V. Rema et al., EXPERIENCE-DEPENDENT PLASTICITY OF ADULT-RAT S1 CORTEX REQUIRES LOCALNMDA RECEPTOR ACTIVATION, The Journal of neuroscience, 18(23), 1998, pp. 10196-10206
The effect of blocking NMDA glutamate receptors in adult rat cortex on
experience-dependent synaptic plasticity of barrel cortex neurons was
studied by infusing D-AP5 with an osmotic minipump over barrel cortex
for 5 d of novel sensory experience. In acute pilot studies, 500 mu M
D-AP5 was shown to specifically suppress NMDA receptor (NMDAR)-depend
ent responses of single cells in cortical layers I-IV. To induce plast
icity, all whiskers except D2 and D1 were cut close to the face 1 d af
ter pump insertion. The animals were housed with 2 cage mates before r
ecording 4 d later. This pairing of two whiskers for several days in a
wake animals generates highly significant biases in responses from D2
layer IV (barrel) cells to the intact D1 whisker as opposed to the cut
D3 whisker. D-AP5 completely prevented the D1/D3 surround whisker bia
s from occurring in the D2 barrel cells (p > 0.6 for D1 > D3, Wilcoxon
). Fast-spike and slow-spike barrel cells were affected equally, sugge
sting parity for inhibitory and excitatory cell plasticity. D-AP5 only
partially suppressed the D1/D3 bias in supragranular layers (layers I
I-III) in the same penetrations (p < 0.042 for D1 > D3). In control an
imals, the inactive L-APS isomer allowed the bias to develop normally
toward the intact surround whisker (p < 0.001 for D1 > D3) for cells i
n all layers. We conclude that experience-dependent synaptic plasticit
y of mature barrel cortex is cortically dependent and that modificatio
n of local cortical NMDARs is necessary for its expression.