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Effects of intrathecally administered dexmedetomidine, MPV‐2426 and tizanidine on EMG in rats
Author(s) -
TALKE P.,
Xu M.,
Paloheimo M.,
Kalso E.
Publication year - 2003
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1034/j.1399-6576.2003.00068.x
Subject(s) - dexmedetomidine , tizanidine , medicine , anesthesia , medetomidine , clonidine , muscle relaxant , sedation , nociception , agonist , saline , pharmacology , spasticity , heart rate , receptor , blood pressure
Background: When administered intrathecally, alpha‐2 adrenergic agonists produce spinally mediated antinociception, but also rapidly redistribute to supraspinal sites. This investigation the compared EMG effects of intrathecally administered dexmedetomidine, MPV‐2426 (fadolmidine), and tizanidine in Sprague‐Dawley rats, which has not been previously described. Methods: We studied electromyographic (EMG) responses of the head and gastrocnemius muscles, antinociception using the tail‐flick test, and sedation by using observer assessment. Saline, dexmedetomidine (0.5 µg, 2.5 µg and 12.5 µg), MPV‐2426 (2 µg, 10 µg and 50 µg) and tizanidine (2 µg, 10 µg and 50 µg) were administered intrathecally. Results: Tizanidine 50 µg, MPV‐2426 10 µg and 50 µg, and dexmedetomidine 2.5 µg and 12.5 µg, decreased EMG activity ( P < 0.005). Dexmedetomidine 12.5 µg, MPV‐2426 50 µg, and tizanidine 10 µg and 50 µg increased tail‐flick latencies ( P < 0.01). Dexmedetomidine alone significantly increased the magnitude of observer‐assessed sedation ( P < 0.0001). Conclusion: We conclude that in rats, intrathecally administered dexmedetomidine, MPV‐2426 and tizanidine have dose‐dependent effects on EMG. At antinociceptive doses, the EMG effects of these three alpha‐2 adrenergic agonists differ (dexmedetomidine > MPV‐2426 > tizanidine).