ubp296 and Hypoxia

NMDA receptors mediate hypoxia-induced ventilatory frequency and blood pressure increases in fish. Here we continue to resolve whether non-NMDA receptors participate in chemoreflexes. Shorthorn sculpins, instrumented for cardiorespiratory measurements, were kept unrestrained or positioned in a stereotaxic frame. Chemoreflexes were elicited (hypoxia/NaCN-induced) before/after administration of either the specific AMPA receptor antagonist, GYKI52466 (systemically), or the specific kainate receptor antagonist, UBP293 (microinjections into fourth ventricle). Immunohistochemistry was performed on medullary cross-sections to identify non-NMDA receptor subunits in the chemoreflex-pathway. Kainate receptors mediate the chemoreflex-mediated increase in ventilation amplitude, since the response was abolished by UBP293. GYKI52466 attenuated the ventilatory frequency increase, and induced more regular breathing patterns and higher heart rate in both normoxic and hypoxic conditions, suggesting that AMPA receptors also partake in cardiorespiratory control. This together with immunohistochemical findings of both AMPA and kainate receptor subunits in the chemoreflex-pathway, show that non-NMDA receptors play a role in both chemoreflex-activation and normoxic cardiorespiratory regulation in fish.

Topics: Alanine; Animals; Benzodiazepines; Blood Pressure; Chemoreceptor Cells; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Fishes; Glutamic Acid; Heart Rate; Hypoxia; Immunohistochemistry; Medulla Oblongata; Microinjections; Oxygen; Poisons; Receptors, AMPA; Receptors, Kainic Acid; Reflex; Respiratory Mechanics; Seasons; Sodium Cyanide