The study of antinociceptive effects of anesthetics and analgesics using dorsal root ganglia cells.

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The effects of anesthetics on ion channels have been the focus of several studies. During the last decade, major advances have been made in our understanding of the physiology and pharmacology of G-protein coupled receptor (GPCR) signaling. Further studies have shown that GPCRs are targets for anesthetics. However, less is known about the mechanisms of action of anesthetics on GPCRs, ion channels and ligand-gated ion channels in spinal cords levels. The Xenopus oocyte expression system has been used widely to study numerous brain ion channels and GPCRs. A large number of types have been found on primary afferent neurons, either on their central or peripheral processes or on the cell bodies of the dorsal root ganglion (DRG) cells and it is have been reported the presence of several GPCRs. Therefore the DRG have been used for the study of nociception.(1)We studied the effects of anesthetics on substance P-evoked intracellular [Ca^<2+>] ([Ca^<2+>]_i)increasing in cultured DRG cells. Substance P induced a rapid [Ca^<2+>]_i increase in single DRG cell. Volatile anesthetics halothane inhibited the substance P-evoked increases in [Ca^<2+>]_i.(2)Tramadol, metabolite M1 and alphaxalone inhibited voltage dependent Na channels expressed in Xenopus oocytes that expressed M_3. High concentration of dexmedetomidine inhibited voltage dependent Na channels expressed in Xenopus oocytes that expressed M_3.(3)Most volatile anesthetics inhibited substance P receptor function expressed in Xenopus oocytes that expressed M_3. Moreover, ketamine and pentobarbital inhibited substance P receptor function expressed in Xenopus oocytes that expressed M_3.(4)We studied the effects of anesthetics on orexin A and neuropeptide FF-evoked [Ca^<2+>]_i increasing in cultured DRG cells. Orexin A and neuropeptide FF induced a rapid [Ca^<2+>]_i increase in single DRG cell suggesting that these receptors exist in DRG.Our present results would be useful for understanding the mechanisms of anesthetics.