Objective:To prepare ((2-(2-chlorophenyl)-3-(4-((2- 18F-fluoroethyl)oxy)phenyl)-5, 6, 7, 8-tetrahydrooxepino[3, 2-c]pyrazol-8-yl)amino)methanoic acid methyl ester ( 18F-JR-1001) and evaluate its binding affinity to the cannabinoid type 1 receptor (CB1R). Methods:18F-JR-1001 was synthesized using an integrated automated synthesis module, and its radiochemical yield (RCY) and molar activity were determined. Cell-specific uptake, lipid-water partition coefficient (log P), competitive binding assays, and in vitro stability tests were performed. Rimonabant-fed rat models (blocking group) with pre-occupied CB1R were established. Radioautography and microPET/CT imaging were conducted on both the blocking group and normal Sprague-Dawley (SD) rats to evaluate the brain uptake of 18F-JR-1001 and its blood-brain barrier (BBB) penetration capability. Results:The RCY of the synthetic 18F-JR-1001 after decay correction was (32.5±9.2)% ( n=10), with the molar activity of (194.6±67.3)GBq/μmol. Cell experiments demonstrated that 18F-JR-1001 exhibited specificity for CB1R, with log P of 3.40±0.11 ( n=3) and half-maximal inhibitory concentration of 0.975nmol/L. Within 3h at 37℃, the radiochemical purity of 18F-JR-1001 in physiological saline and blood remained above 92%, with no significant radioactive by-product peaks observed. Radioautography showed that the whole brain uptake of 18F-JR-1001 in the blocking group was 65.6% of that in normal SD rats. MicroPET/CT imaging showed that the mean whole brain uptake of 18F-JR-1001 in the blocking group was 0.4706, which was lower than that in normal SD rats (1.0561). Additionally, continuous scanning for 60min demonstrated that 18F-JR-1001 exhibited good BBB penetration capability. Conclusion:The synthesized 18F-JR-1001 meets the requirements of production and application, and is proved the potential as a CB1R-targeted tracer in the in vitro experiments, microPET/CT imaging and radioautography.

Objective:To develop and validate a novel PET tracer, N-cyclohexyl-4-((2, 4-dichlorophenyl)(4-(fluoro- 18F)phenyl)methyl)piperazine-1-carboxamide ( 18F-SQKJ-2), targeting cannabinoid type 1 (CB1) receptors for diagnosing psychiatric disorders associated with fear memory. Methods:18F-SQKJ-2 was prepared using a nucleophilic substitution radiochemical synthesis method. For the CB1 receptor blocking experiment, 7 ICR mice were divided into blocking group ( n=4; rimonabant for blocking treatment) and control group 1 ( n=3; no rimonabant blocking treatment). The affinity and specificity of 18F-SQKJ-2 for CB1 receptors were analyzed based on the differences in 18F-SQKJ-2 uptake (percentage injected dose per gram of tissue, %ID/g) by various organs between two groups. The metabolic stability of 18F-SQKJ-2 in vitro was studied using animal tissue homogenates. Ten C57 mice were used to establish fear memory mouse models (fear group, n=6; control group 2, n=4), and the percentage of freezing time was compared between 2 groups. MicroPET scans were used to detect the intracranial distribution of 18F-SQKJ-2, and the relative uptake in each brain region compared to total brain uptake was calculated. Statistical analysis was conducted to compare the differences in CB1 receptor relative total brain uptake in fear-related brain regions between 2 groups. Independent-sample t test and Mann-Whitney U test were used to analyze the data. Results:18F-SQKJ-2 was successfully synthesized with a radiochemical purity ≥98.0% and a corrected radioactive yield of (12.3±6.0)%( n=4). In vitro metabolic stability experiments showed that 18F-SQKJ-2 was basically stable in the liver, blood, and brain within 60min. The CB1 receptor blocking experiment demonstrated that the uptake of 18F-SQKJ-2 in the brains of mice in blocking group was significantly lower than that in control group 1 ((0.95±0.28) vs (3.44±1.16) %ID/g; t=-3.57, P=0.023). The percentage of freezing time in fear group was significantly higher than that in control group 2 (43.28%(39.46%, 52.93%) vs 2.74%(1.52%, 4.85%); Z=-2.45, P=0.010). 18F-SQKJ-2 microPET imaging showed that the uptake of 18F-SQKJ-2 in the cerebral cortex of mice in fear group was significantly increased compared with that in control group 2 ((5.83±0.47)% vs (5.00±0.52)%; t=2.42, P=0.046). Conclusion:18F-SQKJ-2 is successfully prepared with acceptable radiochemical purity and metabolic stability, demonstrating potential for visualizing and quantifying fear memory.

Objective:To prepare ((2-(2-chlorophenyl)-3-(4-((2- 18F-fluoroethyl)oxy)phenyl)-5, 6, 7, 8-tetrahydrooxepino[3, 2-c]pyrazol-8-yl)amino)methanoic acid methyl ester ( 18F-JR-1001) and evaluate its binding affinity to the cannabinoid type 1 receptor (CB1R). Methods:18F-JR-1001 was synthesized using an integrated automated synthesis module, and its radiochemical yield (RCY) and molar activity were determined. Cell-specific uptake, lipid-water partition coefficient (log P), competitive binding assays, and in vitro stability tests were performed. Rimonabant-fed rat models (blocking group) with pre-occupied CB1R were established. Radioautography and microPET/CT imaging were conducted on both the blocking group and normal Sprague-Dawley (SD) rats to evaluate the brain uptake of 18F-JR-1001 and its blood-brain barrier (BBB) penetration capability. Results:The RCY of the synthetic 18F-JR-1001 after decay correction was (32.5±9.2)% ( n=10), with the molar activity of (194.6±67.3)GBq/μmol. Cell experiments demonstrated that 18F-JR-1001 exhibited specificity for CB1R, with log P of 3.40±0.11 ( n=3) and half-maximal inhibitory concentration of 0.975nmol/L. Within 3h at 37℃, the radiochemical purity of 18F-JR-1001 in physiological saline and blood remained above 92%, with no significant radioactive by-product peaks observed. Radioautography showed that the whole brain uptake of 18F-JR-1001 in the blocking group was 65.6% of that in normal SD rats. MicroPET/CT imaging showed that the mean whole brain uptake of 18F-JR-1001 in the blocking group was 0.4706, which was lower than that in normal SD rats (1.0561). Additionally, continuous scanning for 60min demonstrated that 18F-JR-1001 exhibited good BBB penetration capability. Conclusion:The synthesized 18F-JR-1001 meets the requirements of production and application, and is proved the potential as a CB1R-targeted tracer in the in vitro experiments, microPET/CT imaging and radioautography.

Objective:To develop and validate a novel PET tracer, N-cyclohexyl-4-((2, 4-dichlorophenyl)(4-(fluoro- 18F)phenyl)methyl)piperazine-1-carboxamide ( 18F-SQKJ-2), targeting cannabinoid type 1 (CB1) receptors for diagnosing psychiatric disorders associated with fear memory. Methods:18F-SQKJ-2 was prepared using a nucleophilic substitution radiochemical synthesis method. For the CB1 receptor blocking experiment, 7 ICR mice were divided into blocking group ( n=4; rimonabant for blocking treatment) and control group 1 ( n=3; no rimonabant blocking treatment). The affinity and specificity of 18F-SQKJ-2 for CB1 receptors were analyzed based on the differences in 18F-SQKJ-2 uptake (percentage injected dose per gram of tissue, %ID/g) by various organs between two groups. The metabolic stability of 18F-SQKJ-2 in vitro was studied using animal tissue homogenates. Ten C57 mice were used to establish fear memory mouse models (fear group, n=6; control group 2, n=4), and the percentage of freezing time was compared between 2 groups. MicroPET scans were used to detect the intracranial distribution of 18F-SQKJ-2, and the relative uptake in each brain region compared to total brain uptake was calculated. Statistical analysis was conducted to compare the differences in CB1 receptor relative total brain uptake in fear-related brain regions between 2 groups. Independent-sample t test and Mann-Whitney U test were used to analyze the data. Results:18F-SQKJ-2 was successfully synthesized with a radiochemical purity ≥98.0% and a corrected radioactive yield of (12.3±6.0)%( n=4). In vitro metabolic stability experiments showed that 18F-SQKJ-2 was basically stable in the liver, blood, and brain within 60min. The CB1 receptor blocking experiment demonstrated that the uptake of 18F-SQKJ-2 in the brains of mice in blocking group was significantly lower than that in control group 1 ((0.95±0.28) vs (3.44±1.16) %ID/g; t=-3.57, P=0.023). The percentage of freezing time in fear group was significantly higher than that in control group 2 (43.28%(39.46%, 52.93%) vs 2.74%(1.52%, 4.85%); Z=-2.45, P=0.010). 18F-SQKJ-2 microPET imaging showed that the uptake of 18F-SQKJ-2 in the cerebral cortex of mice in fear group was significantly increased compared with that in control group 2 ((5.83±0.47)% vs (5.00±0.52)%; t=2.42, P=0.046). Conclusion:18F-SQKJ-2 is successfully prepared with acceptable radiochemical purity and metabolic stability, demonstrating potential for visualizing and quantifying fear memory.