Fig. 2.

Examples of calcium-imaging traces from experiments investigating glutamate receptors in dissociated VRC cells presented as in Fig. 1. (A) Examples of traces from class A cells. (B) Examples of traces from class B cells. In A and B there was no response to NMDA/d-ser in the presence of Mg²⁺ at minute 22 (because Mg²⁺ blocks NMDA receptors without a depolarizing stimulus; compare with NMDA/d-ser application at minute 57 in the absence of Mg²⁺), indicating that the subsequent responses to 300 μM glutamate were mediated by AMPA/kainite receptors and/or metabotropic glutamate receptors. The black horizontal bar below the x-axis indicates the presence of 100 μM AP5 (an NMDA receptor inhibitor) in the bath. The presence of 100 μM AP5 did not block the response to the second application of 300 μM glutamate, confirming that these responses were not mediated by NMDA receptors. The open horizontal bar below the x-axis indicates the presence of 10 μM CNQX (an AMPA/kainite receptor inhibitor) in the bath. In general, CNQX partially blocked glutamate-elicited responses, indicating expression of a mix of AMPA/kainite receptors and metabotropic glutamate receptors. The gray horizontal bar below the x-axis indicates the time point when the bath solution (aCSF) was changed to Mg²⁺-free aCSF. The application of NMDA/d-ser in the absence of Mg²⁺ demonstrated that about half of class A cells but only a small minority of class B cells expressed NMDA receptors. (C) Compilation of data for class A and B cells. This dataset was compiled for 2,483 cells from eight independent experimental trials, using cells prepared separately from five different mice. Notably, there are some minor discrepancies between the data compiled in C from the experimental protocol depicted in A and B and the data compiled in Table 2 from the experimental protocol depicted in Fig. 1; these discrepancies demonstrate a range of experimental variability.