Role of NAADP-sensitive Ca²⁺ stores in H1 receptor signaling. Ca²⁺ release in cells stimulated with 100μM TMPH after treatment with (A) vehicle alone (control); (B) 1μM thapsigargin for 15 minutes; and (C) 500nM bafilomycin A1 for 1 hour. Maximum Ca²⁺ concentrations after 100μM TMPH stimulation (D) and 2 U/mL thrombin (E) are summarized. Error bars represent SEM; n = 3; *P < .05 by Student t test.