Vagus nerve stimulation -induced anxiolytic and neurotrophic effect in healthy rats

Memory, learning, anxiety, and depression have concerned science for years, increasingly leading to research into new therapeutic targets. The study investigated the effect of acupuncture stimulation of the auricular branch of the vagus nerve (ABVN) on memory, anxiety-like and depression-like behaviors in healthy rats. Healthy rats were divided into groups: (1) control, without treatment; (2) acupuncture in the left ABVN; and (3) acupuncture in the right ABVN. Tests were conducted to evaluate memory (inhibitory avoidance and object recognition), anxiety-like (open field, elevated plus maze, and light/dark box), and depressive-like (sucrose preference and forced swimming) behaviors. In addition, the concentration of brain-derived neurotrophic factor (BDNF) in the hippocampus of the rats was evaluated. The control group did not show any changes in the behavioral tests. The animals that received acupuncture (ABVN-R and ABVN-L) remained longer on the light side of the light/dark box test compared to the control group. Acupuncture in the ABVN-R also increased the concentration of BDNF in the hippocampus of the animals. Accordingly, acupuncture stimulation of the ABVN did not show an antidepressant effect or improve memory in healthy animals; however, it did show an anxiolytic effect and increased neurotrophic levels in the hippocampus.