Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Hypoxic chemotransmission in the rat carotid body (CB) is mediated in part by ATP acting on suramin-sensitive P2X purinoceptors. Here, we use RT-PCR, cloning and sequencing techniques to show P2X2 and P2X3 receptor expression in petrosal neurones, some of which develop functional chemosensory units with CB receptor clusters in co-culture. 2. Single-cell RT-PCR revealed that hypoxia-responsive neurones, identified electrophysiologically in co-culture, expressed both P2X2 and P2X3 mRNA. 3. Isohydric hypercapnia (10 % CO(2); pH 7.4) caused excitation of chemosensory units in co-culture. This excitation depended on chemical transmission, with ATP acting as a co-transmitter, since it was inhibited by reduction of the extracellular Ca(2+):Mg(2+) ratio and by the purinoceptor blocker suramin (50-100 microM). 4. Hypoxia and isohydric hypercapnia could separately excite the same chemosensory unit, and together the two stimuli interacted synergistically. 5. Using confocal immunofluorescence, co-localization of P2X2 and P2X3 protein was demonstrated in many petrosal somas and CB afferent terminals in situ. Taken together, these data indicate that ATP and P2X2-P2X3 purinoceptors play important roles in the peripheral control of respiration by carotid body chemoreceptors.
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PMID:Expression of P2X2 and P2X3 receptor subunits in rat carotid body afferent neurones: role in chemosensory signalling. 1174 46

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.
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PMID:Pivotal role of nucleotide P2X2 receptor subunit of the ATP-gated ion channel mediating ventilatory responses to hypoxia. 1467 95