title: Selective blockade by yohimbine of descending spinal inhibition from lateral reticular nucleus but not from locus coeruleus in rats.
abstract: The present study was undertaken to compare the effects of the alpha 2-adrenoceptor antagonist yohimbine on inhibition of C-fiber-evoked responses of dorsal horn neurons produced by electrical stimulation of the lateral reticular nucleus (LRN) and the Locus coeruleus (LC) in the rat. In the majority of neurons, C-fiber-evoked responses were significantly inhibited by 53.84 +/- 5.02% and 57.63 +/- 5.79% of control by LRN and LC stimulation, respectively, whereas in less than half of the neurons, A-fiber-evoked responses were reduced by 20.99 +/- 6.06% and 21.78 +/- 4.48% of control, respectively. After systemic or spinal administration of yohimbine, LC-induced inhibition of C-fiber-evoked responses was not affected. In contrast, LRN-induced inhibition was markedly attenuated by yohimbine. The results suggest that alpha 2-adrenoceptors may be involved in mediation of inhibition of spinal nociception induced by stimulation of LRN but not by LC.
authors.affiliation: Shanghai Brain Research Institute, Chinese Academy of Sciences.
authors.forename: R H
authors.initials: RH
authors.lastname: Liu
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Zhao
mesh_terms: D000287:Administration, Topical; D000818:Animals; D004525:Efferent Pathways / Q000187:drug effects; D004558:Electric Stimulation; D007275:Injections, Intravenous; D008125:Locus Coeruleus / Q000502:physiology*; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012154:Reticular Formation / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology*
chemical_list: D015016:Yohimbine