Lowering of pH does not directly affect the junctional resistance of crayfish lateral axons

The effect of pH was tested on the junction between crayfish lateral axons. By means of a glass capillary inserted into one of the axons, one side of the junction was perfused with solutions of known pH while the junctional resistance, Rj, was monitored. Integrity of the gap junction was checked electron microscopically. Rj remained unchanged when the pH of the perfusate was lowered from 7.1 to 6.0. However, when the pH of the unperfused side of the junction was lowered by substituting acetate for chloride in the external solution, Rj rose, attesting to the integrity of the junction and its capacity to uncouple in the perfused state. We suggest that H+ does not affect the junctional channels directly, but acts through an intermediary which is inactivated or removed by the perfusion.