Abstract

A rhythmic motor program, termed the scratch reflex, can be elicited by gentle mechanical stimulation of the shell in an immobilized, spinal turtle. Microelectrodes will be inserted into the somata of limb motor neurons in order to record the synaptic potentials controlling the activities of these cells. These recordings will reveal the output characteristics of the spinal cord generator for the scratch program. Manipulations of membrane voltage and cellular ionic content will allow us to explore the ionic mechanisms underlying these synaptic potentials. The descending neuronal signal driven by cutaneous afferents from the shell will be recorded and its effect on the scratch generator explored. Our hypothesis is that this decending signal may exhibit characteristics of """"""""command"""""""" neurons found in invertebrates and fishes. The objectives of this work are to characterize the basic properties of turtle spinal cord neurons involved in the generation of motor programs. Since many features of spinal cord are invariant throughout the vertebrates, it is our hope that our results on turtle will serve as useful working hypotheses for the exploration of the motor mechanisms in more complex vertebrates.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS015049-06
Application #
3395924
Study Section
Neurology B Subcommittee 1 (NEUB)
Project Start
1979-09-24
Project End
1986-02-28
Budget Start
1984-12-01
Budget End
1986-02-28
Support Year
6
Fiscal Year
1985
Total Cost
Indirect Cost

  Institution

Name
Washington University
Department
Type
Schools of Arts and Sciences
DUNS #
062761671
City
Saint Louis
State
MO
Country
United States
Zip Code
63130

  Publications

Stein, P S; Victor, J C; Field, E C et al. (1995) Bilateral control of hindlimb scratching in the spinal turtle: contralateral spinal circuitry contributes to the normal ipsilateral motor pattern of fictive rostral scratching. J Neurosci 15:4343-55
Currie, S N; Stein, P S (1990) Cutaneous stimulation evokes long-lasting excitation of spinal interneurons in the turtle. J Neurophysiol 64:1134-48
Mortin, L I; Stein, P S (1990) Cutaneous dermatomes for initiation of three forms of the scratch reflex in the spinal turtle. J Comp Neurol 295:515-29
Mortin, L I; Stein, P S (1989) Spinal cord segments containing key elements of the central pattern generators for three forms of scratch reflex in the turtle. J Neurosci 9:2285-96
Stein, P S (1989) Spinal cord circuits for motor pattern selection in the turtle. Ann N Y Acad Sci 563:1-10
Currie, S N; Stein, P S (1989) Interruptions of fictive scratch motor rhythms by activation of cutaneous flexion reflex afferents in the turtle. J Neurosci 9:488-96
Stein, P S; Schild, C P (1989) N-methyl-D-aspartate antagonist applied to the spinal cord hindlimb enlargement reduces the amplitude of flexion reflex in the turtle. Brain Res 479:379-83
Currie, S N; Stein, P S (1988) Electrical activation of the pocket scratch central pattern generator in the turtle. J Neurophysiol 60:2122-37
Stein, P S (1988) Motor mechanisms in the turtle spinal cord. Acta Biol Hung 39:155-60
Stein, P S; Camp, A W; Robertson, G A et al. (1986) Blends of rostral and caudal scratch reflex motor patterns elicited by simultaneous stimulation of two sites in the spinal turtle. J Neurosci 6:2259-66

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