An in vivo model for investigating bilateral synaptic plasticity across CA3/CA1 synapses in guinea pig dorsal hippocampus

A method is described for concurrent investigation of long-term potentiatio n (LTP) in the left and right CA1 synapses in dorsal hippocampi in guinea p ig in vivo. Briefly, animals are anesthetized with urethane, and small acce ss holes are made in the skull through which electrodes are lowered to stim ulate the left CA3 and record from both CA1 regions. Using this animal mode l, we have found that LTP is produced in both CA1 regions, following condit ioning stimulation to the left CA3. However, in some animals LTP occurred i n the left CA1 without concomitant synaptic potentiation in the contralater al CA1. We also observed that in some experiments synaptic potentiation in the contralateral CA1, when present, decayed to baseline levels even though LTP persisted in the ipsilateral CA1. To conclude, our data on bilateral L TP demonstrates findings that are best addressed in vivo. (C) 2001 Elsevier Science B.V. All rights reserved.