Tetrodotoxin-induced Homeostatic Plasticity In Cultured Hippocampal Neuronal Networks On Multi-electrode Array

Neuronal plasticity plays an important role in the functional stabilization in the development of neural system. Homeostatic plasticity is one of the main forms of neural plasticity and is the basic of stabling brain function. In present, the methods of studying homeostatic plasticity mostly include patch clamp, morphological, immunofluorescent assay and so on. In this paper, with multi-electrode array (MEA) system, the hippocampal neuronal networks were cultured stably for a long term, and then the homeostatic plasticity was investigated on neuronal network level.The neuron culture technique was improved on, and the hippocampal neuronal networks were cultured up to 5 months. With multi-electrode array system, electrophysiological and pharmacological characteristic of cultured networks were carried. The results indicated that the spontaneous firing patterns included random single spike pattern, high-frequency spike pattern, synchronized burst pattern and so on. Spontaneous activity was totally blocked by 1μM tetrodotoxin.In virtues of MEA, the effect of tetrodotoxin on hippocampal neuronal networks was investigated. After washout following treated with 1μM tetrodotoxin for 4 h, the firing rate increased to 334.8±32.8% comparing with control condition, and the firing pattern transformed from single spike to synchronized burst oscillation, accompany with increasing in correlation coefficient between two sites in the network. Along with the delay time following washout, the firing gradually returned to control level, then at about 6 h after washout, the firing pattern transformed back to single spike.These findings indicated that the spontaneous activities of cultured hippocampal neuronal networks had kinds of firing patterns that came from the opening of sodium channels. After being treated with 1μM tetrodotoxin for 4 h, the emergence and disappearance of synchronized burst indicated that the homeostatic plasticity on networks level was different from that in single cell level and in vivo.