Properties of Excitatory Synaptic Responses in Fast-spiking Interneurons and Pyramidal Cells from Monkey and Rat Prefrontal Cortex

Department of Psychiatry, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15213-2593, USA.
Cerebral Cortex (Impact Factor: 8.67). 05/2006; 16(4):541-52. DOI: 10.1093/cercor/bhj002
Source: PubMed


In the prefrontal cortex (PFC) during working memory tasks fast-spiking (FS) interneurons might shape the spatial selectivity of pyramidal cell firing. In order to provide time control of pyramidal cell activity, incoming excitatory inputs should excite FS interneurons more vigorously than pyramidal cells. This can be achieved if subthreshold excitatory responses of interneurons are considerably stronger and faster than those in pyramidal neurons. Here we compared the functional properties of excitatory post-synaptic potentials (EPSPs) between pyramidal cells and FS interneurons in slices from monkey dorsolateral PFC and rat prelimbic cortex. Miniature, unitary (in connected pairs or by minimal stimulation) and compound (evoked by electrical stimulation of the white matter) EPSPs were recorded in whole cell mode. We found that EPSPs were significantly larger and faster in FS interneurons than those recorded from pyramidal cells, consistent with the idea of more efficient recruitment of FS interneurons compared to pyramidal neurons. Similar results were obtained in monkey and rat PFC, suggesting a stable role of FS interneurons in this circuitry across species.

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    • "Inhibitory mIPSCs and miniature excitatory synaptic currents (mEPSCs) could regulate interneuron activity in vivo, when firing activity in the monkey DLPFC network is low. In FS neurons of monkey DLPFC, the mEPSC frequency is ϳ20 Hz (Povysheva et al. 2006), thus significantly higher than mIPSP and mIPSC frequency (ϳ4 Hz; see Figs. 4 and 8). A high mEPSC-to-mIPSC ratio could make monkey DLPFC FS neurons readily responsive to external inputs arriving when the local network is in a low-firing activity state. "
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