Fig. 10. Effect of prolonged treatment of 7 DIV granule cells with 100 µM NMDA or 50 µM AP5 on cGMP content in either NO-stimulated or non-stimulated cells (basal response). The indicated concentrations of NMDA (, ) and AP5 (, ) were re-applied every 24 hours with fresh medium. At the required time, cells were washed and preincubated with 0.5 mM IBMX, and then stimulated with either 1 µM DEA/NO (, ) or vehicle (basal, , ) for 10 minutes and their content in cGMP determined. Results are expressed as pmol/10⁶ cells and are the mean ± s.e.m. of four experiments performed in triplicate using different cultures. Values significantly different to those of non-NMDA or AP5-treated cells are indicated: ^**P< 0.01; ^***P< 0.001.