BOMBESIN-MEDIATED CALCIUM FLUXES IN MYENTERIC PLEXUS NEURONS

Dual excitation microfluorimetry (Fura-2) was used to measure changes in intra-cellular calcium ([Ca2+](i)) in individual cultured guinea pi g myenteric neurons. Bombesin (5-500 nM) induced concentration-depende nt increases in [Ca2+](i) responses, with a maximal effect at 500 nM ( 56% of neurons responding, mean peak Ca2+ response 244 +/- 25 nM vs. b asal 65 +/- 7 nM). Removal of Ca2+ from the medium did not affect the initial [Ca2+](l) peak but eliminated the subsequent plateau phase. Th e [Ca2+](l) response to bombesin was abolished by preincubation with t hapsigargin (1 mu M), a Ca2+-ATPase inhibitor (91 +/- 7% inhibition). [Ca2+](l) responses to bombesin were inhibited by U73122 (1 mu M), an inhibitor of phospholipase C (84 +/- 6% inhibition).