The effects of hypercapnia and hypocapnia on the activities of the cardiac and pulmonary vagal single fibers were examined in the decerebrated, unanesthetized, paralyzed, and vagotomized cats. The animals breathed 100% O 2 . Fractional end tidal CO 2 concentration was raised to 9% by adding CO 2 into the O 2 inlet. Average discharge rate of efferent cardiac vagal units (n=10) increased from 1.0±0.3 to 2.2±0.3 Hz. Hypocapnia apnea was produced by hyperventilation. Activities of cardiac vagal units tested (n = 4) showed dramatic decrease (0.1±0.0 Hz). Mean arterial blood pressure did not change significantly under these conditions. In contrast, only instantaneous firing rate during inspiration was significantly increased for efferent pulmonary vagal units (n = 11) during hypercapnia. The activities of the 3 pulmonary vagal units tested with hypocapnia decreased significantly. We concluded that cardiac and pulmonary vagal neurons were excited by chemoreceptor input.
|Number of pages||5|
|Journal||Chinese Journal of Physiology|
|Publication status||Published - 2000 Mar 31|
- Parasympathetic preganglionic neuron
- Single unit recording
ASJC Scopus subject areas
- Physiology (medical)