Simulation of perforant path evoked field and intracellular potentials in hippocampal CA1 area

✍ Scribed by Dr. Lai-Wo Stan Leung

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 611 KB
• Volume: 5
• Category: Article
• ISSN: 1050-9631
• DOI: 10.1002/hipo.450050208

✦ Synopsis

We (Lcung et al., in press) used current source densiry (CSD) analysis to show that medial perforant path stimulation evoked a current sink at the distal apical dendrites of CAI (Fig. I), in addition to the excitation (sink) at the middle molecular layer of the dentate gyrus. Both CAI and dentate sinks were activated at short latencies (<3 ms), suggesting a monosynaptic excitation. However, CA1 and dentate sinks showed different properties in time courses, paired-pulse facilitation, and long-term potentiation (Leung et al., in press).

The purpose of this report is to simulate the field and intracellular responses of CA1 pyramidal cells to a distal dendritic input using a compartment-volume-conduction model (Leung, 1984). It is shown that a distal dendritic excitation combined with widespread mid-dendritic inhibition could simulate the field potential and current source density data in vivo. In addition, the simulated intracellular potentials indicate that an inhibitory postsynaptic potential (IPSP) dominates the proximal dendritic and so- matic recordings, whereas an excitatory postsynaptic potential (EPSP) dominates at the distal apical dendrites. Thus, the model explains well the data observed in several laboratories, using in vivo and in vitro preparations.

A compartment-volume-conduction model (Leung, 1984) is used to simulate the intracellular and field potentials obtained in the experiments. A typical CA1 pyramidal cell is modeled by 17 linked compartments (Fig. 2A). The current at each compartment is described by the equation (Rall, 1964):

--(I + f, + 2u) v, + UVI+l + UV,-,