Figure 2. AMPK-dependent regulation of carotid body excitation by hypoxia.

A, from left to right: brightfield image of an isolated and fixed carotid body type I cell; z section showing immuno-labelling for the AMPK-α1 catalytic subunit isoform (green) tyrosine hydroxylase (red) and the DAPI labelled nucleus (blue); 3D reconstruction. B, schematic diagram describing the proposed mechanism of carotid body excitation by hypoxia: hypoxia inhibits mitochondrial oxidative phosphorylation in carotid body type I cells, which leads to an increase in the AMP/ATP ratio, AMPK activation, AMPK-dependent inhibition of K⁺ channels in the plasma membrane, voltage-gated Ca²⁺ influx, neurosecretion and a consequent increase in afferent fibre discharge.