| Several anatomical studies using either degeneration or tract-tracing methods have demonstrated the efferent and afferent connections of the interpolaris subnucleus of the spinal trigeminal nucleus (Vi). Up to now, however, a systematic study of the overall pattern of the efferent and afferent connections of the Vi is still lacking. Therefore, the present study has been done to examine all the sources that are connected with the Vi, by means of the retrograde and anterograde tracer trcaing method. I. The efferent connections of the ViAfter injecting the anterograde tracer biotinylated dextrin amine (BDA) into the Vi, the BDA labeled fibres and terminals were noted in the regions as follow:Spinal cord Following injection of anterograde tracer into the Vi, the BDA labeled fibres and terminals were localized in III-VI layers of the cervical cord, and the number of BDA labeled fibres were decreased at more caudal levels in the cervical cord. Medullary oblongata Only a few fibres were found in the contralateral Vi. the dorsal cochlear nucleus (DC) and the hypoglossal nucleus (XII). The moderate labeled fibres and terminals were found in the inferior olivary nucleus (10). the spinal trigeminal oral (Vo) and caudal subnuclei (Vc), the gigantocellular reticular nucleus (Gi). The most heavily BDA labeled region in the medullary was observed in the parvocellular reticular nucleus (PCRt).Pons In the parabrachial nucleus (PB), including KF nucleus and the superior olivary nucleus, several BDA labeled fibres were encounted. The moderate BDA labeled fibres were located in the pontine reticular nucleus (Pn) and facial motor nucleus (VII). Midbrain Several BDA labeled axons were observed in theperiaqueductal gray matter (PAG). The moderate BDA labeledterminals were found in the lateral superior colliculus (SC). TheBDA labeled fibres and terminals were most heavily distributed inthe deep mesencephalic nucleus.Cerebellum A few BDA labeled fibres in the simple lobule and cmsI and II, lobule VI, VII, IX and X were observed.Diencephalon The most heavily BDA labeled fibres were found inthe ventral posterior medial nucleus (VPM). The moderate BDAlabeled fibres and terminals were found in the zona incerta (ZI) andposterior thalamic nucleus (Po). In the medial geniculate nucleus,parse BDA labeled fibres could be observed.The present results suggested that the Vi can transfer the oral-facial information to some regions in the central nervous system. So the Vi might be involved in the forming of the multi-circuits that transfer the oral-facial sensory information or might play a role in some reflex processes. II. The afferent connections of the ViAfter injecting retrograde tracer fluoro-gold (FG) into the Vi. the FG labeled neurons could be found in the following regions: Spinal cord Several FG labeled neurons were located in the dorsal horn of the spinal cord.Medullary oblongata Some FG labeled neurons distributed in the ipsilateral Vo and Vc.Pons A few FG labeled neurons were noted in PB (including KF). Midbrain The FG labeled neurons were sparsely localized in PAG and DR.Diencephalons Some labeled neurons were located in the prerubral nucleus.The present results indicated that the Vi, which received the afferent projections from both peripheral and central nervous system, might be involved in the information modification and play a role in primary sensory information convergence. III. The cervical cord receiving the projections from the ViIn the present research, retrograde tracer FG was used to observe the efferent connection from the Vi to the cervical cord.The FG labeled neurons were found in the Vi after injecting FGinto the cervical cord.When injecting the ventral horn of the cervical cord, no labeled neurons were observed in the Vi.The dorsal horn of the cervical cord received the projections from lateral, middle and ventral Vi.The intermediate zone of the cervical cord received the projections from lateral, dorsal and ventral Vi.The present resul...
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