Neuroplastin65 调节焦虑样行为的机制研究

以焦虑、恐惧、紧张为主要特征的焦虑障碍已成为影响人类健康的主要精神疾病，病因不明、治疗手段有限。脑特异性的、细胞粘附分子、突触膜糖蛋白neuroplastin 65(NP65)，高表达于海马和大脑皮层。我们前期实验发现，在旷场实验、黑白箱穿梭等焦虑水平的测试实验中，NP65敲除小鼠呈显著的焦虑样行为。并观察到敲除小鼠色氨酸羟化酶TPH2、5-羟色胺3A受体表达显著降低。初步提示NP65与焦虑样行为有关。为此，本研究利用NP65敲除小鼠，给予NP65合成肽、5-HT3A受体、GABA A受体激动剂观察焦虑行为的变化；观察中缝核-海马5-HT通路及其对GABA能中间神经元-锥体细胞调控、海马神经再生、HPA轴的调控作用；观察海马锥体细胞的 GABA A受体及兴奋性/抑制性突触传递是否异常，初步阐明NP65调节焦虑样行为机制。本研究结果可能为焦虑障碍治疗提供新线索。

Anxiety disorders are characterized by excessive anxiety and maladaptive fear responses to anticipated danger or imminent threats. They can be regarded as the most devastating psychiatric disorders because of their early development, high prevalence and detrimental effects on quality of life. Although our knowledge of the neural substrates and brain areas that are involved in generating fear and anxiety have been tremendously improved by past researches, it remains to be determined how dysfunction of these brain circuits may contribute to anxiety disorders. As a type of brain- and neuronal- specific Immunoglobulin Superfamily Cell Adhesion Molecule, neuroplastin65 (NP65) is predominantly expressed in several brain regions, including cortex, hippocampus, striatum and amygdala. It is highly presented in synaptic regions, especially the postsynaptic density (PSD). Decades of research has identified a pivotal role of NP65 in regulating neuritogenesis, synapse formation, synaptic plasticity as well as the maintenance of excitatory/inhibitory balance. In recent years, animal models of neuroplastin-deficient mice have shown that deficiency of neuroplastin could lead to decreased hippocampal excitatory synapses, reduction of GABAA receptor α2 subunit, impaired excitatory and inhibitory synaptic transmission. Our previous findings suggest that NP65 knockout(KO) mice exhibited alterations in excitatory synaptic structure and dendritic morphology. In addition, enhanced anxiety-like behaviors and impaired fear memory were observed in NP65 KO mice. Our unpublished results indicate that NP65 ablation could affect the serotonergic system by decreasing the expressions of tryptophan hydroxylase 2 (TPH2) and 5-HT receptor 3A (HTR3A). Thus, our study establishes a novel role of NP65 in the regulation of emotional states like anxiety and fear. In the following studies, we will elucidate the potential mechanisms underlying these events. First, we want to determine whether intracerebral administration of 5-HT, NP65 mimetic peptides, 5-HT3A receptor agonist and GABAA receptor agonist can alleviate the anxiety-like behaviors in NP65 KO mice. Meanwhile, we will reveal the expression changes of NP65 in mice with anxiety disorders of wild type mice induced by restrained stress. Next, the specific role of NP65 in participating the regulation of anxiety will be shown. To address this, we will investigate the effects of NP65 on the serotonergic projections from raphe nucleus to hippocampus and how dysregulation of this brain circuits may contribute to anxiety disorders through influencing serotonin synthesis, adult hippocampal neurogenesis, and HPA axis activity. Another goal of our study is to characterize the functions of NP65 in maintaining GABA-ergic synaptic functions by examining the excitatory and inhibitory synaptic transmission, distribution of GABAA receptor at the synapse, and whether these alterations are involved in behavioral deficits of NP65 KO mice. Taken together, our researches will provide new mechanistic insights for anxiety, and therefore implicate in developing new therapeutics treatment of anxiety.