Fig 1.
The slope of the input–output (I/O) relationship, but not paired-pulse facilitation was increased in CA1 neurons from 2-day FZP-withdrawn rats. (A) Evoked EPSC (VH = -80 mV) amplitude (pA) was plotted as a function of stimulus intensity (V). Linear regression of pooled I/O relationships showed a ∼2.5 fold increase in the stimulus response relationship in CA1 neurons from FZP-withdrawn (open circles, n=9) compared to control (closed circles, n=7) rats. Inset: Representative traces of eEPSCs elicited at 3.6V (solid line: CON; broken line: FZP). Scale as in inset in C. (B) The mean slope of the I/O curve derived from the fits of individual I/O curves generated in neurons from FZP-withdrawn rats (440.0 ± 79.4 pA/V, n=9) was also significantly greater than that from control rats (205.3 ± 44.5 pA/V, n=7). The data are consistent with an increase in CA1 neuron AMPAR synaptic efficacy in FZP-withdrawn rats. Asterisks denote p<.05. (C) Paired-pulse facilitation (PPF) of AMPAR was unchanged in 2-day FZP withdrawn rats. The amplitude of AMPAR-mediated eEPSCs (VH = -80 mV) following half-maximal stimulation of the Schaffer-collateral pathway. Paired-pulse stimulation was applied and the response was recorded at the inter-stimulus intervals ranging from 25-200 ms in 25 ms increments. Inset: Representative paired EPSC traces recorded in CA1 neurons from control and FZP-withdrawn rats. Paired EPSC amplitudes were calculated as the difference between baseline before the stimulus artifact and EPSC peak. PPF was calculated as (EPSC2-EPSC1)/EPSC1 × 100. Percent facilitation was plotted (CON, closed circles, n = 5; FZP: closed circles, n = 5) and fit with a single exponential decay function. No significant differences between groups were found at any interstimulus interval suggesting that glutamate release onto CA1 neurons was unaltered.