Figure 2.
PD98059 reduced neuronal excitability in neurons from trained rats. A, Examples for the effect of PD98059 on repetitive spike firing in a neuron from a pseudo-trained rat and a neuron from a trained rat. With a stimulus intensity of Ith × 2, a 1 s depolarizing pulse generates repetitive firing throughout the stimulation period. Although PD98059 has no effect on the pseudo-trained neuron, repetitive firing of the trained neuron is significantly suppressed by the same agent. B, Whereas PD98059 (PD) application has no effect on the number of spikes evoked in neurons from pseudo-trained rats, it significantly reduces the averaged number of spikes in neurons from trained rats (**p < 0.001). Consequently, the difference in spike numbers between neurons from the pseudo-trained and trained groups disappears in the presence of the ERK inhibitor. The number of spikes in NSR solution was measured in neurons from 8 pseudo-trained and 11 trained rats. The number of spikes in PD98059 was measured in neurons from five pseudo-trained and seven trained rats. Stimulus intensity was kept constant in each cell throughout the recording period. Values represent mean ± SE.