Cardiorespiratory reflexes in mice.

The various transgenic strains of mice make this species an attractive experimental model. We compared qualitatively some cardiorespiratory reflexes in two different preparations of mouse: in vivo urethane anaesthetised and a working heart-brainstem preparation (WHBP). Cardiorespiratory reflexes were evoked by stimulating baroreceptors, pulmonary vagal C fibres and cardiac receptors in both preparations, while peripheral chemoreceptors were also stimulated in the WHBP. In anaesthetised mice, activation of baroreceptors, pulmonary C fibres and cardiac receptors evoked an atropine-sensitive bradycardia (range: 21-414 bts/min) and depressed ventilation. A reflex fall in arterial pressure was also observed during pulmonary C fibre and cardiac receptor stimulation. Similar reflex bradycardia (range 81-164 bts/min) and respiratory responses were observed in the WHBP following stimulation of baro-, pulmonary C fibre and cardiac receptors. Additionally, sodium cyanide stimulation of peripheral chemoreceptors in the WHBP produced an atropine-sensitive bradycardia and increased respiratory frequency and amplitude. Thus, the cardiorespiratory reflex responses elicited in the mouse are similar to those reported in other species. It is concluded that the qualitatively similar reflex performances between the in vivo anaesthetised mouse and the WHBP make the latter an adequate model for studying central mechanisms controlling the cardiorespiratory system.