Fig. 4.

THC induces a delayed increase in intracellular Ca²⁺ that is dependent on extracellular Ca²⁺. [Ca²⁺]_i of THC-treated primary hippocampal neurons was monitored by fura-2 fluorescent imaging. The calibrated [Ca²⁺]_i (nm) was plotted against time (minutes). A, THC was added to neurons in the presence of 1.5 mm CaCl₂ (THC + Ca²⁺) at the indicated time (arrow). No increase in intracellular Ca²⁺ was seen when the ethanol carrier (0.01%) was added alone (data not shown) or when THC was added to cells incubated without Ca²⁺ in the presence of 5 mm EGTA (THC − Ca²⁺). Four mm LaCl₃(B) or 5 μm SR141716A (C) blocked increases in [Ca²⁺]_i caused by 10 μmTHC.