Participation of the Breuer-Hering inflation reflex in regulation of respiration frequency in anaesthetized rats.

The respiration frequency and Breuer-Hering inflation reflex (BHIR) values were compared in anaesthetized rats after unilateral vagotomy. Nos significant differences were found in the decrease in respiration frequency after transection of the right of left vagus and there were no differences in BHIR values in correlation to conduction by the right or left vagus. With unilateral vagotomy and an inflation pressure of 20 cm H20 the BHIR values fell to about one fourth of the control values. Progressive cooling of the contralateral vagus led at 8-10 degrees C to a non-significant decrease in respiration frequency to 87% of the initial value; in this state the BHIR could not be elicited. Further cooling of the vagus to 0 degrees C reduced respiration frequency to the same values as in bilateral vagotomy. The discrepancy between the mild decrease in respiration frequency and simultaneous disappearance of the BHIR shows that changes in respiration frequency in anaesthetized rats are not directly correlated to the presence of the BHIR.