TY - JOUR T1 - Neurotoxin-sensitive sodium channels in neurons developing in vivo and in vitro JF - The Journal of Neuroscience JO - J. Neurosci. SP - 192 LP - 198 DO - 10.1523/JNEUROSCI.06-01-00192.1986 VL - 6 IS - 1 AU - F Couraud AU - N Martin-Moutot AU - A Koulakoff AU - Y Berwald-Netter Y1 - 1986/01/01 UR - http://www.jneurosci.org/content/6/1/192.abstract N2 - Fetal mouse brain cells were investigated by 22Na+ flux assays with the aim to determine the ontogenetic time course of appearance of functional voltage-sensitive sodium channels. Their pharmacological properties were assessed by measurement of the response to known neurotoxins, acting at site 1, 2, or 3 of the Na+ channel. Brain cell suspensions, prepared at 11–19 d of prenatal development in vivo, and fetal brain neurons in culture were explored. In vivo neurotoxin- sensitive Na+ influx becomes detectable at 12 d of gestation, in concordance with the time of appearance of saturable binding sites for alpha-scorpion toxin (alpha-ScTx) and saxitoxin. Progression in fetal age or in time in vitro is accompanied by an increase in the initial rate and in the amplitude of Na+ uptake stimulated by batrachotoxin or veratridine. The general pharmacological properties of developing Na+ channels are very similar to the known properties of voltage-dependent Na+ channels in adult nerve: Batrachotoxin acts as a full channel agonist and veratridine as a partial agonist. Their respective apparent affinities are increased in presence of alpha-ScTx, in agreement with the known positive cooperativity of toxins acting at sites 2 and 3 of the Na+ channel. alpha-ScTx alone induces a small increase in Na+ permeability; its effect is greatly amplified in the presence of batrachotoxin or veratridine. The apparent affinity of alpha-ScTx is reduced by cell depolarization. Tetrodotoxin and saxitoxin block the increase in Na+ permeability induced by batrachotoxin, veratridine, and alpha-ScTx.(ABSTRACT TRUNCATED AT 250 WORDS) ER -