Different patterns of respiratory responses to chemical stimulation of muscle receptors in the rabbit
Tallarida, G.; Baldoni, F.; Peruzzi, G.; Raimondi, G.; Massaro, M.; Abate, A.; Sangiorgi, M.
Journal of Pharmacology and Experimental Therapeutics 223(2): 552-559
1982
ISSN/ISBN: 0022-3565 PMID: 7131304 Document Number: 186033
The 2 different patterns of reflex circulatory responses which can be elicited in the rabbit by i.a. injection of chemical substances into skeletal muscle were associated with 2 distinct patterns of reflex respiratory responses. In the anesthetized rabbit, bradykinin, K, sodium citrate and acid sodium phosphate caused a reflex decrease in arterial pressures and heart rate accompanied by hyperpnea achieved mainly with an increase in breathing frequency. The expiratory duration (Te) was shortened more than the inspiratory period (Ti) and Te/Ti relationship was lowered. Hypertonic solutions of NaCl or glucose caused reflex hypertension, tachycardia and hyperpnea mainly due to an increase in tidal volume. The expiratory period was less reduced and Te/Ti relationship did not change significantly. The characteristic ventilatory changes were obtained with or without intact cardotid sinus, aortic and vagus nerves. Respiratory responses were not secondary to the circulatory changes inasmuch as they were still observed when the circulatory reflexes were prevented by pharmacologic blockade of the adrenergic nerves. These 2 distinct patterns of cardiorespiratory chemoreflexes, elicited from the musculature of the rabbit, are accounted for by the presence in the skeletal muscle of 2 functionally different types of neural receptors for coordinated cardiocirculatory and respiratory changes, connected with pressor and depressor afferent fibers in the somatic nerves. These chemoreflexes might have a role in the reflex cardiovascular and respiratory adjustments during muscle exercise.