Lack of monosynaptic corticomotoneuronal EPSPs in rats : disynaptic EPSPs mediated via reticulospinal neurons and polysynaptic EPSPs via segmental interneurons.

• In the rat, some findings have been taken to suggest the existence of monosynaptic corticomotoneuronal (CM) connections. Because this connection is believed to be largely responsible for the ability to make independent digit movements in primates and man, it has been inferred that the monosynaptic CM connection in the rat is likewise important for skilled prehension. Comparison of intra- and extracellular recordings from forelimb motoneurons in anesthetized rats, revealed no monosynaptic CM excitatory postsynaptic potentials (EPSPs). The fastest descending excitation in forelimb motoneurons was disynaptically mediated via a corticoreticulospinal pathway and slowly conducted excitation via corticospinal fibers and segmental interneurons. The findings stress the importance of di- and trisynaptic excitatory corticofugal pathways to forelimb motoneurons in the control of skillful digit movements.

Nyckelord

Animals

Decerebrate State/physiopathology

Electric Stimulation

Evoked Potentials/radiation effects

Excitatory Postsynaptic Potentials/*physiology

Female

Functional Laterality

Interneurons/*physiology/radiation effects

Male

Motor Neurons/physiology/radiation effects

Neural Inhibition/physiology/radiation effects

Neural Networks (Computer)

Neural Pathways/*physiology/radiation effects

Rats

Rats; Wistar

Reticular Formation/*cytology/physiology/radiation effects

Spinal Cord/*cytology/physiology/radiation effects

Synapses/classification/*physiology/radiation effects

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