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Stimulus interaction between CO and CO2 in the cat carotid body chemoreception
S Osanai1, D K Chugh, A Mokashi
1Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104-6085, USA.
Brain Research
|March 4, 1996
Summary
High partial pressure of carbon monoxide (PCO) interacts with carbon dioxide (PCO2) to stimulate carotid body chemoreceptors in the dark. This interaction, similar to hypoxia, influences chemosensory excitation.
Area of Science:
- Physiology
- Neuroscience
- Respiratory System
Background:
- High partial pressure of carbon monoxide (PCO) mimics hypoxia at carotid body chemoreceptors.
- Hypoxia is known to interact with carbon dioxide (CO2) in chemosensory excitation.
Purpose of the Study:
- To test the hypothesis that high PCO interacts with PCO2 in stimulating chemosensory excitation in the dark.
- To investigate the effects of light on these interactions.
Main Methods:
- In vitro perfusion and superfusion of cat carotid body with controlled PO2 (~100 Torr).
- Chemosensory discharges were measured at varying PCO2 levels under different PCO conditions (500 Torr and 150 Torr) and in the presence/absence of light.
Main Results:
- In the dark, high PCO with normocapnia (PCO2 ~30 Torr) stimulated sensory discharges, with hypocapnia (PCO2 ~18 Torr) showing lower activity, indicating stimulus interaction.
- Hypercapnia appeared to saturate activity under high PCO.
- An intermediate PCO (150 Torr) showed clear interaction with hypercapnia in the dark.
- Bright light promptly reduced activity to baseline under high PCO, with subsequent increases upon light withdrawal.
Conclusions:
- High PCO exhibits stimulus interaction with PCO2 in the dark, affecting carotid body chemosensory excitation.
- Light significantly modulates the chemosensory response to PCO and PCO2.
- The findings support the hypothesis of PCO-PCO2 interaction in chemoreception.