NMDAR-mediated nNOS/NO activation and zinc release. A: SNAP release of endogenous zinc from cortical synaptosome membranes obtained from wild-type and HINT1-/- mice. SNAP (100 μM) was added to cortical membranes and the assay was carried out at RT, as described . Left panel: Calibration curve for Zincon detection of Zn2+. Right panel: The NO donor was incubated with the membranes for 30 min and Zinc release was monitored by its complexing with the reporter (zinc chelator, Zincon). The absorbance at 600 nm was recorded at RT on a BioChrom Ultrospec 2100 spectrophotometer (Cambridge, UK) and the data represent the mean ± SEM of three independent assays. *Significantly different from the respective control group (without SNAP), p<0.05. SNAP produced comparable release of zinc ions from wild-type and HINT1-/- synaptosome membranes. B: NMDAR-mediated production of NO and the subsequent release of zinc ions from endogenous stores. The spontaneous endogenous zinc release was determined in Control (untreated) sections. The data shown were obtained at 30 min post-treatment. The effect of NMDAR activation on zinc mobilization was then studied. Control: baseline vehicle; A stands for the agonist NMDA used at 3 μM; MK801+A = 3 μM MK801 (NMDAR antagonist) + 3 μM NMDA; L-NNA+A = 10 μM L-NNA (NOS antagonist) + 3 μM NMDA. The images were color indexed and presented in pseudocolor.