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Integration in descending motor pathways controlling the forelimb in the cat. 10. Inhibitory pathways to forelimb motoneurones via C3-C4 propriospinal neurones. 1984

B Alstermark, and A Lundberg, and S Sasaki

A further analysis has been made of inhibitory pathways to motoneurones via C3-C4 propriospinal neurones (PNs). Intracellular recording was made from triceps brachi motoneurones and effects from higher centres and forelimb afferents on corticospinal IPSPs were investigated after transection of the corticospinal tract at the C5/C6 border. The shortest latencies of the IPSPs evoked by stimulation of the pyramid were as brief as those of the pyramidal EPSPs (Illert et al. 1977). It is postulated that the minimal linkage of the pyramidal IPSPs is disynaptic via inhibitory C3-C4 PNs projecting directly to motoneurones. It was confirmed that pyramidal IPSPs usually are depressed by volleys in forelimb motor axon collaterals (Illert and Tanaka 1978). A quantitative comparison was made of the recurrent depression of pyramidal IPSPs and of IPSPs caused by activation of the Ia inhibitory interneurones. The result support the hypothesis of two parallel inhibitory cortico-motoneuronal pathways via C3-C4 PNs, one disynaptic via the inhibitory PNs and the other trisynaptic via excitatory PNs and Ia inhibitory interneurones. Pyramidal volleys also evoked late IPSPs which in some cases were not depressed from forelimb motor axon collaterals. It is postulated that the late IPSPs are partly due to activation of inhibitory C3-C4 PNs. Disynaptic pyramidal IPSPs were effectively facilitated by volleys in rubro-, tecto- and reticulospinal fibres - but not from vestibulospinal fibres - showing a convergence from the former descending tracts on common inhibitory C3-C4 PNs. Projection from forelimb afferents and corticospinal fibres on common inhibitory C3-C4 PNs was revealed by strong facilitation of disynaptic pyramidal IPSPs from cutaneous forelimb afferents. No corresponding effect was evoked from C2 neck afferents. Stimulation in the lateral reticular nucleus (LRN) evoked monosynaptic IPSPs in some motoneurones. The results of threshold mapping in and around the LRN suggest that the IPSPs are caused by antidromic stimulation of ascending collaterals of inhibitory neurones also projecting to motoneurones, possibly the inhibitory C3-C4 PNs.

UI MeSH Term Description Entries
D007395 Interneurons Most generally any NEURONS which are not motor or sensory. Interneurons may also refer to neurons whose AXONS remain within a particular brain region in contrast to projection neurons, which have axons projecting to other brain regions. Intercalated Neurons,Intercalated Neuron,Interneuron,Neuron, Intercalated,Neurons, Intercalated
D009132 Muscles Contractile tissue that produces movement in animals. Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D009433 Neural Inhibition The function of opposing or restraining the excitation of neurons or their target excitable cells. Inhibition, Neural
D009435 Synaptic Transmission The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES. Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
D011712 Pyramidal Tracts Fibers that arise from cells within the cerebral cortex, pass through the medullary pyramid, and descend in the spinal cord. Many authorities say the pyramidal tracts include both the corticospinal and corticobulbar tracts. Corticobulbar Tracts,Corticospinal Tracts,Decussation, Pyramidal,Corticobulbar Tract,Corticospinal Tract,Pyramidal Decussation,Pyramidal Tract,Tract, Corticobulbar,Tract, Corticospinal,Tract, Pyramidal,Tracts, Corticobulbar,Tracts, Corticospinal,Tracts, Pyramidal
D011930 Reaction Time The time from the onset of a stimulus until a response is observed. Response Latency,Response Speed,Response Time,Latency, Response,Reaction Times,Response Latencies,Response Times,Speed, Response,Speeds, Response
D002415 Cats The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801) Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D005071 Evoked Potentials Electrical responses recorded from nerve, muscle, SENSORY RECEPTOR, or area of the CENTRAL NERVOUS SYSTEM following stimulation. They range from less than a microvolt to several microvolts. The evoked potential can be auditory (EVOKED POTENTIALS, AUDITORY), somatosensory (EVOKED POTENTIALS, SOMATOSENSORY), visual (EVOKED POTENTIALS, VISUAL), or motor (EVOKED POTENTIALS, MOTOR), or other modalities that have been reported. Event Related Potential,Event-Related Potentials,Evoked Potential,N100 Evoked Potential,P50 Evoked Potential,N1 Wave,N100 Evoked Potentials,N2 Wave,N200 Evoked Potentials,N3 Wave,N300 Evoked Potentials,N4 Wave,N400 Evoked Potentials,P2 Wave,P200 Evoked Potentials,P50 Evoked Potentials,P50 Wave,P600 Evoked Potentials,Potentials, Event-Related,Event Related Potentials,Event-Related Potential,Evoked Potential, N100,Evoked Potential, N200,Evoked Potential, N300,Evoked Potential, N400,Evoked Potential, P200,Evoked Potential, P50,Evoked Potential, P600,Evoked Potentials, N100,Evoked Potentials, N200,Evoked Potentials, N300,Evoked Potentials, N400,Evoked Potentials, P200,Evoked Potentials, P50,Evoked Potentials, P600,N1 Waves,N2 Waves,N200 Evoked Potential,N3 Waves,N300 Evoked Potential,N4 Waves,N400 Evoked Potential,P2 Waves,P200 Evoked Potential,P50 Waves,P600 Evoked Potential,Potential, Event Related,Potential, Event-Related,Potential, Evoked,Potentials, Event Related,Potentials, Evoked,Potentials, N400 Evoked,Related Potential, Event,Related Potentials, Event,Wave, N1,Wave, N2,Wave, N3,Wave, N4,Wave, P2,Wave, P50,Waves, N1,Waves, N2,Waves, N3,Waves, N4,Waves, P2,Waves, P50
D005116 Extrapyramidal Tracts Uncrossed tracts of motor nerves from the brain to the anterior horns of the spinal cord, involved in reflexes, locomotion, complex movements, and postural control. Extrapyramidal Tract,Tract, Extrapyramidal
D005552 Forelimb A front limb of a quadruped. (The Random House College Dictionary, 1980) Forelimbs

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