Antinociceptive interaction between spinal clonidine and lidocaine in the rat formalin test: An isobolographic analysis

Shuanglin Hao, Osamu Takahata, Hiroshi Iwasaki

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Abstract

Clinical and basic science studies suggest that spinal α-2-adrenergic receptor agonists and local anesthetics produce analgesia, but interaction between α-2-adrenergic receptor agonists and local anesthetics in the persistent pain model has not been examined. In the present study, using isobolographic analysis, we investigated the antinociceptive interaction of intrathecal clonidine and lidocaine in the rat formalin test. Sprague-Dawley rats were implanted with chronic lumbar intrathecal catheters, and were tested for paw flinch by formalin injection. Biphasic painful behavior was counted. Intrathecal clonidine (3-12 nmol) was administered 15 min before formalin, and intrathecal lidocaine (375-1850 nmol) was administered 5 min before formalin. To examine the interaction of intrathecal clonidine and lidocaine, an isobolographic design was used. Spinal administration of clonidine produced dose-dependent suppression of the biphasic responses in the formalin test. Spinal lidocaine resulted in dose-dependent transient motor dysfunction and the motor dysfunction recovered to normal at 10-15 min after administration. Spinal lidocaine produced dose-dependent suppression of phase-2 activity in the formalin test. Isobolographic analysis showed that the combination of intrathecal clonidine and lidocaine synergistically reduced Phase-2 activity. We conclude that intrathecal clonidine synergistically interacts with lidocaine in reducing the nociceptive response in the formalin test.

Original languageEnglish
Pages (from-to)733-738
Number of pages6
JournalAnesthesia and Analgesia
Volume92
Issue number3
StatePublished - Mar 13 2001
Externally publishedYes

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Clonidine
Pain Measurement
Lidocaine
Formaldehyde
Adrenergic Agonists
Local Anesthetics
Analgesia
Sprague Dawley Rats
Catheters
Pain
Injections

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

Cite this

Antinociceptive interaction between spinal clonidine and lidocaine in the rat formalin test : An isobolographic analysis. / Hao, Shuanglin; Takahata, Osamu; Iwasaki, Hiroshi.

In: Anesthesia and Analgesia, Vol. 92, No. 3, 13.03.2001, p. 733-738.

Research output: Contribution to journalArticle

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