Impairment of Avoidance Behavior Produced by Destruction of the Cholinergic Projection from the Pedunculopontine Nucleus to the Medial Thalamus
The pedunculopontine nucleus (PPN) is located bilaterally in the lower midbrain and pons. The larger PPN neurons utilize acetylcholine as a neurotransmitter (Kimura et al., 1981). The major ascending efferent fibers of the PPN project to the medial thalamus (Med Thal), substantia nigra, subthalamic nucleus, and almost all parts of the diencephalon and the limbic system, while other efferent fibers descend to the brainstem reticular formation and spinal cord (Niijima and Yoshida, 1988). Although the function of the PPN is not yet clearly understood, it is thought to modulate the sleep cycle and consciousness level by its cholinergic excitatory action. The PPN might also activate the midbrain dopamine neurons in the pars compacta of the substantia nigra and ventral tegmental area. Also, the nucleus is thought to be one of the locomotor centers (Fujimoto et al., 1989).
KeywordsPassive Avoidance Progressive Supranuclear Palsy Dark Chamber Superior Cerebellar Peduncle ChAT Activity
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