Experimental and Modeling Study on the Stabilization Mechanism of Neuronal Network by Aminergic System

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We fabricated a probe of microdialysis with stainless steel microelectrodes which was inserted into the lateral geniculate nucleus of a cat. A single neuronal activity was recorded for more than several hours stably during sleep-waking states, during which 10^<-2>M serotonin was perfused. Following results were obtained :(1) During slow wave sleep of control state, the neuronal activity was characterized by a burst and silence type of firing with a low mean discharge rate, and had white noise like dynamics, whereas it showed a tonic and higher firing rate with 1/* fluctuations for serotonin perfusion.(2) During REM sleep the firing rate was tonically increased due to serotonin perfusion. The 1/* fluctuations were constantly observed for both control and drug supply.(3) The tonic membrane depolarization was observed during serotonin perfusion.After all, so far, it is the following three states when 1/* fluctuations have been observed in a single neuronal activity of the central nervous system :(1) REM sleep(2) the state in which the brain serotonin is depleted.(3) slow wave sleep during which serotonin of high concentration was diffused through a microdialysis probeOn the other hand, the white noise like dynamics has been observed both during slow wave sleep and during arousal state in which an animal is highly attended to the environment. Therefore, imbalance of neuromodulatory substances such as serotonin, noradrenaline, acetylcholine, etc.would produce 1/* fluctuations in a neuronal activity of the central nervous subsystem we call "executive system".