Effects of dopaminergic blockade upon carotid chemosensory activity and its hypoxia-induced excitation.
The effects of domperidone, antagonist of D2 receptors, on arterial chemoreceptor activity were studied in spontaneously breathing and pentobarbitone anesthetized cats, in which recordings of chemosensory impulse activity were obtained simultaneously from both cut carotid (sinus) nerves. Intravenous injections of domperidone 50 micrograms/kg produced a maintained increase in the basal frequency of chemosensory discharges, after which hyperoxic tests (breathing 100% O2 for 30 s) evoked larger falls in the rate of chemosensory impulses. Chemosensory responses evoked by hypoxic hypoxia (100% N2 tests) and by cytotoxic hypoxia (i.v. injections of NaCN) reached higher impulse rates after domperidone treatment. The effects of domperidone reveal that a resting release of dopamine from glomus cells maintains a low level of basal chemosensory activity under normoxic conditions. Domperidone turns off such restraining dopaminergic control and enhances the transient chemosensory responses to hypoxic stimuli. Present data support a modulatory role for dopamine within the chemoreceptor process, but not its participation as excitatory transmitter between glomus cells and sensory nerve endings.
Laboratory of Neurobiology, Catholic University of Chile, Santiago.
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R
Iturriaga
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C
Larraín
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P
Zapata
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002346:Carotid Sinus / Q000294:innervation*; D002415:Cats; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D004294:Domperidone / Q000008:administration & dosage / Q000494:pharmacology*; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D000860:Hypoxia; D007275:Injections, Intravenous; D008297:Male; D009411:Nerve Endings / Q000502:physiology; D012966:Sodium Cyanide / Q000008:administration & dosage / Q000494:pharmacology; D013990:Tidal Volume / Q000187:drug effects; D013997:Time Factors
D065127:Dopamine D2 Receptor Antagonists; D004294:Domperidone; D012966:Sodium Cyanide