Authors are in alphabetical order since they all contributed equally to this work.
Tuning and playing a motor rhythm: how metabotropic glutamate receptors orchestrate generation of motor patterns in the mammalian central nervous system
Article first published online: 5 APR 2006
The Journal of Physiology
Volume 572, Issue 2, pages 323–334, April 2006
How to Cite
Nistri, A., Ostroumov, K., Sharifullina, E. and Taccola, G. (2006), Tuning and playing a motor rhythm: how metabotropic glutamate receptors orchestrate generation of motor patterns in the mammalian central nervous system. The Journal of Physiology, 572: 323–334. doi: 10.1113/jphysiol.2005.100610
- Issue published online: 5 APR 2006
- Article first published online: 5 APR 2006
- (Received 24 October 2005; accepted after revision 9 February 2006; first published online 9 February 2006)
Repeated motor activities like locomotion, mastication and respiration need rhythmic discharges of functionally connected neurons termed central pattern generators (CPGs) that cyclically activate motoneurons even in the absence of descending commands from higher centres. For motor pattern generation, CPGs require integration of multiple processes including activation of ion channels and transmitter receptors at strategic locations within motor networks. One emerging mechanism is activation of glutamate metabotropic receptors (mGluRs) belonging to group I, while group II and III mGluRs appear to play an inhibitory function on sensory inputs. Group I mGluRs generate neuronal membrane depolarization with input resistance increase and rapid fluctuations in intracellular Ca2+, leading to enhanced excitability and rhythmicity. While synchronicity is probably due to modulation of inhibitory synaptic transmission, these oscillations occurring in coincidence with strong afferent stimuli or application of excitatory agents can trigger locomotor-like patterns. Hence, mGluR-sensitive spinal oscillators play a role in accessory networks for locomotor CPG activation. In brainstem networks supplying tongue muscle motoneurons, group I receptors facilitate excitatory synaptic inputs and evoke synchronous oscillations which stabilize motoneuron firing at regular, low frequency necessary for rhythmic tongue contractions. In this case, synchronicity depends on the strong electrical coupling amongst motoneurons rather than inhibitory transmission, while cyclic activation of KATP conductances sets its periodicity. Activation of mGluRs is therefore a powerful strategy to trigger and recruit patterned discharges of motoneurons.