Antinociceptive effects of tizanidine, diazepam and eperisone in isolated spinal cord-tail preparations of newborn rat.
Antinociceptive effects of three centrally acting muscle relaxants, tizanidine, diazepam and eperisone, were studied using an isolated newborn rat spinal cord-tail preparation. Potentials were recorded from a lumbar ventral root (L3-L5) extracellularly using a suction electrode. Pinch stimulation applied to the tail elicited a depolarizing response in the ventral root lasting 15-30 sec, referred to as the tail-pinch potential. Electrical stimulation of the ipsilateral dorsal root of the same segment with a single shock induced depolarizing responses in the ventral root. The responses consisted of monosynaptic and polysynaptic reflexes with a fast time course, followed by a slow depolarizing response lasting about 20 sec. The latter slow response was designated the ipsilateral slow ventral root potential (VRP). Both the tail-pinch potential and the ipsilateral slow VRP were depressed by application to the spinal cord of tizanidine (2-3 microM), diazepam (2 microM) and eperisone (100-200 microM). The effect of tizanidine was reversed by alpha 2-adrenoreceptor antagonists, yohimbine and idazoxan, but not by an alpha 1-antagonist, prazosin. The effect of diazepam was reversed by the benzodiazepine antagonist, flumazenil.
Ishizuki
Masafumi
M
Department of Orthopaedic Surgery, Faculty of Medicine, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113 Japan Department of Pharmacology, Faculty of Medicine, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113 Japan.
Yanagisawa
Mitsuhiko
M
D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D003975:Diazepam / Q000494:pharmacology*; D005071:Evoked Potentials / Q000502:physiology; D066298:In Vitro Techniques; D009125:Muscle Relaxants, Central / Q000494:pharmacology*; D010812:Physical Stimulation; D011427:Propiophenones / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex / Q000187:drug effects / Q000502:physiology; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology; D013126:Spinal Nerve Roots / Q000502:physiology; D013623:Tail / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D000700:Analgesics; D009125:Muscle Relaxants, Central; D011427:Propiophenones; C030848:eperisone; C023754:tizanidine; D003000:Clonidine; D003975:Diazepam