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FURTHER EVIDENCE FOR THE INVOLVEMENT OF Na + CHANNELS IN THE RELEASE OF ADRENAL CATECHOLAMINE: THE EFFECT OF SCORPION VENOM AND GRAYANOTOXIN I
Author(s) -
ITO S.,
NAKAZATO Y.,
OHGA A.
Publication year - 1981
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1981.tb09105.x
Subject(s) - hexamethonium , catecholamine , venom , medicine , endocrinology , atropine , chemistry , scorpion , scorpion venoms , tetrodotoxin , pharmacology , biology , biochemistry
1 The effects of venom from the scorpion, Leiurus quinquestriatus , and grayanotoxin I on catecholamine secretion were studied in the perfused adrenal glands of guinea‐pig. 2 Scorpion venom (0.1 to 10 μg/ml) caused a dose‐dependent increase in catecholamine output. The response to the venom was partially inhibited by atropine (0.5 m m ) plus hexamethonium (1 m m ). The dose‐response curve was shifted to the right in the presence of these blocking agents. 3 Grayanotoxin I (0.1 to 0.5 m m ) caused a dose‐dependent increase in catecholamine output which was significantly reduced by atropine (0.5 m m ) plus hexamethonium (1 m m ). However, when grayanotoxin I (0.1 m m ) was applied together with scorpion venom (0.1 μg/ml, a concentration which alone, was almost ineffective) the maximum catecholamine output was reached even in the presence of atropine plus hexamethonium. 4 Tetrodotoxin (0.1 or 0.2 μ m ) reversibly inhibited the secretory responses induced by scorpion venom (10 μg/ml) and grayanotoxin I (0.1 m m ) plus scorpion venom (0.1 μg/ml). 5 Scorpion venom and grayanotoxin I plus scorpion venom did not cause catecholamine secretion in the absence of extracellular Na + or Ca 2+ ions. However, the secretory response was restored by reintroduction of Na + or Ca 2+ ions. 6 It is suggested that both scorpion venom and grayanotoxin I activate Na + channels on the chromaffin cell and result in catecholamine secretion.