Neuropeptide Y-like immunoreactivity in cat spinal cord with special reference to autonomic areas

Abstract

The distribution of nerve terminal-like structures (herein called nerve terminals), fibers, and neurons containing neuropeptide Y-like immunoreactivity (NPY-ir) was studied immunohistochemically in cat spinal cord with and without colchicine treatment. Rexed laminae II and III of the dorsal horn contained large amounts of immunoreactive nerve terminals and few fibers at all levels of the cord whereas laminae I and IV–VI contained fewer terminals and numerous fibers. In segments C 7 T 3, fibers with NPY-ir in the superficial laminae collected into bundles which travelled ventromedially toward the dorsal gray commissure (DGC). In addition, another bundle of fibers was present in segments C 8 T 2 and T 11 S 2; these fibers also originated from the upper dorsal laminae and travelled along the dorsomedial border of the gray matter to cross the midline in the DGC. In the intermediate and central gray, most immunoreactivity was found in the autonomic areas: terminals and fibers containing NPY-ir were found in the intermediolateral cell column pars principalis (IMLp) in all segments between C 8 and L 4 with the densest accumulation in segments T 6 and T 7. All other autonomic areas contained immunoreactive structures in nearly all thoracolumbar segments except for the IML pars funicularis, which contained small numbers of immunoreactive fibers only between segments T 2 and T 8, inclusive. In the sacral cord, the autonomic areas in the intermediate and central gray also contained relatively large numbers of immunoreactive terminals and fibers. The ventral horn was almost devoid of immunoreactivity except for the lower lumbar segments, where small numbers of fibers were found at the ventrolateral border of the gray matter. Immunoreactive neurons were seen only after colchicine treatment and appeared at and below segment T 3. Numbers of neurons with NPY-ir were small; they increased in number down the cord, reaching 18 in number in any given section taken from segment S 2. Most neurons were found in lamina VII at all levels, although a small number of neurons was found in laminae VI and IX. All immunoreactive neurons were morphologically similar and ranged from medium to large in size (>15 μm in diameter).