Nature of anthopleurin-B-induced release of norepinephrine from adrenergic nerves

Anthopleurin-B (AP-B), a new polypeptide from sea anemone (Anthopleura xanthogrammica), markedly increased the amount of norepinephrine (NA) released from the guinea pig isolated vas deferens. The AP-B-induced release of NA was inhibited or abolished by pretreatment with reserpine and by guanethidine or procaine but remained almost unaffected by mecamylamine. D 600, nifedipine, diltiazem, Mn2+, and Mg2+ markedly inhibited the NA releasing action of AP-B. The AP-B-induced release of NA increased in a linear fashion with increasing Na+ concentrations (85-150 mM). Also the NA release by AP-B increased with an increase in the concentration of external Ca2+ from 0 to 0.8 mM but decreased with an increase in the Ca2+ concentration from 0.8 to 2.0 mM. These results suggest that AP-B increases the permeability across the nerve cell membrane to both Na+ and Ca2+ and that this plays an important role in the NA release from the adrenergic nerve.