Lin Q, Peng Y, Willis W D
Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77555-0843.
Brain Res. 1994 Aug 22;654(2):286-302. doi: 10.1016/0006-8993(94)90491-x.
Amino acids are demonstrated to be important neurotransmitters mediating the inhibitory transmission from nucleus raphe magnus to spinal nociceptive dorsal horn neurons. In this study, the role of glycine and GABA in the inhibitory processes evoked by stimulation in periaqueductal gray (PAG) of responses of primate spinothalamic tract (STT) neurons to cutaneous mechanical and thermal stimuli was investigated by examining the effects of strychnine and bicuculline, antagonists of glycine and GABAA receptors, respectively, introduced into the dorsal horn through a microdialysis fiber. The inhibitory effects of iontophoretic application of glycine and GABAA agonists on STT cell activity evoked by noxious mechanical stimulation of the skin were selectively blocked by their specific antagonist, strychnine or bicuculline, infused into the dorsal horn. Similarly, intra-spinal application of strychnine or bicuculline resulted in a significant reduction in the PAG stimulation-induced inhibition of responses of STT cells to cutaneous stimuli. This reduction was mainly on the PAG-induced inhibition of the responses to noxious mechanical stimuli. Our results suggest that glycinergic and GABAergic inhibitory interneurons in the spinal cord dorsal horn synapsing on STT cells are activated during stimulation in PAG and contribute to descending antinociceptive actions.
氨基酸被证明是重要的神经递质，介导从中缝大核到脊髓伤害性背角神经元的抑制性传递。在本研究中，通过检测分别作为甘氨酸和GABAA受体拮抗剂的士的宁和荷包牡丹碱经微透析纤维导入背角后的作用，研究了甘氨酸和GABA在中脑导水管周围灰质（PAG）刺激诱发的对灵长类动物脊髓丘脑束（STT）神经元对皮肤机械和热刺激反应的抑制过程中的作用。注入背角的甘氨酸和GABAA激动剂离子导入对皮肤有害机械刺激诱发的STT细胞活动的抑制作用，被其特异性拮抗剂士的宁或荷包牡丹碱选择性阻断。同样，脊髓内注射士的宁或荷包牡丹碱导致PAG刺激诱导的STT细胞对皮肤刺激反应的抑制作用显著降低。这种降低主要是针对PAG诱导的对有害机械刺激反应的抑制。我们的结果表明，在PAG刺激期间，脊髓背角中与STT细胞形成突触的甘氨酸能和GABA能抑制性中间神经元被激活，并有助于下行性抗伤害感受作用。
