CHARACTERIZATION OF THE INWARD CURRENT INDUCED BY GROUP I METABOTROPIC GLUTAMATE RECEPTOR STIMULATION IN THE SUBSTANTIA GELATINOSA NEURONS OF RATS

초록

Metabotropic glutamate receptors (mGluRs) of spinal dorsal horn neurons have been known to play important roles in pain modulation through gating diverse ionic conductances and modulating synaptic transmission. To determine the cellular mechanism for action of group I mGluR on excitability of substantia gelatinosa (SG) neuron, we have used whole-cell patch clamp recordings from SG neurons in spinal cord slices of rats (p7~13). At a holding potential of -60mV, 2M quisqualate, group I mGluR agonist, reversibly induced an inward current, and this current had a reversal potential at near 27mV. The quisqualate-induced inward current was inhibited by the selective group I mGluR antagonist, (RS)-1-aminoindan-1,5- dicarboxylic acid (AIDA). When internal solution with BAPTA 10 mM was used, this current was still observed. It was suggested that the quisqualate-induced inward current might be not associated with intracellular Ca2+ concentration. In addition, gadolinium, a non-selective cationic channel blocker, and KB-R7943, a Na+-Ca2+ exchanger blocker, did not affect this current. The transient receptor potential (TRP) channel antagonists, La3+, and 2-aminoethoxydiphenylborane (2-APB) inhibited the quisqualate-induced inward current. Taken together, group I mGluR-activated current may be mediated by activation of an ion channel which has several properties of TRP family.