Fig. 4.

AMPA receptor activation and a rise in [Ca²⁺]_i are required for the glutamate-induced increase in I_h. (A) Time course of the amplitude of I_h, recorded at a relative membrane potential of -60 mV during application of 100 μM glutamate (filled circles). In the continuous presence of 50 μM CNQX (open squares), the glutamate-induced increase in I_h was absent, whereas in the continuous presence of 100 μM d(-)-2-amino-5-phosphonopentanoic acid (AP5, open circles), the increase in I_h was reduced and its onset delayed. (B) The continuous presence of 100 μMNi²⁺ and 100 μMCd²⁺ (open squares) prevented the increase in I_h. The effect of glutamate on I_h was prevented for up to 20 min after the start of glutamate application by loading the cells with 50 μM BAPTA-AM to buffer intracellular Ca²⁺(open circles). Data points represent mean ± SEM of four to seven cells.