Figure 6.

Nicotinic activity required intact synaptic mechanisms to influence synaptic plasticity. A, Injection of current (100 pA, 0.5 s) into the postsynaptic neuron 2 s before the electrical stimulation (arrows) produced action potentials, but it did not boost the STP to LTP. B, When postsynaptic Na⁺ channels where blocked by QX-314 in the recording pipette, then the ACh puff (horizontal bar) did not produce action potentials, and the STP was not boosted to LTP. C, When postsynaptic calcium signals were buffered by BAPTA (20 mm) in the recording pipette, then the ACh puff (horizontal bar) did not boost the STP to LTP. The BAPTA or QX-314 in the recording pipette were allowed to diffuse into the cell for 10-15 min before the recordings began. Calibration: 0.5 s, 20 mV for the depolarization; 50 ms, 2 mV for the PSPs.