Figure 3.
Different sensitivities of uIPSCs to P/Q- and N-type VDCC blockers in connections sharing a presynaptic FSN. A, Firing properties of presynaptic FSNs and two different postsynaptic non-FSNs in response to depolarizing current pulse injection. B, Effects of CgTx (3 μm) on IPSC amplitudes in the FSN→non-FS connections. Ba, Note that these connections exhibited different sensitivities of uIPSCs to CgTx. Bb, Scaled traces clearly showed that CgTx increased the PPR in the FSN→non-FSN2 connection. C, The effects of AgTx (200 nm) on the PPR in the FSN1→FNS2 connection. Ca, Repetitive spike firing of presynaptic and postsynaptic FSNs (FSN1 and FSN2, respectively). Cb, Effects of AgTx on uIPSCs in the FSN1→FSN2 connection. Cc, Scaled traces in the control and the N-type VDCC-mediated components isolated by AgTx showed the suppression of PPR. D, Summary of the effects of AgTx (a) and CgTx (b) on FSN→FSN/non-FSN connections. Note the significant suppression and facilitation of the PPR by AgTx (n = 16) and by CgTx (n = 22), respectively (*p < 0.05, paired t test). E, Relationship between the PPR obtained from control (PPRcontrol, abscissa) and the percentage of AgTx-sensitive uIPSCs (ordinate) recorded from one (open circles), two (crosses), and three (closed circles) connections consisting of common presynaptic FSNs. The plots with the same colors represent paired connections with a common presynaptic FSN. Note a positive correlation between PPRcontrol and the percentage of AgTx-sensitive uIPSCs (ρ = 0.479, p < 0.0001, n = 65, Spearman correlation). F, Relationship of CgTx sensitivities (a) and AgTx sensitivities (b) between two postsynaptic neurons receiving synaptic inputs from a common FSN. The sensitivities to CgTx (a) and AgTx (b) with high and low values are plotted onto the abscissa and ordinate, respectively (CgTx, n = 11; AgTx, n = 13). Note the sparse distribution of plots.