Effects of TMB-8 on constriction of pial arteries in rats

AIM: To study the effects of 8-(N, N-diethylamino)-n-octyl-3, 4, 5-trimetho xybenzoate (TMB-8) on constriction of pial arteries(PA). METHODS: The chang e of PA in rats was observed continuously and directly through cranial wind ow using microcircular image-shearing system. RESULTS: Nimodipine (Nim) 1 m u mol.L-1 produced dilatation: of PA immediately and the maximal response o ccurred in 2 min. But the diameter was not changed by TMB-8 50 mu mol.L-1. PA diameter decreased: immediately after the application of CSF containing KCl. TMB-8 25, 50 mu mol.L-1 apparently inhibited KCl-induced PA constricti on. When persistent constriction was evoked by 5-HT, diameter of PA were in creased in a concentration-dependent manner after application of TMB-8, whi ch was inhibited by N-omega-nitro-L-arginine methyl,ester (,L-NAME). CONCLU SION: TMB-8 inhibited the contraction induced by 5-HT or KCI in cerebral ar tery, probably via its calcium antagonization and nitric oxide release.