Sprouse J S, Baker T, Riker W F
J Pharmacol Exp Ther. 1985 Dec;235(3):864-72.
Neostigmine-induced muscle fasciculations, quantitated as fasciculatory muscle action potentials, served as an indirect in vivo indicator of motor nerve ending (MNE) excitability. By this method, MNE excitability was depressed in adrenalectomized rats compared to matched intact controls. Daily or continuous administration of the mineralocorticoids aldosterone or desoxycorticosterone acetate restored MNE excitability toward normal; corticosterone, the endogenous corticosteroid having both mineralo- and glucocorticoid activity, was variably effective. There was a strong negative correlation (r = -0.95) between log plasma [K+]and the fasciculatory response to neostigmine. Dietary restriction of K in adrenalectomized rats lowered plasma [K+]to near normal and significantly increased MNE excitability. This effect of adrenalectomy on MNE excitability was further demonstrated by recording directly the neostigmine-induced repetitive neural discharges responsible for the muscle fasciculations. In adrenalectomized animals, neostigmine-induced neural discharges were reduced in intensity; restoration of neostigmine responsiveness was attained by lowering plasma [K+]through dietary restriction. Stimulus strength-duration relationships for both ventral and dorsal roots disclosed deficits in axonal excitability after adrenalectomy. These returned toward normal when plasma [K+]was lowered by K withdrawal from the diet. From these studies, it is concluded that 1) in adrenalectomized rats, peripheral nerve excitability, including the unmyelinated endings of motor nerve, is depressed; 2) mineralocorticoids play a significant role in restoring MNE excitability in these animals; 3) mineralocorticoid-induced changes in MNE excitability relate to the lowering of an elevated plasma [K+].
新斯的明诱发的肌肉束颤，以束颤性肌肉动作电位进行定量，作为运动神经末梢（MNE）兴奋性的一种间接体内指标。通过这种方法，与匹配的完整对照相比，肾上腺切除大鼠的MNE兴奋性降低。每日或持续给予盐皮质激素醛固酮或醋酸脱氧皮质酮可使MNE兴奋性恢复正常；皮质酮，一种具有盐皮质激素和糖皮质激素活性的内源性皮质类固醇，效果不一。血浆[K⁺]对数与对新斯的明的束颤反应之间存在强烈的负相关（r = -0.95）。对肾上腺切除大鼠进行饮食钾限制可使血浆[K⁺]降至接近正常水平，并显著增加MNE兴奋性。通过直接记录导致肌肉束颤的新斯的明诱发的重复性神经放电，进一步证明了肾上腺切除术对MNE兴奋性的这种影响。在肾上腺切除的动物中，新斯的明诱发的神经放电强度降低；通过饮食限制降低血浆[K⁺]可恢复对新斯的明的反应性。腹根和背根的刺激强度-持续时间关系揭示了肾上腺切除术后轴突兴奋性的缺陷。当通过饮食中去除钾使血浆[K⁺]降低时，这些缺陷恢复正常。从这些研究得出结论：1）在肾上腺切除大鼠中，包括运动神经无髓鞘末梢在内的外周神经兴奋性降低；2）盐皮质激素在恢复这些动物的MNE兴奋性中起重要作用；3）盐皮质激素诱导的MNE兴奋性变化与升高的血浆[K⁺]降低有关。
