橋本 謙二

The role of a receptors in the induction of heat shock protein (HSP)-70 by non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists (+)-MK-801 (dizocilpine) and phencyclidine (PCP) was studied. HSP-70 is induced in the posterior cingulate and retrosplenial cortex of rat brain 24 hours after a single administration of dizocilpine (1 mg/kg) or PCP (50 mg/kg). The induction of heat shock protein HSP-70 by dizocilpine or PCP was attenuated partially by pre-treatment with the antipsychotic drug haloperidol (3 mg/kg, i.p., 15 minutes previously). However, pre-treatment with high potent and selective a receptor ligands, 4-phenyl-4-(1-phenylbutyl)piperidine (4-PPBP, 3 mg/kg, i.p., 15 minutes previously) and N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine monohydrochloride) (NE-100, 3 mg/kg, i.p., 15 minutes previously) did not alter the induction of HSP-70 by dizocilpine or MCP. These findings suggest that a receptors may not play a significant role in the induction of HSP-70 by non-competitive NMDA receptor antagonists dizocilpine and PCP, and that protective effects of haloperidol on induction of HSP-70 protein by dizocilpine or PCP may be due to other effect(s) except a receptors.

Iyo M, Bi Y, Hashimoto K, Tomitaka SI, Inada T, Fukui S, Annals of the New York Academy of Sciences, 1996, vol. 801, pp. 377-383

Amantadine (1-aminoadamantane) induced Fos expression in the central, dorsal-medial and ventral-medial part of the striatum. The distribution pattern of Fos induced by amantadine was more similar to those seen with dopaminomimetics than with N-methyl-d-aspartate (NMDA) receptor antagonists. Pretreatment with the dopamine D1 receptor antagonist, SCH23390, and the NMDA receptor antagonist, MK-801, blocked amantadine induction of Fos in the striatum. However, amantadine induction of Fos in the striatum was unaffected by the dopamine D2 receptor antagonist, sulpiride. These results suggest that amantadine induction of Fos in the rat striatum is related to dopamine D1 and NMDA receptors. © 1995.

We studied the mechanism of antagonism of p-chloroamphetamine-induced neurotoxicity by dextromethorphan. The pretreatment with potent and selective sigma receptor ligands, 4-phenyl-4-(1-phenylbutyl)piperidine (4-PPBP) and N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine monohydrochloride (NE-100), did not alter the reduction of 5-hydroxytryptamine and 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in the cerebral cortex by repeated administration of p-chloroamphetamine. These results suggest that sigma receptors might not play a significant role in the antagonism of p-chloroamphetamine-induced neurotoxicity by dextromethorphan.

We studied the mechanism of antagonism of p-chloroamphetamine-induced neurotoxicity by dextromethorphan. The pretreatment with potent and selective σ receptor ligands, 4-phenyl-4-(1-phenylbutyl)piperidine (4-PPBP) and N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine monohydrochloride (NE-100), did not alter the reduction of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in the cerebral cortex by repeated administration of p-chloroamphetamine. These results suggest that σ receptors might not play a significant role in the antagonism of p-chloroamphetamine-induced neurotoxicity by dextromethorphan. © 1995.

We investigated the effects of rolipram, a selective cyclic adenosine 3',5'-monophosphate phosphodiesterase type IV inhibitor, and isobutylmethylxanthine, a nonselective phosphodiesterase inhibitor, on purposeless spontaneous chewing movements and tongue protrusions produced by 24 weeks treatment with haloperidol decanoate (25 mg/kg every 4 weeks i.m.) in rats, to examine our hypothesis that restoration of striatal cyclic adenosine 3',5'-monophosphate levels previously reduced due to dopamine D-2 receptor supersensitivity, may suppress these movements. Tests were performed 8 weeks after the final injection. Haloperidol treatment significantly increased dyskinetic movements and striatal dopamine D-2 receptor density compared with controls. Rolipram (0.1-1.0 mg/kg i.p.) suppressed these movements in a dose-dependent manner, whereas isobutylmethylxanthine (2 mg/kg i.p.) only slightly suppressed the syndrome and doses higher than 5 mg/kg i.p, produced other intensive movements. These results support our hypothesis and suggest that rolipram may have a therapeutic effect on tardive dyskinesia.

Since striatal dopamine D2 receptor supersensitivity in the etiology of tardive dyskinesia has been suggested and dopamine D2 receptors are known to inhibit adenylate cyclase activity resulting in a decrease of cyclic adenosine 3′,5′-monophosphate (cAMP) levels, we hypothesized that an increase in cAMP levels ameliorates the condition. In the present study, 21-day haloperidol treatment (1.5 mg/kg I.P.) in rats resulted in an increase in striatal [3H]-spiperone (D2) binding whereas [3H] SCH23390 (D1) binding was unaltered. This haloperidol treatment also induced a significantly increase in the frequency of involuntary chewing movements and tongue protrusions, which are considered as a model of tardive dyskinesia. These dyskinetic movements were suppressed by administration of rolipram (0.5 and 1.0 mg/kg I.P.), an inhibitor of the cAMP phosphodiesterase type IV. The present results suggest that selective cAMP phosphodiesterase type IV inhibitors could be putative therapeutic drugs for tardive dyskinesia. © 1995.

4‐Phenyl‐1‐(4‐phenylbutyl)piperidine(4‐PPBP) is a very potent ligand for σ (Sigma) receptors. The present study was undertaken to evaluate [3H]4‐PPBPas a radioligand for in vivo labeling of cerebral σ receptors. After intravenous administration of [3H]4‐PPBP to mice, there is high uptake of radioactivity in the brain. The regional distribution of radioactivity in the brain 2 h after intravenous injection of [3H]4‐PPBP parallels the in vitro binding of the radioligand in rat brain (pons/medulla &gt cerebellum ≥ prefrontal cortex ≥ parietal cortex &gt hypothalamus &gt olfactory tubercle ≥ thalamus &gt hippocampus &gt striatum). Pretreatment with haloperidol (2 mg/kg) significantly decreases the radioactivity measured in the brain 30–120 min after injection of [3H]4‐PPBP. Pretreatment with unlabeled 4‐PPBP or ifenprodil also significantly decreases radioactivity in the brain 2 h after injection of [3H]4‐PPBP, in a dosedependent manner. The in vivo binding of [3H]4‐PPBP in the brain also is significantly inhibited by SL 82.0715, BMY 14802, 1,3‐di‐o‐tolylguanidine (DTG), and (+)‐enantiomers of pentazocine, SKF 10,047, and 3‐PPP, but not by the corresponding (−)‐enantiomers, consistent with stereoselectivity of inhibition obtained in in vitro binding studies. In contrast, pretreatment with dizocilpine and spiperone does not inhibit in vivo binding of [3H]4‐PPBP. The results indicate that [3H]4‐PPBP would be a suitable radioligand for in vivo labeling of σ receptors in brain. © 1995 Wiley‐Liss, Inc. . Copyright © 1995 Wiley‐Liss, Inc.

The reduction of 5-hydroxytryptamine (5-HT) in rat brain 3 h after administration of 3,4-methylenedioxymethamphetamine (MDMA) was attenuated significantly by coadministration of benzylpiperazine derivatives (p-nitrobenzylpiperazine, p-chlorobenzylpiperazine and 1-piperonylpiperazine), which were weak inhibitors of [3H]5-HT uptake into rat brain synaptosomes. However, the coadministration of desipramine and imipramine which were more potent 5-HT uptake inhibitors than these benzylpiperazines, did not attenuate the reduction of 5-HT by MDMA. These results suggest that these benzylpiperazines might inhibit the acute effects of MDMA by a novel neuropharmacological effect other than 5-HT uptake inhibition. © 1993.

The neurotoxicity of 3,4-methylenedioxymethamphetamine (MDMA) in rat brain was attenuated significantly by coadministration of several benzylpiperazines (p-nitrobenzylpiperazine, p-chlorobenzylpiperazine and 1-piperonylpiperazine), which were weak inhibitors for [3H]6-nitroquipazine binding to the 5-hydroxytryptamine (5-HT) transporter in rat brain. These results suggest that these benzylpiperazines may inhibit the MDMA-induced neurotoxicity by a novel neuropharmacological effect other than 5-HT uptake inhibition. © 1992.

[3H]6-Nitroquipazine bound to rat lung membranes at 37° with a dissociation constant (Kd) of 0.310 ± 0.13 nM and a maximal number of binding sites (Bmax) of 1752 ± 334 fmol/mg protein (mean ± SD, N = 4). The binding was saturable, of high affinity and sodium dependent. Drug inhibition studies indicated that [3H]6-nitroquipazine binding in the lung is similar to that already reported in the rat brain and human platelets. Scatchard analysis indicated that 5-hydroxytryptamine (5-HT) inhibited [3H]6-nitroquipazine binding to rat lung membranes in a competitive manner. The present results suggest that [3H]6-nitroquipazine binding sites in the rat lung are associated with the uptake system of 5-HT. © 1991.

The characteristics of the binding [3H]6-nitroquipazine, a very potent and selective inhibitor of 5-hydroxytryptamine (5-HT serotonin) uptake, to human platelet membranes were studied at a physiological temperature of 37°C. The presence of a single saturable high-affinity binding component for [3H]6-nitroquipazine was demonstrated. Non-specific binding was estimated in the presence of 1 μM paroxetine. Scatchard analysis revealed an apparent equilibrium dissociation constant (Kd) of 0.450 ± 0.04 nM and a maximal number of binding sites (Bmax) of 2508 ± 360 fmol/mg protein (mean ± S.D., n = 4). The kinetically derived dissociation constant (Kd) was 0.431 nM. [3H]6-Nitroquipazine binding was inhibited selectively by 5-HT uptake inhibitors, and the potency of various drugs to inhibit [3H]6-nitroquipazine binding closely correlated with their inhibitory effects on [3H]5-HT uptake into synaptosome. Moreover, Ki values for drug inhibition of [3H]6-nitroquipazine binding to human platelet membranes were significantly correlated with the corresponding Ki values for inhibition of [3H]paroxetine binding at 37°C. The present results suggest that the binding sites for [3H]6-nitroquipazine are associated with the 5-HT transporter in human platelets. © 1990.

6-Nitroquipazine is a very potent and selective inhibitor of neuronal 5-hydroxytryptamine (5-HT serotonin) uptake. We have characterized the specific binding of [3H]6-nitroquipazine to rat brain membranes at 22°C. The present results indicate the presence of a single saturable high-affinity binding component for [3H]6-nitroquipazine. Scatchard analysis revealed an apparent equilibrium dissociation constant (Kd) of 93.0 ± 2.23 pM, and a maximal number of binding sites (Bmax) of 831.7 ± 18.7 fmol/mg protein (mean ± S.D., n = 4). The kinetically derived dissociation constant was 74.5 pM. [3H]6-Nitroquipazine binding was inhibited selectively by 5-Ht uptake inhibitors, and a good correlation was demonstrated between the potency of various drugs to inhibit [3H]6-nitroquipazine binding and [3H]5-HT uptake. The highest densities of [3H]6-nitroquipazine binding were obtained in the hypothalamus and midbrain, intermediate binding was observed in the striatum, hippocampus, medulla oblongata and cortex, and the lowest binding was observed in the cerebellum. Lesioning of 5-HT neurons with p-chloroamphetamine resulted in a 72% reduction in [3H]6-nitroquipazine binding compared to controls. These results indicate that the binding site specifically labelled by [3H]6-nitroquipazine is associated with the neuronal 5-HT transporter complex. [3H]6-Nitroquipazine is an excellent radioligand for the study of the 5-HT uptake system. © 1990.

The synthesis of 6-nitroquipazine, a very potent and selective 5-hydroxytryptamine (5-HT; serotonin) uptake inhibitor, labeled with tritium is described. High specific activity [³H] 6-nitroquipazine could be prepared by the nitration of [³H] quipazine using a mixture of equal volumes of sulfuric acid and nitric acid. The radiochemical yield was approximately 50% based on [³H] quipazine. The radiochemical purity was more than 95% from high performance liquid chromatography (HPLC) and thin layer chromatography (TLC) determinations. [³H] 6-Nitroquipazine would be a new suitable radioligand for studying 5-HT transporter complex in brain and platelets.

³H-paroxetine投与後の脳各部位における放射能分布は, 視床下部において最も高く, つぎに大脳皮質において中程度であり, 小脳は最も少なかった。また, 視床下部および大脳皮質における放射能分布は6-nitroquipazineとparoxetineの投与によって有意に減少した。以上の結果より, ³H-paroxetnieはマウス脳内セロトニン再吸収部位のインビボ研究に有用なラジオリガンドになることが分かった。

Carbon-11-labeled N,N-dimethylphenylethylamine ([11C]DMPEA) was synthesized by the reaction of N-methylphenylethylamine with [11C]methyl iodide. This newly synthesized radiotracer was developed for the purpose of in vivo measurement of monoamine oxidase-B activity in the brain using a metabolic trapping method. Initially, biodistribution was investigated in mice. The rapid and high uptake of 11C radioactivity in the brain was observed following intravenous injection of [11C]DMPEA, the peak of which was reached at 1 min, followed by a decrease at 1-5 min and slowly thereafter. The kinetics of [11C]DMPEA in the human brain were determined using positron emission tomography (PET) and showed that 11C radioactivity increased gradually over 60 min following initial rapid uptake of 11C radioactivity, with basal ganglia and thalamus showing high accumulation.

Using 11C-labeled Ro15-1788 and positron emission tomography, studies of benzodiazepine binding sites in the human brain were performed on four normal volunteers. Rapid and high accumulation of 11C activity was observed in the brain after i.v. injection of [11C]Ro15-1788, the maximum of which was within 12 min. Initial distribution of 11C activity in the brain was similar to the distribution of the normal cerebral blood flow. Ten minutes after injection, however, a high uptake of 11C activity was observed in the cerebral cortex and moderate uptake was seen in the cerebellar cortex, the basal ganglia, and the thalamus. The accumulation of 11C activity was low in the brain stem. This distribution of 11C activity was approximately parallel to the known distribution of benzodiazepine receptors. Saturation experiments were performed on four volunteers with oral administration of 0.3-1.8 mg/kg of cold Ro15-1788 prior to injection. Initial distribution of 11C activity following injection peaked within 2 min and then the accumulation of 11C activity decreased rapidly and remarkably throughout the brain. The results indicated that [11C] Ro15-1788 associates and dissociates to specific and nonspecific binding sites rapidly and has a high ratio of specific receptor binding to nonspecific binding in vivo. Carbon-11 Ro15-1788 is a suitable radioligand for the study of benzodiazepine receptors in vivo in humans.

The potency of PK11195, which is a potent antagonist of peripheral type benzodiazepine receptor, as a radioligand for the in vivo study was evaluated by using 3H-labelled compound. 3H-PK11195 was highly distributed into mouse lung, heart and adrenal within 1 min after intravenous injection, and radioactivity in lung and heart rapidly decreased, while radioactivity in adrenal slightly increased. Saturation study using carrier Ro5-4864 indicated that more than 75% of total radioactivity in lung and heart was due to the specific binding with receptor, however the specific binding of this tracer in brain and adrenal was not clear in this study. This preliminary result strongly suggested that 11C-PK11195 has a high potential as a radiopharmaceutical for the in vivo study of peripheral type benzodiazepine receptor function especially in lung, heart and adrenal.

Ethyl 8-fluoro-5,6-dihydro-5-[11C]methyl-6-oxo-4H-imidazo [1,5-a][1,4]benzodiazepine-3-carboxylate ([11C]RO 15-1788) has been prepared automatically with high specific activity for in vivo visualization or quantitative analysis of brain benzodiazepine receptors. The yield, radiochemical yield, radiochemical purity and specific activity of the product ready for an i.v. injection were 276 ± 76 mCi, 50.8 ± 7.8%,99.3 ± 0.3% and 2.9 ± 0.5 Ci/μmol, respectively, taking an average of the latest 3 runs. The time required was about 25 min. Each product was sufficient to carry out three successive clinical studies by positron emission tomography (PET). All the procedures other than evaporation and filtration at the final stage were carried out with specially designed equipment connected to a central control system for radioisotope production. © 1985.