Figure 2.
Effects of theta-burst stimulation on numbers of spines with high concentrations of pPAK. a, TBS was delivered to the apical branch of the Schaffer-commissural projections and field EPSPs were recorded from the proximal apical dendrites of field CA1 in hippocampal slices from adult rats. The illustrated results are from one of two converging afferent populations used in each experiment. The traces are responses collected immediately before delivery of TBS (left side) and from the minute before the slices were collected (at right). Graphs summarize the mean (±SEM) initial slope of fEPSPs elicited by single stimulation pulses pre-TBS and post-TBS for groups of slices (n = 4/group). Calibration: 0.5 mV, 10 ms. TBS was applied at time 0 (arrow). b, c, Laser-scanning confocal micrographs showing pPAK immunostaining in slices that received either control (cont; b) or theta-burst (c) stimulation. Image intensity values are inverted to more easily observe densely labeled puncta. Note that TBS resulted in an increase in the frequency of immunoreactive spine-like puncta (arrows). Scale bar, 10 μm. d, Bar graph showing the number of pPAK+ spines in proximal str. radiatum (the recording site in a) from slices fixed 0.5 min (n = 3), 2–7 min (n = 5), or 15–30 min (n = 5) after the delivery of TBS. Control slices (open bar; n = 7) received baseline stimulation. The overall effect of time after stimulation was significant (p = 0.024, one-way ANOVA) and the 2–7 min group was significantly different from both control (*p = 0.021, Tukey's HSD) and 15–30 min post-TBS groups. E, Theta-burst stimulation did not measurably affect the total number of PSD95-IR spines in the same sections in which it increased numbers of pPAK-IR puncta (p = 0.37).