Article Figures & Data
Figures
- Figure 1.
Excitatory glutamatergic synaptic transmission in dLGN and SC. A, Whole-cell voltage-clamp recordings showing the excitatory postsynaptic activity evoked by repetitive electrical stimulation of the OT for dLGN (left) and SC (right) neuron. Repetitive stimulation at 20 Hz evoked a train of EPSCs that rapidly depressed with each successive pulse. B, Paired stimulation (ISI, 50 ms) also led to strong paired-pulse depression in which the amplitude of the second (EPSC2) is greatly reduced compared with the initial one (EPSC1). Responses were abolished (red traces) by the bath application of glutamate receptor antagonists (AMPA: DNQX 25 μm) and (NMDA: d-CPP 20 μm). All responses recorded at −70 mv.
- Figure 2.
The effects of Cae on dLGN and SC synaptic responses. Whole-cell voltage-clamp recordings showing the EPSCs evoked by repetitive OT stimulation. A, Examples of dLGN (left) and SC (right) EPSCs evoked by repetitive stimulation at 20 Hz during wash-in of 1.5 mm Cae, followed by 3.0 mm and then 1.5 mm Cae. B, Below each example are the summary plots for dLGN (n = 6) and SC (n = 6) neurons showing mean ± SD changes in EPSC amplitude as a function of stimulus number within the stimulus train during 1.5 Cae (black symbols) and 3.0 mm Cae (red symbols) C, Examples of dLGN (left) and SC (right) EPSCs evoked by paired OT stimulation (50-ms ISI) during wash-in of 1.5 mm Cae (black) and 3.0 mm Cae (red). Adjacent summary plots depict PPRs (left y-axis) for individual neurons (dLGN, n = 5; SC, n = 4) as well as group mean ± SEM values (large symbols). Also included (right y-axis) are paired differences for each neuron, along with error bars that reflect the 95CI. Dotted horizontal lines depict the group mean at 1.5 mm Cae (top) and the average difference between group means (effect size). For both dLGN and SC neurons, an increase in Cae led to larger initial responses and stronger paired pulse depression (dLGN *p = 0.0019; SC *p = 0.0081). All responses recorded at −70 mv.
- Figure 3.
The effects of selective Ca2+ channel subtype blockade on the synaptic responses of dLGN and SC neurons. A, Examples of EPSCs evoked by OT stimulation for dLGN (left) and SC (right) neurons before (black, Control) and during bath application of L-type channel blockade by nimodipine (red) and R-type channel blockade by SNX (red) L-type and R-type blockade had no effect on the synaptic responses of dLGN and SC neurons. B, Examples of EPSCs evoked by OT stimulation for a dLGN and SC neuron before (Control, black) and during N-type blockade by ω-CgTx GVIA (CgTX, blue) and P/Q blockade by ω-Aga IVA (AgTX, red). Below each example are plots for an dLGN and SC neuron showing the changes in EPSC amplitude as a function of time before and during N (CgTX) and P/Q (AgTX) channel, and glutamate receptor (DNQX+CPP) blockade. The bar under each drug represents the time course and duration of drug application. C, Summary plots for dLGN (n = 17) and SC neurons (n = 16) showing the degree of EPSC suppression associated with N-type blockade by ω-CgTx GVIA (blue) and PD173212 (gray), and P/Q blockade by ω-Aga IVA (red). Each point represents an individual neuron, with bars representing group means and SEMs. Adjacent graphs (right) depict differences between the means for each drug treatment. Symbols reflect difference means and error bars the 95CIs. Dotted horizontal line shows a value of 0 (no difference). N and P/Q channel blockade differentially regulated synaptic transmission. For dLGN, P/Q blockade by ω-Aga IVA (n = 7) led to a ∼65% reduction in EPSC, whereas N-type blockade by ω-CgTx GVIA (n = 6) or PD 173212 (n = 4) led to a 12–13% reduction. Differences between the means for these drug treatments showed that for dLGN, P/Q blockade reduced amplitude 50% more than N-type blockade. For SC neurons, N-type blockade by ω-CgTx GVIA (n = 6; 69%) or PD 173212 (n = 5; 58%) led to a 58–69% reduction in amplitude, whereas P/Q blockade by ω-Aga IVA (n = 5) led to a 17% reduction. Differences between the means showed that for SC neurons N-type blockade reduced amplitude between 41% and 52% more than P/Q blockade. All responses recorded at −70 mv.
- Figure 4.
The effects of N and P/Q channel blockade on paired pulse depression in dLGN and SC neurons. A, B, Summary plots that depict PPRs for individual dLGN (A, n = 5) and SC (B, n = 6) neurons, along with the group mean ± SEM (large symbols). Also included (right y-axis) are paired differences for each neuron, along with error bars that reflect the 95CI. Dotted horizontal lines depict the group mean difference (effect size) during drug treatment (top) and the mean for predrug values. Selective blockade of P/Q for dLGN (*p = 0.0078) and N for SC (*p = 0.0027) led to an increase in PPRs, and thus a weakening in paired pulse depression. All responses recorded at −70 mv.
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