PT  - JOURNAL ARTICLE
AU  - MASAHIRO OHTA
AU  - TOSHIO NARAHASHI
AU  - RICHARD F. KEELER
TI  - EFFECTS OF VERATRUM ALKALOIDS ON MEMBRANE POTENTIAL AND CONDUCTANCE OF SQUID AND CRAYFISH GIANT AXONS
DP  - 1973 Jan 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 143--154
VI  - 184
IP  - 1
4099  - http://jpet.aspetjournals.org/content/184/1/143.short
4100  - http://jpet.aspetjournals.org/content/184/1/143.full
SO  - J Pharmacol Exp Ther1973 Jan 01; 184
AB  - Eleven alkaloids obtained from Veratrum have been compared for their effects on the membrane potential and conductances of squid and crayfish giant axons. They can be classed in three groups. 1) Veratridine, cevadine and protoveratrines A and B cause the membrane to depolarize. The potency decreases in that order, and the concentrations of veratridine and cevadine required for 50% maximum depolarization are estimated to be 3.3 x 10-5 M and 3.7 x 10-3 M, respectively. The depolarization by veratridine is due primarily to a selective increase in resting sodium permeability of time membrane and is antagonized by tetrodotoxin. All of them are effective in augmenting and prolonging the negative (depolarizing) afterpotential. 2) Veratramine, isorubijervine, muldaimine (5-veratranine-3β, 11α-diol-11-acetate) and 5-veratranine-3β, 1lα-diol (1 x 10-4 M) are capable of blocking the action potential with little or no depolarization. 5-Veratranine-3β, 1lα-diol blocks both sodium and potassium conductance increases. 3) Cyclopamine, jervine, rubijervine and veratrosine have no effect on the resting and action potentials. Possible structure-activity relationships for these effects are discussed. © 1973 by The Williams & Wilkins Company