Fig. 8. Representative recording of the basolateral membrane voltage (V_b) in a principal cell challenged sequentially with 100 nmol l^–1 Anoga-DH₃₁, 100 nmol l^–1 Anoga-DH₄₄ and 100 µmol l^–1 8-bromo-cyclic AMP. Note that only Anoga-DH₄₄ gives a triphasic response beginning with a brief hyperpolarisation. Horizontal bars indicate when peptides or cyclic AMP analogue were present in the bath. Arrows show when the principal cell was impaled (downward arrow) and the microelectrode withdrawn (upward arrow).