Biomaterial Database

Activity of medullary reticulospinal neurons during fictive locomotion. 1993

M C Perreault, and T Drew, and S Rossignol

Département de Physiologie, Faculté de Médecine, Université de Montréal, Quebec, Canada.

1. The pattern of discharge of medullary reticulospinal neurons, identified by antidromic stimulation applied at the L1-L2 segment of the spinal cord, was studied during fictive locomotion, occurring spontaneously, or evoked by stimulation of the mesencephalic locomotor region in high-decerebrate, paralyzed cats. Unitary recordings were made in the medial reticular formation (P5.0-14.0 mm; L0.5-2.0 mm), and the fictive locomotor pattern was monitored by recording the electroneurogram (ENG) of representative flexor and extensor muscle nerves from each of the four limbs. 2. In total, 117 reticulospinal neurons were recorded in 15 cats. Among these, 73.5% (86/117) modified their discharge at the onset of locomotion. These cells were divided into three subpopulations: 34/86 of the cells always maintained a fixed temporal relationship with the activity of one of the recorded nerves (ENG-related = 39.6%); the pattern of discharge of 42/86 cells was related to the locomotor rhythm [(LR-related-48%)] but was not temporally correlated with any of the recorded nerves; and the remaining 10 cells increased their firing frequency at the onset of locomotion but remained tonic (TONIC-11.6%). 3. Of the ENG-related neurons, 64.8% were temporally correlated to extensor nerve activity, whereas the remaining 35.2% were correlated to flexor nerves. These neurons were either related to forelimb (55.9%) or hindlimb (44.1%) nerves lying either ipsilateral (38.2%) or contralateral (61.8%) to the recording site. A few neurons (n = 3; 8.8%) were related to nerve activity of more than one limb. 4. The pattern of discharge of the LR-related neurons, although not correlated to the activity of any one recorded nerve, could be preferentially related to the locomotor rhythm in either the forelimbs (12/23) or hindlimbs (11/23). 5. ENG- and LR-related reticulospinal neurons were intermingled in the medial reticular formation. In both cases, cells related to the forelimbs were located more dorsally than those related to the hindlimbs. It is suggested that both the ENG- and LR-related neurons represent a single functional population of reticulospinal neurons that is part of an intrinsically organized reticulospinal system that functions to coordinate the activity of the skeletal musculature. 6. The present results show that the majority of reticular neurons projecting as far as the lumbar spinal cord are phasically modulated during locomotion, even in the absence of phasic peripheral afferent inputs. Moreover, the complexity of the discharge patterns in paralyzed animals was found to be similar to that observed in the intact cat.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D008124	Locomotion	Movement or the ability to move from one place or another. It can refer to humans, vertebrate or invertebrate animals, and microorganisms.	Locomotor Activity,Activities, Locomotor,Activity, Locomotor,Locomotor Activities
D008526	Medulla Oblongata	The lower portion of the BRAIN STEM. It is inferior to the PONS and anterior to the CEREBELLUM. Medulla oblongata serves as a relay station between the brain and the spinal cord, and contains centers for regulating respiratory, vasomotor, cardiac, and reflex activities.	Accessory Cuneate Nucleus,Ambiguous Nucleus,Arcuate Nucleus of the Medulla,Arcuate Nucleus-1,External Cuneate Nucleus,Lateral Cuneate Nucleus,Nucleus Ambiguus,Ambiguus, Nucleus,Arcuate Nucleus 1,Arcuate Nucleus-1s,Cuneate Nucleus, Accessory,Cuneate Nucleus, External,Cuneate Nucleus, Lateral,Medulla Oblongatas,Nucleus, Accessory Cuneate,Nucleus, Ambiguous,Nucleus, External Cuneate,Nucleus, Lateral Cuneate
D008636	Mesencephalon	The middle of the three primitive cerebral vesicles of the embryonic brain. Without further subdivision, midbrain develops into a short, constricted portion connecting the PONS and the DIENCEPHALON. Midbrain contains two major parts, the dorsal TECTUM MESENCEPHALI and the ventral TEGMENTUM MESENCEPHALI, housing components of auditory, visual, and other sensorimoter systems.	Midbrain,Mesencephalons,Midbrains
D008839	Microelectrodes	Electrodes with an extremely small tip, used in a voltage clamp or other apparatus to stimulate or record bioelectric potentials of single cells intracellularly or extracellularly. (Dorland, 28th ed)	Electrodes, Miniaturized,Electrode, Miniaturized,Microelectrode,Miniaturized Electrode,Miniaturized Electrodes
D009431	Neural Conduction	The propagation of the NERVE IMPULSE along the nerve away from the site of an excitation stimulus.	Nerve Conduction,Conduction, Nerve,Conduction, Neural,Conductions, Nerve,Conductions, Neural,Nerve Conductions,Neural Conductions
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D012154	Reticular Formation	A region extending from the PONS & MEDULLA OBLONGATA through the MESENCEPHALON, characterized by a diversity of neurons of various sizes and shapes, arranged in different aggregations and enmeshed in a complicated fiber network.	Formation, Reticular,Formations, Reticular,Reticular Formations
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
D003655	Decerebrate State	A condition characterized by abnormal posturing of the limbs that is associated with injury to the brainstem. This may occur as a clinical manifestation or induced experimentally in animals. The extensor reflexes are exaggerated leading to rigid extension of the limbs accompanied by hyperreflexia and opisthotonus. This condition is usually caused by lesions which occur in the region of the brainstem that lies between the red nuclei and the vestibular nuclei. In contrast, decorticate rigidity is characterized by flexion of the elbows and wrists with extension of the legs and feet. The causative lesion for this condition is located above the red nuclei and usually consists of diffuse cerebral damage. (From Adams et al., Principles of Neurology, 6th ed, p358)	Decerebrate Posturing,Decorticate Rigidity,Decorticate State,Rigidity, Decerebrate,Rigidity, Decorticate,Decerebrate Posturings,Decerebrate Rigidity,Decerebrate States,Decorticate Rigidities,Decorticate States,Posturing, Decerebrate,Posturings, Decerebrate,Rigidities, Decorticate,State, Decerebrate,States, Decerebrate
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.