Abstract
Publisher Summary This chapter shows that the pedunculopontine nucleus (PPN) and the subthalamic nucleus (STN) could be a source of strong excitatory inputs that control firing patterns of substantia nigra pars compacta (SNc) dopamine (DA) neurons. Activities of SNc DA neurons of the rat were studied using a combination of intracellular electrophysiological recording in vitro and subsequent immunocytochemical double-labeling techniques. The results indicate a convergence of glutamatergic and cholinergic excitatory inputs from the PPN to SNc DA neurons. The most characteristic property of a DA neuron is its regular pacemaker firing pattern. The sodium spikes are triggered from a peak of each rhythmically oscillating membrane wave, which is known to be calcium dependent. When a single spike is triggered from each summit of oscillatory wave, it promptly repolarizes, and each spike is followed by a strong spike-afterhyperpolarization (AHP). In the study of muscarine and carbachol effects on DA cell-firing patterns, which is described in this chapter, the duration of the rising phase of each oscillatory wave was prolonged as a plateau-like depolarization, with a decrease in its amplitude by application of cholinergic agents; these effects were antagonized by atropine or pirenzepine.
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