Aa, histogram depicting the increase in sEPSC frequency induced by two successive applications of 5-HT (30 μm). Ab, plot comparing the response elicited by 5-HT (30 μm; n = 4) on consecutive administrations. Although the second 5-HT administration tended to elicit somewhat smaller responses, this difference did not reach statistical significance (P = 0.2, Student's paired t test). Ba, histogram illustrating the antagonism of the 5-HT-induced increase in sEPSCs by SB-269970 (1 μm). Bb, plot summarizing the effect of SB-269970 (1 μm). SB-269970 significantly inhibited the effect of 5-HT on sEPSCs (n = 6; P < 0.01, Student's paired t test).