Neuropeptides in Central Movement Disorders of Man

Abstract

Of the more than 35 neuropeptides presently known, a major part is found in brain areas involved in the control of movement. The neural circuits and the neuroactive substances of basal ganglia of the rat have been surveyed in this volume [37]. In the cerebral cortex of rat and other mammals small neurons contain somatostatin, neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), enkephalin [9, 19, 21, 26, 30, 31]. In some cortical VIP neurons a coexistence with choline acetyltransferase, the biosynthetic enzyme of acetylcholine, has been shown [19]. Cortical neurons projecting to the striatum contain glutamate [34]. In the striatum the majority of neurons is GABA-ergic; most perikarya are medium-size spiny striato-fugal projection neurons, and a minority are medium- to large-size cells representing local circuit neurons. Few striatal neurons are cholinergic [45]. Somatostatin is contained in medium-size as-piny interneurons [17]. Met-, leuenkephalin, substance P [40] and dynorphin [49] are contained in striatal neurons projecting to the pallidum. A coexistence of met-, leuenkephalin and substance P has been found in GABA-ergic striatal neurons [2, 4]. In the pallidum the majority of neurons is GABA-ergic, most of them being projection neurons. GABA-ergic projection neurons of the striatum terminate in the substantia nigra at dopaminergic neurons [29]; some of these dopamine neurons contain CCK [30]. These neurons reciprocally project to GABA-ergic and cholinergic neurons in the striatum. GABA-ergic pallidal neurons project further to thalamus, tectum, subthalamic nucleus and possibly to the substantia nigra pars compacta Unknown are the transmitters of the neurons projecting from the thalamus back to the cortex, and from the subthalamic nucleus back to the thalamus.