Effects of sagittal medullary section on high-frequency oscillation in rabbit phrenic neurogram.

Six rabbits were anaesthetized with chloralose and urethane and were subjected to sagittal section of the medulla in the region of obex to a few mm rostral to obex. The sections had an initial rostro-caudal length of 4 mm and were gradually extended until the respiratory rhythms on the two sides of the animal, as seen in phrenic discharges, became dissociated. High-frequency oscillation in the phrenic discharge, assessed either by visual inspection of the neurogram or by cross-correlation between the discharges in the two phrenic roots on one side, was abolished by sections for which the intensity of the phrenic discharge was hardly affected. These sections were smaller than those required to dissociate the respiratory rhythms on the two sides of the animal.