Acetylcholine (Ach) is very widely distributed in the brain, occurring in all parts of the forebrain (including the cortex), midbrain and brainstem, though there is little in the cerebellum. The anterior horns and roots of the spinal cord, and the motor nuc­­lei of the cranial nerves contain much more Ach than other part of CNS, reflecting the presence of cholinergic motoneurons supplying skeletal muscle (Fig.4).There is a diffuse cholinergic innervation supplying all areas of the forebrain, and the cell bodies of these cholinergic neurons lie in small area of the basal forebrain, forming the magnocellular forebrain nuclei.