D2 dopamine receptor response to endophyte-infected tall fescue and an antagonist in the rat.
Effects on rat brain D2 dopamine receptors by endophyte-infected tall fescue seed consumption and antagonist injection were characterized. Forty-eight male Wistar rats (225 g) in three separate trials were exposed to either 22 or 32 degrees C. Diets, to maintain similar concentrations of ergovaline, contained 10% (Trial 1) or 15% (Trials 2 and 3) endophyte-infected (E+; 325 average ppb of ergovaline) or uninfected (E-; 0 ppb of ergovaline) tall fescue seed. Rats were injected i.p. daily with either placebo (PL) or an experimental D2 dopamine antagonist (DA, .0375 mg/kg BW). No effects (P > .10) on diet DM intake by E+ ingestion or DA injection were detected at 22 degrees C. However, ingestion of E+ reduced (P < .01) and injection of DA improved (P < .05) DM intake of rats housed in 32 degrees C (11.1 vs 15.4 g of DM/d for E+ vs E-, respectively). Whole brain D2 dopamine receptor density (Bmax) and mRNA were reduced (P < .05) by E+ and increased (P < .05) by DA in Trial 1. No treatment effects (P > .10) on cerebral cortex alpha 1- and alpha 2-adrenergic or striatal D2 dopamine receptor Bmax were measured in Trials 2 and 3. In summary, dietary E+ reduced whole brain D2 dopamine mRNA and Bmax, whereas injection of DA increased D2 dopamine mRNA. Thus, long-term regulation of monoamine receptors seems to be affected by E+ ingestion or DA injection.
Larson
B T
BT
Department of Animal Sciences, University of Missouri, Columbia 65211.
Sullivan
D M
DM
Samford
M D
MD
Kerley
M S
MS
Paterson
J A
JA
Turner
J T
JT
D000818:Animals; D015152:Blotting, Northern; D001923:Brain Chemistry; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004879:Ergotamines / Q000494:pharmacology; D008297:Male; D010939:Plant Poisoning / Q000503:physiopathology*; D006109:Poaceae / Q000469:parasitology; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D017448:Receptors, Dopamine D2 / Q000235:genetics / Q000502:physiology*; D012639:Seeds; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D018492:Dopamine Antagonists; D004879:Ergotamines; D012333:RNA, Messenger; D017448:Receptors, Dopamine D2; D014662:Vasoconstrictor Agents; C076760:ergovaline