Regulatory Effects of Ionotropic and GroupⅠ Metabotropic Glutamate Receptors on Temperature Hypersensitivity in Rats / 中国医科大学学报

ABSTRACT

Objective To study the effects of ionic and group Ⅰ metabotropic glutamate receptors on rats' thermal hypersensitivity by intraplantar administration of drugs. Methods After intraplantar administration of glutamate receptor agonists,L-glutamic acid (Glu), N-methyl-D-aspartic-acid (NMDA),and (RS)-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid hydrobromide (AMPA);a Group Ⅰ mGluR agonist, (S) 3,5-dihydroxyphenylglycine [(S)-DHPG];a noncompetitive NMDA receptor antagonist, (+)-MK801 maleate (MK-801);a competitive AMPA/kainate receptor antagonist,6-cyano-7-nitroquinoxaline-2,3-dione (CNQX);and a selective GroupⅠ mGluR antagonist,7-hydroxyiminocyclo propan[b]chromen-1a- carboxylic acid ethyl ester (cpccoEt) into the left hind paws of rats whose L5-6 nerves were sham-operated or ligated,we examined the response of the rats to thermal stimuli provided by radiant heat. Results In sham-operated rats,glutamate,NMDA,AMPA,and (S)-DHPG reduced paw withdrawal latency (PWL) but did not have any effect on SNL rats. However,in SNL rats,MK-801,CNQX,and cpccoEt increased PWL but exerted no effect on sham-operated rats. Conclusion These results suggest that changes in sensitivity of peripheral ionic and group Ⅰ metabotropic glutamate receptors can lead to changes in peripheral nerve plasticity;the generation and maintenance of neuropathic pain caused by nerve injury is based on this plasticity.