title: Thiamylal antagonizes the inhibitory effects of dorsal column stimulation on dorsal horn activities in humans.
abstract: In humans, peripheral somatosensory information converges upon dorsal horn neurons in the spinal cord, which can be recorded from the dorsal epidural space as spinal cord potentials (SCPs) following segmental dorsal root stimulation (SS) employing epidural catheter electrodes. Antidromic action potentials and descending inhibition from the dorsolateral funiculus may contribute to SCPs following dorsal column stimulation (DCS). Effects of thiamylal (2.5-7.5 mg/kg, i.v.) on SCPs evoked by independent DCS or SS were compared with those evoked by simultaneous DCS and SS (DCS/SS). DCS- and SS-evoked SCPs recorded from the lumbar enlargement consisted of a sharp negative (N) followed by a slow positive (P) potential. Thiamylal induced dose-dependent increases in amplitude and duration of both N and P potentials evoked by DCS and SS, whether the responses were summed or evoked simultaneously. In awake subjects, N and P potentials produced by simultaneous DCS/SS were significantly smaller than the sum of independent responses. Thiamylal anesthesia antagonized this inhibition; responses to simultaneous DCS/SS were larger than the sum of independent responses. These results suggest that in wakefulness DCS inhibits dorsal horn neuron activity in the lumbar spinal cord, while thiamylal antagonizes DCS-induced inhibition in dose-dependent fashion.
authors.affiliation: Department of Physiology, Kurume University School of Medicine, Asahi-machi 67, Kurume 830-0011, Japan. eacht@med.kurume-u.ac.jp
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Tanaka
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Tobita
authors.forename: Yoshinaka
authors.initials: Y
authors.lastname: Murai
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Okabe
authors.forename: Aya
authors.initials: A
authors.lastname: Yamada
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kano
authors.forename: Hideho
authors.initials: H
authors.lastname: Higashi
authors.forename: Koki
authors.initials: K
authors.lastname: Shimoji
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000344:Afferent Pathways / Q000187:drug effects* / Q000502:physiology; D018686:Anesthetics, Intravenous / Q000494:pharmacology; D002648:Child; D004305:Dose-Response Relationship, Drug; D004599:Electric Stimulation Therapy / Q000379:methods; D004566:Electrodes; D004594:Electrophysiology / Q000295:instrumentation / Q000379:methods; D004824:Epidural Space / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects / Q000502:physiology; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D010146:Pain / Q000188:drug therapy / Q000503:physiopathology; D020671:Posterior Horn Cells / Q000187:drug effects* / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D013126:Spinal Nerve Roots / Q000502:physiology; D013840:Thiamylal / Q000494:pharmacology*; D014851:Wakefulness / Q000502:physiology
chemical_list: D018686:Anesthetics, Intravenous; D013840:Thiamylal