Hirata K, Ohno-Shosaku T, Sawada S, Yamamoto C
Research Laboratories, Toyama Chemical Co., Ltd., Japan.
Neurosci Lett. 1995 Mar 10;187(3):205-8. doi: 10.1016/0304-3940(95)11377-9.
Effects of the GABAB agonist baclofen on GABAergic transmission were examined before and after treatment with N-type (CgTX) and P-type (AGTX) Ca2+ channel blockers in cultured rat hippocampal neurons. Baclofen reduced GABAergic synaptic currents (IPSCs) without affecting the postsynaptic sensitivity to GABA. The presynaptic inhibition by baclofen was not blocked by Ba2+, a K+ channel blocker. IPSCs were reduced by treatment with either CgTX or AGTX, and completely abolished by treatment with both toxins. Both IPSCs after treatment with CgTX and those after AGTX treatment were similarly reduced by baclofen. The results indicate that both the transmission mediated by AGTX-sensitive Ca2+ channels and that by CgTX-sensitive Ca2+ channels are sensitive to baclofen, suggesting that activation of presynaptic GABAB receptors might inhibit both types of Ca2+ channels contributing to the GABAergic transmission in the hippocampus.
在培养的大鼠海马神经元中，在用N型（CgTX）和P型（AGTX）钙通道阻滞剂处理之前和之后，研究了GABAB激动剂巴氯芬对GABA能传递的影响。巴氯芬降低了GABA能突触电流（IPSCs），而不影响突触后对GABA的敏感性。巴氯芬的突触前抑制作用不被钾通道阻滞剂Ba2+阻断。用CgTX或AGTX处理可降低IPSCs，而用两种毒素处理则可完全消除IPSCs。用CgTX处理后的IPSCs和用AGTX处理后的IPSCs都同样被巴氯芬降低。结果表明，由AGTX敏感的钙通道介导的传递和由CgTX敏感的钙通道介导的传递都对巴氯芬敏感，这表明突触前GABAB受体的激活可能抑制两种类型的钙通道，这些钙通道参与海马体中的GABA能传递。
