Respiratory responses to stimulation of large fibers afferent from muscle receptors in cats

Experiments were carried out on cats to re-examine the respiratory effects of the stimulation of the large afferent fibers originating in the receptors of the hindlimb muscles. During the contraction of the triceps surae induced by stimulating the ventral roots, pulmonary ventilation increased due to an increase in tidal volume and, usually, in respiratory frequency. An increase in ventilation occurred also during stimulation at group I strength of the central end of the previously cut nerves to the triceps surae (LGS + MG) and to the posterior biceps plus the semitendinosus (PBST) muscles. Appreciable increase in ventilation was seen for stimuli near threshold for group I (Ia + Ib) afferent fibers of the LGS + MG nerves, while stimuli at group Ib strength were needed to produce the same effects when using the PBST nerves. It is concluded that group Ib fibers afferent from muscle receptors play a role in the reflex control of respiration.