Tetrodotoxin-sensitive ion channels characterized in glial and neuronal cells from rat brain

Ion channels were studied in primary neuronal and in primary glial cultures from rat brain by measuring the uptake of guanidinium, an ion that can permeate the Na+ channel. Neuronal cells exhibit a veratridine-stimulated (EC50 30 microM) guanidinium uptake, which is blocked by tetrodotoxin (IC50 30nM). This demonstrates the presence of a voltage-dependent Na+ channel. In glial cells veratridine + scorpion toxin, but not veratridine or scorpion toxin alone can stimulate a tetrodotoxin-sensitive ion uptake, thus indicating a 'silent' Na+ channel in the glial cells. Phentolamine, propranolol and various local anesthetic drugs (e.g. tetracaine, dibucaine) blocked the two different kinds of Na+ channels in the two cell populations investigated.