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Segmental effects on motor function following different intrathecal receptor agonists and antagonists in rabbits
Author(s) -
BORGBJERG F. M.,
FRIGAST C.
Publication year - 1997
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 - 10.1111/j.1399-6576.1997.tb04748.x
Subject(s) - medicine , agonist , naltrindole , yohimbine , pharmacology , (+) naloxone , opioid , anesthesia , opioid receptor , antagonist , receptor
Background: The occurrence of motor impairment after intrathecal drug administration is infrequently reported in the literature and the methods of determining motor function vary. Methods: Motor function was examined in rabbits after a wide dose range of a variety of intrathecally administered opioid agonists, α‐adrenergic agonists, non‐competitive NMDA antagonists, a benzodiazepine agonist, a sigma agonist, paracetamol, isotonic and acidified saline. The opioids, sigma agonist and NMDA antagonists were additionally examined following pre‐treatment with naloxone. The opioid antagonists naltrindole and MR2266 (δ‐ and K‐opioid receptor antagonists, respectively) were administered before the δ agonist and the K agonist. The δ adrenergic antagonist yohimbine was given before administration of dexmedetomidine and xylazine. Motor function was evaluated by a five‐point scale of motor impairment ranging from normal function to total paralysis of the hindlegs. Results: DPDPE (δ agonist), paracetamol, naloxone, naltrindole, yohimbine, isotonic and acidified saline did not affect motor function. MR2266 produced minor motor impairment. The α‐adrenergic agonist dexmedetomidine reduced motor function slightly and dose independently. The remaining compounds affected motor function in a dose‐dependent fashion. High doses of morphine produced hypersensitivity and myoclonus. An irreversible paralysis of the hindlegs was observed following intrathecal administration of the sigma agonist SKF10047 in high doses. Naloxone and MR2266 attenuated the effects of U50488H (K agonist). Conclusion: The present results reveal a dose‐dependent reduction in motor function after intrathecal administration of some of the investigated compounds. The mechanisms behind these effects appear to be multifactorial.