The effects of N-methyl-D-aspartate antagonist MK-801 and adenosine receptor agonists on mononeuropathic rats

Abstract

The present study was to determine whether administration of adenosine A1 receptor agonist cyclohexyladenosine (CHA) and adenosine A1/A2 receptor agonist 5?N-ethylcarboxamidoadenosine (NECA) and N-methyl-D-aspartate antagonist MK-801 on thermal nociception in rat chronic constriction injury model. 48 Sprague Dawley male rats weighting 185-225 g were included to the study. The right common sciatic nerves were ligated loosely with four 4/0 chromic gut under barbiturate anesthesia. Drugs were administered and nociceptive test performed for four days after 7 days' recovery. NECA, CHA and MK-801 were administered two times at doses of 0.1 mg/kg, 1 mg/kg, and 1 mg/kg respectively. The doses were inclined to the half while both of two drug were given. Noci-ceptive threshold was determined by hot plate test at 46°C during treatment period. Time to jumping or licking of the limb on the operated site was determined. The thermal test results of MK-801 given animals were demonstrated antinociception initially, but declined to the baseline through the treatment period. Antiallodynic effects reduced on CHA group when combined with MK-801. The nociceptive treshold of NECA treated animals were as the same with NECA+MK-801. Antiallodynic effects of NECA were partly due to its motor blocking properties. The results we obtained appear to be disappointing while both of two class of drugs given systemically acting as glutamate antagonist. The future studies may be directed to the other routes which may act synergistically.