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Volume 17, Number 9, Issue of May 1, 1997 pp. 3322-3333
Copyright ©1997 Society for Neuroscience

Glycinergic Inhibition Contributes to the Generation of Rostral Scratch Motor Patterns in the Turtle Spinal Cord

Received Oct. 31, 1996; revised Feb. 11, 1997; accepted Feb. 14, 1997.

Scott N. Currie and Steven Lee

Department of Neuroscience, University of California, Riverside, California 92521

Cutaneous stimulation within the rostral scratch receptive field in a low spinal-immobilized turtle elicits a fictive rostral scratch reflex characterized by robust rhythmic motor output from ipsilateral hindlimb muscle nerves and weaker, alternating motor discharge in contralateral nerves. Simultaneous bilateral stimulation elicits bilateral rostral scratch motor patterns in which activity on the right and left sides alternates.

We investigated the role of glycinergic inhibition in the generation and coordination of fictive rostral scratch motor patterns. Glycine (2 or 5 mM) and strychnine (5-50 µM), a glycine antagonist, were superfused over the anterior spinal hindlimb enlargement while fictive rostral scratch motor output was recorded bilaterally from hindlimb muscle nerves in the form of electroneurograms (ENGs). Although glycine reduced rostral scratch burst frequencies, strychnine tended to increase burst frequency. Strychnine also changed the shape of hip flexor ENG bursts, resulting in more abrupt burst onsets, indicating an earlier recruitment of motor neurons with large ENG spikes. During bilateral stimulation, strychnine increased the variability of interlimb phase values (left vs right hip flexor bursts) but did not abolish right-left alternation.

These results indicate that glycinergic neurons in or near the anterior hindlimb enlargement contribute to the overall timing of the rostral scratch rhythm and to the recruitment timing of individual hip flexor motor neurons within each scratch burst. Our data also indicate that glycinergic mechanisms contribute to, but are not critically important for, maintaining an alternating interlimb coordination during bilateral scratch motor patterns.

Key words: turtle; spinal; scratch reflex; central pattern generator; inhibition; , strychnine

This article has been cited by other articles:

				R. F. Samara and S. N. Currie Location of Spinal Cord Pathways That Control Hindlimb Movement Amplitude and Interlimb Coordination During Voluntary Swimming in Turtles J Neurophysiol, April 1, 2008; 99(4): 1953 - 1968. [Abstract] [Full Text] [PDF]

				R. F. Samara and S. N. Currie Crossed Commissural Pathways in the Spinal Hindlimb Enlargement Are Not Necessary for Right Left Hindlimb Alternation During Turtle Swimming J Neurophysiol, October 1, 2007; 98(4): 2223 - 2231. [Abstract] [Full Text] [PDF]

				M.-C. Perreault Motoneurons Have Different Membrane Resistance during Fictive Scratching and Weight Support J. Neurosci., September 15, 2002; 22(18): 8259 - 8265. [Abstract] [Full Text] [PDF]

				R. D. de Leon, H. Tamaki, J. A. Hodgson, R. R. Roy, and V. R. Edgerton Hindlimb Locomotor and Postural Training Modulates Glycinergic Inhibition in the Spinal Cord of the Adult Spinal Cat J Neurophysiol, July 1, 1999; 82(1): 359 - 369. [Abstract] [Full Text] [PDF]

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				S. N. CURRIE and G. G. GONSALVES Crossed Reciprocal Inhibition and Scratch Rhythmogenesis in the Turtle Spinal Cord Ann. N.Y. Acad. Sci., November 16, 1998; 860(1): 458 - 460. [Full Text] [PDF]

				P. S. G. Stein, M. L. McCullough, and S. N. Currie Reconstruction of Flexor/Extensor Alternation during Fictive Rostral Scratching by Two-Site Stimulation in the Spinal Turtle with a Transverse Spinal Hemisection J. Neurosci., January 1, 1998; 18(1): 467 - 479. [Abstract] [Full Text] [PDF]

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