Biomedical subjects

S Okuyama

Publications and source records attributed to S Okuyama.

At least 55 records · Page 3Linked to original sources

PubMed1999

Receptor binding, behavioral, and electrophysiological profiles of nonpeptide corticotropin-releasing factor subtype 1 receptor antagonists CRA1000 and CRA1001.

Receptor binding, behavioral, and electrophysiological profiles of 2-[N-(2-methylthio-4-isopropylphenyl)-N-ethylamino]-4-[4-(3-flu orophe nyl)-1,2,3,6-tetrahydropyridin-1-yl)-6-methylpyrimidine (CRA1000) and 2-[N-(2-bromo-4-isopropylphenyl)-N-ethylamino]-4-[4-(3-fluoropheny l)- 1,2,3,6-tetrahydropyridin-1-yl)-6-methylpyrimidine (CRA1001), putative novel and selective antagonists for corticotropin-releasing factor1 (CRF1) receptor were examined. Both CRA1000 and CRA1001 inhibited 125I-ovine CRF binding to membranes of rat frontal cortex with IC50 values of 20.6 and 22.3 nM, respectively. Likewise, CRA1000 and CRA1001 inhibited 125I-ovine CRF binding to membranes of rat pituitary. In contrast, both CRA1000 and CRA1001 were without affinity for the CRF2beta receptor when examined using rat heart. In mice orally administered CRA1000 and CRA1001 reversed the swim stress-induced reduction of the time spent in the light area in the light/dark exploration task. In nonstress conditions, CRA1000 and CRA1001 were without effect on the time spent in the light area in the same task in mice. Orally administered CRA1000 and CRA1001 dose dependently reversed the effects of i.c.v. infusion of CRF on time spent in the open arms in the elevated plus-maze in rats. Lesioning of olfactory bulbs induced hyperemotionality, and this effect was inhibited by either acute or chronic oral administration of CRA1000 and CRA1001 in rats. The firing rate of locus coeruleus neurons was increased by i.c.v.-infused CRF. This excitation of locus coeruleus neurons was significantly blocked by pretreatment with i.v. administration of CRA1000 and CRA1001. CRA1000 and CRA1001 had no effects on the hexobarbital-induced anesthesia in mice, the rotarod test in mice, the spontaneous locomotor activity in mice, and a passive avoidance task in rats. These observations indicate that both CRA1000 and CRA1001 are selective and competitive CRF1 receptor antagonists with potent anxiolytic- and antidepressant-like properties in various experimental animal models, perhaps through inhibition of CRF1 receptors. CRA1000 and CRA1001 may prove effective for treating subjects with depression- and/or anxiety-related disorders without the side effects seen in the related currently prescribed medications.

Animals↗

PubMed1999

In vivo receptor labeling of peripheral benzodiazepine receptor by ex vivo binding of [3H]PK11195.

In vivo receptor labeling of the peripheral benzodiazepine receptor was investigated using ex vivo binding of [3H]-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline-carb ox-amide ([3H]PK11195). In autoradiographic studies, high level specific binding of [3H]PK11195 was observed in the olfactory bulb. Intravenous administration of PK11195 dose-dependently (0.03-3 mg/kg) inhibited ex vivo binding of [3H]PK11195 in the olfactory bulb. Likewise, N-(2,5-dimethoxybenzyl)-N-(5-fluoro-2-phenoxyphenyl)acetamide (DAA1106), a newly identified peripheral benzodiazepine receptor-specific ligand, dose-dependently (0.1-100 mg/kg) reduced ex vivo binding of [3H]PK11195, when administered intraperitoneally. In contrast, clonazepam, a central benzodiazepine receptor-specific agonist, had negligible effects on ex vivo binding of [3H]PK11195. We propose that the ex vivo receptor binding technique we used will facilitate determination of in vivo receptor occupancy of the peripheral benzodiazepine receptor.

Animals↗

PubMed1998

A novel E2F binding protein with Myc-type HLH motif stimulates E2F-dependent transcription by forming a heterodimer.

The human embryonal carcinoma cells NEC14 can be induced to differentiate morphologically by the addition of 10(-2) M N, N'-hexamethylene-bis-acetamide and cease to grow in several days. Transcription factors of the E2F/DP family have been shown to be closely related to the regulation of cell proliferation. To analyse cellular proteins which interact with E2F in NEC14 cells, cDNA clones encoding E2F binding proteins were isolated from a lambdaZAP II NEC14 cell library with the 32P-labeled GST (Glutathione S-transferase)-E2F-1 fusion protein as a probe. One of the clones encodes E2FBP1 which has the helix-loop-helix (HLH) motif, but lacks the basic domain and the zipper structure usually found at N- and C-terminal sides to the HLH motif, respectively. The arrangement of amino acids in the helix 1 and helix 2 regions is quite similar to those of Mxi and Mad, but different from those of E2F-1 and DP-1. Western blot analysis of the immunoprecipitates prepared with anti-E2FBP1 antibody showed that E2FBP1 associates with both E2F-1 and DP-1 in vivo. E2FBP1 alone has no DNA binding activity, but bind to the E2F site through heterodimerization with E2F-1 but not with DP-1. Although E2FBP1 lacks the transactivation domain, it stimulates E2F site-dependent transcription in cooperation with E2F-1.

Acetamides↗

PubMed1998

Functions of the two glutamate transporters GLAST and GLT-1 in the retina.

In the retina, the glutamate transporter GLAST is expressed in Müller cells, whereas the glutamate transporter GLT-1 is found only in cones and various types of bipolar cells. To investigate the functional role of this differential distribution of glutamate transporters, we have analyzed GLAST and GLT-1 mutant mice. In GLAST-deficient mice, the electroretinogram b-wave and oscillatory potentials are reduced and retinal damage after ischemia is exacerbated, whereas GLT-1-deficient mice show almost normal electroretinograms and mild increased retinal damage after ischemia. These results demonstrate that GLAST is required for normal signal transmission between photoreceptors and bipolar cells and that both GLAST and GLT-1 play a neuroprotective role during ischemia in the retina.

ATP-Binding Cassette Transporters↗

PubMed1998

Regulation of NMDA-induced [3H]dopamine release from rat hippocampal slices through sigma-1 binding sites.

To examine the interaction between ionotropic glutamate receptors and sigma binding sites, we made use of [3H]dopamine release from rat hippocampal slices. Agonists for ionotropic glutamate receptors such as N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and kainate evoked release of [3H]dopamine from rat hippocampal slices, in a dose-dependent manner. (+)-Pentazocine, a prototype sigma1 agonist, attenuated the NMDA-induced [3H]dopamine release dose-dependently and significantly as did non-competitive NMDA antagonists such as 5-methyl-10,11-dihydro-5H-dibenzo(a,b)cyclohepten-5,10-imine maleate (MK-801) and phencyclidine. In contrast, (+)-pentazocine had no effect on AMPA- or on kainate-induced [3H]dopamine release. Sigma-1 receptor antagonists including N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl] ethylamine monohydrochloride (NE-100), 1(cyclopropylmethyl)-4-(2'-(4"-fluorophenyl)-2'-oxoethylpiperidine (DuP734) and 1-(cyclopropylmethyl)-4-(2',4"-cianophenyl)-2'-oxoethyl)-pip eridine hydrobromide (XJ448) prevented significantly the inhibitory effect of (+)-pentazocine on NMDA-induced [3H]dopamine release, without affecting the release of [3H]dopamine evoked by NMDA. The inhibitory effect of (+)-pentazocine on [3H]dopamine release was preserved even in the presence of tetrodotoxin. These results suggest that sigma1 binding sites selectively interact with the NMDA receptor channel complex among ionotropic glutamate receptors, and that sigma1 binding sites may be involved in modulating the release of dopamine in the rat hippocampus by interacting with the NMDA receptor on dopaminergic nerve terminal.

Animals↗

PubMed1998

Motor discoordination and increased susceptibility to cerebellar injury in GLAST mutant mice.

To study the function of GLAST, a glutamate transporter highly expressed in the cerebellar Bergmann astrocytes, the mouse GLAST gene was inactivated. GLAST-deficient mice developed normally and could manage simple coordinated tasks, such as staying on a stationary or a slowly rotating rod, but failed more challenging task such as staying on a quickly rotating rod. Electrophysiological examination revealed that Purkinje cells in the mutant mice remained to be multiply innervated by climbing fibres even at the adult stage. We also found that oedema volumes in the mutant mice increased significantly after cerebellar injury. These results indicate that GLAST plays active roles both in the cerebellar climbing fibre synapse formation and in preventing excitotoxic cerebellar damage after acute brain injury.

ATP-Binding Cassette Transporters↗

PubMed1998

[Data management for clinical trials at the data center].

Data Management is a series of procedures and a research field which assure the quality control in clinical trials. Poorly performed data management can cause various biases in the results of clinical trials. Data management is important especially in cancer clinical trials because of their multiple endpoints, dealing with multiple therapeutic drugs and modalities. Data checks performed by data center staff and composed of manual and computer checks are the main procedures in data management. It is most important that all participants of clinical trials, physicians, nurses, biostatisticians and data managers, understand the data management processes and collaborate with one other from the earliest stage of conducting clinical trials.

Biometry↗

PubMed1997

Epilepsy and exacerbation of brain injury in mice lacking the glutamate transporter GLT-1.

Extracellular levels of the excitatory neurotransmitter glutamate in the nervous system are maintained by transporters that actively remove glutamate from the extracellular space. Homozygous mice deficient in GLT-1, a widely distributed astrocytic glutamate transporter, show lethal spontaneous seizures and increased susceptibility to acute cortical injury. These effects can be attributed to elevated levels of residual glutamate in the brains of these mice.

ATP-Binding Cassette Transporters↗

PubMed1997

Murine isograft studies of gut immunity: recirculation and homing of mononuclear cells.

BACKGROUND & AIMS: Recirculation of lymphocytes requires appropriate signals on the lymphocytes as well as the vascular endothelium. The aim of this report was to study the expression of the mucosal addressin required for Peyer's patch-selective lymphocyte homing during ontogeny of the murine intestine and investigate the role of this addressin in recirculation of mononuclear cells. METHODS: Immunohistochemistry and murine intestinal isografts were used in which the small intestine from neonatal mice is implanted subcutaneously in mice with severe combined immunodeficiency disease. RESULTS: Expression of the mucosal addressin cell adhesion molecule 1 during murine intestinal ontogeny was detected from embryonic day 15 in developing gut and in adult Peyer's patches and lamina propria. Isografted intestine developed normally; it was not exposed to luminal contents but expressed the mucosal addressin cell adhesion molecule 1. Mononuclear cells recirculated to native and isografted intestine and recirculation was inhibited by monoclonal antibody to mucosal addressin in a regionally specific manner with greatest inhibition in the distal intestine. CONCLUSIONS: The mucosal vascular addressin is expressed early in ontogeny and can be detected in lamina propria in addition to Peyer's patches of the gut. The isograft not only developed into a morphologically normal intestine but also expressed differentiation antigens required for normal lymphoid homing to gut without exposure to luminal contents or lymphocytes.

Animals↗

PubMed1997

The first attempt at radioisotopic evaluation of the integrity of the nose-brain barrier.

The first attempt at radioisotopic assessment of the integrity of the nose-brain barrier was performed on an anosmic patient by spraying an aliquot of a mixture of 99mTc-DTPA and hyaluronidase onto the olfactory mucosa with the patient's head positioned vertically and subsequently measuring the cerebral radioactivity. A significant rise in cerebral radioactivity was observed 5 minutes after introduction of the radioisotope. This simple technique will aid in assessing olfactory impairment from selected etiologies and also in testing the integrity of the nose-brain barrier. In view of the study of diseases such as viral encephalitis and Alzheimer's disease, the clinical implications of this method cannot be overemphasized. This principle may also facilitate developing novel pharmaceuticals for some brain diseases.

Aged↗

PubMed1997

Decrease in cerebral free magnesium concentration following closed head injury and effects of VA-045 in rats.

1. We examined the alterations in cerebral free Mg2+ concentration in closed head injury (CHI) in rats and the effects of VA-045, a novel apovincaminic acid derivative, on them with in vivo 31P-NMR. 2. Free Mg2+ decreased by about 30% within 20 min after head impact and, afterward, it gradually decreased further to reach about 60% of the control level after 3 hr. VA-045 inhibited the decrease. 3. In nonimpacted rats, VA-045 did not alter the free Mg2+ level. 4. The decrease in cerebral free Mg2+ following CHI may be a critical factor in the development of irreversible tissue injury, and VA-045 may prevent it.

Animals↗

PubMed1997

The atypical antipsychotic profile of NRA0045, a novel dopamine D4 and 5-hydroxytryptamine2A receptor antagonist, in rats.

1. The atypical antipsychotic profile of (R)-(+)-2-amino-4-(4-fluorophenyl)-5-[1-[4-(4-fluorophenyl)-4-oxobutyl] pyrrolidin-3-yl] thiazole (NRA0045), a potent dopamine D4 and 5-hydroxytryptamine (5-HT)2A receptor antagonist, was examined in rats. 2. Spontaneous locomotor activity was decreased dose-dependently with i.p. administration of clozapine (ED50 3.7 mg kg-1), haloperidol (ED50 0.1 mg kg-1) and chlorpromazine (ED50 0.9 mg kg-1), whereas inhibition of this type of behaviour induced by i.p. administration of NRA0045, at doses up to 10 mg kg-1, did not exceed 50%. 3. Locomotor hyperactivity induced by methamphetamine (MAP, 2 mg kg-1, i.p.) in rats (a model of antipsychotic activity) was dose-dependently antagonized by NRA0045 (ED50 0.4 mg kg-1, i.p., and 0.3 mg kg-1, p.o., respectively), clozapine (ED50 0.3 mg kg-1, i.p. and 0.8 mg kg-1, p.o., respectively), haloperidol (ED50 0.02 mg kg-1, i.p. and 0.1 mg kg-1, p.o., respectively), chlorpromazine (ED50 0.3 mg kg-1, i.p. and 3.3 mg kg-1, p.o., respectively). In contrast, the MAP (3 mg kg-1, i.v.)-induced stereotyped behaviour in rats (a model of extrapyramidal symptoms) was not affected by NRA0045 or clozapine, at the highest dose given (30 mg kg-1, i.p.). Haloperidol (ED50 0.3 mg kg-1, i.p.) and chlorpromazine (ED50 4.8 mg kg-1, i.p.) strongly blocked the MAP-induced stereotyped behaviour. NRA0045 and clozapine selectively blocked behaviour associated with activation of the mesolimbic/mesocortical dopamine neurones rather than nigrostriatal dopamine neurones. 4. Extracellular single-unit recording studies demonstrated that MAP (1 mg kg-1, i.v.) decreased the firing rate in the substantia nigra (A9) and ventral tegmental area (A10) dopamine neurones in anaesthetized rats. NRA0045 completely reversed the inhibitory effects of MAP on A10 dopamine neurones (ED50 0.1 mg kg-1, i.v.), whereas the inhibitory effects of MAP on A9 dopamine neurones were not affected by NRA0045, in doses up to 1 mg kg-1 (i.v.). Clozapine completely reversed the inhibitory effects of MAP on A10 dopamine neurones (ED50 1.9 mg kg-1, i.v.) and on A9 dopamine neurones (ED50 2.5 mg kg-1, i.v.). Haloperidol completely reversed the inhibitory effects of MAP on A10 (ED50 0.03 mg kg-1, i.v.) and on A9 dopamine neurones (0.02 mg kg-1, i.v.). NRA0045, like clozapine, was more potent in reversing the effects of MAP on A10 than A9 dopamine neurones. 5. Prepulse inhibition (PPI) is impaired markedly in humans with schizophrenia. The disruption of PPI in rats by apomorphine (0.5 mg kg-1, s.c.) was reversed significantly by NRA0045 (3 mg kg-1, i.p.), clozapine (3 mg kg-1, i.p.) and haloperidol (0.3 mg kg-1, i.p.). 6. Phencyclidine (PCP) elicits predominantly psychotic symptoms in normal humans and in schizophrenics. NRA0045 (0.03-0.3 mg kg-1, i.p.) and clozapine (0.1-1 mg kg-1, i.p.) significantly and dose-dependently shortened the PCP(1.25 mg kg-1, i.p.)-induced prolonged swimming latency in rats in a water maze task, whereas haloperidol (0.01-0.1 mg kg-1, i.p.) did not significantly alter swimming latency. 7. These findings suggest that NRA0045 may have unique antipsychotic activities without the liability of motor side effects typical of classical antipsychotics.

Animals↗

PubMed1997

Effect of VA-045, a novel apovincaminic acid derivative, on closed head injury-induced neurological dysfunction in aged rats.

Effects of VA-045, a novel apovincaminic acid derivative, on behavioral outcome following closed head injury (CHI) were examined in aged (21-28 months) rats. CHI was induced by dropping a 400 g weight through a tube from 150 cm above a steel helmet placed on the vertex. Beam balancing latency, neurological deficits and body weight were recorded before CHI and for up to 14 days after CHI. When compared with the sham group, all measurements of parameters of behavioral outcome in the CHI group were significantly worsened after CHI. Intraperitoneal administration of VA-045 (1 and 3 mg kg-1) or thyrotropin-releasing hormone (TRH, 10 mg kg-1) and vehicle was started 24 h after CHI, and continued once daily for 13 days. VA-045 but not TRH significantly overcame the CHI-induced neurological deficits, shortened the latency of beam balancing and decreased body weight loss. VA-045 may prove useful for treating aged patients with disturbances of consciousness or motor deficits after CHI.

Age Factors↗

PubMed1997

In vitro and in vivo characterization of the dopamine D4 receptor, serotonin 5-HT2A receptor and alpha-1 adrenoceptor antagonist (R)-(+)-2-amino-4-(4-fluorophenyl)-5-[1-[4-(4-fluorophenyl)-4-oxobutyl] pyrrolidin-3-yl]thiazole (NRA0045).

(R)-(+)-2-Amino-4-(4-fluorophenyl)-5-[1-[4-(4-fluorophenyl)-4-oxobutyl]+ ++pyrrolidin-3-yl]thiazole (NRA0045), a novel thiazole derivative, has high affinities for the human cloned dopamine D4.2, D4.4 and D4.7 receptors, with Ki values of 2.54, 0.55 and 0.54 nM, respectively. NRA0045 is approximately 91-fold more potent at the dopamine D4.2 receptor, compared with human cloned dopamine D2L receptor. NRA0045 also has high affinities for the serotonin (5-HT)2A receptor (Ki = 1.92 nM) and alpha-1 adrenoceptor (Ki = 1.40 nM) but weak affinities (IC50 values are approximately 1 microM) for six other neurotransmitter receptors (adenosine1, 5-HT1A, 5-HT1C, dopamine transporter, alpha2A and alpha2A) and negligible affinities (IC50 values are over 10(-5) M) for 42 other receptors, including neurotransmitters and hormones, ion channels and second messenger systems. Locomotor hyperactivity induced by methamphetamine (1 mg/kg i.p.) in mice was dose-dependently antagonized by NRA0045 (ED50 = 0.5 mg/kg i.p. and 1.9 mg/kg p.o., respectively). Methamphetamine (10 mg/kg i.p.)-induced stereotyped behavior in mice was dose-dependently antagonized by NRA0045, whereas NRA0045 did not exceed 50% inhibition even at the highest dose given (30 mg/kg i.p.). Catalepsy was dose-dependently and significantly induced by NRA0045 in rats, whereas NRA0045 did not exceed 50% induction even at the highest dose given (30 mg/kg i.p.). Thus NRA0045 blocks behaviors associated with activation of the mesolimbic/mesocortical dopaminergic neurons more selectively than behaviors associated with nigrostriatal dopaminergic neurons. In rats, tryptamine-induced clonic seizure, a 5-HT2 receptor-mediated behavior, was also dose-dependently inhibited by NRA0045 (ED50 = 1.7 mg/kg i.p.). Norepinephrine-induced lethality is regarded as being induced through the alpha-1 adrenoceptor. NRA0045 dose-dependently antagonized norepinephrine-induced lethality in rats (ED50 = 0.2 mg/kg i.p.). Thus NRA0045 may have a unique antipsychotic activity with regard to dopamine D4 and 5-HT2A receptors and alpha-1 adrenoceptor antagonistic activities, without producing the extrapyramidal side effects.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1996

Phencyclidine alters regional concentrations of neuropeptide Y and peptide YY in rat brain.

The psychotomimetic effects of Phencyclidine (PCP) often have a delayed onset and extend far from the time plasma drug levels reach their peak. PCP at a low dose is considered selective for actions on the N-methyl-D-aspartate-PCP receptor. We evaluated effects of PCP (2 and 10 mg/kg, IP) on regional content of neuropeptide Y (NPY)-like immunoreactivity (LI) and peptide YY (PYY)-LI, in the rat brain. Thirty minutes after administration of PCP, NPY-LI levels were significantly elevated in some limbic structures following both doses. A significant, widespread increase in NPY-LI levels was induced 2 hours after administration of the higher dose of PCP. On the contrary, NPY-LI was significantly decreased in a number of the regions 24 hours after PCP. The extent of reduction was less following the higher dose of PCP than following the lower dose. PCP did not cause a consistent effect on PYY-LI. The findings suggest that effects of PCP on brain NPY content might depend on the dose and the interval between administration of the drug and sacrifice.

Animals↗

PubMed1996

The world of archaea: genome analysis, evolution and thermostable enzymes.

Pyrococcus sp. KOD1 is a newly isolated hyperthermophilic archaeon from a solfatara at a wharf on Kodakara Island, Kagoshima, Japan. A physical map of the KOD1 chromosome was constructed using pulsed-field gel electrophoresis of restriction fragments generated by AscI, PacI and PmeI. The order of the AscI fragments was deduced from Southern hybridization using the AscI, PmeI and PacI fragments as a probe. The derived physical map indicates that KOD1 possesses a circular-form genome and its size was estimated to be 2036 kb. Several cloned genes were hybridized to restriction fragments to locate their positions on the physical map. Some genes involved in the central dogma were located on the restricted segment of the genome. Novel characteristics of KOD1 enzymes are also introduced in this article.

Archaea↗

PubMed1996

Possible expression of a sigma 1 site in rat pheochromocytoma (PC12) cells.

To examine the functional interaction between the sigma binding sites and nicotinic acetylcholine receptors, we investigated the effects of various sigma receptor ligands on nicotine-evoked Ca2+ uptake in differentiated PC12 cells. The IC50 values of sigma receptor ligands tested in this uptake study did not correlate with their Ki values in the [3H]1, 3-di(2-tolyl) guanidine ([3H]DTG) binding to guinea pig brain reported by Rothman et al. (1991). To clarify further the binding characteristics of the sigma binding sites on PC12 cells, we examined the effects of sigma receptor ligands on [3H]N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine HCl ([3H]NE-100) binding to PC12 membranes. The Ki values of the various drugs tested for [3H]NE-100 binding site closely correlated with their Ki values for the DTG site-1 reported by Rothman et al. (1991). This study showed that PC12 cells express sigma 1-like sites and the inhibitory effect of sigma receptor ligands on the nicotine-evoked Ca2+ uptake was not directly coupled with either the sigma 1 or sigma 2 sites.

Animals↗

PubMed1996

Solubilization and characterization of binding sites for [3H]NE-100, a novel and potent sigma 1 ligand, from guinea pig brain.

The binding sites for [3H]NE-100, a newly defined sigma 1 ligand, was solubilized from guinea pig brain, using zwitterionic detergent 3-[(3-c holamidopropyl) dimethylamino]-1-propanesulfonate (CHAPS), and the properties of the solubilized binding sites were compared to those for [3H](+)-pentazocine, a selective sigma 1 ligand. The pharmacological selectivity of solubilized sites for both [3H]NE-100 and [3H](+)-pentazocine was identical to that obtained from membrane preparations. Stereoselectivity of benzomorphan such as pentazocine and SKF10,047 was preserved in displacing [3H]NE-100 binding in solubilized preparations as observed in membrane preparations. The inhibitory potencies of several sigma ligands on [3H]NE-100 binding were similar to those on [3H](+)-pentazocine binding, indicating that the pharmacological characteristics of the binding sites for [3H]NE-100 are retained after solubilization. Phenytoin augmented the binding of [3H](+)-3-(3-hydroxyphenyl)-N-(1-propyl) piperidine hydrochloride (3-PPP) to solubilized sigma binding sites while it had no effect on the binding of [3H]NE-100. Furthermore, the inhibitory effect of putative sigma receptor agonists such as (+)-3-PPP and dextromethorphan were enhanced by phenytoin; the effects of haloperidol, a putative sigma receptor antagonist, were unaltered. Molecular weight of [3H]NE-100 binding protein was estimated to be 440KDa by Sepharose CL-6B gel filtration chromatography, and the value was identical to that of [3H](+)-pentazocine binding protein, a putative sigma 1 binding protein. These findings indicate that [3H]NE-100 binding sites are putative sigma 1 binding sites, and that NE-100 may act as an antagonist at sigma 1 binding sites.

Animals↗