Fig. 3.

In vivo intracellular recording showing examples of membrane oscillations and the activity patterns of identified PFC projection neurons from amphetamine-withdrawn rats. In the withdrawn rats, limbic cortical neurons exhibited primarily a burst-discharge pattern. A, An example of a spontaneously burst-firing neuron identified in layer 5 infralimbic cortex in a rat after 14 d of withdrawal from repeated exposure to amphetamine for 4 weeks. This neuron had a resting membrane potential of −79 mV. This neuron fired spontaneous spikes at 7 Hz within bursts with two to four spikes riding on membrane depolarization plateau potentials. B, In ∼40% of PFC neurons recorded in amphetamine-withdrawn rats, the cell membrane oscillated in a rhythmic manner at ∼1 Hz. C, Histogram showing the distribution of membrane potential with respect to the percentage of time that the membrane existed at each potential. This histogram reveals the presence of two peaks, with equal time spent in the up (−59 mV) and down (−70 mV) states.