Fig 5.

Postsynaptic depolarization in spiny projection neurons is linearly correlated with number of presynaptic action potentials during burst firing. (A) Connection with high failure rate at 35 Hz presynaptic burst firing (V_{Rest post} = −74 mV). (B) Change in PSP amplitudes during presynaptic action potential bursts at different burst frequencies. (Left) Increasing PSP amplitudes at 18 Hz (filled arrow). (Center) Relatively constant PSP amplitudes at 24 Hz. (Right) Facilitated PSP responses during early burst period (open arrow) followed by decreased PSP amplitudes that merge into a plateau-like depolarization at 36 Hz (*). Same neuron (V_{Rest pre} = −80 mV and V_{Rest post} = −83 mV). (C) Uncovering of synaptic steady-state depolarization during high frequency bursts (arrowheads). PSP in response to presynaptic bursts of action potentials at increasing burst frequency. Note absence of postsynaptic response at low burst frequency (open arrows; V_{Rest pre} = −68 mV and V_{Rest post} = −87 mV). Note also slow depolarization that recovers 35 s after burst series. (D) Overlay plot of two PSP in response to presynaptic bursts from C (time periods indicated by bars). (E) Monotone increase of integrated PSP area over time during 500-ms lasting presynaptic bursts (numbers of action potentials indicated on the right). (F) Total postsynaptic depolarization is linearly correlated with number of presynaptic action potentials (500-ms current pulse duration; n = 8 neurons, all culture).