Progressive elevations in AMPA and GABAA receptor levels in deafferented somatosensory cortex.
Restricted receptive fields (RFs), a hallmark of mature sensory systems, are actively maintained by a balance between ascending excitation and local inhibition in the cortex. Deafferentation disrupts this balance, allowing a sequence of changes in neuronal response properties that culminate in the reorganization of cortical RFs. To explore the molecular basis of deafferentation-induced RF reorganization, we tracked changes in AMPA receptor (AMPAR), NMDA receptor (NMDAR) and GABAA receptor (GABAAR) levels in the deafferented somatosensory cortex of adult raccoons following single-digit amputation. In synaptoneurosomes prepared from deafferented cortex, we observe a significant increase in AMPARs, but no change in NMDARs, 1-9 days post-deafferentation, coincident with the appearance of new excitatory inputs and enlarged RFs. We observe a significant increase in GABAARs 2-7 weeks post-deafferentation, coincident with a return of inhibitory input and shrinking RFs. These experience-dependent changes in the levels of the major cortical ionotropic receptors were transient, returning to pre-experimental baseline by > or = 17 weeks post-deafferentation, when RFs return to original size, but are remapped to different loci. This suggests that deafferentation-induced cortical reorganization may be generated by activity-dependent potentiation of weak excitatory synapses, followed by an increase in the strength of inhibitory synapses, resulting in finely tuned, remapped cortical RFs.
Department of Biology, University of Maryland, College Park, Maryland 20742, USA.
Hai-Yan
HY
He
Douglas D
DD
Rasmusson
Elizabeth M
EM
Quinlan
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002452:Cell Count / Q000379:methods; D005260:Female; D005552:Forelimb / Q000293:injuries* / Q000294:innervation; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology; D011821:Raccoons; D018091:Receptors, AMPA / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000378:metabolism*; D012683:Sensory Deprivation / Q000502:physiology; D013003:Somatosensory Cortex / Q000378:metabolism* / Q000503:physiopathology; D013997:Time Factors
D018091:Receptors, AMPA; D011963:Receptors, GABA-A