Regular 2 Hz oscillations in PFC also occur in rats anesthetized with urethane (Kiss et al. 2011a; Kiss et al. 2011d). In this preparation, theta rhythm has been routinely recorded in HC, where it spontaneously alternates with wide-band delta (large irregular activity, (Kramis et al. 1975)) or is elicited by electrical stimulation of the pontine reticular formation (RPO) (Vertes 1981; McNaughton and Sedgwick 1978; Li et al. 2007; Ly et al. 2013). The dominant frequency of spontaneous theta under urethane anesthesia is around 4 Hz, but tail pinch or RPO stimulation shift the frequency up, across the entire theta range (4–10 Hz). RPO-elicited theta under urethane involves both atropine-sensitive and atropine-resistant mechanisms (Li et al. 2007), and the linear correlation between RPO stimulus intensity and theta frequency and amplitude provides an experimental model to study neuronal mechanisms and to use as biomarker in drug discovery (McNaughton et al. 2007). PFC 2 Hz rhythm was not studied in this experimental paradigm and thus the first goal of this study was to test whether RPO stimulation can modify the slow PFC rhythm
