抄録
A large portion of the monkey thalamic parafascicular nucleus (Pf) receives vagus afferent input (Ito & Craig; J Neurophysiol, 2005) and projects to the associative part of the striatum (Ito & Craig; J Comp Neurol, 2008). To elucidate the origin of this sensory input, its afferent projections were investigated using fluorescent dextrans or biotinylated dextran amine. Cynomolgus monkeys were anesthetized with pentobarbital. The cervical vagus nerve was electrically stimulated and evoked potential responses were mapped in the thalamus with a microelectrode. Tracers were injected into the vagus evoked potential focus in the parafascicular nucleus either iontophoretically or by pressure, and after survival of two to three weeks retrogradely labeled cells in the hindbrain were examined. Ipsilateral parabrachial nucleus (PB) was the most densely and consistently labeled area in the hindbrain. Most cells were in the ventral part of the medial subnucleus (PBm), spreading into Kolliker-Fuse (KF). Only a few cells were labeled in the lateral subnucleus (PBl). Contralateral PB also contained labeled cells, albeit fewer. A few cells were labeled in the solitary tract nucleus (NTS); labeled cells were sparsely located laterally in or around the nucleus at caudal, middle and rostral levels. Consistent labeling was also found in the contralateral deep cerebellar (dentate) nucleus. These results suggest that viscerosensory input to the parafascicular nucleus from vagal afferents mainly ascends by way of the ipsilateral parabrachial nucleus. [J Physiol Sci. 2008;58 Suppl:S158]
