Figure 4. Effects of vasopressin agonists on vasopressin release in vitro.

A, application of a mixture of V_1a and V₂ (1 μm) agonists significantly increased vasopressin release from the isolated SON in vitro, but did not potentiate subsequent K⁺-induced release. B, this response was only partially blocked by preapplication of a mixture of Ca²⁺-channel blockers. C, however, pretreatment with Ca²⁺-channel blockers blocked the high-K⁺ evoked response in vasopressin release. Data are means ± s.e.m., t tests, n = 4 per group for each experiment.