The complexities of mammalian locomotion with the PatchStar micromanipulator

Electrophysiologists at the University of St Andrew have made important steps towards understanding mammalian motion using Scientifica’s PatchStar micromanipulator.

Mammalian locomotion is controlled by the neuronal activity of networks of spinal interneurons called central pattern generators (CPG’s). These CPG’s communicate via many subtypes of receptors; in this study the team focused on the metabotropic glutamate receptors (mGluRs). These receptors regulate rhythmic motor behaviours via intrinsic control of neurons and synaptic transmission.

Miles et al studied whether the mGluRs were responsible for modulating the intensity of the motor output by the CPG’s; this included characterising the amplitude and frequency of locomotor-related motorneuron output.

They applied mGluR agonist (S)-3,5-dihydroxyphenylglycin (DHPG) to the isolated mouse spinal cord preparations, they then made extracellular recordings from ventral roots and whole cell patch clamp recordings from spinal motoneurons using the PatchStar; the data was amplified, filtered and analaysed using Molecular Devices Multiclamp 700B, Digidata and pClamp software to monitor the spinal networks response to the drug.

Recordings from ventral roots revealed that application of DHPG reduced the amplitudeand increased the frequency of bursts of locomotor-related motorneuron output. Analyses at the single cell level demonstrated that activation of mGluR receptors on motoneurons had an inhibitory effect on motoneuron firing and decreased the amplitude of locomotor-related excitatory input to motoneurons.

These findings demonstrate the important control exerted by mGluRs and suggest that they play a role in limiting motoneuron output, which might serve to protect motoneurons from excitotoxic damage. It is therefore important to explore the role of mGluRs further, as a gateway for controlling motor output as well as a possible area of treatment in the future for diseases that attack the central nervous system.

Activation of group I metabotropic glutamate receptors modulates locomotor-related motoneuron output in mice Noboru Iwagaki and Gareth B. Miles J Neurophysiol 105:2108-2120, 2011. First published 23 February 2011; doi: 10.1152/jn.01037.2010