Effects of endophyte-infected tall fescue, environmental temperature and prazosin injection on the rat

Abstract

Effects of an α 1 antagonist, prazosin, injection on the rat ( Rattus rattus) exposed to warm vs normal environments and fed endophyte-infected (E+) or -free (E−) tall fescue seed were studied. Rats were injected IP daily with placebo or prazosin (1 mg/kg BW). Daily skin and rectal temperatures and food intake measurements were recorded. Selected brain tissues were dissected to determine treatment effects on monoamine receptor density. Rats fed E+ and injected with placebo had reduced ( P < 0.01) food intake compared with all other treatments. By day 5 of injection, an endophyte × temperature interaction for increased ( P < 0.03) skin and rectal temperatures was measured when rats were fed E+ and housed at 32 °C. Also by day 5, injection of rats consuming E+ with prazosin reduced ( P < 0.01) skin and rectal temperatures 0.4 °C compared with those consuming E+ and injected with placebo. Monoamine receptor ( α 1, α 2, and D 2) densities were similar ( P > 0.10) among treatments. Prazosin injection reduced E+ induced body temperature increases chronically and increased food intake acutely to E− levels. Monoamine receptor densities were unchanged; therefore, E+ effects via monoamine receptors may be due to acute modulation of receptor-associated activity.