Effects of adrenaline and noradrenaline on the heat production of warm- and cold-acclimated sheep.
The heat production (HP), heart rate (HR), respiration rate, rumen motility, and body temperature responses to 2.5-h adrenaline (A) and noradrenaline (NA) intrajugular infusions at 0.00, 0.15, 0.30, 0.60, and 0.90 micrograms.kg-1.min-1 were studied in 10 shorn wethers which had been chronically (3-8 weeks) exposed to warm (19-24 degrees C) or moderately cold (8-13 degrees C) temperatures. Heat production, as estimated from respired gas analysis, increased 40-45% with all doses of A and the effect was potentiated by chronic cold exposure. Only the higher dose rates of NA induced an increase in HP. The maximum HP increase due to NA was 30% and the effect was not influenced by chronic cold exposure. Thermoneutral HP was greater by 16-19% in cold-acclimated as compared with warm-acclimated sheep. Corresponding to the HP effects of A and NA, all doses of A and the highest dose of NA resulted in slight increases in rectal temperature. Respiration rate increased with increased dose rate of NA but only the highest dose of a resulted in an increase in respiration rate. HR, rectal temperature, and respiration rate responses to A and NA were not influenced by cold acclimation.
D000064:Acclimatization; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D004837:Epinephrine / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects; D012756:Sheep / Q000502:physiology*; D013696:Temperature
D009638:Norepinephrine; D004837:Epinephrine