Figure 5.

Modulation by serotonin 5-HT2A agonist TCB2 (30 nM) of the 5-HT1A affinity is based on ³H-8-OH-DPAT/ipsipirone competition experiments in membrane preparations from the hippocampus (A, B) and frontal lobe (C, D). Thus, competition experiments involving 5-HT1A receptor agonist [³H]-8-OH-DPAT binding vs increasing concentrations of ipsipirone were performed in hippocampus (A) and frontal lobe (C) membranes in the presence or absence of the 5-HT2A agonist TCB2 (30 nM) as indicated. Nonspecific binding was defined as the binding in the presence of 200 μM serotonin. The curves are based on the mean ± SEM of five rats, each one performed in triplicate. The binding values are given in percent of specific binding at the lowest concentration of ipsipirone employed. A histogram of the K_i values (nM) obtained from the competition curves is shown for both the hippocampus (B) and frontal lobe (D). TCB2 (30 nM) produces a marked change in the reduction of the K_i values (p < 0.05) in the hippocampus (B) and frontal lobe (D). This change in the reduction of the K_i value is blocked by ketanserin (1 μM) (p < 0.05) in membrane preparation from the frontal lobe (D), one-way ANOVA followed by post hoc Turkey’s multiple comparison test. In the hippocampus, the ketanserin-treated group was not significant from control.