p-Chlorophenylalanine eliminates long-term modulation of the exercise ventilatory response in goats.
Repeated hypercapnic exercise augments future exercise ventilatory responses, an effect termed long-term modulation. We hypothesized that serotonin depletion with p-chlorophenylalanine (PCPA, 100mg kg(-1) i.v.) would attenuate long-term modulation. Ventilation, CO(2) production and arterial blood gases were measured at rest and during exercise (4kmh(-1), 5% grade) in goats before and after training (14 hypercapnic exercise trials). Six post-training exercise trials were performed. Trials 1-3 and 4-6 were grouped for analysis (post-training 1 and 2, respectively). Without PCPA, training exaggerated the Pa(CO(2)) decrease from rest to exercise (pre-training: 1.4+/-3mmHg; post-training 1: 3.1+/-3mmHg; post-training 2: 2.3+/-3mmHg; P<0.05), indicative of long-term modulation. The Pa(CO(2)) decrease from rest to exercise was unaffected by training following PCPA (pre-training: 1.4+/-1mmHg; post-training 1: 1.4+/-3mmHg; post-training 2: 1.1+/-5mmHg; P>0.05). Thus, PCPA abolishes long-term modulation, implicating serotonin in its underlying mechanism.
Johnson
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RA
University of Wisconsin, Department of Comparative Biosciences, 2015 Linden Drive, Madison, WI 53706, USA. pipob@svm.vetmed.wisc.edu
Mitchell
G S
GS
D000818:Animals; D001784:Blood Gas Analysis; D002628:Chemoreceptor Cells / Q000187:drug effects; D005260:Female; D010134:Fenclonine / Q000494:pharmacology*; D006041:Goats / Q000502:physiology*; D006935:Hypercapnia / Q000503:physiopathology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000096:biosynthesis; D012702:Serotonin Antagonists / Q000494:pharmacology*
D012702:Serotonin Antagonists; D012701:Serotonin; D010134:Fenclonine