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Responses of the lizard and the rabbit thoracic aortae to acetylcholine were studied. Acetylcholine (ACh) (10 nM-100 microM), carbachol (10 nM-50 microM) and PGF2 alpha (100 nM-100 microM) produced concentration-dependent contractions of the lizard thoracic aorta (LTA) with rapid tachyphylaxis. On the other hand, acetylcholine and carbachol relaxed the rabbit thoracic aorta (RTA) dose-dependently. There was no tachyphylaxis. Tachyphylaxis in the LTA was prevented by indomethacin (1 microM) or by rubbing the endothelium. Endothelial removal abolished ACh-induced relaxation of the RTA. Relaxation of the RTA and contractions of LTA were blocked by atropine, pirenzepine, acetoxy-N-methyl-piperidine methbromide (4-DAMP) and diltiazem. Removal of the endothelium rendered RTA insensitive to ACh. However, ACh-induced contractions of the LTA were not so influenced by removal of endothelial cells. It is concluded that the lizard thoracic aorta releases a metabolite of arachidonic acid that mediates tachyphylaxis. Relaxation of the RTA after ACh is mediated via the release of endothelium-dependent relaxing factor.
O A Ogundahunsi, and
F M Tayo
December 1999,
Cerebral cortex (New York, N.Y. : 1991),
O A Ogundahunsi, and
F M Tayo
February 1969,
Journal of ultrastructure research,
O A Ogundahunsi, and
F M Tayo
November 1970,
Comparative biochemistry and physiology,
O A Ogundahunsi, and
F M Tayo
February 1974,
General and comparative endocrinology,
O A Ogundahunsi, and
F M Tayo
September 1969,
Comparative biochemistry and physiology,
O A Ogundahunsi, and
F M Tayo
January 1969,
Tsitologiia,
O A Ogundahunsi, and
F M Tayo
October 1981,
Life sciences,
O A Ogundahunsi, and
F M Tayo
January 1965,
Federation proceedings. Translation supplement; selected translations from medical-related science,
O A Ogundahunsi, and
F M Tayo
December 1987,
Scanning microscopy,
O A Ogundahunsi, and
F M Tayo
June 1947,
Archivos del Instituto de Cardiologia de Mexico,
