[Background and evoked activity of septal and hippocampal neurons transplanted into the neocortex of the rat].

Embryonic tissue of the septum and hippocampus was transplanted into a cavity made in parietal neocortex of adult rats. Extracellular recording 4-6 months after grafting revealed units with background spike activity in the grafted tissue. The activity (mean rate 3.6 +/- 0.4 spikes per s) had a random pattern without pathological features. About 90% of the graft cells responded to electrical stimulation of neighbouring cortical tissue with latencies 5-43 ms. The optimal frequencies for driving spike discharges were 5-10 Hz. Postactivatory suppression was observed in most units. The same proportion of the graft cells responded to tactile stimulation of the host animal. Phasic reactions of on-off type with latencies of 50-600 ms were observed. The normalization of the activity in intrabrain grafts as compared to intraocular ones and functional integration of graft units with the host brain are discussed.