Cardiovascular response to exogenous serotonin in healthy calves.
OBJECTIVE
To characterize the cardiovascular response to i.v. administration of serotonin (5-hydroxytryptamine [5-HT]) in calves.


METHODS
5 healthy unsedated Friesian calves.


METHODS
41 5-HT administrations were performed: II slow infusions (duration, 5 minutes) and 30 bolus infusions (duration, 5 seconds). Cardiovascular function values were recorded before, during, and after the infusion.


RESULTS
Slow infusion of 5HT first resulted in a brief period of severe bradycardia, then in sustained tachycardia with a concomitant increase in cardiac output. Systemic initial hypotension concomitant with bradycardia, then a pressor phase associated with an increase in systemic vascular resistance, and finally, a long-lasting hypotensive phase associated with decreased systemic vascular resistance. Pulmonary hypertension was associated with increased pulmonary vascular resistance, reflecting intense pulmonary vasoconstriction. Bolus infusion at increasing dosages resulted in dose-dependent bradycardia and systemic hypotension, followed by dose-dependent systemic hypertension. Unlike with slow infusion, neither the second tachycardiac nor the third systemic hypotensive phases were evident.


CONCLUSIONS
5-HT induces dose-dependent cardiovascular responses, including a reflex response followed by pulmonary and systemic vasoconstriction, in healthy calves.


CONCLUSIONS
Determining the type of serotonergic receptors responsible for these responses may help to determine whether 5-HT is involved in the mechanisms underlying brisket disease in cattle.
Linden
A S
AS
Department of Bacteriology, Faculty of Veterinary Medicine, University of Liege, Belgium.
Desmecht
D J
DJ
Amory
H
H
Beduin
J M
JM
Lekeux
P M
PM
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001919:Bradycardia / Q000139:chemically induced / Q000503:physiopathology / Q000662:veterinary; D002302:Cardiac Output / Q000187:drug effects / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000187:drug effects*; D002417:Cattle / Q000502:physiology*; D004283:Dog Diseases / Q000139:chemically induced / Q000503:physiopathology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D007262:Infusions, Intravenous; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D013610:Tachycardia / Q000139:chemically induced / Q000503:physiopathology / Q000662:veterinary; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology
D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D012701:Serotonin