Fig. 5. Effects of Na⁺-free saline on basolateral membrane potential and intracellular pH in 10^–6 mol l^–1 5-HT stimulated Malpighian tubules. Representative simultaneous recordings of basolateral membrane potential (A) and intracellular pH (B). Downward-pointing arrow indicates impalement of the cell and upward-pointing arrow the removal of the electrode from the cell. Tubules were exposed to Na⁺-free saline for the period indicated by the horizontal bar. (C) pH_i (mean + s.e.m.) before and 2 min after exposure to Na⁺-free saline (N=3). The asterisk indicates a significant difference (P<0.05, paired Student's t-test).