The effect of acute alloxan diabetes on the sensitivity of the rat skeletal neuromuscular junction to drugs.

Preparations from alloxan diabetic rats showed a reduced sensitivity to the neuromuscular blocking action of (+)-tubocurarine but no alteration in sensitivity to the depolarizing neuromuscular blocking drug decamethonium. Physostigmine was less effective in augmenting twitch height in preparations from alloxan diabetic rats and such preparations had a significantly lowered total cholinesterase activity compared with control preparations. An additional observation was a reduction in the effectiveness of the pre-junctionally active agent beta-bungarotoxin in producing neuromuscular blockade in physostigmine-treated preparations from alloxan diabetic rats.

The effects of release and depletion of endogenous noradrenaline on the transmission of impulses in the mouse vas deferens.

1 The effects of endogenous noradrenaline released by tyramine and the influence of depletion of the tissue noradrenaline with reserpine and/or alpha-methyl-p-tyrosine on the twitch responses of the field-stimulated mouse vas deferens have been studied.2 Tyramine (10-40 muM) inhibited the twitch responses to field stimulation and failed to produce a contraction. The inhibition decreased as the rate of stimulation increased.

The relationship between cholinesterase inhibition in the chick biventer cervicis muscle and its sensitivity to exogenous acetylcholine.

The effect of physostigmine has been studied on cholinesterase in homogenates of chick biventer cervicis muscles and on the contractile responses of the intact muscles to acetylcholine and carbachol. The concentration of physostigmine required to produce the maximum increase in sensitivity to acetylcholine almost completely inhibited the cholinesterase in muscle homogenates. This concentration of physostigmine had no effect on muscle contractures elicited by carbachol.

Antibiotic-induced paralysis of the mouse phrenic nerve-hemidiaphragm preparation, and reversibility by calcium and by neostigmine.

Certain antibiotics can induce neuromuscular paralysis, but the mechanism of this action is largely unknown. The purpose of this study was to compare the neuromuscular blocking potencies and reversibilities of 16 antibiotics in the isolated mouse phrenic nerve-hemidiaphragm preparation. The antibiotics tested were five aminoglycosides (neomycin, gentamicin, streptomycin, dihydrostreptomycin and kanamycin), tetracycline and oxytetracycline, polymyxins B and E, penicillins G and V, cephradine, cephaloridine, erythromycin, lincomycin, and clindamycin.

Some effects of the aminoglycoside antibiotic amikacin on neuromuscular and autonomic transmission.

The effects of the new aminoglycoside antibiotic amikacin on neurohumoral transmission were tested in the anaesthetized cat, and in mouse, rat and chick isolated nerve-muscle preparations. Amikacin had blocking actions on both autonomic and neuromuscular transmission. The autonomic effects were caused mainly by ganglion blockade and were reversed by calcium.

alpha-Adrenoceptors in the mouse vas deferens and their effects on its response to electrical stimulation.

1 Noradrenaline (ID50, 0.75 micrometer) and clonidine (ID50, 2.8 nM) produced a dose-related inhibition of the twitch response of the isolated vas deferens of the mouse to electrical stimulation, their effectiveness decreasing as frequency of stimulation increased from 0.

Investigations of reasons for the avirulence of the A7 strain of Semliki Forest virus in adult mice.

A strain of Semliki Forest virus (A7) which is avirulent in adult mice killed baby mice in a similar manner to strain V13 which was also virulent for adult mice. In the muscle and brains of baby mice A7 and V13 replicated and produced haemagglutinating activity similarly. Our previous suggestion that defective interfering particles were present in the brains of A7-infected adult mice appears not to be so.

An inhibitory role for noradrenaline in the mouse vas deferens.

1 Noradrenaline (0.1-3.0 muM) inhibited the twitch responses to single pulse field stimulation of the isolated vas deferens of the mouse.

The actions of three diaminopyridines on the chick biventer cervicis muscle.

The effects of 2,3-, 2,6- and 3,4-diaminopyridine were investigated on the isolated chick biventer cervicis muscle preparation. All three compounds reversed tubocurarine blockade and augmented twitch height in indirectly stimulated preparations. Less twitch augmentation was observed in directly stimulated preparations.

The facilitatory actions of aminopyridines and tetraethylammonium on neuromuscular transmission and muscle contractility in avian muscle.

The actions of 3,4-diaminopyridine, 4-aminopyridine and tetraethylammonium were studied on the chick biventer cervicis muscle preparation. All three compounds produced a greater augmentation of indirectly elicited twitches than of directly elicited twitches. The compounds did not restore transmission in OmMCa2+ solutions but rather produced contractures that were inhibited by acetylcholine receptor antagonists.

The actions of aminopyridines on avian muscle.

The effects of 2-, 3-, and 4-aminopyridines were investigated on the isolated chick biventer cervicis nerve-muscle preparation and on nerve-free cell cultures of embryonic chick skeletal muscle. All 3 compounds reversed tubocurarine blockade and augmented twitch height in indirectly stimulated biventer cervicis preparations. 4-Aminopyridine was approximately 10 times more potent than 2-, or 3-aminopyridine.