Takano K, Kirchner F, Tiebert B, Terhaar P
Abteilung Pathoneurophysiologie, Universität Göttingen, F.R.G.
Toxicon. 1989;27(4):431-8. doi: 10.1016/0041-0101(89)90205-5.
Tetanus toxin at doses of 2-2000 mouse MLD/kg was injected into the gastrocnemius muscle of the left hind limb of the cat. Acute experiments were performed at various times thereafter, when the intoxicated hind leg was strongly extended. Presynaptic inhibition of the monosynaptic reflex (MSR) of gastrocnemius motoneurones was tested by applying conditioning single electric stimuli to the antagonistic deep peroneal nerve. In most intoxicated animals the delayed inhibition of the MSR could still be observed at time intervals typical for presynaptic inhibition. However, the amplitude of the MSR often showed a strong toxin-induced facilitation at about 30 msec after the conditioning stimulus which could mask the presynaptic inhibition and sometimes made it difficult to observe it at all. After spinal transection at the Th1 level the inhibition could be better observed in such cases. Further evidence for the resistance of the presynaptic inhibitory system against the tetanus toxin in the given dose range was given by recordings of distinct dorsal root potentials which were abolished, together with the MSR inhibition by i.v. injection of picrotoxin. It is concluded that the mechanism of presynaptic inhibition remains intact or is even lengthened during local tetanus after i.m. injection of moderate, clinically relevant, toxin doses.
将剂量为2 - 2000小鼠最小致死量/千克的破伤风毒素注射到猫左后肢的腓肠肌中。此后在不同时间进行急性实验，此时中毒的后腿强烈伸展。通过对拮抗的腓深神经施加条件单电刺激来测试腓肠肌运动神经元单突触反射（MSR）的突触前抑制。在大多数中毒动物中，在突触前抑制典型的时间间隔仍可观察到MSR的延迟抑制。然而，在条件刺激后约30毫秒，MSR的幅度常常表现出强烈的毒素诱导的易化作用，这可能掩盖突触前抑制，有时甚至完全难以观察到。在胸1水平进行脊髓横断后，在这种情况下抑制作用可以更好地观察到。静脉注射印防己毒素使明显的背根电位以及MSR抑制作用消失，这为突触前抑制系统在给定剂量范围内对破伤风毒素的抗性提供了进一步的证据。得出的结论是，在肌肉注射中等剂量、临床相关的毒素后发生局部破伤风期间，突触前抑制机制保持完整甚至延长。
