P991

         J Physiol (Paris) 1985;80(3):173-6

        [Postnatal development of the Hering-Breuer reflex in the rat]

        [Article in French]

        Smejkal V, Palecek F, Frydrychova M.

        The intensity of the Breuer-Hering inflation reflex was studied in

        newborn (1 day old), in young (8 days old) and in adult rats (90 days

        old) under urethane general anaesthesia (1.3 g/kg i.p.). The inflation

        pressure was adjusted with the aid of a water-valve. The reflex was

        present in all 3 age groups. An inflation pressure of 0.2 kPa applied in

        the course of expiration produced a long lasting apnoea in newborn rats

        which lasted 48 normal respiratory cycles. An inflation pressure of 0.5

        kPa in young rats induced an apnoea lasting for only 3 normal

        respiratory cycles, whereas a pressure of 1 kPa in adult rats led to an

        apnoea which lasted for 20 normal respiratory cycles. The compliance of

        the respiratory system in relation to lung weight is approximately 5

        times higher in adult rats compared with that of newborn rats. It is

        approximately double in comparison with young rats. The pressures of

        inflation mentioned in the 3 age categories can be considered as

        equieffective from the point of stimulation pulmonary stretch receptors.

        It can be concluded from these findings that the reflex of Breuer-Hering

        in newborn rats is more potent in comparison with adult rats, but it is

        lower in young rats at the age of 8 days. It is suggested that the

        differences observed are due to functional and anatomical maturation.