The impact of hypoxia and low glucose on the release of acetylcholine and ATP from the incubated cat carotid body

Abstract

The carotid body (CB) is a polymodal sensor which increases its neural output to the nucleus tractus solitarii with a subsequent activation of several reflex cardiopulmonary responses. Current reports identify acetylcholine (ACh) and adenosine triphosphate (ATP) as two essential excitatory neurotransmitters in the cat and rat CBs. This study explored the impact of hypoxia, low glucose, and the two together on the release of both ACh and ATP from two incubated cat CBs. The CBs were prepared with standard procedures in accordance with the policies and regulations of the Institutional Animal Care and Use Committee. When normalized to their controls, a significant increase of ACh in the incubation medium was measured in response to hypoxia, low glucose, and the combined stimuli. When normalized to their controls, a significant increase in ATP in the incubation medium was measured in response to hypoxia and to the combined stimuli. Low glucose generated an increase in ATP which was not statistically significant ( P > 0.05). Second, normalizing the initial 3–4 or 2–3 min Time Segment of the challenge Stage to the final 3–4 or 2–3 min Time Segment of the control Stage for both ACh and ATP generated significant increases in response to hypoxia, low glucose (ACh only), and the combined stimuli. The data suggested the possibility that in the cat the increased CB neural output in response to low glucose might be due primarily to ACh.