Interactions between 5-hydroxytryptamine, noradrenaline and the thromboxane-A2 mimetic U44069 in the marmoset isolated aorta.
1. The effects of 5-hydroxytryptamine (5-HT) in the absence and presence of noradrenaline (NA) or the thromboxane-A2 mimetic, U44069, were investigated in ring preparations of marmoset aorta. 2. 5-HT (0.001-10 mumol/L) produced little or no contractile response in preparations at basal tone. When the tone was elevated to 50% of maximum with NA the predominant response to 5-HT was relaxation. The 5-HT2 receptor antagonist LY53857 (0.1 mumol/L) unmasked a contractile response to low concentrations of 5-HT (0.01-1.0 mumol/L) and reduced relaxation to high concentrations of 5-HT (1.0-10 mumol/L) in vessels precontracted with NA. 3. In U44069-contracted vessels, 5-HT was contractile in the range 0.01-1 mumol/L and relaxant in concentrations of 6.0-10.0 mumol/L. Ketanserin (1.0 mumol/L) had no effect on the contraction or relaxation to 5-HT. 4. The relaxant response to 5-HT was not significantly diminished in endothelium-impaired arteries. 5. In conclusion, 5-HT exerts complex inhibitory and excitatory actions on the marmoset aorta. The inhibitory actions are not endothelium-dependent and the excitatory actions do not appear to involve the 5-HT2 receptor.
Dyer
S M
SM
Department of Clinical and Experimental Pharmacology, University of Adelaide, Australia.
Bexis
S
S
Mano
M T
MT
de la Lande
I S
IS
Frewin
D B
DB
Head
R J
RJ
D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000502:physiology; D002144:Callithrix; D004347:Drug Interactions; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology*; D013928:Thromboxane A2 / Q000494:pharmacology*
D011450:Prostaglandin Endoperoxides, Synthetic; D012701:Serotonin; C028429:U 44069; D013928:Thromboxane A2; D009638:Norepinephrine