Adrenergic and non-adrenergic vasoconstrictor mechanisms in the human nasal mucosa

The possible occurrence of adrenergic and non-adrenergic vasoconstrictor mechanisms has been studied in human nasal mucosa biopsies. The tissue contractions (reflecting vascular tone variation) in response to exogenous noradrenaline (NA), neuropeptide Y (NPY) and somatostatin (SOM) were measured in vitro. Dose-dependent contraction of the nasal mucosa was observed for the three agents studied and the rank order of their vasoconstrictive potency was NA > SOM > NPY. On a molar basis NPY showed an 80% less potent vasoconstrictive activity than SOM. Pretreatment with the alpha-adrenoceptor antagonist phenoxybenzamine (10(-6) M) almost completely abolished the vasoconstrictive response to NA, whereas the effects of NPY and SOM remained intact. The responses to SOM were significantly reduced after pretreatment with high dose of the competitive SOM-antagonist analog cyclo(7-aminoheptanoyl-PHE-D-TRP-LYS-THR[BZL]). When SOM was administered simultaneously with NA, the contractile response was significantly reduced as compared to the effect of NA alone. In contrast, concomitant administration of NPY and NA potentiated the vasoconstrictive effect of NA. The present data suggest that both adrenergic and non-adrenergic vasoconstrictor mechanisms are present in the human nasal mucosa vascular bed. Furthermore, NPY and SOM may act as modulators of the NA-induced vasoconstrictive effects.