Induction of L-LTD with 1-Hz stimulation was blocked by inhibitors of
translation and transcription. (a) Application of the
protein synthesis inhibitor anisomycin (30 μM) (beginning 15 min
before the 1-Hz depression protocol until 15 min afterward, horizontal
bar) blocked L-LTD for time points subsequent to 40 min
(n = 9). (b) When anisomycin
application was delayed until 30 min after the 1-Hz depression
protocol, there was no effect on L-LTD maintenance
(n = 3). (c) Similarly, when the
protein synthesis inhibitor emetine (20 μM) was applied (beginning 15
min before the 1-Hz stimulus until 15 min afterward), the induction of
L-LTD was prevented for time points later than 40 min
(n = 4). Field EPSPs after anisomycin or emetine
application were both significantly different from control EPSPs
(P < 0.01, measured 1 h after the 1-Hz
stimulus). (d) Application of the transcriptional
inhibitor actinomycin D (20 μM) (beginning 15 min before the 1-Hz
stimulus and continuing until 15 min afterward) blocked L-LTD for time
points subsequent to 60 min (n = 6;
P < 0.05, as compared with control EPSPs, measured
1 h after the 1-Hz stimulus).