Optical recording of trisynaptic pathway in rat hippocampal slices with a voltage-sensitive dye.
Changes in membrane potentials were recorded from rat hippocampal slices with a voltage-sensitive dye using a real-time optical recording system, which had high spatial resolution of 128 x 128 points with a high time resolution of 0.6 ms. Serial excitatory propagation was recorded in the dentate gyrus. CA3 and CA1 after stimulation of the perforant pathway, and the optical signals were clearly divided into two components in the dentate gyrus adjacent to the stimulus site. The slow component was suppressed in Ca(2+)-free solution, but the fast component in the molecular layer was not affected. However, the application of 1 microM tetrodotoxin fully abolished both components. These results suggest that the fast and slow components mainly reflect Na(+)-dependent action potentials and excitatory postsynaptic potentials, respectively. The excitatory response duration in the stratum radiatum of CA3 was significantly longer than that in other hippocampal areas. The long-lasting excitation in CA3 is probably related to the CA3 associational projections, because direct stimulation of CA3 pyramidal cell layer also produced similar results. The long-lasting dendritic excitation is probably important to integrate synaptic transmission and may be related to epileptogenesis. When long-term potentiation was induced by a tetanic stimulation (100 Hz for 1 s), the onset latency in the stratum radiatum of CA1 was reduced to as much as 65%, suggesting an increase of excitatory propagation. The analysis of the spatial-temporal optical signals contributes to understanding information processes in the hippocampus, related to learning and memory including long-term potentiation.
Nakagami
Y
Y
Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
Saito
H
H
Matsuki
N
N
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004396:Coloring Agents; D004558:Electric Stimulation; D006624:Hippocampus / Q000166:cytology* / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology; D007858:Learning / Q000502:physiology; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008568:Memory / Q000502:physiology; D009434:Neural Pathways; D009473:Neuronal Plasticity / Q000502:physiology; D016249:Optical Storage Devices; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D004396:Coloring Agents; D013779:Tetrodotoxin; D002118:Calcium