Reduction of Freezing Behavior by Acupuncture Stimulation at HT7 in Contextual Fear-Conditioned Mice

Abstract

Objective: Acupuncture at acupoint Shenmen (HT7) is used for the treatment of neuropsychological disorders, such as anxiety disorders, in oriental medicine. In the present study, to elucidate the influence of HT7-acupuncture on the reduction of fear memory, we examined freezing responses in contextual fear-conditioned mice with or without acupuncture treatment at HT7. Materials and Methods: Adult male C57BL/6J mice were subjected to electric foot-shock, which represents a common animal model of post-traumatic stress disorder (PTSD), in a foot-shock cage. The mice were then immediately returned to their home cages and randomly divided into two groups, an HT7 and a sham groups. In the HT7 group, 30 seconds of bilateral acupuncture at HT7 was applied for 7 consecutive days. We then placed the mice from both groups either in their home cages or in the foot-shock cage and observed their freezing behavior for 2 minutes. Results: In the home cage, HT7 and sham mice displayed almost no freezing responses. In the foot-shock cage, in contrast, the sham group showed freezing responses for 51.3 ± 16.7% in 2 minutes, indicating that in these mice, fear memory was strongly maintained even after 1 week. Surprisingly, the freezing responses of the HT7 group mice in the foot-shock cage were significantly lower, at 25.7 ± 14.9% in 2 minutes. Conclusions: These findings suggest that acupuncture treatment at HT7 might be effective in reducing fear memories in PTSD.