促甲状腺素释放激素调制对侧腹外侧索下行激活离体脊髓运动神经元的作用

目的:探讨促甲状腺素释放激素(TRH)调制对侧腹外侧索(cVLF)下行激活离体脊髓运动神经元(MN)的作用。方法:应用新生大鼠(8～14d龄)脊髓切片MN细胞内记录技术,TRH灌流给药,观察其对cVLF电刺激诱发的兴奋性突触后电位(cVLF-EPSP)的影响。结果:在7个测试的MN,灌流TRH(0.2μmol/L)2～5min产生去极化反应,其去极化值为(11.8±8.2)mV(P<0.05),其作用具有浓度依赖性,并可增加诱发或自发锋电位发放频率。在2个记录到cVLF-EPSP的MN,灌流TRH(0.2μmol/L)在引起去极化的同时,还具有易化cVLF-EPSP的作用,cVLF-EPSP出现锋电位发放或增强反应。使用印防己毒素(30μmol/L)和士的宁(1.0μmol/L)阻断抑制性氨基酸受体后,灌流TRH(0.2μmol/L)15min仍然在3个MN呈现了易化cVLF-EPSP的作用。结论:TRH具有易化cVLF电刺激诱发的兴奋性突触传递作用,以调制cVLF下行激活脊髓MN的作用,这种易化作用可能独立于抑制性氨基酸受体。

Modulatory effects of thyrotropin-releasing hormone on contralateral descending activation of spinal cord motoneurons in vitro

Objective ： To observe the modulatory effects of thyrotropin-releasing hormone （TRH） on contraiateral descending activation of motoneurons （MNs） in neonatal rat spinal cord slices. Methods： The conventional intraeellular recordings were conducted in MNs of spinal cord slices isolated from neonata/rats （8 - 14 days old）. Observed in MNs were the effects of TRH on excitatory postsynaptic potentials （EPSPs） evoked by contralateral ventrolateral funieulus （cVLF） stimulation （ i. e. cVLF-EPSPs）. Results： Perfusion of TRH （0.2 μmol/L） for2 -5 min induced a depolarizing response of （ 11.8 ± 8.2 ） mV in the 7 tested MNs （ P 〈 0.05 ） in a concentration-dependent manner, and still increased both spontaneous and evoked firing frequency of MNs. During TRH-indueed depolarization,cVLF-EPSPs in the 2 MNs were facilitated to discharge spikes or enhance the response. By pretreatment of pierotoxin （30 μmol/ L） and strychnine （1.0 μmol/L） ,inhibitory amino acid receptor antagonists,the potentiation of eVLF-EPSPs by TRH was kept effective in 3 MNs. Conclusion： TRH can produce modulatory effects on contralateral descending activation of MNs in spinal cord slices, suggesting that it may be independent on γ-aminobutyrie acid A receptors and glycine receptors.