An Immunohistochemical and Immunoelectron Microscopic Study of Distribution of Neuropeptide Y in the Cat Spinal Trigeminal Subnucleus Caudalis after Pulpectomy

Lee, Seung Pyo; Paik, Ki Suk; Kim, Myung Kook

Abstract

The purpose of this study was to investigate the distribution of neuropeptide Y (NPY) in the cat spinal trigeminal subnucleus caudalis following pulpectomy of mandibular premolars and molar by means of an immunohistochemical and immunoelectron microscopic study. The animals were divided into normal and experimental group which were sacrificed at 14 days after pulpectomy. The results were as follows; 1. On the light microscopic observation of the spinal trigeminal subnucleus caudalis in normal group, NPY-immunoreactivity (IR) was weak within lamina I and lamina II outer. In pulpectomy group, NPY-IR was strong and appeared to extend into lamina I and lamina II inner at 14 days. 2. On the immunoelectron microscopic observation of the spinal trigeminal subnucleus caudalis in normal group, NPY-IR was revealed in axon terminals, dendrites, myelinated axons and unmyelinated axons. NPY-IR was associated with membrane structures within microtubules, synaptic vesicles, outer membrane of mitochondria and inner surface of the axolemma. In NPY-immunoreactive structure, there was a small amount of DAB precipita-tions. 3. On the immunoelectron microscopic observation of the spinal trigeminal subnucleus caudalis at 14 days in pulpectomy group, the number of NPY-immunoreactive axon terminals, dendrites, myelinated axons and unmyelinated axons was increased than normal group. DAB precipitations in NPY-immunoreactive structure was increased than normal group. Some NPY-immunoreactive axon terminal formed synaptic glomerulus and axoaxonic synapse. 4. The results indicate that NPY-IR was increased in the spinal trigeminal subnucleus caudalis after pulpectomy, and it is speculated that the increased NPY by injury of peripheral nerve may participate in the processing of nociception.