[The electrophysiological characteristics of long-term homo- and heterotopic cortical transplants in the rat motor cortex].

Microelectrode experiments were performed on the transplants (TPs) in the motor cortex, MI, of adult rats 2 to 6 mo and 8 to 11 mo after grafting TPs taken from one of hemispheres of newborn rat. Within TPs, latencies of neuronal responses evoked by means of electrocutaneous stimulation of forelimbs, hindlegs and vibrissal pads were ranged, from 13 to 30 ms, 17 to 38 ms and 10 to 15 ms, respectively. The values are similar with those in intact MI in both experimental and normal rats. A trend to widening receptive fields was observed in many neurons recorded in long-surviving TPs. In some units, a predominance of ipsilateral somesthetic inputs over contralateral ones was demonstrated which is more usual phenomenon for immature neurons in MI during early normal development. It indicates on the deficiency of maturation's mechanisms for synaptic inputs into the TPs. No motor responses were induced by low-threshold microstimulation in TPs and only on the depths lower than 2000 microns motor responses were obtained in a few cases, presumably due to the activation of white matter axons.