Effect of loxiglumide (CR 1505) on CCK-induced contractions and 3H-acetylcholine release from guinea-pig gallbladder.
Release of [3H]-acetylcholine (3H-ACh) and muscle contractions in response to cholecystokinin (CCK) were measured and recorded simultaneously from isolated guinea-pig gallbladder. Cholecystokinin octapeptide (CCK8) (10(-10)-10(-7) M) enhanced the release of [3H]ACh and the contractions of the muscle. TTX (10(-6) M) inhibited the CCK-induced release of 3H-ACh by only 30%. In Ca(2+)-free medium CCK8 had no effect. Loxiglumide, (CR 1505), a newly synthesized nonpeptide CCK-A-receptor antagonist, D.L-(3,4-dichlorbenzoilamino)-5-/N-(3-methoxypropyl)-pentylamin o-5-oxo-pentanoi c acid, antagonized both the ACh-releasing effect of CCK and the contractions in a dose-dependent manner. The affinity (pA2) of CR 1505 to CCK-receptors, determined by the shift of the concentration-response curves for CCK8 was 8.36. It was 5 logarithmic orders higher than the pA2 of proglumide. The IC50 value of CR 1505 calculated by the CCK-induced release of 3H-ACh was 10 nM. The results suggest the existence not only of muscular CCK receptors but also neuronal receptors for CCK probably located on cholinergic nerves.
Rakovska
A
A
Institute of Physiology, Bulgarian Academy of Sciences.
Sgaragli
G
G
Mantovani
P
P
Valoti
M
M
Milenov
K
K
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002766:Cholecystokinin / Q000037:antagonists & inhibitors*; D005260:Female; D005704:Gallbladder / Q000187:drug effects*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D011377:Proglumide / Q000031:analogs & derivatives* / Q000494:pharmacology; D014316:Tritium
D014316:Tritium; C053737:loxiglumide; D002766:Cholecystokinin; D011377:Proglumide; D000109:Acetylcholine