Task2 potassium channels set central respiratory CO_2 and O_2 sensitivity

摘要

Task2 K~+ channel expression in the central nervous system is surprisingly restricted to a few brainstem nuclei, including the retro-trapezoid (RTN) region. All Task2-positive RTN neurons were lost in mice bearing a Phox2b mutation that causes the human congenital central hypoventilation syndrome. In plethysmography, Task2~(-/-) mice showed disturbed chemosensory function with hypersensitivity to low CO_2 concentrations, leading to hyperven-tilation. Task2 probably is needed to stabilize the membrane potential of chemoreceptive cells. In addition, Task2~(-/-) mice lost the long-term hypoxia-induced respiratory decrease whereas the acute carotid-body-mediated increase was maintained. The lack of anoxia-induced respiratory depression in the isolated brainstem-spinal cord preparation suggested a central origin of the pheno-type. Task2 activation by reactive oxygen species generated during hypoxia could silence RTN neurons, thus contributing to respiratory depression. These data identify Task2 as a determinant of central O_2 chemoreception and demonstrate that this phenomenon is due to the activity of a small number of neurons located at the ventral medullary surface.