Tongue-palatal contact changes in patients with skeletal mandibular prognathism after sagittal split ramus osteotomy: an electropalatography study.

The purpose of this study was to investigate the changes in tongue-palatal contact patterns using electropalatography (EPG) before and after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. Nine clients who underwent SSRO for mandibular setback and seven control subjects were participated in this study. Tongue-palatal contact patterns for /t/, /s/ and /k/ production were investigated using EPG before surgery and 3 months after surgery. The mean value of whole total of palate contact (WT) in the maximum contact frame was examined before and after SSRO. The correlation quantity between the change of center of gravity (COG) value and the amount of mandibular setback was also evaluated. The mean value of WT for /t/ and /s/ significantly increased after SSRO, and the EPG pattern became normal. However, a remarkable change in WT for /k/ was not observed, and the mean value was significantly larger in the SSRO group before and after surgery than in the control group. A negative correlation between COG variation and the amount of mandibular setback for /t/ and positive correlation for /s/ was observed. This study demonstrated that tongue-palatal contact patterns for /t/ and /s/ articulation improved clearly after SSRO. There was a significant correlation between COG variation and the amount of mandibular setback. However, no significant change was detected through perceptual assessment before and after SSRO. Further investigation is needed to determine whether these results will change over time.

Lack of GPR40/FFAR1 does not induce diabetes even under insulin resistance condition.

AIMS: G protein-coupled receptor/free fatty acid receptor 1 (GPR40/FFAR1 ) regulates free fatty acid-induced insulin secretion. This study has been performed to clarify whether or not loss of GPR40/FFAR1 function exacerbates diabetes, that is, whether GPR40 has an essential physiological role in the development of diabetes or not. METHODS: We generated GPR40/FFAR1 knockout (KO) mice and analysed their phenotypes in vitro and in vivo under the condition of dietary or genetically induced insulin resistance. RESULTS: GPR40/FFAR1 KO mice kept on a high-fat diet became obese, developed glucose intolerance to a similar degree as GPR40/FFAR1 wild-type (WT) mice. In addition, the phenotype of KO mice harbouring diabetogenic KK background genes showed glucose intolerance at a level similar to level for control KK mice. In both mouse models with insulin resistance, insulin secretion after oral glucose load and homeostasis model assessment-insulin resistance (HOMA-IR) did not change between GPR40/FFAR1 KO and WT mice. Although glucose-induced insulin secretion under high palmitate concentration was significantly lower in KO than in WT islets, pancreatic insulin content and insulin secretion stimulated with glucose alone were not different between KO and WT mice. CONCLUSIONS: GPR40/FFAR1 has a major role in regulating fatty-acid-mediated insulin secretion, but the lack of GPR40/FFAR1 does not exacerbate glucose intolerance and insulin resistance induced by high-fat diet or diabetogenic KK gene. Our findings indicate that loss of GPR40/FFAR1 function does not play an important role in inducing or exacerbating diabetes.

Circulating KL-6 levels in patients with drug induced pneumonitis.

BACKGROUND: The circulating level of KL-6/MUC1 is a sensitive marker for various interstitial lung diseases. Previous case reports have suggested that KL-6 may also be increased in some patients with drug induced pneumonitis. A study was undertaken to determine whether serum KL-6 could be a marker for particular types of drug induced pneumonitis. METHODS: The findings of high resolution computed tomographic (HRCT) chest scans of 30 patients with drug induced pneumonitis were reviewed separately by two independent observers. The pneumonitis was classified into four predominant patterns: widespread bilateral consolidation (diffuse alveolar damage, DAD; n=7), fibrosis with or without consolidation (chronic interstitial pneumonia, CIP; n=11), consolidation without fibrosis (bronchiolitis obliterans organising pneumonia or eosinophilic pneumonia, BOOP/EP; n=8), and diffuse ground glass opacities without fibrosis (hypersensitivity pneumonitis, HP; n=4). Serum KL-6 levels were measured by a sandwich enzyme linked immunosorbent assay. RESULTS: The overall sensitivity of serum KL-6 in detecting drug induced lung disease was 53.3%, which was lower than its sensitivity in detecting other interstitial lung diseases. However, the KL-6 level was increased in most patients with a DAD or CIP pattern (16/18; 88.9%) and was closely correlated with their clinical course. In contrast, serum KL-6 levels were within the normal range in all patients with a BOOP/EP or HP pattern. CONCLUSIONS: Particular patterns detected by HRCT scanning, such as DAD and CIP but not the BOOP/EP or HP patterns, are associated with increased circulating KL-6 levels in drug induced pneumonitis. Serum KL-6 levels may reflect the clinical activity of the particular disorders.

Experimental and theoretical studies of the effect of electrode polarisation on capacitances of blood and potassium chloride solution.

The effects of electrode polarisation on the observed capacitances of electrolytic solutions, including whole blood, plasma and potassium chloride solution, have been investigated experimentally in the frequency region from 10 to 10(5) Hz, by varying the area of the electrodes using plate and mesh electrodes, by varying the electrode distance, and by varying the concentration of KCl in the potassium chloride solution. The effects of the electrode polarisation on the observed capacitances were most significant in the frequencies lower than 10(2) Hz, but cannot be neglected in any frequency region. The so-called alpha dispersion observed in the frequencies lower than about 10(3) Hz was reproduced theoretically with an equivalent circuit model, using constant values independent of frequency for the four circuit parameters: sample capacitance, sample conductivity, electrode polarisation capacitance and electrode polarisation conductivity. It was concluded that the observed alpha dispersion is not a real one that represents the specific features of the samples themselves, but an apparent one that represents the characteristics of the whole measurement system, including the electrode polarisation.

Increased antibody levels to desmogleins 1 and 3 after administration of carbamazepine.

Desmoglein (Dsg) 1 and Dsg3 are recognized as the autoantigens in pemphigus foliaceus and pemphigus vulgaris. Pemphigus-like syndromes have been reported to occur in individuals after exposure to a variety of drugs, but pemphigus caused by carbamazepine is not common. We found that anti-Dsg1 and anti-Dsg3 antibody titres were increased in three individuals administered carbamazepine. Antibody titres against Dsgs 1 and 3 were measured by enzyme-linked immunosorbent assay (ELISA). Of 42 serum samples (25 patients administered carbamazepine, eight patients administered valproic acid and nine healthy volunteers) tested by ELISA, three patients administered carbamazepine showed positive reactivity against both Dsg1 and Dsg3. The patient with the highest titre against Dsg1 and Dsg3 (the index values of anti-Dsg1 and anti-Dsg3 were 79.3 and 86.4, respectively) was a 23-year-old woman (Case 1). The other two patients with positive reactivity were a 5-year-old boy (Case 2) and a 65-year-old man (Case 3). In addition, indirect immunofluorescence study showed intercellular antibodies to the cell surface of the whole epidermis with a titre of 1 : 64 in Case 1 and 1 : 2 in Cases 2 and 3. However, no skin or mucosal involvement was found in any of these cases. There was no difference in the serum concentrations of carbamazepine between the three positive cases and the 22 negative cases of carbamazepine administration. From these facts, the lack of skin diseases may be explained by relatively low values of anti-Dsg 1 and 3 antibodies in Cases 2 and 3. However, it cannot be excluded that undefined exogenous and/or endogenous factors are involved in an outbreak of pemphigus. Furthermore, these findings might be helpful for preventing susceptible individuals from exposure to the suspect drugs.

A mechanism of the high frequency AC iontophoresis.

The efficiency and the voltage dependence of the AC iontophoresis were studied in vitro. Two cylindrical glass cells separated by a cellophane film were used, where the donor cell was filled with the solution of target electrolytes and the receptor cell with distilled water. The sinusoidal AC voltage with a frequency of 1 kHz was applied between the two platinum plates located at the opposite ends of two cells. The time variation of the ion concentration was evaluated by measuring the impedance of the solution in the receptor cell. The transportation velocity of the ions increased with the amplitude of the voltage applied between two platinum plate electrodes apart 20 mm up to approximately 15 V, and leveled off above approximately 15 V. A theoretical model is proposed on the AC iontophoresis, where each ion moves together with the surrounding water molecules when it is hydrated. The effective Stokes radius of an ion is assumed to be half of the whole size of the ion with hydrating water molecules. When the external alternating electric field strongly vibrates the ion, the ion-dipole interactions between the ion and water molecules are broken, resulting in the reduced effective Stokes radius, which leads to the increase of the diffusion efficiency.

Relationship between regional severity of emphysema and coronary heart disease.

We analyzed the relationship between regional severity of emphysema, which was evaluated by three-dimensional fractal analysis (3D-FA) of Technegas SPECT images, and coronary heart disease (CHD). For 22 patients with emphysema who underwent Technegas SPECT, we followed up CHD events. The follow-up period was 5.4+/-0.5 (mean +/- SD) years. We defined the upper-lung fractal dimension (U-FD) and lower-lung fractal dimension (L-FD) obtained with 3D-FA of Technegas SPECT images as the regional severity of emphysema. FD became greater with the progression of emphysematous change. During the follow-up period, CHD events occurred in 6 (27%) of the 22 patients. The ratio of U-FD to L-FD for patients with CHD events (0.87+/-0.22) was significantly smaller than for patients without CHD events (1.52+/-0.38) (p = 0.0015). These findings suggest that severer emphysema in the lower lung indicates a higher risk of CHD than that in the upper lung.

Skeletal muscle apoptosis after burns is associated with activation of proapoptotic signals.

Critical illness is associated with muscle wasting and muscle weakness. Using burn injury as a model of local and systemic inflammatory response, we tested the hypothesis that thermal injury causes apoptosis in muscle. After a 40% body surface area burn to rats, abdominal muscles beneath the burn and limb muscles distant from the burn were examined for apoptosis at varying times after burn. Ladder assay, ELISA, and histological methods showed evidence of apoptosis in the abdominal muscles within 4-12 h with peak changes occurring at 3-7 days. Maximal apoptosis was also evident at distant limb muscles at 3-7 days. Investigation of proapoptotic pathways indicated mitochondrial membrane potential to be altered by 1 h after burn. Starting at 15 min after burn, cytochrome c was released from the mitochondria into the cytosol, followed by increased activity of caspase-3, starting at 6 h after burn. These studies suggest that mitochondria and caspase-mediated apoptotic pathways may be an additional mechanism of muscle weight loss in burns and may be potential therapeutic targets for prevention of muscle wasting.

Quantitative analysis of technegas SPECT: evaluation of regional severity of emphysema.

UNLABELLED: The purpose of this study was to quantify the regional severity of emphysema by 3-dimensional fractal analysis of technegas (99mTc-carbon particle radioaerosol) SPECT images. METHODS: Technegas SPECT was performed on 22 patients with emphysema. The lungs were delineated using 4 cutoff levels (15%, 20%, 25%, and 30% of the maximal pixel radioactivity), and the total number of pixels was measured in the areas surrounded by the contours obtained with each cutoff level. We calculated fractal dimensions from the relationship between the total number of pixels and cutoff levels transformed into logarithms. Fractal dimension for total or regional lung was defined as the severity of emphysema. RESULTS: Total lung fractal dimension (T-FD), upper lung fractal dimension (U-FD), and lower lung fractal dimension (L-FD) for patients with emphysema were 1.84 +/- 0.46 (mean +/-SD), 2.22 +/- 0.61, and 1.77 +/- 0.49, respectively. U-FD was significantly greater than was L-FD. Patients with the ratio of U-FD to L-FD of <1.16 had a significantly greater percentage forced vital capacity (FVC) than did patients with the ratio of >1.16. Patients with an L-FD of <1.8 had a significantly greater forced expiratory volume in 1 s (FEV1)/FVC than did patients with that of >1.8. No significant difference was found between patient groups stratified by U-FD. CONCLUSION: The regional severity of emphysema was well shown by these fractal dimensions.

Curved planar reformatted CT angiography: usefulness for the evaluation of aneurysms at the carotid siphon.

BACKGROUND AND PURPOSE: Three-dimensional CT angiography uses the data obtained on a contrast-enhanced CT brain scan to generate 3D images of the intracranial vasculature. We describe the methodology of curved planar reformatting (CPR) for CT angiography and characterize its usefulness in the evaluation of aneurysms at the carotid siphon, comparing it with the shaded surface display technique (SSD). METHODS: Eighty-seven patients with suspected intracranial aneurysms at CT angiography were examined by conventional cerebral angiography, and the patients with aneurysm(s) at the carotid siphon were selected for study. For these patients, the visibility of the neck and fundus of the aneurysms on CT angiograms was compared for those obtained with SSD and those with CPR, and observer reproducibility was evaluated with the kappa statistic. RESULTS: Eighteen patients were confirmed to have an aneurysm at the carotid siphon on conventional angiograms. Seventeen aneurysms were depicted at CT angiography with SSD; 18 aneurysms with CPR. The number of visible aneurysmal necks and fundi was nine and 12, respectively, with SSD; 18 and 18, respectively, with CPR. CONCLUSION: CPR allows better demonstration of the body and neck of an aneurysm at the carotid siphon, which has a tortuous course and is surrounded by complex bony structures. CPR may be a useful adjunct for the evaluation of aneurysms in this region.

Quantitative analysis of pulmonary emphysema: three-dimensional fractal analysis of single-photon emission computed tomography images obtained with a carbon particle radioaerosol.

OBJECTIVE: The purpose of this study was to quantify the heterogeneous distribution of a carbon particle radioaerosol in the lungs of patients with pulmonary emphysema using single-photon emission computed tomography (SPECT) and fractal analysis. SUBJECTS AND METHODS: Ventilation SPECT was performed on 19 patients with pulmonary emphysema, seven patients with suspected pulmonary emphysema, and 14 healthy volunteers. We delineated the lungs using five cutoff levels (15%, 20%, 25%, 30%, and 35% of the maximal pixel radioactivity) and measured the total number of pixels in the areas surrounded by the contours obtained with each cutoff level. We calculated fractal dimensions from the relationship between the total number of pixels and cutoff levels transformed into logarithms. RESULTS: The fractal dimensions increased with the severity of pulmonary emphysema. The fractal dimensions for patients with pulmonary emphysema, patients with suspected pulmonary emphysema, and healthy volunteers were 2.03+/-0.61 (mean +/- SD), 0.77+/-0.09, and 0.59+/-0.06, respectively. A significant difference (p < .0005) in the fractal dimension was found when any of these three groups was compared with any other group of subjects. CONCLUSION: Three-dimensional quantitative evaluation of the emphysematous lung was possible using SPECT and fractal analysis. Our results suggest that fractal analysis can quantify the heterogeneity of the distribution of a carbon particle radioaerosol in the lung. Fractal analysis appears to be applicable for routine clinical use because it is simple and the fractal dimensions can be obtained easily without using special software.

Three-dimensional endoscopic mode for observation of laryngeal structures by helical computed tomography.

We produced high-quality three-dimensional (3D) endoscopic images of the larynx using helical scanning computed tomography. Subjects included two normal volunteers and 10 patients: five with laryngeal cancer, four with unilateral recurrent laryngeal nerve (RLN) palsy, and one with atrophied vocal folds. Two vertically split hemilaryngeal images were displayed together with the oral and tracheal views. Although motion artifacts were seen in four patients, laryngeal structures including the vocal fold, ventricular fold, and ventricle were clearly identified in all subjects. In the patients with cancer, axial images showing the extent of the tumor in each patient provided more information than 3D endoscopic images. In the patients with RLN palsy and atrophied vocal fold, combination of 3D endoscopic and cross-sectional images offered more diagnostic information than axial images alone.

Mapping of change in cerebral glucose utilization using fluorine-18 fluorodeoxyglucose double injection and the constrained weighted-integration method.

The authors developed a method for mapping the change in cerebral glucose utilization at two different physiological states using [(18 )F]fluorodeoxyglucose (FDC) double infection and the constrained weighted-integration method. The authors studied young normal subjects without (baseline-baseline group, n=5) and with (baseline-stimulation group, n=5) vibrotactile stimulation of the fingertips of the right hand. Dynamic scans were performed using positron emission tomography (PET) following an initial dose (the first session, 0-30 min) and an additional dose (the second session, 30-60 min). The parametric images of the net clearance of FDG from blood to brain (K*), unidirectional blood-to-brain clearance (K(1)*), and cerebral metabolic rate of glucose (CMR(glc)) of the two sessions were generated. The averaged subtraction (second minus first session) and t-statistic images were generated, which were rendered into Talairach's stereotaxic coordinates and merged with the averaged magnetic resonance imaging (MRI) image. In the baseline-baseline group, regional K*, K(1)* and CMR(glc) in the first and second sessions were strongly correlated (r(2)=0.953, 0.935, and 0.951, respectively, n=330). In the baseline-stimulation group, significant increases in these estimates were obtained in the contralateral primary somatosensory cortex (SI) (from 3.43+/-0.78 to 4.02+/-1.01 ml/100 g/min for K*, 7.85+/-1.88 to 9.09+/-1.71 ml/100 g/min for K(1)*, and 280+/-5.9 to 32.3+/-5.5 mumol/100 g/min for CMR(glc)), while there were no significant changes in the ipsilateral SI (from 3.45+/-0.83 to 359+/-0.72 ml/100 g/min for K*, 8.17+/-2.33 to 837+/-1.75 ml/100 g/min for K(1 )* and 29.5+/-8.1 to 29.1+/-8.2 mumol/100 g/mln for CMR (glc)), Significant increases in K* and CMR(glc) in the contralateral SI were clearly demonstrated in the t-statistic image. In conclusion, the proposed method allows mapping of changes in cerebral glucose utilization during physiological stimulation of the brain, and will be useful for studying the relationship between neural activity and regional cerebral glucose metabolism.

Molecular cloning of insect pro-phenol oxidase: a copper-containing protein homologous to arthropod hemocyanin.

Pro-phenol oxidase [pro-PO; zymogen of phenol oxidase (monophenol, L-dopa:oxygen oxidoreductase, EC 1.14.18.1)] is present in the hemolymph plasma of the silkworm Bombyx mori. Pro-PO is a heterodimeric protein synthesized by hemocytes. A specific serine proteinase activates both subunits through a limited proteolysis. The amino acid sequences of both subunits were deduced from their respective cDNAs; amino acid sequence homology between the subunits was 51%. The deduced amino acid sequences revealed domains highly homologous to the copper-binding site sequences (copper-binding sites A and B) of arthropod hemocyanins. The overall sequence homology between silkworm pro-PO and arthropod hemocyanins ranged from 29 to 39%. Phenol oxidases from prokaryotes, fungi, and vertebrates have sequences homologous to only the copper-binding site B of arthropod hemocyanins. Thus, silkworm pro-PO DNA described here appears distinctive and more closely related to arthropod hemocyanins. The pro-PO-activating serine proteinase was shown to hydrolyze peptide bonds at the carboxyl side of arginine in the sequence-Asn-49-Arg-50-Phe-51-Gly-52- of both subunits. Amino groups of N termini of both subunits were indicated to be N-acetylated. The cDNAs of both pro-PO subunits lacked signal peptide sequences. This result supports our contention that mature pro-PO accumulates in the cytoplasm of hemocytes and is released by cell rupture, as for arthropod hemocyanins.

Regional striatal DOPA transport and decarboxylase activity in Parkinson's disease.

METHODS: We measured blood-brain barrier transport and decarboxylation of 6-[18F]fluoro-L-DOPA (FDOPA) using PET in patients with Parkinson's disease (n = 7, 57 +/- 7 yr) and age-matched control subjects (n = 7, 60 +/- 6 yr). To visually present regional changes of FDOPA uptake in Parkinson's disease, we introduced maps of FDOPA uptake relative to occipital cortex, averaged across control subjects and Parkinson's disease patients in an MRI-based stereotaxic coordinate space. RESULTS: There was no significant changes in the blood-to-brain transport of FDOPA (KD1) in Parkinson's disease. The KD1 values of the head of caudate were lower than those of putamen in both normal subjects and Parkinson's disease patients. In Parkinson's disease, the activity of L-DOPA decarboxylase (DDC) was differentially reduced in subdivisions of striatum. The residual DDC activity was 63% of the control value in the head of caudate nucleus, 54% in the anterior putamen and 39% in the posterior putamen. The DDC activity in frontal and occipital cortices remained unchanged by the disease. Subtraction of averaged FDOPA uptake maps (control minus Parkinson's disease) visualized a spatial pattern of pathological changes in FDOPA uptake common to Parkinson's disease patients. CONCLUSION: The striatal blood-to-brain transport of FDOPA remained unchanged while the DDC activity was differentially reduced within the striatum in Parkinson's disease. We found the FDOPA uptake maps useful in identifying altered patterns of FDOPA metabolism common in Parkinson's disease.

Reexamination of properties of prophenoloxidase isolated from larval hemolymph of the silkworm Bombyx mori.

Prophenoloxidase in hemolymph of the silkworm (Bombyx mori) was purified by the method of Ashida (Ashida, M. (1971) Arch. Biochem. Biophys. 144, 749-762) with slight modifications to further increase the purity, and its properties were reinvestigated. The purified prophenoloxidase gave two discrete bands in isoelectric focusing-polyacrylamide gel electrophoresis (IEF-PAGE) (pI 4.95 and 4.98) and in native-polyacrylamide gel electrophoresis with 4.5% separating gel. Each band in IEF-PAGE was separated into two bands in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with mobilities corresponding to 71.5- and 71-kDa polypeptides. In HPLC on octadecyl column the prophenoloxidase preparation gave two well-separated symmetrical peaks (proPO polypeptide I and proPO polypeptide II). The molecular masses of the proPO polypeptides I and II were determined to be 71.5 and 71 kDa in SDS-PAGE and 78,880 and 81,105 Da by matrix-assisted laser desorption ionization mass spectrometry, respectively. Native prophenoloxidase was eluted at a position corresponding to 126-kDa protein in gel permeation chromatography. Amino acid compositions and peptide mappings of proPO polypeptides indicated that both polypeptides differ in their primary structures. These results are discussed in relation to the subunit structure, the presence of bicopper cluster, and the polymorphism of prophenoloxidase in silkworm hemolymph.

Elevated dopa decarboxylase activity in living brain of patients with psychosis.

The hypofrontality theory of the pathogenesis of schizophrenia predicts that cortical lesions cause psychosis. During a search for abnormalities of catecholaminergic neurotransmission in patients with complex partial seizures of the mesial temporal lobe, we discovered an increase of the rate of metabolism of an exogenous dopa tracer (6-[18F]fluoro-L-dopa) in the neostriatum of a subgroup of patients with a history of psychosis. When specifically assayed for this abnormality, patients with schizophrenia revealed the same significant increase of the rate of metabolism in the striatum. The finding is consistent with the theory that a state of psychosis arises when episodic dopamine excess is superimposed on a trait of basic dopamine deficiency in the striatum. The finding is explained by the hypothesis that cortical insufficiency, a proposed pathogenetic mechanism of both disorders, causes an up-regulation of the enzymes responsible for dopa turnover in the neostriatum as well as the receptors mediating dopaminergic neurotransmission.

Striatal L-dopa decarboxylase activity in Parkinson's disease in vivo: implications for the regulation of dopamine synthesis.

L-DOPA is a large neutral amino acid subject to transport out of, as well as into, brain tissue. Competition between dopamine synthesis and L-DOPA egress from striatum must favor L-DOPA egress if decarboxylation declines relatively more than transport in Parkinson's disease. To test this hypothesis, we injected patients with Parkinson's disease with a radiolabeled analogue of L-DOPA and recorded regional brain radioactivity as a function of time by means of positron emission tomography. We simultaneously estimated the activity of the decarboxylating enzyme and the amino acid transport. In the striatum of patients, we found the L-DOPA decarboxylase activity to be reduced in the head of the caudate nucleus and the putamen. However, the rate of egress of the DOPA analogue was unaffected by the disease and thus inhibited dopamine synthesis more than predicted in the absence of L-DOPA egress.

Unusual cranial metastasis from hepatoma presenting as isolated unilateral hypoglossal nerve paresis--case report.

A 45-year-old male presented with a rare right hypoglossal nerve paresis due to an unusual cranial metastatic tumor from hepatoma. Despite multi-drug chemotherapy and arterial embolization, he died about 1 year later. Such metastasis should be considered as the cause of isolated unilateral hypoglossal nerve paresis.

[Evaluation of the discriminative stimulus effect of an enkephalin analog, EK-399, in the rat].

Four groups of rats were trained to discriminate between the no-drug conditions (saline, s.c.) and the effect of s.c. injection of the novel enkephalin analog Tyr-D-Met (O)-Gly-EtPhe-NHNHCOCH3.AcOH (EK-399, 1 mg/kg), morphine (3 mg/kg), ethylketocyclazocine (EKC, 0.3 mg/kg) or N-allylnormetazocine (NANM, 3 mg/kg) in a two-lever choice, water reinforced procedure. All groups of animals acquired the ability to discriminate EK-399, morphine, EKC or NANM from saline. Naloxone (0.03-0.3 mg/kg, s.c.) completely antagonized the discriminative stimulus effects of EK-399, morphine and EKC, but not that of NANM. In stimulus generalization tests, morphine (10 mg/kg) and buprenorphine (0.03 mg/kg), mu-opioid receptor agonists, completely substituted for EK-399 in groups trained with EK-399, whereas EK-399 (0.1-3 mg/kg) only partially substituted for morphine in rats trained with morphine. EKC (0.01-0.1 mg/kg), a kappa-opioid receptor agonist, partially substituted for EK-399, and EK-399 (0.1-3 mg/kg) partially substituted for EKC. NANM (0.3-10 mg/kg), a sigma-receptor agonist, partially substituted for EK-399, but EK-399 (0.1-3 mg/kg) did not substitute for NANM. These results suggest that the discriminative stimulus effect of EK-399 in rats mainly involves mu-opioid receptor-mediating action and also involves, to a lesser extent, other receptor (probably delta-opioid receptor)-mediating actions.