Asymmetrical regional changes in energy metabolism of the central nervous system during walking

Cats were injected with 2-deoxy- [14C]glucose (2-DG) while walking on a moving treadmill (experimental group), or sitting down on a stationary one (controls). After a 45-min equilibration period they were anesthetized, and their central nervous system (CNS) was removed rapidly and frozen. The tissue blocks were sectioned serially, and X-ray film exposed to the sections was used for quantitative densitometric analysis by Sokoloff's method. The utilization of glucose in a CNS region (LCMRg) was regarded as a measure of that region's energy metabolic activity and--indirectly--of its functional status. The walking cats exhibited significantly higher LCMRg in many but not all places of the neuraxis, compared to the control group. Also, LCMRg was symmetrical (side to side) in the control group but significantly asymmetrical in certain regions of the CNS in the experimental group. In all but one of these cats the LCMRg was greater in the right side of the gray matter of the cervical spinal cord and in the left visual and motor cortices and caudate nucleus. The finding that the motor cortex and other supraspinal regions become more active during walking suggests they may contribute to the control of locomotion and/or processing of related sensory data. The side to side asymmetry in the spinal cord and hemispheres during walking may be related to the phenomenon of lateral dominance.