Kappa opioid receptor density is consistent along the rostrocaudal axis ofthe female rat spinal cord

Kappa opioid receptors (KORs) were immunocytochemically localized at four d ifferent levels of the spinal cord of normally-cycling female rats in estru s or diestrus. KOR labeling was primarily observed in fine processes and a few neuronal cell bodies in the superficial dorsal horn and the dorsolatera l funiculus. Quantitative light microscopic densitometry of the superficial dorsal horn revealed that there were no significant differences in KOR den sities among spinal segments C1-C2, T2- T13-L1. and L6-S1 in either the est rus or diestrus phases. These results suggest that the potential for KOR-me diated antinociceptive responses is consistent along the rostrocaudal axis of the female rat spinal cord. (C) 2001 Elsevier Science B.V. All rights re served.