Direct determination of acetylcholine release by radioimmunoassay and presence of presynaptic M1 muscarinic receptors in guinea pig ileum

K. Kawashima, Kazuko Fujimoto, Takeshi Suzuki, H. Oohata

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Abstract

Radioimmunoassay for acetylcholine (ACh) with a sensitivity of 10 pg/tube was applied to the direct determination of ACh output from the nerve endings in longitudinal muscle strips of guinea pig ileum. The strips were preincubated with an irreversible cholinesterase inhibitor and superfused with Krebs' solution under various experimental conditions. Pirenzepine (0.1-10 μM) and atropine (10-100 nM) produced an increase in electrically evoked ACh output through the inhibition of presynaptic muscarinic receptors. Contractile response to endogenous ACh released by electrical stimulation was enhanced by pirenzepine and atropine at lower concentrations, whereas the highest concentrations of pirenzepine (10 μM) and atropine (100 nM) caused a reduction in the enhanced contractile response and a significantly diminished response, respectively. These results demonstrate that the concentrations of pirenzepine and atropine, effective in inhibiting presynaptic muscarinic receptors, differ from those inhibiting postsynaptic muscarinic receptors and suggest the possibility that presynaptic M1 muscarinic receptors regulating ACh output may be present in the guinea pig ileum.

Original languageEnglish
Pages (from-to)1036-1039
Number of pages4
JournalJournal of Pharmacology and Experimental Therapeutics
Volume244
Issue number3
Publication statusPublished - 1988

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Muscarinic M1 Receptors
Pirenzepine
Muscarinic Receptors
Atropine
Ileum
Acetylcholine
Radioimmunoassay
Guinea Pigs
Presynaptic Receptors
Nerve Endings
Cholinesterase Inhibitors
Electric Stimulation
Muscles

ASJC Scopus subject areas

  • Pharmacology

Cite this

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abstract = "Radioimmunoassay for acetylcholine (ACh) with a sensitivity of 10 pg/tube was applied to the direct determination of ACh output from the nerve endings in longitudinal muscle strips of guinea pig ileum. The strips were preincubated with an irreversible cholinesterase inhibitor and superfused with Krebs' solution under various experimental conditions. Pirenzepine (0.1-10 μM) and atropine (10-100 nM) produced an increase in electrically evoked ACh output through the inhibition of presynaptic muscarinic receptors. Contractile response to endogenous ACh released by electrical stimulation was enhanced by pirenzepine and atropine at lower concentrations, whereas the highest concentrations of pirenzepine (10 μM) and atropine (100 nM) caused a reduction in the enhanced contractile response and a significantly diminished response, respectively. These results demonstrate that the concentrations of pirenzepine and atropine, effective in inhibiting presynaptic muscarinic receptors, differ from those inhibiting postsynaptic muscarinic receptors and suggest the possibility that presynaptic M1 muscarinic receptors regulating ACh output may be present in the guinea pig ileum.",
author = "K. Kawashima and Kazuko Fujimoto and Takeshi Suzuki and H. Oohata",
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AU - Kawashima, K.

AU - Fujimoto, Kazuko

AU - Suzuki, Takeshi

AU - Oohata, H.

PY - 1988

Y1 - 1988

N2 - Radioimmunoassay for acetylcholine (ACh) with a sensitivity of 10 pg/tube was applied to the direct determination of ACh output from the nerve endings in longitudinal muscle strips of guinea pig ileum. The strips were preincubated with an irreversible cholinesterase inhibitor and superfused with Krebs' solution under various experimental conditions. Pirenzepine (0.1-10 μM) and atropine (10-100 nM) produced an increase in electrically evoked ACh output through the inhibition of presynaptic muscarinic receptors. Contractile response to endogenous ACh released by electrical stimulation was enhanced by pirenzepine and atropine at lower concentrations, whereas the highest concentrations of pirenzepine (10 μM) and atropine (100 nM) caused a reduction in the enhanced contractile response and a significantly diminished response, respectively. These results demonstrate that the concentrations of pirenzepine and atropine, effective in inhibiting presynaptic muscarinic receptors, differ from those inhibiting postsynaptic muscarinic receptors and suggest the possibility that presynaptic M1 muscarinic receptors regulating ACh output may be present in the guinea pig ileum.

AB - Radioimmunoassay for acetylcholine (ACh) with a sensitivity of 10 pg/tube was applied to the direct determination of ACh output from the nerve endings in longitudinal muscle strips of guinea pig ileum. The strips were preincubated with an irreversible cholinesterase inhibitor and superfused with Krebs' solution under various experimental conditions. Pirenzepine (0.1-10 μM) and atropine (10-100 nM) produced an increase in electrically evoked ACh output through the inhibition of presynaptic muscarinic receptors. Contractile response to endogenous ACh released by electrical stimulation was enhanced by pirenzepine and atropine at lower concentrations, whereas the highest concentrations of pirenzepine (10 μM) and atropine (100 nM) caused a reduction in the enhanced contractile response and a significantly diminished response, respectively. These results demonstrate that the concentrations of pirenzepine and atropine, effective in inhibiting presynaptic muscarinic receptors, differ from those inhibiting postsynaptic muscarinic receptors and suggest the possibility that presynaptic M1 muscarinic receptors regulating ACh output may be present in the guinea pig ileum.

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