Oxotremorine Does Not Enhance Acetylcholine Release From Rat Diaphragm Preparations

Abstract

We have reinvestigated the dramatic effect of oxotremorine on acetylcholine release from the rat diaphragm reported by Das, Ganguly & Vedasiromoni (1978), using a rigorous gas chromatographic mass spectrometric/isotope dilution method for identification and measurement of acetylcholine and choline. Oxotremorine (10 μm) causes no significant change in the spontaneous or evoked (1 or 10 Hz) release or in the tissue levels of acetylcholine or choline.

The Effects of Atropine and Oxotremorine on Acetylcholine Release in Rat Phrenic Nerve‐diaphragm Preparations

“…In trying to explain the discrepancies between our results and theirs we, like Gundersen & Jenden (1980), have had to conclude that the difference probably lies in the greate, specificity of our method in separating, identifying and measuring only acetylcholine.…”

“…They suggested that ACh release might be locally controlled by excitatory presynaptic muscarinic receptors. Recently, Gundersen & Jenden (1980) demonstrated that oxotremorine did not enhance ACh release and indicated that presynaptic muscarinic receptors were unlikely to be present in this tissue. In this paper we describe our results with oxotremorine and with atropine which indicate that there may be presynaptic muscarinic receptors on the terminals of rat phrenic nerves but that these receptors are inhibitory.…”

Atropine Enhances Neuromuscular Transmission in Humans

“…They found that atropine increased whereas oxotremorine (a muscarinic agonist) decreased ACh release. On the other hand, Das et al (1978) suggested that oxotremorine increased transmitter (ACh) release at the rat diaphragm preparation, a claim which was vigorously disputed by Gundersen and Jenden (1980) in the same preparation. Das et ul., (1978) and GanguIy and Das (1979) have suggested the presence of presynaptic muscarinic excitatory receptors, activation of which, oxotremorine, led to a massive release of ACh, which in turn led to a neuromuscular blockade, similar to that observed with suxamethonium.…”

Prejunctional modulation of acetylcholine release from the skeletal neuromuscular junction: link between positive (nicotinic)− and negative (muscarinic)‐feedback modulation

“…Gibb & - Marshall, 1983) and pharmacological (Bowman & Webb, 1976;Bowman, 1980a;Bowman et al, 1988) data, it was suggested that there is a prejunctional nicotinic receptor-mediated facilitation (mobili- As far as the muscarinic negative feedback modulation is concerned, the literature offers very controversial data. While Abbs & Joseph (1981) have shown that oxotremorine reduces and atropine enhances the release of ACh from the neuromuscular junction, others (Gundersen & Jenden, 1980;Haggblad & Heilbronn, 1983) failed to find such an effect. In addition, electrophysiological (Beranek & Vyskocil, 1967) and histochemical data (Gillberg et al, 1984) oppose the presence of muscarinic receptors at the neuromuscular junction.…”