Effect of external chloride replacement on action potentials of giant axons in Periplaneta americana

Abstract

1. 1. The hemolymph Cl − concentration of adult female Periplaneta americana was determined by automatic titration, and the effect of external Cl − replacement on action potentials of giant axons in intact nerve cords of adult P. americana was studied in vitro with external electrodes. 2. 2. The hemolymph Cl − concentration is 112 ± 6·07 mM. 3. 3. When bathed in high Cl − medium, the half-times of action potentials of adult male and female nerve cords are not significantly different. 4. 4. A chloride-free bathing medium with either acetate or SO 4 2− replacing Cl − significantly decreases the half-time of action potentials; no significant difference exists between half-times obtained with acetate and SO 4 2− solutions.