Investigation of afferent activity in the intact phrenic nerve with bipolar electrodes.

The electrical activity of intact branches of the phrenic nerve was studied during spontaneous respiration in the anaesthetized or decerebrate cat. The action potentials were displayed with opposite polarity according to whether their activity was of afferent or efferent origin. The afferent volleys could be grouped according to three modalities. The first group had a clear silent period during diaphragmatic contraction (72 percent). The second group had volleys during inspiration (25 percent). The third group (3 percent) had rhythmic bursts of fast potentials that were independent of the respiratory cycle.