Figure 1.
Binding affinities of Wf-516 and pindolol for central 5-HT1A receptors quantified by in vitro ARG.
(A) Representative autoradiograms showing distribution and intensity of [11C]WAY-100635 radiosignals in rat brain sections containing the hippocampus (arrows) and raphe nucleus (arrowhead) and its attenuation by different concentrations of Wf-516 or pindolol. (B) Inhibition curves of [11C]WAY-100635 binding to the hippocampus (closed symbols) and raphe nucleus (open symbols) by Wf-516 (left) and pindolol (right). Bars indicate S.E. (n = 3).
Figure 2.
Occupancies of 5-HT1A receptors by Wf-516 and pindolol assessed by ex vivo ARG.
(A) Representative autoradiograms showing distribution and intensity of [11C]WAY-100635 radiosignals in rat brain sections containing the hippocampus (arrows) and raphe nucleus (arrowhead) after oral administration of Wf-516 and intraperitoneal administration of pindolol. (B) Relationships between dose of Wf-516 (left) or pindolol (right) and 5-HT1A receptor occupancy in the hippocampus (closed symbols) and raphe nucleus (open symbols). Regression curves in the hippocampus and raphe nucleus are denoted by dashed lines and solid lines, respectively, and were generated by the following equation: Occ = 100×D/(D+ED50), where Occ is 5-HT1A receptor occupancy and D is the dose of the drug. Bars indicate S.E. (n = 3).
Figure 3.
Representative PET images showing distribution of [11C]WAY-100635 in rat brains after oral administration of Wf-516 and intraperitoneal administration of pindolol.
Each pretreatment drug was repeatedly administered to the same rat at different doses. PET images were generated by summation of dynamic data 60–90 min after intravenous injection of [11C]WAY-100635, and were overlaid on the MRI template displayed in the far left column. Coronal brain sections shown here were obtained at −5.2 mm (top row), −7.8 mm (middle row) and −12.5 mm (bottom row) from the bregma. ROIs were placed on the hippocampus (dotted lines), raphe nucleus (solid lines) and cerebellum (dashed lines).
Figure 4.
Time-radioactivity curves for [11C]WAY-100635 in the hippocampus (top panels), raphe nucleus (middle panels) and cerebellum (bottom panels) after pretreatments with Wf-516 (A) and pindolol (B) at representative doses.
Data were generated by placing ROIs on different brain structures on the PET images illustrated in Figure 3. Radiotracer uptake into each region was expressed as a percentage of the injected dose per unit tissue volume (%dose/mL). Bars indicate S.E. (n = 4 and 3 in Wf-516 and pindolol treatment groups, respectively).
Figure 5.
Time course of specific [11C]WAY-100635 binding to 5-HT1A receptors in the hippocampus (top panels) and raphe nucleus (bottom panels) after pretreatments with Wf-516 (A) and pindolol (B) at representative doses.
Data were generated by placing ROIs on different brain structures on the PET images illustrated in Figure 3. Binding was estimated as the difference in radiosignals between target and cerebellar regions, and expressed as the percentage of the injected dose per unit tissue volume (%dose/mL). Bars indicate S.E. (n = 4 and 3 in Wf-516 and pindolol treatment groups, respectively).
Table 1.
BPND of [11C]WAY-100635 and occupancy of 5-HT1A receptors by Wf-516 and pindolol.
Figure 6.
Relationships between dose or plasma concentration of test drugs and 5-HT1A receptor occupancies analyzed with [11C]WAY-100635-PET data.
(A) Receptor occupancies in the hippocampus (closed circles) and raphe nucleus (open circles) plotted against oral dose of Wf-516. Regression curves were generated by the following equation: Occ = Occmax×D/(D+ED50), where Occ, Occmax, D and ED50 are 5-HT1A receptor occupancy, maximal occupancy, dose of Wf-516, and dose of Wf-516 required for 50% of maximal occupancy, respectively. Bars indicate S.E. (n = 4). (B) Receptor occupancies in the hippocampus (closed squares) and raphe nucleus (open squares) plotted against intraperitoneal dose of pindolol. Regression curves were generated by the following equation: Occ = 100×D/(D+ED50). Bars indicate S.E. (n = 3). (C) Receptor occupancies in the hippocampus (closed squares) and raphe nucleus (open squares) plotted against plasma concentration of pindolol. Regression curves were generated by the following equation: Occ = 100×C/(C+EC50), where C is plasma concentration of pindolol. Dashed and solid lines represent regressions in the hippocampus and raphe nucleus, respectively.
Figure 7.
Alteration of BPND for [11C]WAY-100635 in rats treated with a toxicant for 5-HT neurons, 5,7-DHT.
Four rats each underwent three [11C]WAY-100635-PET scans, at baseline, after 5,7-DHT treatment, and after oral administration of 30 mg/kg Wf-516 (5,7-DHT + Wf-516), in the indicated chronological order. Each symbol represents individual BPND in the hippocampus (left) and raphe nucleus (right). These changes of BPND in each region were statistically examined by one-way repeated-measures ANOVA followed by least significant difference test. *p<0.05 compared with each baseline.
Figure 8.
Effects of Wf-516 and pindolol on autoradiographic [35S]GTPγS binding in rat brains.
(A) Representative autoradiograms showing radiolabeling with [35S]GTPγS in the hippocampus and raphe nucleus at baseline (control) or in the presence of 1 µM 8-OH-DPAT (full agonist for 5-HT1A receptors), 10 µM Wf-516, 10 µM pindolol and 1 µM WAY-100635 (full antagonist for 5-HT1A receptors). (B) Ratio of [35S]GTPgγS binding to the control level in the hippocampus (left) and raphe nucleus (right). Changes in radiotracer binding were statistically examined using one-way repeated-measures ANOVA followed by least significant difference test. *p<0.01 compared with 1 µM WAY-100635. In the raphe nucleus, a significant interaction between [35S]GTPγS binding and three concentrations each of Wf-516, pindolol and WAY-100635 was demonstrated by two-way repeated-measures ANOVA (p<0.05, F(4,20) = 3.58).