Comparison of area measurements of free [Ca2+]i responses to AMPA, kainate, NMDA, and KCl stimulation at pH 7.4 and 6.6
| Trigger | No. of cells tested | Area under curve (mean ± SEM, arbitrary units) | Value ratio 6.6/7.4 | Difference at p < 0.05 | |
|---|---|---|---|---|---|
| pH 7.4 | pH 6.6 | ||||
| AMPA | 167 | 11.0 ± 0.2 | 39.1 ± 0.4 | 3.5 | Yes |
| Kainate | 122 | 8.0 ± 0.1 | 15.1 ± 0.2 | 1.9 | Yes |
| NMDA | 212 | 8.2 ± 0.1 | 6.6 ± 0.1 | 0.8 | Yes |
| KCl | 187 | 7.0 ± 0.1 | 6.3 ± 0.1 | 0.9 | Yes |
See Figure 6 legend, Results and Materials and Methods for experimental details. Abbreviated stimulus conditions listed above were as follows: AMPA = 10 μm AMPA + 100 μm cyclothiazide, kainate = 100 μmkainate, NMDA = 20 μm NMDA, KCl = 60 mm KCl. Experiments were carried out at 24°C. All experiments, except the NMDA experiment, were performed in the presence of MK-801 (10 μm) to block secondary activation of NMDA receptors. Measurement of the calcium integral was over 15 min for all pH 7.4 values and NMDA and KCl values at pH 6.6 (all reached baseline measures by this time point) and was over 90 min for AMPA and kainate at pH 6.6. These values correspond to the second and third calcium responses (pH 7.4 vs pH 6.6) for each stimulus shown in Figure 6. Statistical comparisons were performed by Student’s two-tailed independent t test.