Neural beta-adrenergic dilatation of the facial vein in man. Possible mechanism in emotional blushing.
Ring preparations of the superficial buccal segment of the human facial vein, taken from extirpated tissue in 12 patients during neck surgery, were studied in vitro. The vein developed a maintained intrinsic myogenic tone in response to passive stretch and was supplied with alpha- as well as beta-adrenoceptors, both of which could be influenced by transmural nerve stimulation (TNS) and noradrenaline. These unusual characteristics for a vein are basically similar to the ones described for the rabbit facial vein by Pegram, Bevan & Bevan (1976). In man there seemed to be an inter-individual difference with regard to the abundance of 'innervated' alpha- and beta-adrenoceptors. Facial vein specimens from some subjects thus responded with prompt and pronounced net dilatation to TNS with maximum at 4 Hz and those from others with net constriction with maximum at 16 Hz. The latter showed a reversal into neural beta-adrenergic dilatation after alpha-adrenergic blockade. The human external jugular vein was devoid of intrinsic tone and beta-adrenoceptors. It is tentatively proposed that a beta-adrenergic neuro-effector mechanism in superficial ramifications of the facial vein in man might be involved in the emotional blushing reaction.