title: Branchial O(2) chemoreceptors in Nile tilapia Oreochromis niloticus: Control of cardiorespiratory function in response to hypoxia.
abstract: This study examined the distribution and orientation of gill O(2) chemoreceptors in Oreochromis niloticus and their role in cardiorespiratory responses to graded hypoxia. Intact fish, and a group with the first gill arch excised (operated), were submitted to graded hypoxia and their cardiorespiratory responses (oxygen uptake - V˙O(2) , breathing frequency - fR, ventilatory stroke volume - VT, gill ventilation - V˙G, O(2) extraction from the ventilatory current - EO(2) , and heart rate - fH) were compared. Their responses to bolus injections of NaCN into the bloodstream (internal) or ventilatory water stream (external) were also determined. The V˙O(2) of operated fish was significantly lower at the deepest levels of hypoxia. Neither reflex bradycardia nor ventilatory responses were completely abolished by bilateral excision of the first gill arch. EO(2) of the operated group was consistently lower than the intact group. The responses to internal and external NaCN included transient decreases in fH and increases in fR and Vamp (ventilation amplitude). These cardiorespiratory responses were attenuated but not abolished in the operated group, indicating that chemoreceptors are not restricted to the first gill arch, and are sensitive to oxygen levels in both blood and water.
authors: Department of Physiological Sciences, Laboratory of Zoophysiology and Comparative Biochemistry, Federal University of São Carlos (UFSCar), P.O. Box 676, Via Washington Luis, km 235, 13565-905 São Carlos, SP, Brazil.
authors: Vivian M
authors: VM
authors: Zeraik
authors: Thiago C
authors: TC
authors: Belão
authors: Luiz Henrique
authors: LH
authors: Florindo
authors: Ana L
authors: AL
authors: Kalinin
authors: F Tadeu
authors: FT
authors: Rantin
mesh_terms: D000818:Animals; D001934:Branchial Region / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000378:metabolism*; D023681:Cichlids / Q000378:metabolism*; D005880:Gills / Q000187:drug effects / Q000503:physiopathology; D006321:Heart / Q000187:drug effects / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D008168:Lung / Q000378:metabolism / Q000503:physiopathology*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D012119:Respiration / Q000187:drug effects; D012966:Sodium Cyanide / Q000494:pharmacology
chemical_list: D012966:Sodium Cyanide; D010100:Oxygen
keywords: Gill chemoreceptors; Hypoxia; Hypoxic bradycardia; Oreochromis niloticus; Ventilation