抄録
In general, neural signals in the neocortex propagate by way of cortical neural circuits based on NMDA and non-NMDA receptor activities. Here we investigated contribution of these receptors to determination of the signal traveling routes between the primary (Oc1) and secondary visual cortices (Oc2) of rat brain slices. Electrical stimulation was delivered to the white matter in the Oc1 under bath-application of caffeine, and spatio-temporal aspects of traveling signals were observed by using optical recording methods. When 1/4 Hz-stimulation was applied, signal traveled horizontally along deep layers from Oc1 to Oc2, and climbed up into the Oc2, and then returned along layer II/III from Oc2 to Oc1. On the contrary, when stimulation frequency was changed to 1/64 Hz after 1/4 Hz-stimulation, signal climbed up into the Oc1, and traveled horizontally along layer II/III from Oc1 to Oc2 in parallel with signal traveling along deep layers, in which signal intensity in the layer II/III was much higher than that in the deep layers. The traveling signal in the former way was NMDA receptor activity-dependent, and that in the latter was non-NMDA recepor activity-dependent. These results suggest that the visual cortex has an ability to change routes of signal traveling in the visual cortical circuits based on the relative balance between NMDA and non-NMDA receptors. [J Physiol Sci. 2008;58 Suppl:S125]
