Hounsgaard J, Hultborn H, Jespersen B, Kiehn O
Exp Brain Res. 1984;55(2):391-4. doi: 10.1007/BF00237290.
In decerebrate cats a train of impulses in Ia afferents may lead to a sustained increase in excitability of alpha-motoneurones of homonymous and heteronymous muscles. It was previously suggested that this long-lasting excitability increase reflects a maintained synaptic input to the motoneurones from excitatory interneurones. With intracellular recording from motoneurones we here demonstrate that the sustained increase of alpha-motoneurone activity is due to an all-or-none plateau depolarization. This plateau can be induced by a short train of excitatory synaptic potentials or a brief, intracellularly injected depolarizing current pulse and is terminated by a short train of inhibitory synaptic potentials or a hyperpolarizing current pulse. It is concluded that maintained motor unit firing triggered by a brief train of impulses in Ia afferent reflects an intrinsic bistable behaviour of alpha-motoneurones.
在去大脑猫中，Ia传入纤维中的一串冲动可能导致同名肌和异名肌的α运动神经元兴奋性持续增加。以前有人提出，这种持久的兴奋性增加反映了兴奋性中间神经元对运动神经元的持续突触输入。我们在此通过对运动神经元进行细胞内记录表明，α运动神经元活动的持续增加是由于全或无的平台去极化。这种平台可由一串短暂的兴奋性突触电位或一个短暂的、细胞内注入的去极化电流脉冲诱导产生，并由一串短暂的抑制性突触电位或一个超极化电流脉冲终止。得出的结论是，由Ia传入纤维中的一串短暂冲动触发的运动单位持续放电反映了α运动神经元固有的双稳态行为。
