Non-periodic Sensitivity" In Substantia Nigra Compacta Neurons

"Non-periodic Sensitivity" in Substantia Nigra Compacta NeuronsStudent:Liu Guo-Peng Supervisor: Prof. Hu San-JueAbstractWith the development of non-linear dynamic theory, it provides an effective means to study the activity of neural system. Previous research proved that deterministic chaos exists in the activity of neuron or neural system (including time series of neuron firing), found that the activity of neuron or neural system correlated closely with their non-linear dynamic state. The responsiveness of neuron was a basic function of neuron, the sensitivity of neuron is related to many factors, but The relationship between sensitivity and firing pattern (dynamic characteristic of neuron firing) is unknown. Our former studying in injured dorsal root ganglion neuron revealed that the sensitivity of neurons had close relationship with the firing pattern, non-periodic firing neurons were more sensitive to external stimulus than periodic firing neurons, deterministic dynamical mechanism was found within time series of non-periodic firing. On the basis of our previous work, we put forward a hypothesis of "non-periodic sensitivity", presumed that phenomenon of "non-periodic sensitivity" was likely to reflect a universal characteristic of excited cells. In order to certify universality of "non-periodic sensitivity" in nervous system, study relationship between the firing pattern and sensitivity of central neural system neuron. We recorded spontaneous activities of substantia nigra compacta (SNc)neurons in brain slice of young rats extracellularly, studied relationship between the sensitivity of neuron and firing pattern. Further, we analyzed the non-linear dynamic of time series of non-periodic firing.Results1. According to the dynamics of interspike interval (ISI), the SNc neurons can be divided into periodic firing neurons (ISIs are equal) and non-periodic firing neurons (ISIs are irregular).2. Non-periodic firing SNc neurons were more sensitive to the suppressive effect of 0.5 ^ 2 ^ 10 uM dopamine than periodic firing neurons, the curve of dose-response relationship of non-periodic neurons shifted toward the left significantly compared to that of the periodic firing neurons(P<0.01, / test).3. Non-periodic firing SNc neurons were more sensitive to the excitatory effect of 0.1 > 1 , 10 uM norepinephrine than periodic firing neurons, the curve of dose-response relationship of non-periodic neurons shifted toward the left significantly compared to that of the periodic firing neurons(/)<0.01, / test).4. Non-periodic firing SNc neurons were more sensitive to the suppressive effect of 1 > 10 > 100 nM norepinephrine than periodic firing neurons(/)<0.01, t test). Generally, 1 nM norepinephrine can completely inhibit non-periodic firing neurons; on the contrary, even 100 nM norepinephrine can not completely inhibit periodic firing neurons.5. Non-periodic firing SNc neurons were more sensitive to the excitatory effect of 0.2 > 1 ^ 5 uM glutamate than periodic firing neurons, the curve of dose-response relationship of non-periodic neurons shifted toward the left significantly compared to that of the periodic firing neurons(/)<0.01, / test).6. Non-periodic firing SNc neurons were more sensitive to the suppressive effect of 30 s, 60 s 90 s anoxia than periodic firing neurons, the curve of dose-response relationship of non-periodic neurons shifted toward the left significantly compared to that of the periodic firing neurons(P<0.01, t test).7. Unstable periodic orbits were detected in time series of non-periodic firing.Conclusions1. SNc neurons generated various firing patterns in vitro. Deterministic dynamics contained within time series of non-periodic firing SNc neurons.2. Non-periodic firing neurons were more sensitive to dopamineN norepinephrine glutamate and anoxia than periodic firing neurons, we called it phenomenon of "non-periodic sensitivity".3. The sensitivity of non-periodic activity may depend on the deterministic chaos within their firing dynamic syst...