An NTS microinjection of a low dose of ANGII (5 fmol) produced a significant bradycardia consistently whereas higher doses of ANGII (5–5000 fmol) produced inconsistent effects, the most common being a tachycardia. At all doses of ANGII tested there was a significant decrease in both phrenic nerve activity cycle length and amplitude. The time of the microinjection is indicated by the arrows. The data are taken from two different preparations. Changes in perfusion pressure were very small and not consistent with all doses of ANGII. Note the ongoing respiratory sinus arrhythmia in each preparation. Abbreviations∫PNA, integrated phrenic nerve activity; HR, heart rate; bts/min, beats per minute; PP, perfusion pressure.