Response properties of the non-pyramidal tract neuron in the kitten motor cortex during early postnatal development:...

Response properties of the non-pyramidal tract neurons (non-PTNs) of the kitten motor cortex were examined with intracellular horseradish peroxidase (HRP) staining under Nembutal anesthesia. Thirty-one neurons were identified as non-PTNs and their responses were analyzed with stimulation of the cerebellar nuclei (CN) and/or the medullary pyramid (Py). Excitatory postsynaptic potentials (EPSPs) were induced both by CN and Py stimulation even at birth, whereas inhibitory postsynaptic potentials (IPSPs) were first detected during the third postnatal week in layers II-III pyramidal neurons, which is much later than in PTNs. This indicates that the intracortical circuits responsible for IPSPs in the superficial cortical layers develop later than in layer V.