Reactivity of isolated bovine facial vessels to electric stimulation and to drugs.

The effects of electric stimulation on isometric force generation of isolated helical strips of bovine facial arteries (BFA) and veins (BFV) were investigated. Whereas BFA always contracted, electrically stimulated BFV showed a biphasic response, i.e. a small, transient contraction followed by an intense relaxation. The findings presented suggest a neurogenic response for the vasodilator component of BFV response to electric stimulation. Exogenous catecholamines and serotonin dilated the veins; the effects were antagonized by propranolol and dihydroergotamine, respectively. Dopamine-induced relaxations were only partially inhibited by propranolol; the residual relaxations were antagonized by chlorpormazine and haloperidol. Relaxations of the veins after electric stimulation or after administration of noradrenaline were accompanied by an increase of the cAMP content. In the BFA catecholamines, serotonin and histamine increased the tension, whereas isoprenaline was ineffective. Acetylcholine contracted the veins and relaxed the arteries; both effects were antagonized by atropine.