Delwaide P J, Pennisi G
University Department of Neurology, Hôpital de la Citadelle, Liège, Belgium.
Neurology. 1994 Nov;44(11 Suppl 9):S21-7; discussion S27-8.
Spasticity results from various pathophysiologic abnormalities in spinal cord neuronal circuits. Noninvasive electrophysiologic techniques can be used to study these circuits in humans. The best correlation between briskness of reflexes and results of electrophysiologic testing is found with reduction in vibratory inhibition, a test that reflects presynaptic inhibition. For increase in muscle tone, the best correlation is found with reduction of Ib nonreciprocal inhibition. These test results, which are stable under controlled conditions, are influenced by myorelaxant drugs and may be used to analyze the mode of action of new products because the tests study specific circuits involving known neurotransmitters. Tizanidine reinforces presynaptic inhibition and two types of postsynaptic inhibition: Ia reciprocal and Ib nonreciprocal. It also markedly reduces flexor reflexes. These effects are explained by an action exerted on spinal interneurons deprived of their normal monoaminergic descending innervation. The spectrum of activity for tizanidine is thus broad, making it likely that tizanidine corrects more than one pathophysiologic abnormality. Because tizanidine reinforces presynaptic as well as Ib nonreciprocal inhibition, it may reduce both brisk tendon jerks and muscle hypertonia.
痉挛是由脊髓神经回路中的各种病理生理异常引起的。非侵入性电生理技术可用于研究人类的这些神经回路。在反映突触前抑制的振动抑制测试中，发现反射活跃度与电生理测试结果之间的相关性最佳。对于肌张力增加，在Ib非交互抑制降低方面发现了最佳相关性。这些测试结果在受控条件下是稳定的，会受到肌肉松弛药物的影响，并且可用于分析新产品的作用方式，因为这些测试研究涉及已知神经递质的特定神经回路。替扎尼定增强突触前抑制以及两种类型的突触后抑制：Ia交互抑制和Ib非交互抑制。它还能显著降低屈肌反射。这些作用可通过对缺乏正常单胺能下行神经支配的脊髓中间神经元的作用来解释。因此，替扎尼定的活性谱很广，这使得替扎尼定可能纠正不止一种病理生理异常。由于替扎尼定增强突触前以及Ib非交互抑制，它可能同时降低快速腱反射和肌肉张力亢进。
