Pivotal Role of Nucleotide P2X2 Receptor Subunit of the ATP-Gated Ion Channel Mediating Ventilatory Responses to Hypoxia

In mammals, the ventilatory response to decreased oxygen tension in the arterial blood is initiated by excitation of specialized O2-sensitive chemoreceptor cells in the carotid body that release neurotransmitters to activate endings of the sinus nerve afferent fibers. We investigated the role of ATP...

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Bibliographic Details
Published in:The Journal of neuroscience 2003-12, Vol.23 (36), p.11315-11321
Main Authors: Rong, Weifang, Gourine, Alexander V, Cockayne, Debra A, Xiang, Zhenghua, Ford, Anthony P. D. W, Spyer, K. Michael, Burnstock, Geoffrey
Format: Article
Language:English
Subjects:
Action Potentials
Adenosine Triphosphate - pharmacology
Animals
Behavioral/Systems/Cognitive
Carotid Body - chemistry
Carotid Body - drug effects
Carotid Body - physiopathology
Hypoxia - physiopathology
Immunohistochemistry
Ion Channel Gating
Mice
Mice, Knockout
Protein Subunits
Pulmonary Ventilation
Receptors, Purinergic P2 - analysis
Receptors, Purinergic P2 - genetics
Receptors, Purinergic P2 - physiology
Receptors, Purinergic P2X2
Receptors, Purinergic P2X3
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Summary:In mammals, the ventilatory response to decreased oxygen tension in the arterial blood is initiated by excitation of specialized O2-sensitive chemoreceptor cells in the carotid body that release neurotransmitters to activate endings of the sinus nerve afferent fibers. We investigated the role of ATP acting via ionotropic P2X receptors in the carotid body function and ventilatory response to hypoxia in mice. Mice deficient in P2X2 receptor subunit showed a markedly attenuated ventilatory response to hypoxia, whereas the response to hypoxia in P2X3-deficient mice was comparable with that seen in wild-type controls. P2X2 and P2X3 receptor subunit deficiency did not affect the ventilatory responses to hypercapnia. P2X2 subunit deficiency resulted in a dramatic reduction in the responses of the carotid sinus nerve to hypoxia in the in vitro carotid body-sinus nerve preparation. ATP and its stable analog alpha,beta-methyleneATP both evoked rapid excitation of sinus nerve afferents, and the P2 receptor antagonist PPADS (pyridoxal-5'-phosphate-6-azophenyl-2',4'-disulphonic acid) (100 microm) blocked hypoxia-induced increase in sinus nerve discharge. Immunoreactivities for P2X2 and P2X3 subunits were both detected on afferent terminals surrounding clusters of glomus cells in the wild-type animals but were absent in mice deficient in P2X2 and P2X3 receptor subunits. These observations provide the first definitive evidence that, in the carotid body, ATP is a key transmitter released by chemoreceptor cells to activate endings of the sinus nerve afferent fibers. We conclude that P2X receptors containing the P2X2 subunit play a pivotal role in carotid body function and in mediating ventilatory responses to hypoxia.
ISSN:0270-6474
1529-2401
DOI:10.1523/jneurosci.23-36-11315.2003