Relative selectivity of SP-CTA for NK1, NK2 and NK3 receptors. Concentration response relationships for SP-CTA on the stimulation of cAMP production were performed on CHO cells transiently transfected with NK1 or NK2 receptors. Non-transfected CHO cells were either not exposed to SP-CTA (Ctrl) or treated with 10 ng/ml SP-CTA (Ctrl 10). CHO cells stably transfected with NK3 receptors were treated with a single concentration of 10 ng/ml SP-CTA. (Two way ANOVA of NK1 versus NK2, F = 1.7, df = 1, p = 0.20: Dose, F = 54.61, df = 6, p < 0.0001). Asterisks indicate p < 0.01 (one way ANOVA followed by Dunnett's post hoc test, F = 56.15, df = 83) when compared to control cells not treated with SP-CTA.