FIGURE 5.

Dopamine D₃ receptors decrease the firing rate, firing synchrony and membrane potential oscillations in CA3 pyramidal cells during gamma oscillations. (Aa) LFP recordings from the CA3 pyramidal cell layer (top), the low-pass (100 Hz) filtered LFP signal (middle) and the corresponding intracellular recording from a CA3 pyramidal cell (bottom) after the induction of gamma oscillations by ACh and Physo. (Ab) Effects of the selective D₃ receptor agonist PD-128907 (10 μM) on the LFP recordings (top) and the corresponding intracellular recordings from a CA3 pyramidal cell (bottom). (B) Bars summarize the firing rates before and after PD-128907 application. (Ca) Phase histograms of action potentials (APs) before and after PD-128907 application. The average curve for all measured cells is shown (n = 7). In every cell, 1000 APs were analyzed. 0° represents the troughs of the gamma cycles after low-pass filtering. PD-128907 broadened the distribution of APs during the gamma cycle. (Cb) Bars summarize the mean vector lengths (r) before and after PD-128907 application. r = 1 would mean that all cells fired all APs at the very same phase with maximal synchrony; r = 0 that all APs were equally distributed over the gamma cycle. (D) Bars summarize the peak-to-peak amplitude of membrane potential oscillations from CA3 pyramidal cells before and after PD-128907 application. ^∗p < 0.05 compared to the 10-min baseline period before PD-128907.