P322

         Physiol Bohemoslov 1975;24(1):23-33

        Inflation reflex in the rat.

        Fialová E, Vízek M, Paleček F.

        The Breuer-Hering inflation reflex [BHIR] was elicited in conscious and

        anaesthetized rats by inflating the lungs with constant pressures of

        5--20 cm H2O. The reflex was elicited well in conscious animals, but

        even with the maximum stimulus [inflation of 20 cm H2O, corresponding to

        about 4.5-fold the tidal volume] the duration of apnoea did not exceed 4

        control respiration cycles. In anaesthetized animals, the same stimulus

        let to apnoea lasting 180--400 control respiration cycles on the

        average, according to the type and depth of general anaesthesia. The

        duration of apnoea in occlusion of the air passages in the expiratory

        position increased with the depth of anaesthesia, while in occlusion of

        the air passages at the peak of inspiration it was shortened.

        Stimulation of chemoreceptors [inhalation of a mixture 4% CO2 in O2 or

        of 8% O2 in N2] did not influence the elicitability or duration of the

        BHIR, nor did cooling the rats to 28 degrees C or heating them to 38

        degrees C. The mean respiration frequency was 98 c/min in

        unanaesthetized rats, 96 c/min in urethane anaesthesis and 79--48 c/min

        in halothane anaesthesia, according to the depth of anaesthesia.

        Bilateral cervical vagotomy reduced mean respiration frequency to 35.6

        c/min in conscious rats and to 31 c/min in urethane-anaesthetized

        animals. The results indicate the existence of species-related

        differences between basic regulatory mechanisms in the rat and certain

        other mammals.