Journal of neurophysiology
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1. This study examined the effects of the 15-lipoxygenase product of arachidonic acid metabolism, (8R,15S)-dihydroxyicosa-(5E-9,11,13Z)tetraenoic acid (8R,15S-diHETE), on mechanical thresholds and thermal responses of saphenous nerve cutaneous C-fiber nociceptors that innervate the hairy skin of the rat hindpaw. Single C-fiber mechanoheat nociceptors (C-MH) that had von Frey hair (VFH) thresholds greater than 5 g and were activated by a noxious heat stimulus were chosen for study. ⋯ The 8R,15S-diHETE-induced sensitization of C-MHs to mechanical stimuli was completely antagonized by coadministration with a stereoisomer, 8S,15S-diHETE (n = 10). 4. The mechanical threshold of C-MHs (n = 10), previously injected with the combination of 8R,15S-diHETE and 8S,15S-diHETE, was significantly reduced by a subsequent injection of PGE2. In a separate group of C-MHs (n = 7), PGE2 was co-injected with 8S,15S-diHETE, which failed to antagonize the sensitizing effect of PGE2 on mechanical threshold. 5. 8R,15S-diHETE also sensitized C-MHs (n = 9) to a thermal stimulus consisting of 37 degrees C for 5 min.(ABSTRACT TRUNCATED AT 250 WORDS)
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1. Single-unit electrical activity has been recorded from 34 dorsal horn neurons in the sacral segments (S1-2) of the spinal cord in halothane-anesthetized rats. All of the neurons had cutaneous receptive fields (RFs) on the rat's tail. ⋯ We conclude that the majority of nociceptive dorsal horn neurons are subject to a net tonic descending control of their RF properties. The class 2 neurons in the deep dorsal horn appear to be a heterogeneous population, some cells being under tonic descending excitation and others under tonic descending inhibition. Class 3 cells can be separated into those located in the superficial dorsal horn, whose RF properties show very little change on spinalization, and those in the deep dorsal horn, whose RF properties change markedly on spinalization.(ABSTRACT TRUNCATED AT 400 WORDS)