korean Society for Brain and Neural Sciences

Effect of Acute and Chronic Electroconvulsive Shock on 5-Hydroxytrypamine 6 Receptor Immunoreactivity in Rat Hippocampus

Hyun Jung Kim1, Seungwoo Kang1, Hyun Ju Kim1, Sun-Hye Choi1, Seungkeun Shin1, Hyung Ha Lee1, Hyewhon Rhim2* and Kyung Ho Shin1*

1Department of Pharmacology, Korea University College of Medicine, Seoul 136-705, 2Center for Neuroscience, Korea Institute of Science and Technology, Seoul 136-791, Korea

Correspondence to: *To whom correspondence should be addressed.
Kyung Ho Shin
TEL: 82-2-920-6195, FAX: 82-2-927-0824
e-mail: kyungho@korea.ac.kr
Hyewhon Rhim
TEL: 82-2-958-5923, FAX: 82-2-958-5909
e-mail: hrhim@kist.re.kr

Received: March 18, 2014; Revised: May 30, 2014; Accepted: June 2, 2014

Abstract

Electroconvulsive shock (ECS) induces not only an antidepressant effect but also adverse effects such as amnesia. One potential mechanism underlying both the antidepressant and amnesia effect of ECS may involve the regulation of serotonin (5-hydroxytryptamine) 6 (5-HT6) receptor, but less is known about the effects of acute ECS on the changes in 5-HT6 receptor expression in the hippocampus. In addition, as regulation of 5-HT receptor expression is influenced by the number of ECS treatment and by interval between ECS treatment and sacrifice, it is probable that magnitude and time-dependent changes in 5-HT6 receptor expression could be influenced by repeated ECS exposure. To explore this possibility, we observed and compared the changes of 5-HT6 receptor immunoreactivity (5-HT6 IR) in rat hippocampus at 1, 8, 24, or 72 h after the treatment with either a single ECS (acute ECS) or daily ECS for 10 days (chronic ECS). We found that acute ECS increased 5-HT6 IR in the CA1, CA3, and granule cell layer of hippocampus, reaching peak levels at 8 h and returning to basal levels 72 h later. The magnitude and time-dependent changes in 5-HT6 IR observed after acute ECS were not affected by chronic ECS. These results demonstrate that both acute and chronic ECS transiently increase the 5-HT6 IR in rat hippocampus, and suggest that the magnitude and time-dependent changes in 5-HT6 IR in the hippocampus appear not to be influenced by repeated ECS treatment.

Keywords: electroshock, hippocampus, serotonin 6 receptor