Thiamylal antagonizes the inhibitory effects of dorsal column stimulation on dorsal horn activities in humans

• Published in: Neuroscience Research Vol. 64; no. 4; pp. 391 - 396
• Main Authors: Tanaka, Eiichiro, Tobita, Toshiyuki, Murai, Yoshinaka, Okabe, Yasunori, Yamada, Aya, Kano, Tatsuhiko, Higashi, Hideho, Shimoji, Koki
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01.08.2009; Elsevier BV
• Subjects: Action Potentials; Action Potentials - physiology; Adolescent; Afferent Pathways; Afferent Pathways - drug effects; Afferent Pathways - physiology; Anesthetics, Intravenous; Anesthetics, Intravenous - pharmacology; Child; Dose-Response Relationship, Drug; Electric Stimulation Therapy; Electric Stimulation Therapy - methods; Electrodes; Electrophysiology; Electrophysiology - instrumentation; Electrophysiology - methods; Epidural Space; Epidural Space - physiology; Evoked Potentials, Somatosensory; Evoked Potentials, Somatosensory - drug effects; Evoked Potentials, Somatosensory - physiology; Female; Human; Humans; Intravenous anesthetic; Lumbar Vertebrae; Male; Neural Inhibition; Neural Inhibition - drug effects; Neural Inhibition - physiology; Pain; Pain - drug therapy; Pain - physiopathology; Posterior Horn Cells; Posterior Horn Cells - drug effects; Posterior Horn Cells - physiology; Spinal Cord; Spinal Cord - cytology; Spinal Cord - drug effects; Spinal Cord - physiology; Spinal cord potential; Spinal Nerve Roots; Spinal Nerve Roots - physiology; Thiamylal; Thiamylal - pharmacology; Thiamylal sodium; Wakefulness; Wakefulness - physiology; Human; Thiamylal sodium; Intravenous anesthetic; Spinal cord potential
• ISSN: 0168-0102; 1872-8111; 1872-8111
• DOI: 10.1016/j.neures.2009.04.012

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.