Figure 2.

Inhibition of hippocampal 5-HT2A receptors blocked the spacing effect, while activation of hippocampal 5-HT2A receptors promoted the spacing effect. (A₁,A₂) Diagram for experimental procedures. (B) Representative Nissl staining confirming the implantation sites of the guide cannulas. (C) Hippocampal administration of 5-HT2A receptor antagonist MDL11939 blocked the enhanced fear memory in the spaced training (n = 8). (D) Hippocampal administration of 5-HT2A receptor agonist TCB-2 enhanced fear memory in the massed training (n = 9). All results were presented as mean ± SEM, **p < 0.01, ***p < 0.001.