Brain Uptake In Mice Research Articles

Synthesis and preliminary in vivo evaluation of 4‐[18F]fluoro‐N‐{2‐[4‐(6‐trifluoromethylpyridin‐2‐yl)piperazin‐1‐yl]ethyl}benzamide, a potential PET radioligand for the 5‐HT1A receptor

Abstract4‐Fluoro‐N‐{2‐[4‐(6‐trifluoromethylpyridin‐2‐yl)piperazin‐1‐yl]ethyl}benzamide is a full 5‐HT1A agonist with high affinity (pKi=9.3), selectivity and a c log P of 3.045. The corresponding PET radioligand 4‐[18F]fluoro‐N‐{2‐[4‐(6‐trifluoromethylpyridin‐2‐yl)piperazin‐1‐yl]ethyl}benzamide was synthesized by nucleophilic aromatic substitution on the nitro precursor. The fluorinating agent K[18F]F/Kryptofix 2.2.2 was both dried (9 min, 700 W) and incorporated in the precursor (5 min, 700 W) using a commercially available microwave oven. In a total synthesis time of 60 min, an overall radiochemical yield of 18% (SD=5, n=7, EOS) was obtained. Radiochemical purity was always higher than 99% and specific activity always higher than 81.4 GBq/µmol (2.2 Ci/µmol). Initial brain uptake in mice was 2.19% ID (5.47% ID/g, 2 min) but decreased rapidly (0.17% ID, 0.45% ID/g (60 min)). During the first 20 min p.i., radioactivity concentration of the brain was significantly higher than that of blood demonstrating good brain entry of the tracer. Copyright © 2004 John Wiley & Sons, Ltd.

Evaluation of anesthesia effects on [ 18F]FDG uptake in mouse brain and heart using small animal PET

This study evaluates effects of anesthesia on 18F-FDG (FDG) uptake in mouse brain and heart to establish the basic conditions of small animal PET imaging. Prior to FDG injection, 12 mice were anesthetized with isoflurane gas; 11 mice were anesthetized with an intraperitoneal injection of a ketamine/xylazine mixture; and 11 mice were awake. In isoflurane and ketamine/xylazine conditions, FDG brain uptake (%ID/g) was significantly lower than in controls. Conversely, in the isoflurane condition, %ID/g in heart was significantly higher than in controls, whereas heart uptake in ketamine/xylazine mice was significantly lower. Results suggest that anesthesia impedes FDG uptake in mouse brain and affects FDG uptake in heart; however, the effects in the brain and heart differ depending on the type of anesthesia used.

Rolipram depresses [(3)H]2-deoxyglucose uptake in mouse brain and heart in vivo.

The effects of systemic administration of rolipram, a selective phosphodiesterase type 4 inhibitor, on [(3)H]2-deoxyglucose (DG) uptake in brain and peripheral tissues were examined. Rolipram significantly and dose-dependently decreased [(3)H]DG uptake in brain, heart and skeletal muscle. In contrast, the radioactivity concentrations in the plasma of rolipram-treated mice were significantly higher than those of control mice at all times after injection of the tracer. In the kinetic study, the initial uptake of [(3)H]DG in brain was decreased by rolipram, whereas no significant differences were observed in the uptake in heart and skeletal muscle. However, radioactivity concentrations in the brain, heart and skeletal muscle 30 min after the injection of [(3)H]DG were significantly lowered by rolipram to about 60%, 10% and 10% of control values, respectively. The uptake of [(13)N]ammonia in brain and heart of rolipram-treated mice was slightly decreased, which indicated that rolipram diminished both cerebral and cardiac blood flow. These results indicate that the phosphorylation process via hexokinase rather than the transport of [(3)H]DG might be depressed by rolipram. Together with the previous observations that inhibition of protein kinase A (PKA) markedly enhanced [(14)C]DG uptake in rat brain, these results indicate an important role of the cAMP/PKA systems in the regulation of glucose metabolism in the living brain as well as in peripheral tissues such as the heart and skeletal muscle.

Synthesis and preliminary in vivo evaluation of 4‐[123I]iodo‐N‐{2‐[4‐(6‐trifluoromethyl‐2‐pyridinyl)‐1‐piperazinyl]ethyl}benzamide, a potential SPECT radioligand for the 5‐HT1A receptor

Abstract4‐[123I]Iodo‐N‐{2‐[4‐(6‐trifluoromethyl‐2‐pyridinyl)‐1‐piperazinyl]ethyl}benzamide (1. 123I), a potential SPECT 5‐HT1A radioligand, was synthesized by electrophilic iododestannylation of the tributyltin derivative with n.c.a. [123I]NaI and chloramine‐T under acidic conditions (20 min, ambient temperature). Radiochemical yield averaged around 60 % (sd = 8,n = 22). After HPLC purification, chemical purity was higher than 95 % and radiochemical purity higher than 99 %. Specific activity was always higher than 222 GBq/µmol (6 Ci/µmol). The calculated log P is 4.28. Initial brain uptake in NMRI mice was 1.16 % ID (2 min) and decreased slowly afterwards (0.51 % ID (2 h)). 60 min p.i., the majority of the radioactivity in plasma and brain was present as 1. 123I, respectively 75.15 % and 96.48 %. Copyright © 2001 John Wiley & Sons, Ltd.

Evaluation of 99mTc‐complexes with novel monoamine diamide (MADA) thiolate tetraligands: L‐cysteine acetyldiglycine diethyl ester and L‐β‐methylhomocysteinate acetyldiglycine ethyl ester

Compounds with a monoamine diamide (MADA) thiolate tetraligand structure (L-cysteine acetyldiglycine diethyl ester, L-CAG2D and L-β-methylhomocysteinate acetyldiglycine ethyl ester, L-HAG2ME) were synthesized and labelled with 99mTc to investigate the 99mTc-complexation characteristics of these tetraligands. On reversed-phase HPLC, 99mTc-L-CAG2D and 99mTc-L-HAG2ME each give two peaks, probably isomers. During electrophoresis, all isomers migrate towards the anode indicating a net anionic charge. Octanol-buffer partition coefficients were respectively −0.47 and −0.05 for the isomers of 99mTc-L-CAG2D and −0.51 and −0.32 for the isomers of 99mTc-L-HAG2ME. In addition, brain uptake of all HPLC-isolated isomers was low and did not exceed 0.1% of injected dose at 2 min, 10 min or 30 min post injection. It may be concluded that the MADA-type ligands lose their amine proton upon complexation with 99mTc resulting in hydrophilic, negatively charged 99mTc-complexes which do not exhibit significant brain uptake in mice. Copyright © 2000 John Wiley & Sons, Ltd.

Evaluation of99mTc-complexes with novel monoamine diamide (MADA) thiolate tetraligands:L-cysteine acetyldiglycine diethyl ester andL-β-methylhomocysteinate acetyldiglycine ethyl ester

Compounds with a monoamine diamide (MADA) thiolate tetraligand structure (L-cysteine acetyldiglycine diethyl ester, L-CAG2D and L-β-methylhomocysteinate acetyldiglycine ethyl ester, L-HAG2ME) were synthesized and labelled with 99mTc to investigate the 99mTc-complexation characteristics of these tetraligands. On reversed-phase HPLC, 99mTc-L-CAG2D and 99mTc-L-HAG2ME each give two peaks, probably isomers. During electrophoresis, all isomers migrate towards the anode indicating a net anionic charge. Octanol-buffer partition coefficients were respectively −0.47 and −0.05 for the isomers of 99mTc-L-CAG2D and −0.51 and −0.32 for the isomers of 99mTc-L-HAG2ME. In addition, brain uptake of all HPLC-isolated isomers was low and did not exceed 0.1% of injected dose at 2 min, 10 min or 30 min post injection. It may be concluded that the MADA-type ligands lose their amine proton upon complexation with 99mTc resulting in hydrophilic, negatively charged 99mTc-complexes which do not exhibit significant brain uptake in mice. Copyright © 2000 John Wiley & Sons, Ltd.

Novel 99mTc aminobisthiolato/monothiolato "3 + 1" mixed ligand complexes: structure-activity relationships and preliminary in vivo validation as brain blood flow imaging agents.

A series of neutral, lipophilic 99mTc mixed-ligand complexes of the general formula 99mTcOL1L2, where L1H2 is an N-substituted bis-(2-mercaptoethyl)amine, [X-CH2CH2N(CH2CH2SH)2], [SNS], and L2H is a monodentate thiol (RSH), [S], has been synthesized and evaluated in rodents for potential use in brain blood flow imaging. The complexes were prepared by ligand exchange reaction using 99mTc(V)O-glucoheptonate as precursor and equimolar quantities of the two ligands. In all cases the syn isomer was formed in a high yield, whereas the anti isomer was not always present. The formation of two isomeric complexes-syn and anti-was expected, since the N-substituent (X-CH2CH2N) can assume syn or anti configuration with respect to the 99mTcO3+ core during complexation. One anti and all syn isomers were isolated by HPLC. Their identity was confirmed by comparative HPLC studies with the analogous 99Tc complexes of established structure. In vivo distribution, in particular brain uptake and retention, greatly depended on the type of either tridentate (L1H2) or monodentate (L2H) ligand. All 99mTc complexes showed significant brain uptake in mice (0.78-4.35% injected dose per organ at 5 min postinjection). This initial uptake remained nearly constant for at least 30 min for most of the complexes. Structure-activity relationships of novel 99mTc(V)O SNS/S complexes in mice are reported and discussed. Selected complexes were further studied in rats. High brain uptake, comparable to that of 99mTc-d,l-HMPAO, and sufficient retention 60 min postinjection were provided with complex 18 [X = (C2H5)2N and R = p-CH3OC6H4CH2].

Synthesis and tissue distribution of substituted [ 125I]Iodophenylamine derivatives: Possible brain imaging agents

The synthesis and brain uptake in mice of the radioiodinated derivatives of N,N-dimethyl- N′-(iododimethoxyphenyl)-1, 3-propanediamine, as well as the N-substituted derivatives of (iodoalkylphenyl)isopropyl, iodoalkylphenylethylamine and 3,4-(methylenedioxy)phenyl-amphetamine (MDA) are described. These compounds contain structural features of both IMP and HIPDM, the cerebral perfusion agents currently in clinical use. The radiolabeled analogs were obtained via the [ 125I]I exchange method, or by [ 125I]NaI treatment of the iodo-free precursor in the presence of an oxidant. Following intravenous injection in mice, all compounds showed important radioactivity concentrations in the lungs and kidneys. The N-substituted (iodoalkylphenyl)isopropyl and iodoalkylphenyl-ethylamine derivatives displayed a high initial brain uptake (>10%IDg −1) followed by a rapid clearance phase, resulting in lower brain-to-blood ratios as those reported for IMP and HIPDM. In contrast, N,N-dimethyl- N′-(iododimethoxyphenyl)-1,3-propanediamine derivatives featuring the iodo substituent on the benzene carbon adjacent to the methyl amine group and the methoxy substituents on the 2,5- or 2,4-positions, showed low but more persistant brain uptake. Combined with fast blood clearance, this resulted in high brain-to-blood ratios at later time points. Among all compounds tested, the highest brain-to-blood ratio was observed with compound N,N-dimethyl- N′-(6-iodo-3,4-dimethoxyphenyl)-1, 3-propanediamine (27e), reaching a maximum of >20 at 12 h postinjection.

Synthesis and radiobiological applications of [ 35S] l-homocysteine thiolactone

[ 35S] l-Homocysteine thiolactone ([ 35S] l-HCTL) was synthesized and its biodistribution evaluated as a potential brain radioprotective agent and as a tissue hypoxia marker. Drug uptake in mouse brain exceeded that in s.c. tumor 3 h post injection only. Multiple indicator dilution experiments in the rabbit heart indicate that membrane permeability of [ 35S] l-HCTL does not limit its usefulness as a hypoxia marker. In addition, a positive correlation was observed between regional coronary blood flow and myocardial content of [ 35S]adenosylhomocysteine formed from [ 35S]homocysteine and adenosine.

5-HT 2 receptor binding and 5-HT uptake in mouse brain: developmental changes and the relationship to audiogenic seizure susceptibility in DBA/2J mice

Abnormal function of serotonergic neurones may be involved in the age-related susceptibility of DBA/2J mice to generalised convulsions induced by auditory stimulation. We have measured 5-HT 2 receptor binding sites and synaptosomal 5-HT uptake in 5 brain regions of DBA/2J mice at ages before, during and after their maximal susceptibility to audiogenic seizures and in age-matched C57 BI/6 mice, a strain resistant to audiogenic seizures at all ages. The number of 5-HT 2 binding sites was 20% higher in the cerebral cortex of DBA/2J than C57 BI/6 mice at the time of maximal susceptibility of DBA/2J mice to audiogenic seizures but did not differ at other ages. The number of 5-HT 2 binding sites did not differ between the two strains at the ages studied in forebrain, mid-brain, hippocampus and pons-medulla. A marked reduction in the number of 5-HT 2 binding sites was apparent in the mid-brain, hippocampus and pons-medulla of both strains of mice between 13–15 days of age and 21–23 days of age. Synaptosomal 5-HT uptake did not differ significantly between DBA/2J and C57 BI/6 in any of the brain regions at the ages studied. The higher density of cortical 5-HT 2 binding sites in DBA/2J mice may contribute to their susceptibility to sound-induced seizures.

Mouse brain uptake and metabolism of stearic acid

After injection, labelled stearic acid is transported directly into the brain and incorporated into brain lipids without prior oxydation to acetate and resynthesis of fatty acids. Contamination by blood can be excluded. (The preparation contains all subcellular fraction except cytosol). The labelled stearic acid taken up is partly metabolized in the brain either by elongation or by degradation and in situ resynthesis of fatty acids. The activity in oleic acid and mono-unsaturated chains is hardly detectable. The labelled acids are incorporated into lipids or subcellular particles following characteristic kinetics, which show a diminution by 24 hours. When analysing the evolution of each lipid, it is shown that this profile is followed by phospholipids, but not by cerebrosides and free fatty acids. The formers are still increasing up to 50 hours, the latters are stable (suggesting a physical binding between membranes and free fatty acids). Thus nutrition is an important parameter for the synthesis of brain membranes as far as exogenous saturated fatty acids are needed.

Effects of tetrahydro-β-carbolines on monoamine oxidase and serotonin uptake in mouse brain

Effects of tetrahydro-β-carbolines on monoamine oxidase and serotonin uptake in mouse brain