Direct measurement of the chloride concentration in newt olfactory receptors with the fluorescent probe.

Chloride (Cl-) current in the olfactory cell has been proposed to be excitatory and amplifying the receptor current. As an intracellular concentration of Cl- ([Cl-]i) is critically important for the proposed function, we tried to measure [Cl-]i of the isolated newt olfactory receptors using chloride-sensitive fluorescent dye, N-(6-methoxyquinolyl)-acetoethyl ester (MQAE). We found that the average of Cl- concentration through the cell is about 40 mM. This value is fairly lower than 120 mM that was suggested from reversal potential of tail component of the olfactory response in the low Cl- bath solution. Because the reversal potential for the present [Cl-]i is above the resting potential, opening of the Cl- channels may serve as a booster for the depolarizing odor-response.