Akagi H, Konishi S, Otsuka M, Yanagisawa M
Br J Pharmacol. 1985 Mar;84(3):663-73. doi: 10.1111/j.1476-5381.1985.tb16148.x.
In order to reveal the spinal reflexes involving the transmitter action of substance P (SP), the effects of capsaicin and an SP antagonist on the isolated spinal cord of the neonatal rat studied. When a single shock stimulus was given to a dorsal root (L3-L5) or a sciatic nerve, depolarizing responses of various time courses were recorded extracellularly from both ipsi- and contra-lateral ventral roots of the corresponding segments. The reflex response recorded from the contralateral ventral root consisted of fast and slow components, which will be referred to as contralateral fast and slow ventral root potentials (v.r.ps). The latter contralateral slow v.r.p. had a time-to-peak of 2-5 s and lasted 10-30 s. The threshold for the contralateral slow v.r.p. was about two times higher than that for the monosynaptic reflex, and it coincided with the threshold for activating the slow-conducting afferent fibres. The contralateral slow v.r.p. was abolished after the spinal cord was treated with capsaicin (1 microM for 30 min) in vitro. The contralateral slow v.r.p. was absent in the spinal cord derived from 4-day-old rats that had received capsaicin (50 mg kg-1, s.c.) on the 2nd day of life. The contralateral fast v.r.p. and other reflexes of fast time courses remained unaltered after treatment with capsaicin in vitro or in vivo. Administration of an SP antagonist, [D-Arg1, D-Pro2, D-Trp7,9 Leu11]-SP in concentrations of 5-16 microM depressed the contralateral slow v.r.p., but did not affect the monosynaptic reflex, the dorsal root potential and the contralateral fast v.r.p. [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-SP (5 microM) markedly depressed the SP-induced depolarizing response recorded from the ventral root whereas the responses to noradrenaline, 5-hydroxytryptamine, neurotensin and thyrotrophin releasing hormone (TRH) were unaffected by the SP antagonist. The response of the ventral root to acetylcholine was slightly depressed by the antagonist. The SP antagonist at 5-10 microM did not exert any agonist action on the motoneurones. The present results in conjunction with those of previous studies support the hypothesis that SP released from certain primary afferent fibres acts as a neurotransmitter, producing in dorsal horn neurones slow excitatory postsynaptic potentials which lead to the generation of the contralateral slow v.r.p.
为了揭示涉及P物质（SP）递质作用的脊髓反射，研究了辣椒素和一种SP拮抗剂对新生大鼠离体脊髓的影响。当对背根（L3-L5）或坐骨神经给予单次电休克刺激时，从相应节段同侧和对侧腹根细胞外记录到不同时程的去极化反应。从对侧腹根记录到的反射反应由快速和慢速成分组成，将其称为对侧快速和慢速腹根电位（v.r.ps）。后者的对侧慢速v.r.p.的峰值时间为2-5秒，持续10-30秒。对侧慢速v.r.p.的阈值比单突触反射的阈值高约两倍，并且与激活慢传导传入纤维的阈值一致。在体外将脊髓用辣椒素（1 microM，30分钟）处理后，对侧慢速v.r.p.消失。在出生第2天接受辣椒素（50 mg kg-1，皮下注射）的4日龄大鼠的脊髓中，不存在对侧慢速v.r.p.。在体外或体内用辣椒素处理后，对侧快速v.r.p.和其他快速时程的反射保持不变。给予浓度为5-16 microM的SP拮抗剂[D-Arg1，D-Pro2，D-Trp7,9 Leu11]-SP可抑制对侧慢速v.r.p.，但不影响单突触反射、背根电位和对侧快速v.r.p.。[D-Arg1，D-Pro2，D-Trp7,9，Leu11]-SP（5 microM）显著抑制从腹根记录到的SP诱导的去极化反应，而对去甲肾上腺素、5-羟色胺、神经降压素和促甲状腺素释放激素（TRH）的反应不受SP拮抗剂影响。拮抗剂使腹根对乙酰胆碱的反应略有降低。5-10 microM的SP拮抗剂对运动神经元没有任何激动作用。目前的结果与先前的研究结果共同支持以下假说：从某些初级传入纤维释放的SP作为一种神经递质，在背角神经元中产生缓慢的兴奋性突触后电位，从而导致对侧慢速v.r.p.的产生。
