Temperature-dependent responses of rats to ergovaline derived from endophyte-infected tall fescue.
Ergovaline, found in Acremonium coenophialum-infected tall fescue, is considered to be responsible for many symptoms associated with fescue toxicosis. Rats were tested to determine time-related thermoregulatory responses to acute treatment with ergovaline during specific thermal challenges. Isolated ergovaline was administered to rats (15 micrograms/kg body mass, i.p.) at controlled ambient temperatures (Ta) of 7 to 9 degrees C (cold) and 31 to 33 degrees C (hot). Treatment at cold Ta resulted in a decrease in rectal temperature (Tre) from 38.0 to 37.0 degrees C at 50 min after injection (P < .05) without complete return to preinjection value at 100 min. Tail temperature (Ttail) exhibited a concomitant 1C degree decrease (P < .05) after ergovaline injection at cold Ta. Also, metabolic heat production decreased from 15.7 to 11.7 W/kg at 20 min after injection of ergovaline (P < .05), with return to normal value at 40 min after injection. Injection of ergovaline at hot Ta increased Tre from 39.0 to 40.6 degrees C at 80 min after injection (P < .05), with no return to preinjection value at 100 min. This was attributed to a reduction in heat transfer across the tail as indicated by the decrease in Ttail from 37.1 to 36.4 degrees C at 40 min after injection (P < .05) and an initial increase in metabolic heat production from 8.4 to 9.4 W/kg at 3 min after injection (P < .05). Ambient temperature was found to be a major determinant of ergovaline response, which included alterations in both thermogenic and thermolytic mechanisms that control thermal balance.
Spiers
D E
DE
Animal Sciences Unit, University of Missouri-Columbia 65211, USA.
Zhang
Q
Q
Eichen
P A
PA
Rottinghaus
G E
GE
Garner
G B
GB
Ellersieck
M R
MR
D000164:Acremonium / Q000254:growth & development / Q000378:metabolism; D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D004879:Ergotamines / Q000633:toxicity*; D008297:Male; D006109:Poaceae / Q000382:microbiology*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012044:Regression Analysis; D013696:Temperature; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000633:toxicity*
D004879:Ergotamines; D014662:Vasoconstrictor Agents; C076760:ergovaline