Article Figures & Data
Figures
- Figure 1.
Visual experience modulates mGluR-mediated plasticity of AMPAR synaptic transmission. A, DHPG significantly increased AMPAR mEPSC amplitude in neurons of tadpoles from the dark but not in neurons from tadpoles after visual stimulation. Data are represented as box plots (median surrounded by a box representing the interquartile range (the middle 50% of the data). ∗∗p < 0.002. B, Cumulative frequency plots (20 events per cell, 20–24 cells; Kolmogorov–Smirnov test, ∗p < 0.0001). C, Sample traces of AMPA mEPSC amplitudes before and after DHPG for tadpoles without (top) or with (bottom) recent visual experience. D, Paired-pulse ratios before and after DHPG in tadpoles with (p < 0.59) and without (p < 0.55) recent visual stimulation (13–15 cells in each condition). E, Synaptically evoked AMPAR responses in tectal neurons are affected in the same way as mEPSCs. Retinal ganglion cells, which synapse directly onto tectal cells, were stimulated at the optic chiasm. DHPG significantly increased AMPA amplitude in neurons of tadpoles from the dark after DHPG application compared with visually stimulated or control tadpoles (∗p < 0.03; 5 cells in each condition). F, Relative change in AMPA mEPSC amplitude after DHPG for neurons from animals in dark and from the dark in the presence of LY367385 (mGluR1 antagonist) or MPEP (mGluR5 antagonist). n = 15–24 cells in all conditions. The data are presented as their median and interquartile range. ∗∗p < 0.005.
- Figure 2.
The ratio of Homer1a/Homer1b modulates mGluR-mediated plasticity of AMPAR synaptic transmission. A, Model of Homer1a/Homer1b regulation of mGluR-mediated changes in AMPAR synaptic transmission. After 12–15 h dark, Homer1a/Homer1b is low and mGluR activation enhances AMPA mediated transmission. With visual stimulation, Homer1a/Homer1b increases, reducing the mGluR-mediated increase in AMPAR synaptic transmission. B, Exogenous Homer1b expression significantly increased mGluR-mediated plasticity of AMPAR responses (∗p < 0.03). Exogenous Homer1a significantly decreased AMPA mEPSC amplitude after DHPG application (∗p < 0.01; n = 20–24 cells in each condition). C, Visual stimulation increases Homer1a protein expression in tadpole optic tecta. D, Expression of exogenous Homer1a blocked the increase in AMPA mEPSC amplitude in neurons from tadpoles in the dark. Expression of the mutant Homer1aW24A did not block mGluR-mediated increases in AMPA mEPSC amplitude (∗p < 0.02; n = 19–26 cells in each condition). E, Both actinomycin D (∗p < 0.05) and ectopic expression of Homer 1b (∗p < 0.01) during visual stimulation permitted the mGluR-mediated increases in AMPA mEPSC amplitude (n = 19–26 in all conditions).
- Figure 3.
Homeostatic regulation of mGluR-mediated plasticity of AMPA transmission by experience. A, AMPA mEPSC amplitudes increased with 30 min of visual stimulus compared with mEPSC amplitudes from neurons before (0 min) or after 4 h visual stimulation (∗p < 0.03; n = 20–24 in all conditions). B, The increase in AMPA mEPSC amplitude seen after 30 min of visual stimulation was blocked by the mGluR1 antagonist LY367385 (∗p < 0.02).
