Figure 4

HgCl ₂ induced sustained elevation of intracellular Ca²⁺ concentration ([Ca²⁺] _i ) in cortical neurons and this rise in [Ca²⁺] _i was inhibited by the NMDA receptor antagonist MK 801. A. Representative traces of changes in fura-2 fluorescence ratio before and after the application of HgCl₂ (25 μM) in four different cortical neurons (shown by red, green, blue and black traces). Cells were loaded with fura-2 AM and the ratio of fluorescence intensity, at the 340 and 380 nm excitation wavelengths, was measured B. Representative traces of fura-2 fluorescence ratio recorded before and after application of HgCl₂ (25 μM) in four different cortical neurons (shown by red, green, blue and black traces) that were previously exposed to MK 801 (10 μM), an antagonist of NMDA receptors. C. Fold- rises in fura-2 fluorescence ratio induced by HgCl_2, after 10 and 15 mins of exposure time, in the absence or presence of MK 801. Note that, HgCl₂-induced rise in [Ca²⁺]_i in MK 801-treated neurons was significantly smaller than that in control cells in the period of 10 mins and 15 mins. Arrows indicate the presence of spontaneous Ca²⁺ transients in cortical neurons under resting conditions.