Cetiedil, a Drug That Inhibits Acetylcholine Release in Torpedo Electric Organ

Abstract

The effects of cetiedil, a vasodilatator substance with reported anticholinergic properties, were examined on cholinergic presynaptic functions at the nerve electroplaque junction of Torpedo marmorata using either synaptosomes or slices of intact tissue. Cetiedil abolished the calcium-dependent release of acetylcholine (ACh) triggered by depolarization or by addition of A23187 ionophore, a finding localizing the site of action downstream from the calcium entry step. In addition, a direct effect on the release process itself was indicated by the observation that cetiedil blocks the release of ACh mediated by a recently isolated presynaptic membrane protein, the mediatophore, reconstituted into ACh-containing proteoliposomes. In all three preparations, ACh release was inhibited by cetiedil with a Ki of 5-8 microM. Under the conditions used in these release experiments, the synthesis of ACh and its compartmentation within the nerve terminals were not modified. However, the drug was able to reduce high-affinity choline uptake and vesicular ACh incorporation when it was given together with the radioactive precursor, a result showing that cetiedil has a broad inhibitory action on cholinergic uptake processes.

AH5183 and Cetiedil: Two Potent Inhibitors of Acetylcholine Uptake into Isolated Synaptic Vesicles from Torpedo marmorata

“…4). For cetiedil, a reduction in the translocation of ACh into the vesicles was seen in experiments on isolated nerve endings (Morot Gaudry-Talarmain et al, 1987). We show here on isolated synaptic vesicles that cetiedil is indeed an efficient blocker of ACh transport (Fig.…”

“…An indication that cetiedil interfered with ACh translocation into synaptic vesicles came from experiments on isolated nerve endings (Morot Gaudry- Talarmain et al, 1987). When applied to synaptosomes at micromolar concentrations, cetiedil reduced the incorporation of newly synthesized ACh into the synaptic vesicle compartment to 30-40% of the control.…”

Is the acetylcholine releasing protein mediatophore present in rat brain?

“…The present work shows that the purest presynaptic membrane fraction we could prepare from rat brain synaptosomes possessed mediatophore activity, which is blocked by cetiedil as is the case for Torpedo preparations [2] and rat brain synaptosomes [15]. Active protein was extracted from rat brain in conditions similar to those described for Torpedo mediatophore.…”

“…ACh release was monitored using the choline-oxidase chemiluminescent procedure [lo, 1 l] and a typical curve is shown in fig.ZA. This calcium-dependent ACh release was blocked in the presence of the drug cetiedil ( fig.2A) which has been shown to inhibit the translocation of ACh in Torpedo electric organ [2] and from rat brain synaptosomes [ 151. Inhibition of rat brain mediatophore activity was half maximum at about 12 ,xM ( fig.2B).…”

“…This doughnut-shaped molecule is built up by the association of 15 kDa subunits; no other subunit has been identified until now [l]. More recently it has been found that the ACh translocating properties of the mediatophore were blocked by the drug cetiedil that inhibits the release of ACh from stimulated synaptosomes or electric organ [2]. A polyclonal antibody against Torpedo mediatophore was recently prepared and used to study the [3].…”