Balanced inhibition and excitation drive spike activity in spinal half-centers.
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.
Berg
Rune W
RW
Department of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen DK 2200 Copenhagen N, Denmark.
Alaburda
Aidas
A
Hounsgaard
Jørn
J
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D007395:Interneurons / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D009046:Motor Neurons / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D009431:Neural Conduction; D009433:Neural Inhibition; D010812:Physical Stimulation; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D013331:Strychnine / Q000494:pharmacology; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission; D014426:Turtles / Q000502:physiology*
D013331:Strychnine