title: Intravenous midazolam suppresses noxiously evoked activity of spinal wide dynamic range neurons in cats.
abstract: The effects of intravenously (i.v.) administered midazolam on noxiously evoked activity of spinal wide dynamic range (WDR) neurons were investigated in decerebrate, spinal-cord-transected cats. Extracellular, single-unit recordings were measured during stimulation by pinching the receptive field on the hind paw and the effect of midazolam at doses of 0.25, 0.5, 1, 2, and 4 mg/kg were measured. Two series of experiments were performed to characterize the analgesic effects of midazolam. In the first, dose-response experiments (n = 59) demonstrated a dose-dependent suppression of the noxiously evoked activity of spinal WDR neurons after midazolam administration. This effect of midazolam was maximal at a dose of 1 mg/kg i.v.. The second series of experiments (n = 14) demonstrated that a benzodiazepine antagonist, flumazenil (n = 8), promptly reversed the effect of midazolam, while an opioid antagonist, naloxone (n = 6), had no effect on the effect of midazolam. The present study demonstrates that i.v. administered midazolam suppresses noxiously evoked activity of spinal WDR neurons that is reversible by a benzodiazepine antagonist. This is consistent with an analgesic action of midazolam.
authors: Department of Anesthesiology, Faculty of Medicine, University of Tokyo, Japan.
authors: T
authors: T
authors: Sumida
authors: M
authors: M
authors: Tagami
authors: Y
authors: Y
authors: Ide
authors: M
authors: M
authors: Nagase
authors: H
authors: H
authors: Sekiyama
authors: K
authors: K
authors: Hanaoka
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D004305:Dose-Response Relationship, Drug; D005071:Evoked Potentials; D005260:Female; D005442:Flumazenil / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D007262:Infusions, Intravenous; D008297:Male; D008874:Midazolam / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D013116:Spinal Cord / Q000187:drug effects*
chemical_list: D005442:Flumazenil; D008874:Midazolam