title: Involvement of alpha2-adrenoceptors in mediating sympathetic excitation of injured dorsal root ganglion neurons in rats with spinal nerve ligation.
abstract: The present study examined the effects of sympathetic stimulation on the activity of primary afferent neurons that had peripheral axons being injured previously by a spinal nerve ligation. About 22% of afferents with injured fibers that showed spontaneous discharge were excited by sympathetic stimulation or systemic injection of adrenaline. Most sympathetically-excited afferent neurons had axons that conducted in the A-fiber range. This sympathetically-evoked afferent excitation was not affected by cutting the spinal nerve at a place close to the dorsal root ganglion (DRG). Yohimbine, alpha2-antagonist, suppressed sympathetically-evoked afferent excitation which was not affected by alpha1-antagonist prazosin. Clonidine, alpha2-agonist, exerted an excitatory effect, whereas alpha1-agonist phenylephrine had no effect on the activity of afferents with injured fibers. No afferent fibers in control preparations responded to sympathetic stimulation. The results suggest that after a spinal nerve ligation, injured DRG neurons with fast-conducting fibers become sensitive to sympathetic activity via activation of alpha2-adrenoceptors.
authors.affiliation: Department of Physiology, Yonsei University College of Medicine, Seoul, South Korea. jwleen@yumc.yonsei.ac.kr
authors.forename: J W
authors.initials: JW
authors.lastname: Leem
authors.forename: Y S
authors.initials: YS
authors.lastname: Gwak
authors.forename: T S
authors.initials: TS
authors.lastname: Nam
authors.forename: K S
authors.initials: KS
authors.lastname: Paik
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology*; D008026:Ligation; D008297:Male; D009474:Neurons / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D013127:Spinal Nerves / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D018341:Receptors, Adrenergic, alpha-2; D010656:Phenylephrine; D015016:Yohimbine; D003000:Clonidine; D011224:Prazosin