Variation of gap junction sensitivity to H ions with time of day

Conductance of gap junctions between segments of the lateral axons of the crayfish nerve cord is reduced by cytoplasmic acidification. Simultaneous measurements of axoplasmic pH and junctional conductance at 09.00 and 12.00 h revealed a shift of about 0.25 pH units in the apparent pK of the crayfish electrotonic synapse. These findings indicate that gating mechanisms of gap junctions are not fixed properties, but may rather be modulated by other, possibly humoral, factors.