Ergovaline binding and activation of D2 dopamine receptors in GH4ZR7 cells

• Published in: Journal of animal science Vol. 73; no. 5; pp. 1396 - 1400
• Main Authors: Larson, B. T, Samford, M. D, Camden, J. M, Piper, E. L, Kerley, M. S, Paterson, J. A, Turner, J. T
• Format: Journal Article
• Language: English
• Published: Savoy, IL Am Soc Animal Sci 01-05-1995; American Society of Animal Science; Oxford University Press
• Subjects: adenosine monophosphate; Adenosine Monophosphate - metabolism; adenosinmonofosfato; alcaloide de l' ergot de seigle; Animals; Biological and medical sciences; cell culture; Cell Membrane - chemistry; Cell Membrane - ultrastructure; Cellular biology; cultivo de celulas; culture de cellule; dopamina; dopamine; ergot alkaloids; Ergotamines - metabolism; ergotinas; inhibicion; inhibition; isotope radioactif; Medical sciences; peptide; peptides; peptidos; Pituitary Neoplasms; Plant poisons toxicology; radioisotopes; radioisotopos; Radioligand Assay; Rats; Receptors, Dopamine D2 - analysis; Receptors, Dopamine D2 - metabolism; Rodents; Second Messenger Systems - physiology; Sulpiride - pharmacology; Toxicology; Transfection; Tumor Cells, Cultured; Vasoactive Intestinal Peptide - pharmacology; Vasoconstrictor Agents - metabolism; Toxicity; Fescue; Metabolism; In vitro; Fungi; Infection; Acremonium coenophialum; Alkaloid; D2 Dopamine receptor; Second messenger; Plant origin; Fungi Imperfecti; Mechanism of action; Thallophyta
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/1995.7351396x

Ergovaline inhibition of radioligand binding to the D2 dopamine receptor and ergot alkaloid inhibition of vasoactive intestinal peptide (VIP)-stimulated cyclic AMP production in GH4ZR7 cells, stably transfected with a rat D2 dopamine receptor, were evaluated. Ergovaline inhibition of the binding of the D2-specific radioligand, [3H]YM-09151-2, exhibited a KI (inhibition constant) of 6.9 +/- 2.6 nM, whereas dopamine was much less potent (370 +/- 160 nM). Ergot alkaloids were also effective in inhibiting VIP-stimulated cyclic AMP production, with EC50 values for ergovaline, ergonovine, alpha-egrocryptine, ergotamine, and dopamine of 8 +/- 2, 47 +/- 2, 28 +/- 2, 2 +/- 1, and 8 +/- 1 nM, respectively. Inhibition of cyclic AMP production by ergovaline was blocked by the dopamine receptor antagonist, (-)-sulpiride (IC50, 300 + 150 nM). Our results indicate that ergot compounds, especially ergovaline, bind to D2 dopamine receptors and elicit second messenger responses similar to that of dopamine. These findings suggest that some of the deleterious effects of consumption of endophyte-infected tall fescue, which contains several ergot alkaloids including ergovaline, may be due to D2 dopamine receptor activation.