title: Effects of acetylethylcholine mustard on [3H]quinuclidinyl benzilate binding and acetylcholine release in rat brain synaptosomes.
abstract: The effects of acetylethylcholine mustard and its aziridinium derivative (AMMA) on acetylcholine (ACh) release and [3H]quinuclidinyl benzilate (QNB) binding were studied in rat cortical synaptosomes. After incubation for 5 min at 37 degrees C, AMMA reduced [3H]QNB binding with an IC50 of 9 microM. Following incubation for 5 min with 50 microM AMMA and washing, there was a 62% reduction in the [3H]QNB binding capacity with no change in the KD value for the remaining receptors, a result indicating the irreversibility of the AMMA binding. AMMA and oxotremorine both reduced the basal and 30 mM K+-induced release of newly synthesized [3H]ACh in dose-dependent manners over a 2.5-min period. At identical 50 microM concentrations, AMMA produced a much longer inhibition of basal [3H]ACh release than oxotremorine did. The inhibition of basal and 30 mM K+-induced [3H]ACh release by AMMA (10-250 microM) was blocked by 2 microM atropine during a 2.5-min release incubation, but not during a 30-min release incubation. After synaptosomes were treated with 50 microM AMMA for 5 min and the unbound drug was washed out from the tissue, [3H]ACh release (basal and K+-induced) was reduced. AMMA (50 microM) reduced high-affinity choline uptake and ACh synthesis by greater than 90% in this tissue, but these effects did not account for the [3H]ACh release inhibition, because they were not atropine sensitive and hemicholinium-3 had no effect on [3H]ACh release under the conditions used in these studies, i.e., after extracellular [3H]choline was washed out. Taken together, these results suggest that AMMA may be an irreversible agonist at presynaptic muscarinic autoreceptors.
mesh_terms: D000109:Acetylcholine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001921:Brain / Q000166:cytology* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006426:Hemicholinium 3 / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D010095:Oxotremorine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011812:Quinuclidines / Q000378:metabolism*; D011813:Quinuclidinyl Benzilate / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000378:metabolism*
chemical_list: D011812:Quinuclidines; D006426:Hemicholinium 3; D010095:Oxotremorine; D011813:Quinuclidinyl Benzilate; D001285:Atropine; C050594:acetylethylcholine mustard; D000109:Acetylcholine; D011188:Potassium