Pulmonary response to intravenous administration of 5-hydroxytryptamine after type-2 receptor blockade in healthy calves

Annick S. Linden From the Laboratory for Functional Investigation (Linden, Desmecht, Amory, Rollin, Lekeux) and Department of genetics (Michaux), Faculty of Veterinary Medicine, University of Liege, Bât. B42 Sart Tilman, B-4000 Liege, Belgium.

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Daniel J.-M. Desmecht From the Laboratory for Functional Investigation (Linden, Desmecht, Amory, Rollin, Lekeux) and Department of genetics (Michaux), Faculty of Veterinary Medicine, University of Liege, Bât. B42 Sart Tilman, B-4000 Liege, Belgium.

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Hélène Amory From the Laboratory for Functional Investigation (Linden, Desmecht, Amory, Rollin, Lekeux) and Department of genetics (Michaux), Faculty of Veterinary Medicine, University of Liege, Bât. B42 Sart Tilman, B-4000 Liege, Belgium.

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Frédéric A. Rollin From the Laboratory for Functional Investigation (Linden, Desmecht, Amory, Rollin, Lekeux) and Department of genetics (Michaux), Faculty of Veterinary Medicine, University of Liege, Bât. B42 Sart Tilman, B-4000 Liege, Belgium.

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Charles L. Michaux From the Laboratory for Functional Investigation (Linden, Desmecht, Amory, Rollin, Lekeux) and Department of genetics (Michaux), Faculty of Veterinary Medicine, University of Liege, Bât. B42 Sart Tilman, B-4000 Liege, Belgium.

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Pierre Lekeux From the Laboratory for Functional Investigation (Linden, Desmecht, Amory, Rollin, Lekeux) and Department of genetics (Michaux), Faculty of Veterinary Medicine, University of Liege, Bât. B42 Sart Tilman, B-4000 Liege, Belgium.

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SUMMARY

The purpose of this study was to investigate the mechanism by which 5-hydroxytryptamine (5-ht) modifies respiratory function, specifically, hyperventilation, diffuse bronchoconstriction, and pulmonary arterial hypertension in cattle. We determined whether the IV response to 5-ht in calves was attributable to stimulation of 5-ht2 receptors.

Six healthy unsedated young bull calves of the Friesian (n = 4) and of the Belgian White and Blue (n = 2) breeds were used. A specific 5-ht2 antagonist (metrenperone, 0.05 mg/kg of body weight) was administered IM 30 minutes before the cattle were given a 5-minute IV 5-ht infusion. Pulmonary function values were registered before, during, and after the 5-ht challenge infusion. Minute volume increased significantly, because of an increase in respiratory rate. Conversely, lung dynamic compliance, total pulmonary resistance, and pulmonary arterial pressure were not changed.

We concluded that in cattle, 5-ht-induced ventilatory response is not mediated through activation of 5-ht2 receptors. However, the 5-ht2 receptors are involved in 5-ht-induced broncho- and pulmonary vasoconstriction.

SUMMARY

The purpose of this study was to investigate the mechanism by which 5-hydroxytryptamine (5-ht) modifies respiratory function, specifically, hyperventilation, diffuse bronchoconstriction, and pulmonary arterial hypertension in cattle. We determined whether the IV response to 5-ht in calves was attributable to stimulation of 5-ht2 receptors.

Six healthy unsedated young bull calves of the Friesian (n = 4) and of the Belgian White and Blue (n = 2) breeds were used. A specific 5-ht2 antagonist (metrenperone, 0.05 mg/kg of body weight) was administered IM 30 minutes before the cattle were given a 5-minute IV 5-ht infusion. Pulmonary function values were registered before, during, and after the 5-ht challenge infusion. Minute volume increased significantly, because of an increase in respiratory rate. Conversely, lung dynamic compliance, total pulmonary resistance, and pulmonary arterial pressure were not changed.

We concluded that in cattle, 5-ht-induced ventilatory response is not mediated through activation of 5-ht2 receptors. However, the 5-ht2 receptors are involved in 5-ht-induced broncho- and pulmonary vasoconstriction.

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