Figure 4.
The AMPA receptor-mediated mf-granule cell synaptic currents are absent in waggler mice. (A) Current–voltage relation of AMPA receptor synaptic EPSCs in adult wild-type and waggler mice. The membrane potentials were from −80 mV to +80 mV with 20 mV steps. Recordings were done in the presence of d-2-amino-5-phosphonovaleric acid (APV; 100 μM) and picrotoxin (PTX; 40 μM). (B) Granule cell responses to exogenous AMPA. Wild-type granule cells, but not waggler granule cells, exhibited inward currents in response to AMPA puff (indicated by the bars). (C) AMPA receptor (AMPAR) EPSCs (Vm = −80 mV) at mf-granule cell synapses before and after CNQX (10 μM) application. Developing (P17) wild-type granule cells exhibited responses with a wide range of amplitudes indicating their asynchronized maturation, whereas adult wild-type (>P28) granule cells consistently showed large responses. waggler granule cells failed to develop AMPA receptor EPSCs. (D) GluR-4 mRNA levels.