Fig. 1. Trigeminal neurograms comparing changes in lung- and buccal-related motor output with bath application of 5 µmol l^-1 noradrenaline (NA) concentrations. These recordings illustrate the distinction between the two patterns of respiratory-related neural activity, and show the stage-dependent effects of NA on the neural correlates of respiratory activity. Recordings were obtained from isolated brainstem preparations from pre- and metamorphic tadpoles, and an adult bullfrog.