Laryngeal nerve paraganglia of the rat are morphologically and biochemically unchanged by long-term hypercapnia.

Exposure to hypercapnia (8.2 +/- 0.7% CO2) for 3 weeks failed to change the morphometric characteristics (mean cell area, nuclear, mitochondria and vesicle volume density) of the recurrent laryngeal nerve paraganglia of the rat. Moreover, this treatment had no effect on the dopamine and noradrenaline content of the superior and recurrent laryngeal nerves. The results are in contrast to what is found after exposure to hypoxia which increases the dopamine content and the cell area of the paraganglia and indicate that the mechanisms of the paraganglia in long-term hypoxia and hypercapnia differ.