We took advantage of CF responses because of their large amplitudes (advantage over dendritic Na+ spikes) and because they can be equally selleck compound well recorded on different branches of the dendrite (advantage over the spatially restricted PF responses). To selectively

activate one recording site, we used modified versions of the two protocols described above: (1) depolarizing current pulses injected through one of the dendritic patch electrodes, rather than into the soma, (2) 50 Hz PF stimulation protocol, with the stimulus electrode placed lateral to the dendritic target area (for an example, see Figure 7B), and the stimulus intensity adjusted to evoke smaller PF-EPSPs (n = 5; depolarization: n = 2; 50 Hz PF tetanization: n = 3). In comparison to the dendritic responses obtained Ion Channel Ligand Library manufacturer with 50 Hz PF stimulation in the previous recordings (12.5 ± 1.0 mV; n = 5; Figure 2D), in which the stimulus electrode was randomly placed in the molecular layer, application of the modified PF tetanization protocol resulted in smaller peak response amplitudes (5.3 ± 0.7 mV; n = 3; p = 0.036; Mann-Whitney U test). For simplicity, we use the terms “strong” and “weak” in this study, referring to the dendritic response strength, to address these two induction protocols.

Figure 7E shows an example of weak PF activation resulting in an EPSP train at the conditioned site (red trace), but not at the unconditioned site (blue trace). For comparison, the gray trace on top shows a 50 Hz EPSP train evoked by strong PF activation. Figure 7F shows typical responses to the depolarization protocol. For both protocols, the peak depolarization at the conditioned site was significantly larger than at the unconditioned site (conditioned: 5.5 ± 0.5 mV; unconditioned: 1.6 ± 1.4 mV; n = 5; p = 0.042; Figure 7G). In both conditions, we observed a selective

increase in the CF response amplitude at the activated dendritic recording site (134.7% ± 11.6%; n = 5; last to 5 min; p = 0.013; paired Student’s t test), while at the unconditioned site the responses were not significantly affected (82.7% ± 11.5%; n = 5; p = 0.207; Figures 7H and 7I). These data show that dendritic plasticity can selectively occur at dendritic locations that receive sufficient activation. To obtain a second measure of compartment-specific dendritic plasticity, we performed confocal imaging experiments. The experimental layout was similar to the triple-patch recordings in that CF-evoked complex spikes were measured in the soma using patch-clamp recordings, and local CF responses were monitored in the dendrites. However, in this case, dendritic CF responses were measured using calcium transients.