利用无脊椎动物肽毒素确定大鼠海马切片中CA3-CA1神经传递的Ca2+通道特性。

The use of invertebrate peptide toxins to establish Ca2+ channel identity of CA3-CA1 neurotransmission in rat hippocampal slices.

作者信息

Nooney J M, Lodge D

机构信息

Lilly Research Centre, Windlesham, Surrey, UK.

出版信息

Eur J Pharmacol. 1996 Jun 13;306(1-3):41-50. doi: 10.1016/0014-2999(96)00195-1.

DOI:10.1016/0014-2999(96)00195-1

PMID:8813613

Abstract

The relative contribution(s) of different Ca2+ channel subtypes to synaptic transmission between Schaffer collaterals of hippocampal CA3 pyramidal cells and CA1 pyramidal cell dendrites has been assessed using the synthetic invertebrate peptide toxins omega-conotoxin GVIA to block N-type Ca2+ channels, omega-agatoxin-IVA to block P-type Ca2+ channels and omega-conotoxin MVIIC to block N-, P- and Q-type Ca2+ channels. Omega-Agatoxin-IVA, omega-conotoxin GVIA and omega-conotoxin MVIIC all produced dose-dependent inhibitions of the excitatory post-synaptic field potential (fEPSP) recorded from the CA1 region of transverse hippocampal slices. Application of 300 nM omega-conotoxin GVIA generally produced no further inhibition to that observed with 100 nM, resulting in a maximal 50% inhibition of the fEPSP. By contrast, 30 nM omega-agatoxin-IVA reduced the fEPSP slope by only 4.6 +/- 11.1% (mean +/- S.D., n = 3), suggesting the lack of involvement of classical P-type Ca2+ channels, whereas 300 nM omega-agatoxin-IVA reduced the fEPSP slope by 85.7 +/- 15.3% (n = 3) at the end of 44 min application. Similar applications of 100 and 300 nM sigma-conotoxin MVIIC reduced the fEPSP slope by 30.9 +/- 6.6% and 79.7 +/- 5.7% respectively. Application of 30 nM omega-agatoxin-IVA together with omega-conotoxin GVIA (300 nM) produced no greater inhibition of the fEPSP than that observed with omega-conotoxin GVIA alone, suggesting that the omega-agatoxin-IVA-sensitive and omega-conotoxin MVIIC-sensitive component presents a pharmacology similar to the reported Q-type Ca2+ channel. The inhibition produced by omega-conotoxin GVIA and omega-conotoxin MVIIC showed no recovery with prolonged washing (1-2 h) whereas that produced by omega-agatoxin-IVA was slowly reversible. The observation that omega-agatoxin-IVA, which does not effect N-type Ca2+ channels (Mintz et al. (1992a) Neuron 9, 85), is capable of completely suppressing the fEPSP suggests that, whilst N-type Ca2+ channels may contribute to normal synaptic transmission at Schaffer collateral-CA1 synapses, they are not capable of supporting transmission when Q-type channels are blocked.

摘要

利用合成的无脊椎动物肽毒素ω-芋螺毒素GVIA阻断N型Ca2+通道、ω-蛛毒素-IVA阻断P型Ca2+通道以及ω-芋螺毒素MVIIC阻断N型、P型和Q型Ca2+通道，评估了不同Ca2+通道亚型对海马CA3锥体细胞的Schaffer侧支与CA1锥体细胞树突之间突触传递的相对贡献。ω-蛛毒素-IVA、ω-芋螺毒素GVIA和ω-芋螺毒素MVIIC均对从横向海马切片CA1区记录的兴奋性突触后场电位（fEPSP）产生剂量依赖性抑制。应用300 nM ω-芋螺毒素GVIA通常不会比100 nM时产生进一步的抑制，导致fEPSP最大抑制50%。相比之下，30 nM ω-蛛毒素-IVA仅使fEPSP斜率降低4.6±11.1%（平均值±标准差，n = 3），表明经典P型Ca2+通道未参与，而在应用44分钟结束时，300 nM ω-蛛毒素-IVA使fEPSP斜率降低85.7±15.3%（n = 3）。类似地，100 nM和300 nM ω-芋螺毒素MVIIC的应用分别使fEPSP斜率降低30.9±6.6%和79.7±5.7%。将30 nM ω-蛛毒素-IVA与ω-芋螺毒素GVIA（300 nM）一起应用对fEPSP的抑制作用并不比单独使用ω-芋螺毒素GVIA时更大，这表明对ω-蛛毒素-IVA敏感和对ω-芋螺毒素MVIIC敏感的成分呈现出与报道的Q型Ca2+通道相似的药理学特性。ω-芋螺毒素GVIA和ω-芋螺毒素MVIIC产生的抑制作用在长时间冲洗（1 - 2小时）后未恢复，而ω-蛛毒素-IVA产生的抑制作用则缓慢可逆。ω-蛛毒素-IVA不影响N型Ca2+通道（Mintz等人（1992a）《神经元》9, 85）却能够完全抑制fEPSP这一观察结果表明，虽然N型Ca2+通道可能对Schaffer侧支 - CA1突触的正常突触传递有贡献，但当Q型通道被阻断时它们无法支持传递。