The functional analysis of interneurons in central nervus system.

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1. The cellular origin and mechanism of directional selectivity were investigated by selectively eliminating retinal cholinergic interneurons, namely starburst cells, using the immunotoxin-mediated cell targeting techniques (IMCT). Starburst cell ablation in the retina abolished not only directional selectivity of ganglion cell responses but also an optokinetic eye reflex derived by stimulus movement. Starburst cells therefore serve as the key element that discriminates the direction of stimulus movement through integrative synaptic transmission and play a pivotal role in information processing that stabilizes image motion.2. The physiological role of striatal cholinergic interneurons was investigated with IMCT. Unilateral cholinergic cell ablation caused an acute abnormal turning behavior. These mice showed gradual ecovery but displayed abnormal turning by both excess stimulation and inhibition of dopamine actions. In the acute phase, basal ganglia function was shifted to a hyperactiv … More e state by stimulation and suppression of striatonigral and striatopallidal neurons, respectively. D1 and D2 dopamine receptors were then down-regulated, relieving dopamine-predominant synaptic perturbation but leaving a defect in controlling dopamine responses.3. Chronic exposure to cocaine causes long-lasting behavioral changes associated with cocaine reinforcement and addiction. An important neural substrate for cocaine addiction is the nucleus accumbens (Nac). Although the neural circuit of the Nac is controlled by several other neurotransmitters, their involvement in cocaine addiction remains elusive. We ablated cholinergic interneurons from the adult Nac with IMCT and examined the role of acetylcholine transmitter in adaptive behavioral changes associated with cocaine reinforcement and addiction. In bilaterally cholinergic cell-eliminated mice, chronic cocaine administration induced a prominent and progressive increase in locomotor activity. Moreover, these mice showed robust conditioned place preference with a lower dose of cocaine, compared with wild-type littermates. This investigation demonstrates that acetylcholine in the Nac plays a key role in actions of cocaine. Less