Neurons In The Amygdala Modulate The Mouse Anxiety Behavior

Anxiety is a kind of emotional response in human and animals, which is instinctive and negative. Under normal circumstances, people and animals could feel anxiety and its level corresponding to the real threat. When threats end, the normal anxiety reaction will also extinct. But the level which pathological anxiety display is out of proportion to the objective facts and the anxiety situation. The threat and nervous which animals feel is no reality basis, no specific reason, relatively durable and does not disappear with the solution of the objective problem. Existing experiments result shows that:the amygdala in animal’s brain is the most important subcortical nuclei which participate in the modulation of emotion, and the basolateral amygdala play an important role in the modulation of anxiety and this behavior response. In basolateral amygdala, we find anxiety related neurons. On this basis, we take advantage of Multi-channel in vivo recording techniques, the animal behavior test and the pharmacological method to look into whether the anxiety related neuron in amygdala participate in the encode of drug-induced anxiolytic response.Experiments take place on twenty C57BL/6J mice and we use Multi-channel in vivo recording techniques to observe and record the firing patterns of the basolateral amygdala neurons in open field test and enriched-box test. Base on the different firing patterns of the basolateral amygdala neurons in open field test and enriched-box test, the neurons in basolateral amygdala can divide into three types: anxiety related neuron, environment change on neuron, environment change off neuron. The firing rate of anxiety related neuron displays a slow onset and gradual increased pattern and when the mice back to the homecage, the firing rate return to the normal relative low level accordingly. But in the enriched-box, the firing rate of anxiety related neuron has a significant decrease compared with that in the open field and no significant difference has been seen between the levels when mice in enriched-box and homecage. The analysis of mice behavior in open field and enriched-box shows that the open field can more likely to induce anxiety reaction in mice. Compare the firing pattern of anxiety related neuron with the anxiety-like behavior of mice in open field, so as enriched-box, we consider this kind of neuron involve in the encode of anxiety. So we named it anxiety related neuron.Obviously different from anxiety related neuron, environment change on neuron displays increased firing rate in both open field and enriched-box and significant higher than that of homecage (P< 0.001). Environment change off neuron displays decreased firing rate in both open field and enriched-box and significant lower than that of homecage (P< 0.01).Drugs like benzodiazepine have frequently used in the clinical treatment of pathological anxiety, e.g. diazepam. In our experiment, the mice injected intraperitoneally (i.p.) with diazepam (lmg/kg weight), so that we can observe the change of anxiety-like behavior and the firing pattern of anxiety related neuron. The result shows that after i.p. diazepam, the mice’s anxiety reaction in open field test became lower than that of before i.p. diazepam. Contrast with the synchronized record of anxiety related neuron’s firing pattern, we found that after i.p. diazepam, the average firing rate of anxiety related neuron in open filed decrease significantly.The results above preliminarily confirmed that the basolateral amygdala exist neurons participate in encoding anxiety responses, and this kind of neuron may also participate in encoding drug induced anxiolytic responses.