RT Journal Article
SR Electronic
T1 Direct determination of acetylcholine release by radioimmunoassay and presence of presynaptic M1 muscarinic receptors in guinea pig ileum.
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 1036
OP 1039
VO 244
IS 3
A1 K Kawashima
A1 K Fujimoto
A1 T Suzuki
A1 H Oohata
YR 1988
UL http://jpet.aspetjournals.org/content/244/3/1036.abstract
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 microM) 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 microM) 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.