Medial Prefrontal Cortical Modulation of Whisker Thalamic Responses in Anesthetized Rats

Abstract The medial prefrontal cortex (mPFC) has been implicated in novelty detection and attention. We studied the effect of mPFC electrical stimulation on whisker responses recorded in the ventroposterior medial thalamic nucleus (VPM), the posterior thalamic nucleus (POm) and the primary somatosensory (S1) cortex in urethane anesthetized rats. Field potentials and unit recordings were performed in the VPM or POm thalamic nuclei, in S1 cortex, and in the Zona Incerta (ZI). Somatosensory evoked potentials were elicited by whisker deflections. Current pulses were delivered by bipolar stimulating electrodes aimed at the prelimbic (PL) or infralimbic (IL) areas of mPFC. PL train stimulation (50 Hz, 500 ms) induced a facilitation of whisker responses in the VPM nucleus that lasted minutes and a short inhibition in the POm nucleus. IL stimulation induced a facilitation of whisker responses in both VPM and POm nuclei. Facilitation was due to corticofugal projections because it was reduced after S1 cortical inactivation with lidocaine, and by activation of NMDA glutamatergic receptors because it was blocked by APV. Paired stimulation of mPFC and whiskers revealed an inhibitory effect at short intervals (