ISSN:
1432-1106
Keywords:
Spinal cord
;
Interneurons
;
Reticulospinal
;
Fictive locomotion
;
Cat
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Short-latency excitatory postsynaptic potentials (EPSPs) evoked by stimulation in the medial longitudinal fasciculus (MLF) were recorded intracellularly from motoneurons in the cat lumbosacral spinal cord. Monosynaptic and disynaptic EPSPs occurred in most flexor and extensor motoneurons studied. These EPSPs resulted from the activation of fast (〉 100 m/s) descending axons from the MLF to the spinal cord. Several features distinguished monosynaptic and disynaptic MLF EPSPs. Disynaptic EPSPs exhibited temporal facilitation during short trains of stimulation, whereas monosynaptic EPSPs did not. Disynaptic EPSPs, but not monosynaptic EPSPs, were also facilitated by stimulation of the pyramidal tract and the mesencephalic locomotor region. However, disynaptic MLF EPSPs exhibited little or no facilitation when conditioned by short-latency cutaneous pathways. During fictive locomotion, the amplitude of disynaptic MLF EPSPs was modulated, with maximal amplitudes during the step cycle phase when the recorded motoneuron was active, resulting in reciprocal patterns of modulation of flexors and extensors. No comparable change was seen in the amplitude of monosynaptic MLF EPSPs during fictive stepping. These data suggest that the central pattern generator for locomotion modulates disynaptic MLF excitation at a premotoneuronal level in a phase-dependent manner. The effects of lesions made in the MLF and thoracic cord suggest that the interneurons in the disynaptic pathway from the MLF to motoneurons reside in the lumbosacral cord.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00229029
