Akagi H, Yanagisawa M
Br J Pharmacol. 1987 May;91(1):189-97. doi: 10.1111/j.1476-5381.1987.tb08998.x.
The effects of gamma-aminobutyric acid (GABA) and other drugs which interact with GABA receptors were studied on a reflex of slow time course in the spinal cord preparation isolated from the neonatal rat. A single shock to a dorsal root (L3-L5) elicited a stereotyped series of reflexes, consisting of fast and slow components, recorded from the contralateral ventral root of the corresponding segment. The slow component, i.e. the contralateral slow ventral root potential (v.r.p.) had a time-to-peak of 2-5 s and lasted 20-30 s. Bath-application of GABA (5-20 microM) or muscimol (0.05-0.5 microM) caused a decrease in the amplitude of the contralateral slow v.r.p. without producing any change in the d.c. potential recorded from the ventral root. The monosynaptic reflex recorded from the ipsilateral ventral root was not changed by the drugs at these concentrations. Diazepam (0.1-1 microM) potentiated the depolarizing response of the dorsal root to GABA and markedly depressed the contralateral slow v.r.p. Neither the d.c. potential of the ventral root nor the dorsal root was changed by diazepam. The monosynaptic reflex was also unaffected by the drug. Bicuculline (1 microM) suppressed the GABA-induced depolarization recorded from the dorsal root whilst it markedly potentiated the contralateral slow v.r.p. Baclofen at concentrations from 0.01 to 0.1 microM reduced the contralateral slow v.r.p. The inhibitory action of baclofen on the contralateral slow v.r.p. was more marked than on the monosynaptic reflex. 7 The depolarization of the ventral root induced by a brief application of substance P (SP) was depressed by muscimol, diazepam and baclofen, whereas the depolarization was potentiated by bicuculline. 8 The present results suggest that an intraspinal GABAergic inhibitory mechanism plays a role in the modulation of certain slow spinal reflexes. They also support the hypothesis that SP released from certain primary afferent fibres is a neurotransmitter involved in the contralateral slow v.r.p.
在从新生大鼠分离出的脊髓标本中，研究了γ-氨基丁酸（GABA）和其他与GABA受体相互作用的药物对慢时程反射的影响。对背根（L3-L5）进行单次电击，可引发一系列刻板的反射，包括快速和慢速成分，从相应节段的对侧腹根记录。慢速成分，即对侧慢腹根电位（v.r.p.）的峰值时间为2-5秒，持续20-30秒。浴加GABA（5-20微摩尔）或蝇蕈醇（0.05-0.5微摩尔）可使对侧慢v.r.p.的幅度降低，而腹根记录的直流电位无任何变化。在这些浓度下，药物对同侧腹根记录的单突触反射无影响。地西泮（0.1-1微摩尔）增强了背根对GABA的去极化反应，并显著抑制了对侧慢v.r.p.。地西泮对腹根和背根的直流电位均无改变。单突触反射也不受该药物影响。荷包牡丹碱（1微摩尔）抑制从背根记录的GABA诱导的去极化，同时显著增强对侧慢v.r.p.。浓度为0.01至0.1微摩尔的巴氯芬降低对侧慢v.r.p.。巴氯芬对对侧慢v.r.p.的抑制作用比对单突触反射更明显。7 短暂应用P物质（SP）诱导的腹根去极化被蝇蕈醇、地西泮和巴氯芬抑制，而被荷包牡丹碱增强。8 目前的结果表明，脊髓内GABA能抑制机制在某些慢脊髓反射的调节中起作用。它们还支持这样的假说，即从某些初级传入纤维释放的SP是参与对侧慢v.r.p.的神经递质。
