摘要：

Although there is considerable evidence that primary afferent-derived contributes to the transmission of nociceptive messages at the spinal cord level, the population of neurons that expresses the , and thus are likely to respond to , has not been completely characterized. To address this question, we used an antibody directed against the C-terminal portion of the to examine the cellular distribution of the receptor in spinal cord neurons. In a previous study, we reported that the decorates almost the entire dendritic and somatic surface of a subpopulation of spinal cord neurons. In the present study we have taken advantage of this labeling pattern to identify morphologically distinct subpopulations of -immunoreactive neurons throughout the rostral-caudal extent of the spinal cord. We observed a dense population of fusiform -immunoreactive neurons in lamina I at all segmental levels. Despite having the highest concentration of terminals, the substantia gelatinosa (lamina II) contained almost no -immunoreactive neurons. Several distinct populations of -immunoreactive neurons were located in III-V; many of these had a large, dorsally directed dendritic arbor that traversed the substantia gelatinosa to reach the marginal layer. Extensive labeling was also found in neurons of the intermediolateral cell column. In the ventral horn, we found that labeling was associated with clusters of motoneurons, notably those in Onuf's in the sacral spinal cord. Finally, we found no evidence that primary afferent fibers express the . These results indicate that relatively few, but morphologically distinct, subclasses of spinal cord neurons express the . The majority, but not all, of these neurons are located in regions that contain neurons that respond to noxious stimulation.

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