The effect of isotonic replacement of Na⁺ by choline or N-methyl-D-glucamine (NMDG) on Ca²⁺-elicited rehydration. The experimental protocol was the same as that of Figure 3A, except that 140 mM NaCl in the suspending media was replaced by 140 mM choline chloride in panel B and by 140 mM NMDG chloride in panel C.