Fig. 3. (A) Stage-dependent changes in fictive lung burst frequency during noradrenaline (NA; 5 µmol l^–1) application. The histograms (left) show the mean data and the trigeminal neurograms (V, trigeminal nerve; right) show representative recordings obtained under baseline conditions and following NA bath application. Data are reported for both stage groups (pre-metamorphic: grey bars, N=6; and adults: black bars, N=6). (B,C) The same experiment was performed in the presence of the GABA_A/glycine antagonist mixture (bicuculline 1.25 µmol l^–1/strychnine 1.5 µmol l^–1) in both stage groups. For these experiments, representative trigeminal neurograms showing respiratory-related activity observed under each condition are shown below the histograms. Values are means ± s.e.m. ^*Values statistically different from baseline at P<0.05; value statistically different from corresponding mixture value at P<0.05.