Synapsin Ⅰ is a specific phospho-protein of neuron,it is associated with the cytoplasmic surface of small synapsic vesicles. It is highly conservative in evolution and its gene locates in X-chromosome. By means of null mutation of synapsin Ⅰ gene in mice and investigation of brain slices electrophy-siologically,the mutation is generated by homologous recombination. And it is found that synapsin Ⅰ plays a vital role in physiological events such as neurotransmitter release and synaptic plasticity,etc.