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Science 19 January 2007:
Vol. 315. no. 5810, pp. 390 - 393
DOI: 10.1126/science.1134960
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Reports

Balanced Inhibition and Excitation Drive Spike Activity in Spinal Half-Centers

Rune W. Berg,1 Aidas Alaburda,2 Jørn Hounsgaard1*

Many limb movements are composed of alternating flexions and extensions. However, the underlying spinal network mechanisms remain poorly defined. Here, we show that the intensity of synaptic excitation and inhibition in limb motoneurons varies in phase rather than out of phase during rhythmic scratchlike network activity in the turtle. Inhibition and excitation peak with the total neuron conductance during the depolarizing waves of scratch episodes. Furthermore, spike activity is driven by depolarizing synaptic transients rather than pacemaker properties. These findings show that balanced excitation and inhibition and irregular firing are fundamental motifs in certain spinal network functions.

1 Department of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen DK 2200 Copenhagen N, Denmark.
2 Department of Biochemistry and Biophysics, Faculty of Natural Sciences, Vilnius University, Ciurlionio 21/27, 03101 Vilnius, Lithuania.

* To whom correspondence should be addressed. E-mail: j.hounsgaard{at}mfi.ku.dk

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