Figure 4. Arginine vasopressin secretion was not detected by stimulation with high potassium solution. The arginine vasopressin (AVP) concentration was assayed at 0 min (before stimulation), 15 min, and 30 min after the retina pieces were incubated in the control solution or the high potassium (50 mM) solution (see Methods). The concentration of AVP at each time was estimated under the condition that the concentration was set to 0 in the solution before incubation of the retina. The delta (Δ) AVP concentration shown here is defined as the difference between the concentration of AVP each time and the concentration before the incubation. No significant differences were found (one-way ANOVA with Tukey’s post hoc test). Error bars indicate standard error of the mean (SEM).