THE EFFECT OF VASOACTIVE DRUGS UPON THE SPINAL PAIN MODULATION

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The purpose of this study is to investigate the effects of vasoactive drugs on the wide dynamic range (WDR) neuron of the dorsal horn of the feline lumber spinal cord.Methods : Under nitrous oxide-oxygen-isoflurane anesthesia, cats of both sex were prepared with midcollicular decerebration and lumber laminectomy. The spinal cord win transected at T12-L1. WDR cells, responding primarily to noxious peripheral stimuli, were sampled with a microelectrode at the depth of 1500-2000 micrometer from the cord dorsum. Spontaneous activity and noxiously evoked activity by pinching the receptive field on the hind paw were measured.Diltiazem, as calcium channel blocker, 10 mg /ml (D 10 mg Group) or 20 mg/ml (D 20 mg Group) was administered on the surface of the cord dorsum by the drip method. Then, changes of the cell's firings of spontaneous and evoked activities in WDR were investigated every five minutes. Recoveries of firings were followed until the firings recovered by the control level.Clonidine, as α 2-adrenergic agonist, 5 micro g/ml (C 5 micro g Group) or 50 micro g /ml (C 50 micro g Group) was administered as some manner of diltiazem experiment.Results : All groups showed the suppressive effect. Diltiazem showed the suppressive effect on dose dependent manner. However, clonidine did not show the dose dependent manner.Discussion : Our results suggested that calcium channel blocker and α2 adrenergic agonist have suppressive effects on single-unit activities of WDR neuron. Therefore, both drugs are considered to be applied on the clinical use for the chronic intractable pain patients.Conclusion : Calcium channel and α2-adrenergic receptor are related with pain.