Spike-frequency counting and integrative methods for analysis of aortic nerve activity.

1. -- Aortic nerve activity was simultaneously measured in anaesthetized rabbits by spike-frequency counting and integrative methods during decreases by bleeding in mean blood pressure (MBP) from 130 to 50 mm Hg. Values of counted and integrated activities were expressed in arbitrary units. 2. -- No statistically significant difference between the counted and integrated activity was pointed out in the range of MBP from 130 to 90 mm Hg. 3. -- Below a MBP of 90 mm Hg, the counted activity was significantly higher than the integrated activity. This difference could be the result of a better appraisal of the number of small and medium spikes by the counting equipment than by the integrating system.