Brugger F, Evans R H, Hawkins N S
CIBA-GEIGY, Basel, Switzerland.
Neuroscience. 1990;36(3):611-22. doi: 10.1016/0306-4522(90)90004-n.
Electrical stimulus intensity, capsaicin, excitatory amino acid antagonists and the substance P antagonist, spantide, have been used to investigate the roles of primary afferent C fibres and excitatory amino acid receptors in the generation of long duration (half time 9.1 s +/- 1.1 S.E.M., N = 24) contralateral reflexes recorded in ventral roots of immature rat spinal cords in vitro. The relationship between C fibre compound action potentials recorded in the dorsal root and duration of the dorsal root-evoked contralateral ventral root potential appeared to be coincidental rather than causal. Dorsal root-evoked contralateral ventral root potentials of greater than 2 s in duration could not be evoked in mature mouse spinal preparations. Application of capsaicin (1 microM for 15-120 min) produced a long lasting increase in spontaneous activity of ventral roots as well as blockade of C fibre conduction in dorsal roots. The dorsal root potential evoked following stimulation of adjacent dorsal roots at intensities insufficient for activation of C fibres was depressed by capsaicin. Dorsal root-evoked contralateral ventral root potentials were abolished by kynurenate (EC50 56 +/- 13 microM, N = 3) and depressed to 38.2 +/- 6.9% S.E.M. (N = 7) of pre-drug levels by the N-methyl-D-aspartate receptor antagonist 2-amino-5-phosphonopentanoate (20 microM) or to 51.8 +/- 9.0% (N = 7) by the substance P analogue spantide (33 microM). Spantide consistently antagonised substance P-induced, but not capsaicin-induced, depolarizations recorded in ventral roots (+-)-2-Amino-5-phosphonopentanoic acid (10-50 microM) depressed both substance P- and capsaicin-induced depolarizations. The depressant effect of spantide, unlike that of (+/-)-2-amino-5-phosphonopentanoic acid, was associated with a long lasting excitatory action. In the presence of tetrodotoxin (0.1 microM), spantide (33 microM) failed to antagonize substance P-induced depolarizations. It is suggested that long duration of the dorsal root-evoked contralateral ventral root potential is a consequence of the activation of the N-methyl-D-aspartate receptor operated ion channels by excitatory amino acid transmitters.
电刺激强度、辣椒素、兴奋性氨基酸拮抗剂和P物质拮抗剂spantide，已被用于研究初级传入C纤维和兴奋性氨基酸受体在体外未成熟大鼠脊髓腹根中记录到的长时间（半衰期9.1秒±1.1标准误，N = 24）对侧反射产生中的作用。在背根中记录到的C纤维复合动作电位与背根诱发的对侧腹根电位持续时间之间的关系似乎是巧合而非因果关系。在成熟小鼠脊髓制备物中无法诱发出持续时间超过2秒的背根诱发对侧腹根电位。应用辣椒素（1微摩尔/升，持续15 - 120分钟）可使腹根的自发活动长期增加，同时阻断背根中C纤维的传导。辣椒素可抑制在不足以激活C纤维的强度下刺激相邻背根后诱发的背根电位。犬尿烯酸（半数有效浓度56±13微摩尔/升，N = 3）可消除背根诱发的对侧腹根电位，N - 甲基 - D - 天冬氨酸受体拮抗剂2 - 氨基 - 5 - 膦酰基戊酸（20微摩尔/升）可使其降至给药前水平的38.2±6.9%标准误（N = 7），P物质类似物spantide（33微摩尔/升）可使其降至51.8±9.0%（N = 7）。Spantide始终能拮抗在腹根中记录到的P物质诱导的去极化，但不能拮抗辣椒素诱导的去极化。（±）-2 - 氨基 - 5 - 膦酰基戊酸（10 - 50微摩尔/升）可抑制P物质和辣椒素诱导的去极化。与（±）-2 - 氨基 - 5 - 膦酰基戊酸不同，spantide的抑制作用与长期的兴奋作用有关。在存在河豚毒素（0.1微摩尔/升）的情况下，spantide（33微摩尔/升）无法拮抗P物质诱导的去极化。提示背根诱发的对侧腹根电位的长时间是兴奋性氨基酸递质激活N - 甲基 - D - 天冬氨酸受体操纵的离子通道的结果。
