Figure 7. Effect of halothane on changes in free intrasynaptosomal [Calcium²+] produced by 4-aminopyridine (4-AP) monitored by fura-2 fluorescence. Synaptosomes were loaded with fura-2 acetoxymethyl ester, and the fluorescence ratio at excitation wavelengths 340 and 380 nm was monitored at 510 nm in the absence or presence of 0.9 mM halothane. The following additions were made: 1.3 mM CaCl², 1 mM 4-AP, 6.2 mM Triton X-100 (TX-100), and 7.7 mM ethyleneglycol-bis-(beta-aminoethyl ether) tetraacetic acid (EGTA). For calibration, Triton X-100 was added to release the intracellular fura-2 (maximal signal), and ethyleneglycol-bis-(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid was added to chelate Calcium²+ (minimal signal).