Vasomotor effects of noradrenaline, acetylcholine, histamine, 5-hydroxytryptamine and bradykinin on snake (Trimeresurus flavoviridis) basilar arteries.
We investigated the responsiveness of basilar arterial rings isolated from snakes to noradrenaline (NA), acetylcholine (ACh), histamine (His), 5-hydroxytryptamine (5-HT), mammalian bradykinin (BK) and rattlesnake BK. We also examined whether endothelial cells were involved in the responsiveness to ACh, BK, rattlesnake BK and in their resting vascular tone. NA and 5-HT induced concentration-dependent contractions. The cumulative concentration response curves of NA and 5-HT were shifted to the right in parallel by phentolamine (an alpha antagonist) and methiothepin (a 5-HT(1) and 5-HT(2) antagonist), respectively. However, ketanserin (a 5-HT(2) antagonist) had no effect on the cumulative concentration response curve of 5-HT. His, ACh, BK and rattlesnake BK had no effect on resting vascular tone; however, rattlesnake BK and sodium nitroprusside relaxed arteries precontracted by 5-HT. The rattlesnake BK-induced relaxations were almost abolished by L-nitro arginine (L-NA, a nitric oxide synthase inhibitor). L-NA and indomethacin (a cyclooxygenase inhibitor) had no effect on resting vascular tone or on precontracted arteries. These results suggest that alpha and 5-HT(1) receptor subtypes might be important in arterial contraction. Endothelial cells might play an important role in the responsiveness of snake basilar arteries to rattlesnake BK, but they might not be involved in the responsiveness to ACh, BK and in resting vascular tone.
Yoshinaga
Narihiro
N
Department of Veterinary Pharmacology, Faculty of Agriculture, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
Okuno
Tadatune
T
Watanabe
Yutaka
Y
Matsumoto
Tsukasa
T
Shiraishi
Mitsuya
M
Obi
Takeshi
T
Yabuki
Akira
A
Miyamoto
Atsushi
A
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001488:Basilar Artery / Q000187:drug effects* / Q000473:pathology; D001920:Bradykinin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects; D005260:Female; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008526:Medulla Oblongata / Q000098:blood supply; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology; D017841:Trimeresurus; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology*
D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D012701:Serotonin; D006632:Histamine; D000109:Acetylcholine; D001920:Bradykinin; D009638:Norepinephrine