Fig. 2.
Proctolin-induced IMI activation requires G proteins: effect of GTPγS. GTPγS was pressure injected in a vehicle solution of 500 mM KCl + 20 mM TEA. Control pressure injections used the vehicle solution only. A: averaged I-V curves of proctolin-induced IMI after pressure injection with either control (black) or 10 mM GTPγS (gray) solution in normal (13 mM) calcium. B: same as A but in saline containing low (2 mM) calcium. C: quantification of the effect of GTPγS on IMI amplitude at −15 mV. A 2-way ANOVA showed that GTPγS, but not calcium, was capable of occluding IMI amplitude [calcium: F(1,22) = 2.136, P = 0.158; GTPγS: F(1,22) = 13.562, P = 0.001; interaction: F(1,22) = 0.0817, P = 0.778]. Tukey post hoc test: *P < 0.05; ***P < 0.001; ns, not significant. Error bars are SE. Solid bars indicate normal extracellular Ca2+ (control); hatched bars indicate low calcium level.