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.
Alstermark
B
B
Department of Integrative Medical Biology, Section of Physiology, Umeå University, S-901 87 Umeå, Sweden. Bror.Alstermark@physiol.umu.se
Ogawa
J
J
Isa
T
T
D000818:Animals; D003655:Decerebrate State / Q000503:physiopathology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000528:radiation effects; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D007395:Interneurons / Q000502:physiology* / Q000528:radiation effects; D008297:Male; D009046:Motor Neurons / Q000502:physiology / Q000528:radiation effects; D009433:Neural Inhibition / Q000502:physiology / Q000528:radiation effects; D016571:Neural Networks, Computer; D009434:Neural Pathways / Q000502:physiology* / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D012154:Reticular Formation / Q000166:cytology* / Q000502:physiology / Q000528:radiation effects; D013116:Spinal Cord / Q000166:cytology* / Q000502:physiology / Q000528:radiation effects; D013569:Synapses / Q000145:classification / Q000502:physiology* / Q000528:radiation effects