Temperature-dependent responses of rats to ergovaline derived from endophyte-infected tall fescue

Abstract

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.

Nitric oxide supplementation alleviates hyperthermia induced by intake of ergopeptine alkaloids during chronic heat stress

“…Thus, the hyperthermia-rectifying effect of M+, when combined with E+, was likely due to the suppression of endogenous NO production. Spiers et al (1995) reported indirect evidence of a compromise in peripheral vasculature by ergovaline injection in rats subjected to HS, as evidenced by the rise in rectal temperature accompanying a decline in tail temperature.…”

“…Administration of ergopeptine alkaloids under thermoneutral or cold conditions, results in a decrease in core body temperature (Spiers et al, 1995(Spiers et al, , 2005a, that is due to a reduction in metabolic heat production (Spiers et al, 1995). In contrast, similar treatment during heat stress (HS) induces hyperthermia above the control level (Spiers et al, 1995(Spiers et al, , 2005a.…”

Journal of Range Management, Volume 54, Number 4 (July 2001)

“…This central effect upon body temperature occurs at a lower dosage compared to that necessary to mediate vasoconstriction. Spiers et al (1995) investigated the effects of injecting rats with ergovaline in both a…”

Ergovaline, an endophytic alkaloid. 2. Intake and impact on animal production, with reference to New Zealand

“…Serotonergic-2 receptors have also been shown to be involved in bronchoconstriction in calves (Linden et al 1993). Vasoconstriction of the peripheral vasculature by ergovaline interacting with adrenergic and serotonergic receptors results in a decreased ability to dissipate body heat and can contribute to increased core temperature (Spiers et al 1995). Foote et al (2013) indicated that ergovaline-induced vasoconstriction at the rumen epithelium may affect nutrient absorption, and hypothesised that this may affect intake as well as liveweight gain.…”