Effects of some polymethylene bis(hydroxyethyl)dimethylammonium salts on neuromuscular transmission

Anti-tremor action of C10Dichol, a peripheral acetylcholine synthesis inhibitor

1 Anti-tremor action of decamethylene bis-(hydroxyethyl)-dimethylammonium bromide (C10Dichol), a peripheral acetylcholine synthesis inhibitor, was investigated. 2 C10Dichol inhibited tremor induced by oxotremorine, nicotine and physostigmine and afforded partial protection from physostigmine-induced mortality in mice. 3 In non-paralysing doses, C10Dichol antagonized the neuromuscular effects of oxotremorine, nicotine and physostigmine. 4 Prior administration of C10Dichol failed to prevent tremor and neuromuscular paralysis induced by harmine and arecoline. 5 In the absence of any antimuscarinic property of C10Dichol, its neuromuscular effects appeared to be casually related to its anti-tremor action. 6 This study reveals a possibility for the development of peripherally acting anti-Parkinson drugs.

Effects of some polymethylene bis(hydroxyethyl) dimethylammonium compounds on acetylcholine synthesis

1. The effects of some polymethylene bis(hydroxyethyl)dimethylammonium compounds have been studied on acetylcholine (ACh) synthesis and as substrates for choline acetyltransferase (ChAc).2. The decamethylene analogue (C(10)-dichol) inhibited ACh synthesis by mitochondrial (P(2)) fractions of guinea-pig cerebral cortex suspended in Tris buffer but had no effect on ACh synthesis by P(2) fractions when the membranes surrounding the ChAc enzyme were broken down by homogenization in Triton X-100.3. C(10)-Dichol was acetylated by ChAc almost to the same extent as choline. The initial rate of acetylation, at a concentration of 10(-3)M, was more rapid than for choline; however, the apparent Michaelis-Menten constant for C(10)-dichol was greater than the K(m) for choline, showing a loewr affinity for the ChAc enzyme.4. All the dicholine compounds were acetylated to some extent by ChAc and the rate of acetylation increased with an increase in the length of the methylene chain between the two quaternary nitrogen atoms in each dicholine molecule.5. The rate of acetylation of the dicholine compounds paralleled the activity of these analogues at the prejunctional site at the neuromuscular junction. The possibility is suggested that part of the pharmacological activity of these compounds may be due to their incorporation into cholinergic nerve endings followed by acetylation by ChAc before subsequent release as a false transmitter.

A comparison between the blocking actions of 2-(4-phenylpiperidino) cyclohexanol (AH 5183) and its N-methyl quaternary analogue (AH 5954)

1. The neuromuscular blocking activities of AH 5183 (2-(4-phenylpiperidino) cyclohexanol) and its N-methyl quaternary analogue (AH 5954) were compared in rapidly stimulated nerve-skeletal muscle preparations of the rat, chicken and cat.2. The evidence indicated that in isolated preparations the neuromuscular block produced by both AH 5183 and AH 5954 was primarily pre-junctional in origin. That produced by AH 5954 was readily reversible either by washing the tissue or by reducing the stimulation frequency, whereas that produced by AH 5183 was difficult to reverse in these ways.3. Low doses of AH 5954 sensitized the rat hemidiaphragm preparation to the neuromuscular blocking action of choline. The neuromuscular block produced by choline was reversible by tetraethylammonium but not by neostigmine. This suggested that the blocking action of choline is at least partly pre-junctional in nature.4. In anaesthetized cats AH 5954 possessed a biphasic neuromuscular blocking action. The initial phase was rapid in onset, suggestive of a post-junctional action, whereas the second phase was prolonged and reversible by choline, suggestive of a prejunctional inhibitory action on the choline transport mechanism. AH 5183 produced no initial blocking action and was irreversible by choline.5. Both AH 5183 and AH 5954 possessed local anaesthetic and alpha-adrenoceptor blocking actions. These actions and the neuromuscular blocking action were affected to different degrees by quaternization, suggesting that the three main actions of the two drugs are independent.6. It was concluded that AH 5954 and AH 5183 act at different pre-junctional sites at the neuromuscular junction, AH 5954 acting extraneuronally by inhibiting choline transport and AH 5183 intraneuronally at the level of the synaptic vesicle membrane.

The neuromuscular blocking action of a series of bicyclic bis-oniu esters

1. Thirteen bicyclic dicholine esters have been tested on mammalian and avian skeletal muscle preparations.2. One of the compounds exhibited depolarizing activity in all the preparations.3. Three of the compounds exhibited depolarizing or dual-blocking activity in avian and denervated mammalian preparations, but exhibited non-depolarizing blocking activity in innervated mammalian preparations.4. The remaining compounds exhibited non-depolarizing blocking activity with evidence of an additional facilitatory action.5. The activity exhibited was dependent upon the onium substituents and the structure of the bicyclic ring.6. All the compounds exhibited a choline-reversible block in the rapidly stimulated rat diaphragm preparation and six of them exhibited a secondary choline-reversible block of the rapidly stimulated cat tibialis anterior muscle.