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Epilepsy Res. 2009 Feb;83(2-3):261-4. Epub 2008 Dec 6.
Tolerance to the anticonvulsant effect of morphine in mice: blockage by ultra-low dose naltrexone.
Roshanpour M, Ghasemi M, Riazi K, Rafiei-Tabatabaei N, Ghahremani MH, Dehpour AR.
Department of Pharmacology, School of Pharmacy, Medical Sciences/University of Tehran, Tehran, Iran.
The present study evaluated the development of tolerance to the
anticonvulsant effect of morphine in a mouse model of clonic seizures
induced by pentylenetetrazole, and whether ultra-low doses of the
opioid receptor antagonist naltrexone which selectively block G(s)
opioid receptors were capable of preventing the observed tolerance. The
results showed that the morphine anticonvulsant effect could be subject
to tolerance after repeated administration. Both the development and
expression of tolerance were inhibited by ultra-low doses of
naltrexone, suggesting the possible involvement of G(s)-coupled opioid
receptors in the development of tolerance to the anticonvulsant effect