Effects of carotid chemoreceptor and baroreceptor stimulation upon the sympathetic preganglionic and postganglionic cardiac nerve and single fiber activity in cats.

The stimulation of arterial baroreceptors (blind sack technique) inhibited the preganglionic and postganglionic cardiac sympathetic activity. There were found three populations of single sympathetic preganglionic fibers (Th3) responding in a different way to the stimulation of arterial baroreceptors and arterial chemoreceptors (infusion of the small volume of saline bubbled with CO2 into the carotid sinus): (i) inhibited by carotid baroreceptors and excited by carotid chemoreceptors stimulation, (ii) inhibited by carotid baroreceptors and by carotid chemoreceptors stimulation, (iii) some fibers inhibited by baroreceptors did not change activity during stimulation of chemoreceptors. A functional role of each particular group of preganglionic sympathetic fibers is discussed.