Fig. 1. An epithelial phenotype for norpA: phospholipase Cß (PLCß) is required for neuropeptide stimulation of principal and stellate cells. Fluid transport assays were performed on intact tubules from wild-type (Oregon R), norpA^H52 and norpA^P24 flies as described in the Materials and methods. Either (A) 10^-7 moll^-1 CAP_2b or (B) 10^-7 moll^-1 Drosokinin were added at 30 min (arrow), and transport rates were measured for a further 30 min. Data are expressed as mean secretion rates ± S.E.M. (N=8).