Figure 1

D4 receptor inhibition augments LTP. (a) A schematic representation of a transverse hippocampal slice showing the position of electrodes in the CA1 region of hippocampus. S1 represents a stimulation electrode used to stimulate a single neuronal population. ‘Rec’ represents a recording electrode. (b) Induction of late-LTP by a STET protocol resulted in a long-lasting LTP which was stable for 3 h (n = 9, filled circles). Induction of early-LTP using a WTET protocol resulted in weaker form of LTP which was stable for 90 min (n = 8, open circles). (c) When late-LTP was induced in presence of the D4R antagonist, L-745, 870 (50 nM) the fEPSPs increased to a level significantly higher than in control late-LTP (n = 7, filled circles). (d) A similar experiment as in (c) but with the induction of early-LTP instead of late-LTP (n = 8, filled circles) which resulted in the reinforcement of early-LTP to late-LTP. (e) Late-LTP was induced using a STET protocol; 30 min after the induction of late-LTP, L-745, 870 was applied for 60 min. L-745, 870 did not affect the maintenance of late-LTP (n = 6, filled circles). (f) L-745, 870 did not affect basal fEPSPs (n = 7, filled circles). Here after recording a stable baseline, L-745, 870 was applied for 60 min. Representative fEPSPs at −30 (dotted lines), +30 (dashed line) and 180 min (solid line). WTET represents weak tetanisation to induce early-LTP and STET represents strong tetanisation to induce late-LTP. Horizontal rectangular bars indicate the duration of drug application.