title: The role of the autonomic nervous system in control of cardiac and air-breathing responses to sustained aerobic exercise in the African sharptooth catfish Clarias gariepinus.
abstract: Clarias gariepinus is a facultative air-breathing catfish that exhibits changes in heart rate (ƒH) associated with air-breaths (AB). A transient bradycardia prior to the AB is followed by sustained tachycardia during breath-hold. This study evaluated air-breathing and cardiac responses to sustained aerobic exercise in juveniles (total length~20cm), and how exercise influenced variations in fHassociated with AB. In particular, it investigated the role of adrenergic and cholinergic control in cardiac responses, and effects of pharmacological abolition of this control on air-breathing responses. Sustained exercise at 15, 30 and 45cms-1in a swim tunnel caused significant increases in fABand fH, from approximately 5breathsh-1and 60heartbeatsmin-1at the lowest speed, to over 60breathsh-1and 100beatsmin-1at the highest, respectively. There was a progressive decline in the degree of variation in fH, around each AB, as fABincreased with exercise intensity. Total autonomic blockade abolished all variation in fHduring exercise, and around each AB, but fABresponses were the same as in untreated animals. Cardiac responses were exclusively due to modulation of inhibitory cholinergic tone, which varied from >100% at the lowest speed to <10% at the highest. Cholinergic blockade had no effect on fABcompared to untreated fish. Excitatory β-adrenergic tone was approximately 20% and did not vary with swimming speed, but its blockade increased fABat all speeds, compared to untreated animals. This reveals complex effects of autonomic control on air-breathing during exercise in C. gariepinus, which deserve further investigation.
authors.affiliation: Department of Physiological Sciences, Federal University of São Carlos, 13565-905 São Carlos, SP, Brazil; Joint Graduate Program in Physiological Sciences, Federal University of São Carlos -UFSCar/São Paulo State University, UNESP Campus Araraquara, 14801-903 Araraquara, SP, Brazil. Electronic address: felipebrocco@gmail.com.
authors.forename: Felipe R
authors.initials: FR
authors.lastname: Blasco
authors.affiliation: Department of Physiological Sciences, Federal University of São Carlos, 13565-905 São Carlos, SP, Brazil; Centre for Marine Biodiversity, Exploitation and Conservation, UMR MARBEC (IRD-Ifremer-UM-CNRS), Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France.
authors.forename: David J
authors.initials: DJ
authors.lastname: McKenzie
authors.affiliation: Department of Physiological Sciences, Federal University of São Carlos, 13565-905 São Carlos, SP, Brazil; School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: Edwin W
authors.initials: EW
authors.lastname: Taylor
authors.affiliation: Department of Physiological Sciences, Federal University of São Carlos, 13565-905 São Carlos, SP, Brazil.
authors.forename: F Tadeu
authors.initials: FT
authors.lastname: Rantin
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000465:Algorithms; D000818:Animals; D017756:Aquaculture; D001285:Atropine / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000254:growth & development / Q000502:physiology*; D001522:Behavior, Animal / Q000187:drug effects; D002397:Catfishes / Q000254:growth & development / Q000502:physiology*; D018680:Cholinergic Antagonists / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000254:growth & development / Q000294:innervation* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects; D010807:Physical Endurance / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology; D015203:Reproducibility of Results; D012143:Respiratory Physiological Phenomena / Q000187:drug effects; D012137:Respiratory System / Q000187:drug effects / Q000254:growth & development / Q000294:innervation*
chemical_list: D000319:Adrenergic beta-Antagonists; D018680:Cholinergic Antagonists; D001285:Atropine; D011433:Propranolol
keywords: Adrenergic tone; Cholinergic tone; Heart rate; Swimming