Kainate receptors in terminals of primary afferents,Spring pain research conference

Abstract

KAINATE RECEPTORS IN TERMINALS OF PRIMARY AFFERENTS. S.J. Hwang, A. Rustioni and J.G. Valtschanoff. Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, NC 27599, USA.

Kainate receptors (GluR5/6/7) are densely expressed in the superficial laminae of the rat dorsal horn. With immunocytochemistry, fluorescent staining for GluR5/6/7 was most prominent in puncta in the neuropil of laminae I and II. Some immunoreactive puncta were also stained for the presynaptic marker synaptophysin, especially in weakly fixed tissue. That numerous dorsal root ganglion neurons and fibers in the dorsal roots exhibited immunoreactivity for GluR5/6/7, suggested that double stained terminals are of primary afferent origin. This was confirmed by anterograde labeling with IB4 and cholera toxin B, with electron microscopy, which showed that GluR5/6/7 was present in terminals with morphology of primary afferents, and by the disappearance of the colocalization of GluR5/6/7 with synaptophysin after dorsal rhizotomy. Kainate receptors immunostaining was also present in terminals of primary afferents to the dorsal column nuclei and the spinal trigeminal nucleus, but not in other nuclei of medulla or the ventral postero-lateral thalamic nucleus. We take the present results to indicate a special role for the kainate receptors in the signal processing of various afferent modalities, including pain, exclusively at the level of the first synapse in the somatosensory system. Supported by NIH grant #12440.