title: Recovery of carotid body O2 sensitivity following chronic postnatal hyperoxia in rats.
abstract: Chronic postnatal hyperoxia blunts the hypoxic ventilatory response (HVR) in rats, an effect that persists for months after return to normoxia. To determine whether decreased carotid body O(2) sensitivity contributes to this lasting impairment, single-unit chemoafferent nerve and glomus cell calcium responses to hypoxia were recorded from rats reared in 60% O(2) through 7d of age (P7) and then returned to normoxia. Single-unit nerve responses were attenuated by P4 and remained low through P7. After return to normoxia, hypoxic responses were partially recovered within 3d and fully recovered within 7-8d (i.e., at P14-15). Glomus cell calcium responses recovered with a similar time course. Hyperoxia altered carotid body mRNA expression for O(2)-sensitive K(+) channels TASK-1, TASK-3, and BK(Ca), but only TASK-1 mRNA paralleled changes in chemosensitivity (i.e., downregulation by P7, partial recovery by P14). Collectively, these data do not support a role for reduced O(2) sensitivity of individual chemoreceptor cells in long-lasting reduction of the HVR after developmental hyperoxia.
authors.affiliation: Department of Biology, Bates College, Lewiston, ME 04240, USA. rbavis@bates.edu
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Bavis
authors.forename: Insook
authors.initials: I
authors.lastname: Kim
authors.forename: Nelish
authors.initials: N
authors.lastname: Pradhan
authors.forename: Nawshaba
authors.initials: N
authors.lastname: Nawreen
authors.forename: Elizabeth F
authors.initials: EF
authors.lastname: Dmitrieff
authors.forename: John L
authors.initials: JL
authors.lastname: Carroll
authors.forename: David F
authors.initials: DF
authors.lastname: Donnelly
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D020013:Calcium Signaling / Q000502:physiology; D002344:Carotid Body / Q000378:metabolism* / Q000503:physiopathology; D002628:Chemoreceptor Cells / Q000378:metabolism*; D018496:Hyperoxia / Q000378:metabolism* / Q000503:physiopathology; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000096:biosynthesis; D024683:Potassium Channels, Tandem Pore Domain / Q000096:biosynthesis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: C407082:Kcnk9 protein, rat; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D009419:Nerve Tissue Proteins; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D012333:RNA, Messenger; C420132:potassium channel subfamily K member 3