Journal of Applied Physiology, Vol 68, Issue 3 932-937, Copyright © 1990 by American Physiological Society
Group I afferent fibers: effects on cardiorespiratory system
G. P. Orani and M. Decandia
Istituto di Fisiologia Umana, Universita di Cagliari, Italy.
In anesthetized cats, we examined cardiorespiratory activity during
excitation of large afferent fibers from muscle proprioceptors. We found
that selective stimulation of group I fibers with electric impulses at
200-300 Hz induces an increase in pulmonary ventilation from control value
(mean +/- SE) of 486 +/- 8 to a maximum of 544 +/- 8 ml/min and an increase
in mean systemic arterial pressure from control value of 151 +/- 2 to a
maximum of 160 +/- 2 mmHg. Neither of these increases was produced by the
same stimulation when applied during anodal block of volleys of group I
fibers. Hyperpnea could be obtained independently from changes in
cardiovascular activity, and the pressor response could be obtained during
artificial ventilation at constant tidal volume after curarization.
Consequently, it appears that respiratory and cardiovascular responses to
stimulation of group I fibers can be independent of each other.
