Southan A P, Wann K T
Clinical Research Centre, Harrow, Middlesex.
Br J Anaesth. 1989 Nov;63(5):574-80.
The effects of ketamine and methohexitone have been tested in vitro on rat CA1 pyramidal neurones using conventional extracellular and intracellular recording techniques. Ketamine 20-200 mumol litre-1 predominantly increased excitability by a postsynaptic action: it enhanced the amplitude of the antidromic (field) potential response in extracellular recordings; in intracellular studies depolarized or did not change the resting membrane potential; increased intrinsic excitability (assessed by direct stimulation); and reduced accommodation properties of CA1 neurones. Methohexitone 10-100 mumol litre-1 did not affect the amplitude of the antidromic field potential responses, tended to hyperpolarize and reduce the intrinsic excitability, but did not alter accommodation properties. At these concentrations these agents either did not affect or, in the case of ketamine, enhanced excitatory synaptic transmission on to the CA1 pyramidal neurones. Methohexitone 50 and 100 mumol litre-1 also induced a large, slow (several seconds) after depolarization which followed the conventional orthodromic response and may lead to action potential discharge. It is clear that these agents have multiple actions on CA1 pyramidal neurones in vitro and that ketamine and methohexitone in vitro influence excitability by different mechanisms.
已使用传统的细胞外和细胞内记录技术，在体外对大鼠CA1锥体神经元测试了氯胺酮和甲己炔巴比妥的作用。20 - 200微摩尔/升的氯胺酮主要通过突触后作用增加兴奋性：它增强了细胞外记录中逆向（场）电位反应的幅度；在细胞内研究中使静息膜电位去极化或无变化；增加内在兴奋性（通过直接刺激评估）；并降低CA1神经元的适应性。10 - 100微摩尔/升的甲己炔巴比妥不影响逆向场电位反应的幅度，倾向于使膜超极化并降低内在兴奋性，但不改变适应性。在这些浓度下，这些药物要么不影响，要么就氯胺酮而言，增强了对CA1锥体神经元的兴奋性突触传递。50和100微摩尔/升的甲己炔巴比妥还诱导了一种大的、缓慢的（数秒）去极化后电位，该电位跟随传统的顺向反应，可能导致动作电位发放。很明显，这些药物在体外对CA1锥体神经元有多种作用，并且氯胺酮和甲己炔巴比妥在体外通过不同机制影响兴奋性。
