Physiological identification of afferent fibers and postsynaptic sensory neurons in the spinal cord of the intact, awake cat. 1988

L S Sorkin, and T J Morrow, and K L Casey
Department of Physiology, University of Michigan, Ann Arbor.

A method was developed to record from spinal cord cells in the awake, intact, partially restrained cat. Units were classified as afferent fibers or postsynaptic cells based on their ability to follow 100-Hz peripheral stimulation, the duration and configuration of the action potential waveform, and the number of spikes evoked by a single electrical pulse. These criteria are supported by independent observations of the location of the recording site, size of the receptive field, and adequate stimulus. Of 84 cutaneously activated units, 29 were classified as afferent fibers, 28 as postsynaptic cells, and 27 were not classified. No cutaneously activated unit was spontaneously active. In contrast, all 28 units (7 postsynaptic and 21 not classified) responding to joint position or movement were spontaneously active (5 to 40 Hz). No unit responded to both cutaneous and proprioceptive inputs. Evidence for convergence of cutaneous input from different types of receptors was limited to five postsynaptic neurons that responded to hair movement and to stimuli applied to the skin; two of these cells responded differentially to noxious pinch. Two of 24 postsynaptic cutaneous units ceased responding to electrical cutaneous stimuli when the cat was eating. The responses of 29 primary afferent fibers were not altered by the behavior of the cat. These results suggest that, in the awake cat (i) criteria based on neuronal responsiveness and action potential waveform can be used to distinguish adequately between afferent fibers and postsynaptic cells; and (ii) there is a tonic inhibitory control, greater than in the anesthetized or spinally transected cat, that varies with behavioral state and is directed primarily at spinal neurons receiving cutaneous input.

UI MeSH Term Description Entries
D009412 Nerve Fibers Slender processes of NEURONS, including the AXONS and their glial envelopes (MYELIN SHEATH). Nerve fibers conduct nerve impulses to and from the CENTRAL NERVOUS SYSTEM. Cerebellar Mossy Fibers,Mossy Fibers, Cerebellar,Cerebellar Mossy Fiber,Mossy Fiber, Cerebellar,Nerve Fiber
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
D009475 Neurons, Afferent Neurons which conduct NERVE IMPULSES to the CENTRAL NERVOUS SYSTEM. Afferent Neurons,Afferent Neuron,Neuron, Afferent
D010812 Physical Stimulation Act of eliciting a response from a person or organism through physical contact. Stimulation, Physical,Physical Stimulations,Stimulations, Physical
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
D005260 Female Females
D000344 Afferent Pathways Nerve structures through which impulses are conducted from a peripheral part toward a nerve center. Afferent Pathway,Pathway, Afferent,Pathways, Afferent
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001522 Behavior, Animal The observable response an animal makes to any situation. Autotomy Animal,Animal Behavior,Animal Behaviors
D013116 Spinal Cord A cylindrical column of tissue that lies within the vertebral canal. It is composed of WHITE MATTER and GRAY MATTER. Coccygeal Cord,Conus Medullaris,Conus Terminalis,Lumbar Cord,Medulla Spinalis,Myelon,Sacral Cord,Thoracic Cord,Coccygeal Cords,Conus Medullari,Conus Terminali,Cord, Coccygeal,Cord, Lumbar,Cord, Sacral,Cord, Spinal,Cord, Thoracic,Cords, Coccygeal,Cords, Lumbar,Cords, Sacral,Cords, Spinal,Cords, Thoracic,Lumbar Cords,Medulla Spinali,Medullari, Conus,Medullaris, Conus,Myelons,Sacral Cords,Spinal Cords,Spinali, Medulla,Spinalis, Medulla,Terminali, Conus,Terminalis, Conus,Thoracic Cords

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