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Alkaloid binding and activation of D2 dopamine receptors in cell culture.
- Source :
-
Journal of animal science [J Anim Sci] 1999 Apr; Vol. 77 (4), pp. 942-7. - Publication Year :
- 1999
-
Abstract
- Ergot and pyrrolizidine alkaloids, either extracted from endophyte-infected tall fescue, synthesized, or purchased commercially, were evaluated in cultured cells to estimate their binding to the D2 dopamine receptor and subsequent effects on cyclic AMP production in GH4ZR7 cells, transfected with a rat D2 dopamine receptor. Ergopeptide alkaloid (alpha-ergocryptine, bromocryptine, ergotamine tartrate, and ergovaline) inhibition of the binding of the D2-specific radioligand, [3H]YM-09151-2, exhibited inhibition constants (K(I)) in the nanomolar range, whereas dopamine was less potent (micromolar). The lysergic acid amides (ergine and ergonovine) were 1/100th as potent as the ergopeptide alkaloids. Ergovaline and ergotamine tartrate were equally effective in inhibiting vasoactive intestinal peptide (VIP)-stimulated cyclic AMP production, with consistent nanomolar effective concentration (EC50) values. The remaining ergopeptide alkaloids (alpha-ergocryptine and bromocryptine), lysergic acid amides (ergonovine and ergine), and dopamine were 1/100th as potent. Two representative pyrrolizidines, N-formylloline and N-acetylloline, exhibited no binding activity at the D2 dopamine receptor or effects on the cyclic AMP system within the concentration ranges of nanomolar to millimolar. Our results indicate that the commercially available ergot alkaloids ergotamine tartrate and ergonovine may be used interchangeably in the D2 dopamine receptor system to simulate the effects of extracted ergovaline and ergine and to examine responses in receptor binding and the inhibition of cyclic AMP.
- Subjects :
- Animals
Benzamides metabolism
Cell Line
Cyclic AMP metabolism
Ergolines metabolism
Ergonovine metabolism
Ergotamine metabolism
Ergotamines metabolism
Ligands
Rats
Receptors, Dopamine D2 drug effects
Vasoactive Intestinal Peptide pharmacology
Ergot Alkaloids metabolism
Pyrrolizidine Alkaloids metabolism
Receptors, Dopamine D2 metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-8812
- Volume :
- 77
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Journal of animal science
- Publication Type :
- Academic Journal
- Accession number :
- 10328360
- Full Text :
- https://doi.org/10.2527/1999.774942x