LTP induction is attenuated at puberty: reversal by the stress steroid THP. (A) TBS (dashed line) induced LTP (black) before puberty (Pre-pub, left) and in adult (right), but not in the pubertal (Pub, middle) CA1 hippocampus. THP (red, 30 nM) permitted LTP induction at puberty. (Inset) Representative field EPSPs. TBS, arrow. Scale, 0.5 mV, 50 ms. (B) Pubertal δ−/−. (C) Complete GABAR blockade (Pre-pub, black; Pub, blue). (D) Adult δ−/−. (E) Local application of THP (arrow) to stratum radiatum during TBS under synaptic GABA blockade. (F) THP (arrows) applied before TBS and after TBS (Pub).