Article Figures & Data
Figures
- Figure 1.
Ca2+ signals evoked by flash photorelease of IP3 and by trains of action potentials in strongly responding non-tg and PS1KI cortical neurons. A, Two-photon image showing resting fluorescence of a non-tg neuron loaded with fura-2. The annular region (excluding nucleus) from which Ca2+ measurements were taken is outlined in blue. B, C, Images and corresponding Ca2+ transients evoked by photolysis flashes with respective durations of 20 and 100 msec. Images show fluorescence ratios (F/ΔF) and are pseudocolored so that increasing ratios (increasing free [Ca2+]) are depicted by increasingly “warm” colors. Each ratio image was formed from ∼10 averaged video frames during stimulation and ∼20 averaged control frames. Traces show measurements of fura-2 fluorescence ratios from the region marked in A. Photolysis flashes were delivered when marked by the arrows. D, Ca2+ transients in the same neuron resulting from a train of action potentials evoked by depolarizing current injection (100 nA, 500 msec). E-H, Corresponding images and traces in a PS1KI neuron. I, Superimposed traces show fluorescence ratio signals in the soma of a non-tg cortical neuron, in response to photolysis flashes with durations of 7, 10, 15, 30, 50, and 100 msec. J, Similar traces from a PS1KI neuron obtained using the same flash durations.
- Figure 2.
Enhancement of IP3-evoked Ca2+ signals in PS1KI neurons. Data in this figure were derived by pooling measurements from all neurons examined (i.e., including nonresponding and weakly responding cells). A, Distribution of IP3-Ca2+ responses evoked by photolysis flashes with durations of 10, 20, 50, and 100 msec. Filled symbols (non-tg, gray; PS1KI, black) are measurements from individual neurons; corresponding means and SE are shown as open symbols. B, Mean peak amplitude of fluorescence signals from the soma measured from non-tg (open circles; n = 15) and PS1KI neurons (filled squares; n = 14) and plotted as a function of flash duration. Amplitudes of Ca2+ signals evoked by trains of action potentials are shown at the right. Error bars indicate 1 SEM. C, Bar graph showing average peak amplitudes of IP3-evoked Ca2+ responses in PS1KI neurons as a percentage of that in non-tg neurons at corresponding flash durations. Data for action potential-evoked signals are shown at the right. D, Mean peak amplitude of fluorescence signals from the proximal apical dendrite measured from non-tg (open circles; n = 11) and PS1KI neurons (filled squares; n = 13).
- Figure 3.
Amplitudes and kinetics of IP3-evoked Ca2+ signals in responsive PS1KI and non-tg neurons. Data in this figure were derived after excluding neurons that failed to responded to IP3. A, Dose-response relationships of IP3-evoked Ca2+ signals in non-tg (gray circles; n = 4-12) and PS1KI (black squares; n = 8-14) neurons. B, Mean rising slopes of IP3- and spike-evoked Ca2+ responses for non-tg (open circles; n = 4-12) and PS1KI (filled squares; n = 8-14) neurons. C, Mean decay time constants of IP3- and action potential-evoked Ca2+ signals in non-tg (open circles; n = 4-12) and PS1KI neurons (filled squares; n = 8-14) derived from single exponential fits to the decay of fluorescence signals. D, Representative Ca2+ traces showing response latencies from non-tg (left) and PS1KI neurons (right) in response to photolysis flashes with durations of 20, 50, and 100 msec. Latencies were measured as the interval between the onset of the flash artifact and time at which a straight-line fit to the rising phase of Ca2+ signals (dotted lines in the PS1KI traces) intercepted the baseline. E, Mean latencies in non-tg (gray) and PS1KI (black) neurons after flash durations of 20, 50, and 100 msec (n = 5-12 cells per group). Bars marked by asterisk are significantly different (p < 0.05) between these two groups.
- Figure 4.
IP3-evoked hyperpolarizing membrane potential responses are enhanced in PS1KI neurons. A, Representative traces of membrane potential in a non-tg neuron (left column) and a PS1KI neuron (right) in response to photolysis flashes with durations as indicated in milliseconds. B, Bar graph showing average IP3-evoked hyperpolarizations evoked by these photolysis flashes, pooled from all non-tg (gray bars; n = 15-17) and PS1KI (black bars; n = 11-15) neurons.
