Large-scale plasticity in barrel cortex following repeated whisker trimming in young adult hamsters.
Using the 2DG/immunostaining method [McCasland, J.S., Graczyk, G.M., 2000. Metabolic mapping-Unit 1.6. In: Gerfen, C.R. (Ed.), Current Protocols in Neuroscience. Wiley, New York, pp 1.6.1-1.6.15], we have previously demonstrated large-scale plasticity in whisker/barrel fields of young adult hamsters subject to follicle ablation on postnatal day 7 (P7) [Somatosens. Motor Res. 13 (1996) 245]. This plasticity occurs after the barrel field has formed, but before neuronal differentiation and synaptogenesis are complete. The present study tested for similar large-scale plasticity following whisker deprivation in young adult hamsters, when neuronal and synaptic development are more mature. Beginning around P40, animals had all whiskers except row C trimmed on alternating days for periods ranging from 1 h to 2 weeks, after which they were administered (3)H 2DG (i.p.) and allowed to explore a fresh empty cage. Autoradiograms from these animals showed a clear expansion in the zone of heavy 2DG labeling with continued whisker trimming. Hamsters with row C spared overnight showed markedly higher labeling in the row C barrels, as expected. After 2 weeks of repeated trimming, the pattern of 2DG labeling in the barrel field ranged from complete activation of all large-whisker columns, as in a previous study of P7 follicle ablation, down to a more localized activation of rows B, C, and D. Intermediate periods of trimming produced more localized label in the region of row C. There was a clear trend toward larger areas of activation with longer periods of trimming. Because inhibitory neurons are strongly activated in all cases, this large-scale neuronal plasticity must take place in the presence of strong inhibition. The data show that simple trimming of all but a few whiskers in normally reared adults leads to abnormally widespread metabolic labeling encompassing virtually the entire barrel field. Taken together, our findings suggest that a large-scale synaptic reorganization occurs in barrel fields deprived of normal sensory input in the adult as well as during postnatal development.
Maier
Donna L
DL
Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
Grieb
Ginny M
GM
Stelzner
Dennis J
DJ
McCasland
James S
JS
D000818:Animals; D001345:Autoradiography; D001931:Brain Mapping; D006224:Cricetinae; D003847:Deoxyglucose; D007091:Image Processing, Computer-Assisted; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D012683:Sensory Deprivation / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D014738:Vibrissae / Q000294:innervation*
D003847:Deoxyglucose