Modulatory inputs to trigeminal motoneurons in rat slice preparation

通过切片制备大鼠颌闭合运动神经元（JCMINs）的细胞内记录，研究5-羟色胺（5-HT）对尖峰后中持续超极化（mAHP）的影响以及蛋白激酶的参与。施用50 muM 5-HT时，大多数细胞的膜去极化和输入电阻增加，但不影响mAHP，而高剂量（100或200 muM）的5-HT不仅引起膜去极化和输入电阻增加，而且抑制mAHP振幅。另一方面，当增加[Ca ^<2+1>]增加mAHP振幅时。从2 ~ 6 mM， 5-HT诱导的mAHP振幅衰减增强，甚至50 muM 5-HT也使mAHP振幅降低。这种5- ht诱导的对mAHP的抑制可以通过应用膜渗透性cAMP类似物8-Br- cAMP来模拟，由cAMP特异性磷酸二酯酶抑制剂Ro 20-1724增强，并被蛋白激酶A （PKA）抑制剂H89拮抗。[Ca ^<2+>]升高条件下，50m5 - ht诱导mAHP衰减增强。被蛋白激酶C （PKC）抑制剂chelerythrine阻断，表明PKC参与了这种增强。另一方面，PKC激活剂phorbol 12-肉豆蔻酸酯13-乙酸酯诱导的mAHP衰减几乎被H89完全阻断，提示PKC对mAHP的作用需要PKA激活。我们得出结论，5-HT通过camp依赖性的PKA激活诱导mAHP振幅的剂量依赖性衰减，pkc依赖性的PKA激活也可能参与了升高[Ca^<2+>]下5-HT诱导的mAHP衰减的增强。我们还检测了细胞内钙浓度的变化（[Ca^<2+>]）。[Ca^<2+>]随着电流注入而增加。提示[Ca^<2+>]随运动神经元活动的变化而变化。

Intracellular recordings were obtained from rat jaw-closing motoneurons (JCMINs) in slice preparations to investigate the effects of serotonin (5-HT) on the post-spike medium-duration afterhyperpolarization (mAHP) and an involvement of protein kinases in the effects.Application of 50 muM 5-HT caused membrane depolarization and increased input resistance in the most cells without affecting the mAHP, whereas not only membrane depolarization and an increase in input resistance, but also the suppression of the mAHP amplitude was induced by higher dose of 5-HT (100 or 200 muM).On the other hand, when the mAHP amplitude was increased by raising [Ca ^<2+1>]。 from 2 to 6 mM, 5-HT-induced attenuation of the mAHP amplitude was enhanced and even 50 muM 5-HT reduced the mAHP amplitude.This 5-HT-induced suppression of the mAHP could be mimicked by application of membrane-permeable cAMP analog 8-Br- cAMP, potentiated by the cAMP-specific phosphodiesterase inhibitor Ro 20-1724 and antagonized by protein kinase A (PKA) inhibitor H89.The enhancement of the mAHP attenuation induced by 50 muM 5-HT under raised [Ca ^<2+>]。 was blocked by a protein kinase C (PKC) inhibitor chelerythrine, suggesting an involvement of PKC in this enhancement.On the other hand, the attenuation of the mAHP induced by PKC activator phorbol 12-myristate 13-acetate was almost completely blocked by H89, suggesting that the PKC action on the mAHP requires PKA activation.We conclude that 5-HT induces dose-dependent attenuation of the mAHP amplitude through cAMP-dependent activation of PKA, and that PKC-dependent PKA activation is also likely to be involved in the enhancement of 5-HT-induced attenuation of the mAHP under raised [Ca^<2+>]。We also examied alteration of intracellular calcium concentration ([Ca^<2+>]). [Ca^<2+>] increased when burst firing was eliced by current injection.It is suggested that [Ca^<2+>] changes according to motoneuronal activity.