Comparative studies on the effects of the nootropic drug adafenoxate and of the cerebral vasodilator flunarizine on arterial smooth muscles.
The effects of the nootropic drug adafenoxate and of the cerebral vasodilator flunarizine were studied on smooth-muscle preparations isolated from rabbits (perfused central ear artery and segments of the thoracic aorta). Both drugs tested did not change the smooth muscle tone. When applied extralumenally adafenoxate decreased the noradrenaline (NA)-evoked arterial contractions. Adafenoxate (especially in high concentrations) markedly relaxed the NA-contracted arterial preparations. The arterial contractions in response to low-frequency electrical stimulation (ES) were moderately potentiated by high concentrations of extralumenal adafenoxate, but were decreased by intralumenal administration of the drug. Administered prior to or after NA adafenoxate antagonized its contractile effects on the aortic segments (this effect was much pronounced when the smooth-muscle preparations were contracted by NA). Flunarizine exerted similar but less pronounced inhibitory effects on the NA- or ES-evoked contractions of the smooth-muscle preparations. The only essential difference between the two drugs tested was that extralumenal flunarizine inhibited the arterial contractions in response to ES. It is suggested that if adafenoxate exerts an antivasoconstrictory effect not only on the peripheral arteries but also on the cerebral blood vessels, this effect might play an important role for the realization of the nootropic action of this compound.
Todorov
S
S
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
Petkov
V
V
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001158:Arteries / Q000187:drug effects; D004423:Ear / Q000098:blood supply; D005444:Flunarizine / Q000494:pharmacology*; D006016:Glycolates / Q000494:pharmacology*; D008297:Male; D002504:Meclofenoxate / Q000031:analogs & derivatives / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D011817:Rabbits
D006016:Glycolates; C054061:adafenoxate; D002504:Meclofenoxate; D005444:Flunarizine; D009638:Norepinephrine