Figure 4.

Postsynaptic intracellular injection of cADPR antagonists into CA1 pyramidal neurons does not affect the induction of LTD. (A) Time course of LTD of Schaffer collateral-evoked intracellular EPSPs in CA1 pyramidal neurons (n = 4) impaled with microelectrodes containing 1 mM 8-Br-cADPR. Before baseline recording was commenced, 10–15 min of depolarizing current pulse injection (0.2–0.5 nA/200 ms at 1 Hz) was applied to facilitate drug infusion. In contrast to extracellular application, postsynaptic 8-Br-cADPR did not alter the magnitude or duration of LTD. As in controls, LTD was homosynaptic (control input not shown). (B) Similarly, postsynaptic intracellular infusion of 1 mM 7-deaza-8-Br-cADPR (n = 7) was also unable to block or impair expression of LTD at Schaffer collateral–CA1 synapses. (Insets) Single intracellular EPSPs recorded at times indicated. Scale bars represent 5 mV and 10 ms.