title: Chronic hypoxia attenuates central respiratory-related pH/CO2 chemosensitivity in the cane toad.
abstract: This study examined the effects of chronic hypoxia (CH) and mid-brain transection on central respiratory-related pH/CO(2) chemosensitivity in cane toads (Bufo marinus). Toads were exposed to 10 days of CH (10% O(2)) following which in vitro brainstem-spinal cord preparations, with the mid-brain attached, were used to examine central pH/CO(2) chemosensitivity. A reduction in artificial cerebral spinal fluid (aCSF) pH increased fictive breathing frequency (fR) and total fictive ventilation. CH reduced fictive fR and total fictive ventilation, compared to controls. Mid-brain transection caused an increase in fictive fR, at the lower aCSF pH levels, in both control and CH preparations. In the CH preparations, mid-brain transection restored fictive breathing to control levels. In both groups, mid-brain transection eliminated fictive breath clustering. The data indicate that CH attenuates central pH/CO(2)-sensitive fictive breathing but a mid-brain transection in the middle of the optic lobes abolishes this attenuation. The results suggest that CH induces inhibition of central pH/CO(2) chemoreceptor function via descending inputs from the mid-brain region.
authors.affiliation: Centre for the Neurobiology of Stress, Department of Life Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4 Canada.
authors.forename: Jessica
authors.initials: J
authors.lastname: McAneney
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Reid
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000502:physiology; D002024:Bufo marinus; D002245:Carbon Dioxide / Q000502:physiology*; D002555:Cerebrospinal Fluid / Q000737:chemistry / Q000502:physiology; D002908:Chronic Disease; D003627:Data Interpretation, Statistical; D004566:Electrodes; D004594:Electrophysiology; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000378:metabolism*; D008636:Mesencephalon / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology
chemical_list: D002245:Carbon Dioxide