氯胺酮在大鼠脊髓背角胶状质内对突触前神经递质释放的影响

为探讨临床有效浓度的氯胺酮(ketamine,KTM)在脊髓背角胶状质(substansia gelatinosa,SG)内对突触前神经递质释放的影响及其作用机制,本研究应用红外可视神经组织薄片全细胞膜片钳记录方法,在电压钳模式下,观察了KTM对自发性抑制性和兴奋性突触后电流(spontaneous inhibitory and excitatory postsynaptic currents,sIPSCs and sEPSCs)的频率和幅值的影响。结果显示:(1)钳制电压在0mV时,在人工脑脊液(artificial cerebrospinal fluid,ACSF)中加入10-5mol/LAP-V和10-6mol/LCNQX,可记录到sIPSCs。将此时记录到的频率和幅值都作为前对照组的基础值(100%)。给予10-4mol/LKTM后,与前对照组相比,sIPSCs频率为127.93%±25.17%(P<0.05),幅值为104.78%±11.35%(P>0.05,n=7);(2)钳制电压为-70mV时,在ACSF中加入3×10-7mol/L士的宁和10-6mol/L荷包牡丹碱后,可观察到sEPSCs。加入10-4mol/LKTM后,与前对照组相比,sEPSCs的频率和幅值分别为97.89%±4.06%和101.63%±7.66%(P>0.05,n=8)。以上结果提示:(1)KTM增加了sIPSCs的频率,而对幅值没有明显影响,即KTM引起突触前抑制性神经递质的释放增加,而对突触后神经元的作用不明显;(2)KTM对sEPSCs的频率和幅值均未见明显影响,说明KTM在SG内对兴奋性神经递质的释放无显著影响。由此我们推测KTM在脊髓SG内主要通过增强抑制性信息传递发挥作用,KTM增强SG内突触前抑制性神经递质释放可能与其在脊髓背角发挥麻醉和镇痛作用有关。

THE EFFECT OF KETAMINE ON THE PRESYNAPTIC NEUROTRANSMITTER RELEASE IN THE SUBSTANSIA GELATINOSA OF THE SPINAL CORD IN THE RAT

To investigate the effect of ketamine (KTM) on presynaptic neurotransmitter release in the substansia gelatinosa (SG) of the spinal cord, the clinical effective concentration of KTM was used. Under voltage clamp model and using the infrared visual whole cell patch clamp technique, we observed the effect of KTM on frequencies and amplitudes of the spontaneous inhibitory and excitatory postsynaptic currents (sIPSCs and sEPSCs). The results showed: (1) With the voltage clamped at 0 mV, 10-5 mol/L AP-V and 10-6 mol/L CNQX had been added to artificial cerebrospinal fluid (ACSF), and then the sIPSCs were recorded. The values of freguenly and amplitude recorded at that time were used as basic value (100%) of the pre-control for the late recordings. After applying 10-4 mol/L KTM, the frequency of sIPSCs was 127.93%±25.17% (P<0.05), the amplitude was 104.78%±11.35% (P>0.05, n=7); (2) With the voltage clamped at-70 mV,after 3×10-7 mol/L strychnine and 10-6 mol/L bicuculline added to ACSF, the sEPSCs were observed. 10-4 mol/L KTM had effects on the frequency of sEPSCs at 97.89%±4.06% and the amplitude at 101.63%±7.66% (P>0.05, n=8), respectively. The present results suggest: (1) KTM increases the frequency of sIPSCs, but not obviously influence the amplitude. The effect of KTM in the SG might be mainly through the increase of inhibitory neurotransmitter release. That is, KTM triggers the increasing of presynaptic inhibitory neurotransmitter release in the SG, whereas not obviously influence on postsynaptic neuron at all; (2) KTM had no noticeable effects on the frequency and amplitude of sEPSCs, in other words, KTM in the SG could not influence the excitatory neural signals transmission significantly. Such effects of KTM may be one of its mechanisms underlying the anesthetic and analgesic functions in the SG.