Disynaptic excitation from the medial longitudinal fasciculus to lumbosacral motoneurons: modulation by repetitive activation, descending pathways, and locomotion.

摘要: Short-latency excitatory postsynaptic potentials (EPSPs) evoked by stimulation in the medial longitudinal fasciculus (MLF) were recorded intracellularly from motoneurons cat lumbosacral spinal cord. Monosynaptic and disynaptic EPSPs occurred most flexor extensor studied. These resulted activation of fast (> 100 m/s) descending axons MLF to Several features distinguished monosynaptic EPSPs. Disynaptic exhibited temporal facilitation during short trains stimulation, whereas did not. EPSPs, but not also facilitated pyramidal tract mesencephalic locomotor region. However, little or no when conditioned short-latency cutaneous pathways. During fictive locomotion, amplitude was modulated, with maximal amplitudes step cycle phase motoneuron active, resulting reciprocal patterns modulation flexors extensors. No comparable change seen stepping. data suggest that central pattern generator for locomotion modulates excitation at a premotoneuronal level phase-dependent manner. The effects lesions made thoracic cord interneurons pathway reside