Effect of 5-HT receptor antagonists and agonists on the induction of LTP in 8-week-old rats. (A) The effect of 5-HT receptor antagonists on layer 2/3 LTP induced by TBS to layer 4 (indicated with arrow) in 8-week-old rats. NAN-190 (10 µM, n=7, open triangle), mesulergine (10 µM, n=6, closed circle) and Y-25130 (10 µM, n=5, open square) were co-applied into the bath with 5-HT (10 µM). The right panel shows the representative average traces in a slice marked with corresponding symbols, which were taken at the time period indicated with corresponding numbers. Scales represent 0.4 mV and 2 ms, respectively. (B) The effect of 5-HT receptor agonists on layer 2/3 LTP induced by TBS to layer 4 (indicated with arrow) in 8-week-old rats. 8-OH-DPAT (10 µM, n=7, open triangle), DOI (10 µM, n=7, closed circle) and 2-me-5-HT (10 µM, n=7, open square) were applied into the bath throughout the experiment. The right panel shows the representative average traces in a slice marked with corresponding symbols, which were taken at the time period indicated with corresponding numbers. Scales represent 0.4 mV and 2 ms, respectively. (C) Summary plot of the effect of antagonists for 5-HT receptor subtypes. *p<0.05 and ***p<0.001 compared with the baseline. (D) Summary plot of the effect of agonists for 5-HT receptor subtypes. *p<0.05 compared with the baseline.