Abstract
The methanol extract (mol. wt lower than 3,000 Da) of the sea squirt Phallusia nigra has stimulatory activity on guinea-pig ileum preparations. This effect was inhibited by cyproheptadine and mepyramine, but not by atropine. Mepyramine antagonized competitively the extract activity with a pA2 of 10.09 ± 1.12, suggesting a direct activity on H1 histamine receptors. The extract was also assayed on guinea-pig right atria, however, only a mild increase in spontaneous contractions was observed compared to histamine, showing that the extract was a rather poor activator of cardiac H2 receptors. Histamine was not detected upon TLC analysis of the extract by comparison with an authentic standard.
Original language | English |
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Pages (from-to) | 111-115 |
Number of pages | 4 |
Journal | Comparative biochemistry and physiology. Part C, Pharmacology, toxicology & endocrinology |
Volume | 117 |
Issue number | 1 |
DOIs | |
Publication status | Published - May 1997 |
Keywords
- Phallusia nigra
- tunicates
- histamine agonist
- histamine receptors
- mepyramine
- competitive antagonism
- guinea pig ileum
- guinea pig right atria