NMDA mimics the slow response to glutamate (Glut). A, Microejection of glutamate (arrow) onto a 2/AH neuron (RMP = −57 mV) leads to a prolonged membrane depolarization (slow response) associated with spike activity. Superfusion with DNQX does not block the glutamate-mediated slow response. B, Microejection of NMDA (arrow) onto a 2/AH neuron (RMP = −58 mV) leads to a prolonged membrane depolarization associated with spike activity. The NMDA-mediated depolarization is blocked by AP5, an NMDA antagonist. C, The NMDA-mediated depolarization recorded in a 2/AH neuron (RMP = −56 mV) is blocked by the NMDA antagonist CPP. Responses to NMDA in B and C were obtained in Mg²⁺-free Krebs’ solution that contained glycine (10 μm). D, Glutamate evokes fast and slow responses (associated with spike activity) in a 2/AH neuron (RMP = −58 mV). Superfusion with AP5 inhibits only the slow response to glutamate.