[Postsynaptic potentials of motor neurons in the nucleus of the hypoglossal nerve in cats, evoked by rubrofugal impulses].

The effects of ipsi- and contralateral red nuclei stimulation on the hypoglossal motoneurons were studied in the cats under chloralose-nembutal anesthesia. Repetitive ipsi- and contralateral rubrofugal volleys evoked PSPs in 35 (69%) from 51 investigated motoneurons (3-5 stimuli of threshold intensity at frequency 500-600 per/s were used). EPSPs appeared in 33 motoneurons with latencies from 3.5 to 14.0 ms (mean value 5.7 +/- 0.75 ms for ipsilateral and 6.8 +/- 0.8 ms for contralateral rubral stimulations). In two motoneurons IPSPs were observed with latency 6.2 ms. Stimulation of the lingual nerve evoked EPSPs and action potentials in 31 motoneurons and IPSPs in 4 motoneurons. 16 motoneurons which could not be activated by rubral stimulation also responded by IPSPs to lingual nerve stimulation. The presented data testify to the existence of two rubrobulbar systems connected by polysynaptic pathways mainly with motoneurons of tongue retractor muscle.