Inhibitory effects of dopamine on noradrenaline-induced constriction of arterioles in vivo in the striated cremaster muscle.
The effect of dopamine on the arterioles (50.8-95.2 microns) in the cremaster muscle was examined to determine its effect on microcirculation. Anesthetized rats were used under a light microscope connected to a videocamera. Drugs were applied using small round filter paper (370 microns in diameter) containing the drug and placed in the immediate vicinity of the arteriole on the cremaster with a micromanipulator. The dose of the drug applied was represented by concentration of the drug solution in which the filter paper was immersed. Dopamine (10(-6)-10(-4)M) induced neither constriction nor dilation of the arteriole in the cremaster. Papaverine (10(-2)M) did not dilate the arteriole. However, the arterioles were constricted by noradrenaline (10(-6)-10(-4)M) and vasopressin (10(-7)M) in a dose-dependent manner. Noradrenaline (10(-4)M)-induced constriction was blocked by concomitant application of dopamine (10(-4)M). This effect of dopamine was antagonized by SCH23390 (10(-3)M). However, isoproterenol (10(-3)M) did not affect the arteriole, nor inhibit noradrenaline (10(-4)M)-induced constriction of the arterioles. While forskolin (10(-2)M) alone did not produce constriction or dilation of the arterioles, it inhibited noradrenaline (10(-4)M)-induced constriction of the arteriole. These results suggest that dopamine prevents the constriction of the arteriole induced by noradrenaline, by activation of DA1 receptors, which activates adenylate cyclase.
Matsubayashi
H
H
Department of Pharmacology, Hiroshima University School of Medicine, Japan.
D000009:Abdominal Muscles / Q000098:blood supply*; D000818:Animals; D001160:Arterioles / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000037:antagonists & inhibitors*; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects*; D014667:Vasopressins / Q000494:pharmacology
D014667:Vasopressins; D005576:Colforsin; D007545:Isoproterenol; D004298:Dopamine; D009638:Norepinephrine