Figure 3.
EPSC kinetics are significantly faster in afferents from hearing versus immature rat cochleae.
A
,
B
, Selection of monophasic EPSCs recorded from a P8 (
A
) and a P20 (
B
) afferent at −94 mV with 5.8 mm K+ extracellularly.
C
, Normalized average EPSC waveforms for the two cells presented in
A
and
B
(EPSCs averaged: P8 n = 336, green; P20 n = 216, black).
D
, Average time to peak and τ decay presented for monophasic EPSCs from 12 boutons of P8–11 (time to peak: 0.58 ± 0.1 ms; decay: 1.4 ± 0.6 ms; 5078 EPSCs), 14 boutons of P19–21 (time to peak: 0.29 ± 0.1 ms; decay 0.5 ± 0.2 ms; 6782 EPSCs), and 2 boutons of P60 (time to peak: 0.28 ± 0.002 ms; decay: 0.37 ± 0.002 ms; 3796 EPSCs) rats. EPSC kinetics were significantly faster in boutons from hearing rats (time to peak and τ decay p < 0.0001; comparing P8–11 and P19–21 datasets).
E
, Plot of τ decay against EPSC amplitude for every monophasic EPSC from one P8 afferent (green squares) and one P20 afferent (black squares), same fibers as in
A
and
B
. EPSCs in hearing afferents were significantly faster across the entire amplitude range. Monophasic EPSC waveforms were more uniform in boutons from hearing animals illustrated by the less variable decay time constant for the P20 afferent.
F
, Average time to peak and half-width for multiphasic EPSCs from cochleae of 12 P8–11 (time to peak: 1.1 ± 0.2 ms; half-width: 1.4 ± 0.6 ms; 4616 EPSCs), 14 P19–21 (time to peak: 0.6 ± 0.1 ms; half-width: 0.7 ± 0.3 ms; 2525 EPSCs), and 2 P60 (time to peak: 0.8 ± 0.003 ms; half-width: 0.6 ± 0.1; 2374 EPSCs) rats. Multiphasic EPSCs were significantly faster in boutons from hearing rats (time to peak: p < 0.0001; half-width: p = 0.0005, comparing P8–11 and P19–21 datasets).
G
, Plot of half-width against EPSC amplitude for every multiphasic EPSC from one P8 afferent (green squares) and one P20 afferent (black squares), same fibers as in
A
and
B
. Multiphasic EPSCs were significantly faster across the entire amplitude range.