Figure 3
Learning-induced hyperpolarization of the fIPSP is mediated by persistent PKC activation. (A) Example of the effect of the PKC blocker, GF-109203×, on the fIPSP in a neuron taken from a trained rat. Amplitude of the fIPSP was recorded at several holding potentials. IPSPs were measured at the first peak, as appeared in the most depolarized recording potential. Numbers on the left of the traces note the holding membrane potential. These measurements were then used to calculate the reversal potential of the responses. (B) The reversal potentials of the synaptic responses shown in A were determined by the linear regression line, describing the amplitude of the synaptic potential as a function of the membrane holding potential. Application of GF-109203X resulted in a 9 mV depolarization of the fIPSP reversal potential. Here too, the slope of the curve is not modified by the PKC blocker application. (C) The averaged reversal potential of the fIPSP is reduced in neurons from trained rats only (*P < 0.05 for trained neurons before and after GF-109203X application). Data was taken from 15 trained (dark bars) rats and 20 control rats (light bars). Values represent mean ± SE. (D) Representative blots of actin, KCC2 and phosphorylated KCC2 (from single blot), in piriform cortex homogenates. Bands represent KCC2 monomer43. Blot were cut into two from 70kDa-250kDa and 70 kDa −37kDa. The upper blots were subjected to pKCC2 and KCC2 antibodies, while the lower blots were subjected to actin antibody. (N = naïve, T = trained, P = pseudo trained). (E) The expression level of KCC2 compared with actin is not modified after learning (E1), while phosphorylation of KCC2 is significantly increased (E2). Values represent mean ± SE. (*p < 0.05).
