This histamine-like effects of Phallusia nigra extract: evidences for direct activity at H1 receptors.
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 be 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.
Costa
L V
LV
Departmento de Fisiologia, Universidade de São Paulo, Brasil.
Malpezzi
E L
EL
Berlinck
R G
RG
Rowan
E G
EG
de Freitas
J C
JC
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003533:Cyproheptadine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology / Q000502:physiology*; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D011738:Pyrilamine / Q000494:pharmacology; D011969:Receptors, Histamine H1 / Q000187:drug effects / Q000378:metabolism; D014020:Tissue Extracts / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D014403:Tubocurarine / Q000494:pharmacology; D014561:Urochordata / Q000737:chemistry*
D011969:Receptors, Histamine H1; D014020:Tissue Extracts; D003533:Cyproheptadine; D001285:Atropine; D006632:Histamine; D011738:Pyrilamine; D014403:Tubocurarine