Jx. Wang et al., 5-HYDROXYTRYPTAMINE-INDUCED ENDOTHELIUM-DEPENDENT AND ENDOTHELIUM-INDEPENDENT RELAXATIONS IN ISOLATED DOG ANTERIOR SPINAL SMALL ARTERIES, Canadian journal of physiology and pharmacology, 75(5), 1997, pp. 357-362
The mode of action of 5-hydroxytryptamine (5HT) was investigated in is
olated dog anterior spinal small arteries. Lower concentrations of 5HT
(10(-9)-10(-7) M) caused a dose-dependent contraction and higher conc
entrations (10(-6)-10(-3) M) produced a dose-dependent relaxation of t
he arteries precontracted by 10(-7) M U 46619. The 5HT-induced relaxat
ion was significantly antagonized by methiothepin (10(-9)-10(-6) M). K
etanserin (10(-6) M) and ICS 205-930 (3 x.10(-6) M) did not affect the
5HT-induced relaxation of the arteries. The relaxant response to 5HT
was reduced significantly by mechanical rubbing of the endothelial cel
ls. The 5HT-induced endothelium-independent relaxation was also antago
nized significantly by methiothepin (10(-6) M). Aspirin (5 x 10(-5) Ri
f) or NW-nitro-L-arginine methyl ester (L-NAME) (10(-6) M) significant
ly suppressed the 5HT-induced endothelium-dependent relaxation. L-Argi
nine (10(-3) M) also significantly reversed the L-NAME-induced reducti
on of the 5HT-induced endothelium-dependent relaxation. Treatment with
L-NAME in the presence of aspirin also produced much greater reductio
n of the 5HT-induced endothelium-dependent relaxation. Isocarbacyclin
(10(-9)-10(-5) M) induced a concentration-dependent relaxation of the
isolated spinal small arteries precontracted by 10(-7) M U 46619. Thes
e results suggest that 5HT induces endothelium-dependent and -independ
ent relaxations of the isolated anterior spinal small arteries mainly
via activation of 5HT(1)-like receptor and that endogenous nitric oxid
e and vasodilative prostaglandins may contribute to the 5HT-induced en
dothelium-dependent relaxation of the arteries.