ABSTRACT
Decreased number of the Neuropeptide-Y[NPY] immunoreactive neurons in the corpus striatum and primary motor cortex of aged rat was detected by the immunohistochemical method. The animals were categorized into control and aged group and we used 10 Sprague-Dawley rat weighing 250-300gm for control group. 10 Sprague-Dawley rat weighing over 600gm for aged group. The number of NPY-immunoreactive neurons in corpus striatum and primary motor cortex were counted under the light microscope and the following results were obtained. 1. The NPY-immunoreactive neurons were evenly distributed in corpus striatum and in the primaty motor cortex, the NPY-immunoreactive neurons were concentrated within the layer II, III and layer V, VI. The typical NPY-immunoreactive perikarya was multipolar shape. 2. Decreased number of NPY-immunoreactive neurons were detected in some areas of corpus striatum and primary mortor cortex of the aged rat. 3. Decrease of NPY-immunoreactive neurons were most prominent in the caudate-putamen and there were moderate decrease of NPY-immunoreactive neurons in the primary motor cortex, mild decrease of NPY-immunoreactive neurons in the nucleus accumbens but the NPY-immunoreactive neurons were not observed in the globus pallidus in both control and aged rat. NPY is supposed to act as a neurotransmitter of local circuit neurons in the striatum and may exert its potent vasoconstrictor effects on cerebral vessels which influences on the microcirculation of cerebral cortex and striatum. So our results seems to provide an important data on change of the function in the striatum and primary motor cortex of aged rat brain.