EFFECTS OF AMINO ACID ANTAGONISTS ON SPONTANEOUS DORSAL ROOT ACTIVITY AND EVOKED DORSAL HORN FIELD POTENTIALS IN AN ISOLATED PREPARATION OF RAT SPINAL CORD

Fast and slow dorsal horn field potentials and spontaneous dorsal root activity were recorded from 19–23-day-old rat isolated spinal cord preparations. The effects of GABA, glycine, and glutamate antagonists were tested on these recordings. CNQX, an AMPA/kainate antagonist, reduced all 3 components of the dorsal horn field potential whereas MK801, an NMDA ion channel antagonist, reduced the fast S2 component and the slow wave. Both reduced spontaneous dorsal root activity. NMDA antagonists, D-AP5, 7-chlorokynurenic acid and arcaine, and the metabotropic glutamate antagonists L-AP3 and ethylglutamic acid, while having little effect on the fast components of the field potential, all reduced the slow component. The GABA antagonist, bicuculline, and the glycine antagonist, strychnine, while having no effect on the fast S1 and slow components of the field potential, reduced both the fast S2 component of the field potential and spontaneous dorsal root activity. These results suggest that non-NMDA glutamate receptors are involved in low and high threshold transmission to dorsal horn neurones while NMDA and metabotropic glutamate receptors are primarily involved in high threshold transmission and both GABA and glycine have roles in the transmission or modulation of sensory information within the dorsal horn of the cord.

从19 - 23日龄的大鼠离体脊髓标本中记录到快、慢背角场电位以及自发背根活动。测试了γ - 氨基丁酸（GABA）、甘氨酸和谷氨酸拮抗剂对这些记录的影响。AMPA /红藻氨酸拮抗剂CNQX降低了背角场电位的所有3个成分，而NMDA离子通道拮抗剂MK801降低了快S2成分和慢波。两者都降低了自发背根活动。NMDA拮抗剂D - AP5、7 - 氯犬尿酸和阿柯碱，以及代谢型谷氨酸拮抗剂L - AP3和乙基谷氨酸，虽然对场电位的快成分影响很小，但都降低了慢成分。GABA拮抗剂荷包牡丹碱和甘氨酸拮抗剂士的宁，虽然对场电位的快S1和慢成分没有影响，但降低了场电位的快S2成分和自发背根活动。这些结果表明，非NMDA谷氨酸受体参与了向背角神经元的低阈值和高阈值传递，而NMDA和代谢型谷氨酸受体主要参与高阈值传递，并且GABA和甘氨酸在脊髓背角内的感觉信息传递或调制中都起作用。