Neuronal receptors for caerulein in gallbladder.

Release of [3H]-acetylcholine ([3H]ACh) and muscle contractions in response to caerulein was measured and recorded simultaneously from isolated guinea-pig gallbladder. Caerulein (5 x 10(-9) M) enhanced the release of [3H]ACh and the contractions. Tetrodotoxin (10(-6) M) inhibited the caerulein-induced release of [3H]ACh by only 30%. Proglumide and loxiglumide (CR 1505) antagonized the effect of caerulein on both ACh-release and contractions. Neither proglumide nor loxiglumide affected the DMPP-induced contractions and the ACh release. The results suggest not only muscular but also neuronal receptors for caerulein in guinea-pig gallbladder.