[The comparative characteristics of the neuronal activity in surviving slices of transplanted and intact neocortex]

The background single unit activity and single or multiunit responses to electrical stimulation of the rat's embryonic cortex, grafted into the somatosensory cortex of adult rats were investigated in a slice preparation. The same characteristics of the intact cortex neurons were observed as a control. The percentage of neurons with background activity within grafts was higher, than that within intact neocortex slices (23% and 6%, respectively). However the percentage of neurons responding to electrical stimulation of the recipient neocortex was lower in grafts. The mean latency of multiunit responses of graft neurons was longer, than that of neurons of the intact neocortex recorded at the same distance from the stimulating electrode (19.4 +/- 5.0 and 5.8 +/- 1.1 ms, respectively). Duration of the evoked population discharges was approximately ten times longer in grafts. It is concluded that there are local functional connections between a graft and the host brain and that inhibitory processes within grafts are weak. Functional integration of grafts with the host brain of the recipients after cranial trauma is shown.