Figure 7.

Repeated Stimulation Evokes Dynamic Spike Broadening in Excitatory, but Not Inhibitory, Boutons

(A) Left: pictogram of a whole-cell bouton recording in neocortical culture. Middle: example action potential train (20 action potentials; 20 Hz) recorded from a bouton in culture. Right: overlay of 1^st, 5^th, 10^th, and 20^th action potential during train stimulation.

(B) Left: amplitudes of bouton action potentials in cultures normalized to the 1^st action potential during train stimulation at 20 Hz (black, n = 5) and 50 Hz (magenta, n = 5). Right: half-duration of bouton action potentials in neocortical cultures normalized to the 1^st action potential during the train as mean ± SEM. Brackets indicate last 5 train action potentials used for statistical analysis.

(C) Left: pictogram of a paired bouton-soma recording from a neocortical layer 5 pyramidal neuron. Middle: example trace of a 50-Hz somatic train stimulation (green) and currents simultaneously recorded from the bouton in loose-seal mode (magenta). Right: overlay of currents recorded in the bouton evoked by the 1^st and last train action potential. Circles indicate peaks of current components; brackets indicate peak-to-peak duration of currents.

(D) Action potential propagation successes and failures during 20-Hz and 50-Hz train stimulation in paired recordings from neocortical pyramidal neurons (380 and 720 action potentials in total, respectively).

(E) Peak-to-peak duration of currents in bouton of layer 5 pyramidal neurons during 20 Hz (black, n = 15) and 50 Hz train stimulation (magenta, n = 13; durations normalized to 1^st current duration; bracket indicates last 5 train action potentials used for statistical analysis; n indicates the number of paired recordings; mean ± SEM).

(F) Left: pictogram of a paired bouton-soma recording from a neocortical interneuron. Middle: example 50-Hz somatic train stimulation (green) and currents simultaneously recorded from a bouton in loose-seal mode (magenta). Right: overlay of currents recorded in a bouton evoked by the 1^st and last train action potential. Circles indicate peaks of current components; brackets indicate peak-to-peak current durations.

(G) Action potential propagation successes and failures during 20 Hz, 50 Hz, and 100 Hz train stimulation in paired recordings from neocortical interneurons (580, 440, and 1,100 action potentials in total, respectively).

(H) Duration of action-potential-evoked currents in bouton of neocortical interneurons during 20-Hz (black, n = 4), 50-Hz (magenta, n = 5), and 100-Hz train stimulations (blue, n = 7; durations normalized to 1^st current duration; bracket indicates last 5 train action potentials used for statistical analysis; n indicates the number of paired recordings; mean ± SEM).