Connectivity Pattern Of Action Potentials Network In Prefrontal Cortex Of Rats During Anxiety

Objective Anxiety disorder is a common emotional disorder,which seriously affects the normal life and endangers physical and mental health of patients.The prefrontal cortex(PFC)is responsible for anxiety,and studying the connectivity pattern of action potentials network in medial prefrontal cortex(m PFC)of rats during anxiety state is helpful to further understand the pathogenesis of anxiety disorder.In this study,the action potentials in medial prefrontal cortex of rats during anxiety state in the elevated plus-maze was taken as the object.The causal network of action potentials was built based on maximum likelihood estimation(MLE),and connectivity strength and global efficiency were calculated.We studied the brain network so as to quantitatively characterize the mechanism of brain network in anxiety disorder.Methods1.The experimental animals were 8 Male Sprague-Dawley(SD)rats aged 10-12 weeks with weighting between 300 and 350 g.2.The rats were implanted with a 16-channel microelectrode arrays in the medial prefrontal cortex.Electrical signals of rats were recorded by the neural signal acquisition system,and rats were free to explore in the elevated plus-maze(EPM).Behavioral analysis software was used to analyze the motion trajectory of rats,and a 10-second neural signal recorded from closed arm to open arm of the rats was regarded as the research object.3.Action potentials were obtained through high-pass filtering(500-7500Hz),threshold detection and Spikes sorting.The firing rate of the neural population was calculated individually by selecting a moving window(window width is 500 ms,moving step is 125ms).4.Using the method of maximum likelihood estimation,the causal connectivity strength of action potentials network in the state of anxiety was calculated and the causal network in medial prefrontal cortex was constructed.The functional connectivity strength of the action potentials network was analyzed.5.The global efficiency was calculated as the characteristic parameter of the network and the information transmission efficiency of anxious state network was evaluated.6.Paired sample t-test was used for statistical analysis on the firing rates of neuron population,causal connectivity strength and global efficiency of action potentials network on closed and open arms.The statistical results were expressed as mean±standard error.Results1.Behavioral results of rats in the elevated plus-maze: Eight rats showed normal anxiety level in the elevated plus-maze.The number of times to enter the open arms was 16.5±3.2,accounting for 30.20±3.44% of the total entries.And the duration in the open arms was 160.23±48.22 s,accounting for 26.71±4.04 of the total time.2.Rate coding of neural assembly during anxiety: Action potentials were obtained in8 rats(1st 12 neurons,2nd 15 neurons,3rd 16 neurons,4th 15 neurons,5th 19 neurons,6th 14 neurons,7th 18 neurons and 8th 12 neurons).The average firing rate of rats in the closed arm was 3.3895±0.1178,and the average firing rate in the open arm was 2.7462±0.1042.The firing rates had significant difference between closed arm and open arm(P<0.001).The firing rates of neuron population gradually decreased from the closed arm to the open arm.3.Causal connectivity of action potentials network during anxiety: The average connectivity strength of rats in the closed arm was 0.0173±0.0016,and the average connectivity strength in the open arm was 0.0104±0.0014.The causal connectivity of action potentials network was significantly different between the closed arm and the open arm(P<0.01).The connectivity strength of action potentials network in rats gradually declined from the closed arm to the open arm.4.Global efficiency of action potentials network during anxiety: The average global efficiency of rats in the closed arm was 0.0441±0.0066,and the average global efficiency in the open arm was 0.0348±0.0048.The global efficiency of action potentials network is significantly different between the closed arm and the open arm(P<0.001).The global efficiency of the rats among action potentials network lessened from the closed arm to the open arm.Conclusion Based on the action potentials of normal rats during the state of anxiety in the elevated plus-maze,this study focused on the connectivity mode of the action potentials network in the medial prefrontal cortex during anxiety.The results showed that:1.The firing rate of neural population is higher in the closed arm,and decreased from the closed arm to the open arm.The results suggest that the decreasing of neuronal activity in the medial prefrontal cortex is associated with anxiety states.2.The connectivity strength of the rats and the global efficiency of action potentials network in the closed arm are higher than those in the open arm.The connectivity strength and the global efficiency of the rats during anxiety decrease from the closed arm to the open arm,suggesting that the change of the connectivity strength and the decreasing of information transmission efficiency of action potentials in medial prefrontal cortex is related to anxiety states.