Erowid References Database
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Schmidt MJ, Hill LE.
“Effects of Ergots on Adenylate Cyclase Activity in the Corpus Striatum and Pituitary”.
Life Sci.. 1977;20(5):789-97.
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Abstract
The effects of ergots on adenylate cyclase (AC) activity in the corpus striatum and pituitary were studied. Method AC activity was assayed in homogenates of pituitary or brain of male Wistar rats (250-300 g), by monitoring the conversion of 32P--ATP to 3ZP--AMP, (New England Nuclear) after incubation (isobutyl-methylxanthine (Aldrich) included in the incubation mixture) and purification (Dowex 1 columns; Sigma). Cyclic AMP (cAMP) synthesis was also determined in intact pituitary glands. The effects of various antagonists and argots on dopamine stimulated cAMP synthesis were compared. The assay of AC involving purification of the end product through alumina and Dowex 1 gave a rapid and accurate estimate of enzyme activity. The reaction was linear for 10 min and proportionate to homogenate proteil. concentration from 0-250mcg protein/tube. Dopamine (D) produced a dose-dependent elevation of cAMP with maximal activity (90-130 0ncrease) seen at 10-4 M. This elevation was inhibited by spiroperidol. pimozide, and d butaclamol, but not by low concentrations of phentolamine, propranolol (both Sigma Chem.) or l-butaclamol. D was significantly more active than norepinephrine or epinephrine. All ergot activity was < D. LSD and ergonovine (Sigma Chem.) were most active. ergocristine (Sigma Chem.) was intermediate and lergotrile (Lilly) and ergotamine (Sigma Chem.) were essentially inactive. When D and argots were combined a significant reduction in D-stimulated cAMP synthesis was seen. AC activity in pituitary was in the striatum. While comparing D with other inhibitors of prolactin release. it was found that both D and apomorphine HCl (Merck) significantly increase cAMP synthesis in striatal homogenates. Conclusion Pituitary D-receptors which mediate prolactin release were not associated with AC.
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