AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 4 851-R858, Copyright © 1995 by American Physiological Society
Chemoreceptor-sensitive neurons in commissural subnucleus of nucleus tractus solitarius of the rat
V. C. Chitravanshi and H. N. Sapru
Section of Neurological Surgery, New Jersey Medical School, Newark 07103, USA.
Experiments were carried out in pentobarbital-anesthetized, vagotomized,
paralyzed, and artificially ventilated male Wistar rats with a
pneumothorax. Blood pressure, heart rate, and phrenic nerve activity were
recorded. Extracellular neuronal recordings were made by glass
micropipettes in a midline area in the commissural subnucleus of the
nucleus tractus solitarius. At the end of the experiment, the recording
sites were marked. Chemoreceptors were stimulated by tracheal
administration of N2 or injection of CO2-saturated saline (50 microliters)
near the carotid body. The baroreceptors were stimulated by an intravenous
injection of phenylephrine (1-3 micrograms). Neurons that were excited by
chemoreceptor stimulation but not baroreceptor stimulation were found in
the commissural subnucleus of nucleus tractus solitarius and were
designated as chemoreceptor-sensitive neurons. They exhibited a continuous
discharge (9.9 +/- 1.3 spikes/s) that showed no apparent relation to either
phrenic nerve bursts or arterial pulses. Such neurons were not found in the
rostral portions of the nucleus tractus solitarius. These results confirm
and extend our previous reports in which a discrete chemoreceptor
projection site was identified in the commissural subnucleus of the rat.
