Draft genome sequence of Cupriavidus sp. strain TKC, isolated from a γ-hexachlorocyclohexane-degrading community.

Cupriavidus sp. strain TKC was isolated from a microbial community enriched with γ-hexachlorocyclohexane (γ-HCH). This strain did not show γ-HCH-degrading activity but was one of the major members of the community. Here, we present the draft genome sequence of the strain TKC with a size of 7 Mb.

Sensitivity and optimal clinicopathological features for mutation-targeted liquid biopsy in pN0M0 EGFR-mutant lung adenocarcinoma.

PURPOSE: Liquid biopsy for early-stage lung cancer diagnosis is challenging, and optimal candidates' clinicopathological features are unknown. We investigated utility and clinicopathological features of optimal candidates in somatic mutation-targeted liquid biopsy using droplet digital polymerase chain reaction (ddPCR) in pN0M0 EGFR mutation-positive lung adenocarcinoma patients. METHODS: We performed EGFR mutation-targeted ddPCR liquid biopsy in 100 patients with resected pN0M0 invasive lung adenocarcinoma, whose tumor diameter in high-resolution computed tomography (HRCT) was ≤ 5 cm. Peripheral blood-derived serum was collected preoperatively. Two representative EGFR somatic variants (exon 19 [E746-A750 del (2235_2249 del)]; exon 21 (L858R)) were utilized as liquid biopsy targets. Clinicopathological features including radiological appearance, subhistology, and invasive status were compared between ddPCR-positive and ddPCR-negative patients. RESULTS: Among the 100 patients, 98 showed part-solid or pure-solid appearance in HRCT and 2 showed non-solid appearance; 98 were pathological stage IA1-IB. Of the 66 patients with EGFR mutation detection in ddPCR, 12 were significantly positive and 10 (83.3%, 10/12) exhibited pure-solid appearance in HRCT. Clinical invasive tumor ratio was significantly higher in ddPCR-positive than in ddPCR-negative patients (median: 100% vs. 85.4%, P = 0.0212), whereas other clinicopathological features were not significantly different. CONCLUSION: Mutation-targeted liquid biopsy using ddPCR detected lung cancer in 12.0% (12/100) of pN0M0 EGFR-mutant lung adenocarcinoma patients. In 83.3% of the ddPCR-positive patients, tumors showed pure-solid appearance in HRCT. The detection ratio increased to 21.3% (10/47) among patients with pure-solid appearance tumors. Tumor appearance might be useful for better selection of liquid biopsy candidates.

Synchronicity of genetic variants between primary sites and metastatic lymph nodes, and prognostic impact in nodal metastatic lung adenocarcinoma.

PURPOSE: Nodal positive lung adenocarcinoma includes wide range of survival. Several methods for the classification of nodal-positive lung cancer have been proposed. However, classification considering the impact of targetable genetic variants are lacking. The possibility of genetic variants for the better stratification of nodal positive lung adenocarcinoma was estimated. METHODS: Mutations of 36 genes between primary sites and metastatic lymph nodes (LNs) were compared using next-generation sequencing. Subsequently, mutations in EGFR and BRAF, rearrangements in ALK and ROS1 were evaluated in 69 resected pN1-2M0 adenocarcinoma cases. Recurrence-free survival (RFS), post-recurrence survival (PRS), and overall survival (OS) were evaluated with respect to targetable variants and tyrosine kinase inhibitor (TKI) therapy after recurrence. RESULTS: About 90% of variants were shared and allele frequencies were similar between primary and metastatic sites. In 69 pN1-2M0 cases, EGFR/ALK were positive in primary sites of 39 cases and same EGFR/ALK variants were confirmed in metastatic LNs of 96.7% tissue-available cases. Multivariate analyses indicated positive EGFR/ALK status was associated with worse RFS (HR 2.366; 95% CI 1.244-4.500; P = 0.009), and PRS was prolonged in cases receiving TKI therapy (no post-recurrence TKI therapies, HR 3.740; 95% CI 1.449-9.650; P = 0.006). OS did not differ with respect to targetable variants or TKI therapy. CONCLUSIONS: Cases harbouring targetable genetic variants had a higher risk of recurrence, but PRS was prolonged by TKI therapy. Classification according to the targetable genetic status provides a basis for predicting recurrence and determining treatment strategies after recurrence.

Therapeutic strategies and genetic profile comparisons in small cell carcinoma and large cell neuroendocrine carcinoma of the lung using next-generation sequencing.

Small cell lung cancer (SCLC) and large cell neuroendocrine carcinoma (LCNEC) of the lung are classified as variants of endocrine carcinoma and subdivided into pure or combined type. Clinical benefit of target therapy has not been established in these tumors. This study aimed to compare genetic and clinicopathological features between SCLC and LCNEC or pure and combined types, and explore the possibility of target therapy using next-generation sequencing. In 13 SCLC and 22 LCNEC cases, 72 point mutations, 19 deletions, and 3 insertions were detected. As therapeutically targetable variants, mutations in EGFR (L858R), KRAS (G12D, G12A, G12V), and PIK3CA (E545K) were detected in 5 cases. The case harboring EGFR mutation showed response to EGFR-tyrosine kinase inhibitor. However, there are no clinicopathological features associated with therapeutically targetable cases. And there was no significant genetic feature between SCLC and LCNEC or pure and combined types. In conclusion, although patients with SCLC and LCNEC may benefit from target therapy, they were not identifiable by clinicopathologic background. And there was not significant genetic difference between SCLC and LCNEC, including between pure and combined types. Classifying SCLC and LCNEC in same category is reasonable. However, distinguishing the pure type from combined type was not validated. Comprehensive genetic analysis should be performed to detect targetable variants in any type of SCLC and LCNEC.

Circulating free DNA as non-invasive diagnostic biomarker for childhood solid tumors.

PURPOSE: Our aims are to determine circulating free DNA (cfDNA) in childhood solid tumor patients who underwent surgical intervention and to analyze any relationships with clinical parameters. METHODS: Fourty-four consenting children admitted with solid tumors between 2010 and 2014 were recruited. CfDNAs isolated from 0.5mL plasma obtained before and 1-30days after surgery were analyzed by next-generation sequencing (NGS: IonTorrent Cancer Hotspot panel) and by gene amplification analysis using a digital PCR (dPCR) platform. RESULTS: Total amounts of cfDNA were 54-825ng and were significantly associated with stage of disease. In cfDNA, 15 mutations or deletions (2 ALK, 2 TP53, 1 WT1, 3 CTNNB1, 1 APC, 1 KIT, 1 RET, 1 CDNK2AT, and 3 SMARCB1) were identified. In 10 neuroblastoma suspected cases, 2 showed high copy numbers of MYCN using dPCR. The positive rate in our cohort was 36%, and all of these aberrations were detected in the original tumors. None of the aberrations were detectable in cfDNA after surgery except for three cases whose tumors remained after surgery. CONCLUSIONS: These data demonstrate the feasibility and potential utility of mutation/deletion/amplification screening in cfDNA using NGS and dPCR for the detection of tumor biomarkers in children with solid tumors. These markers also have the potential utility to evaluate complete resection after surgery.

Chlorpheniramine exerts anxiolytic-like effects and activates prefrontal 5-HT systems in mice.

RATIONALE: The traditional antihistamine chlorpheniramine ameliorates panic attacks, phobias, and lowered mood, and this therapeutic effect is independent of the blockade of histamine H(1) receptors. Since chlorpheniramine inhibits the reuptake of serotonin (5-HT), the anxiolytic-like effect of chlorpheniramine may be produced by an increase in serotonergic function. OBJECTIVE: To elucidate the mechanisms underlying the anxiolytic-like effects of chlorpheniramine in mice, we examined the involvement of 5-HT systems in the prefrontal cortex that is a crucial region in the regulation of emotional function. RESULTS: Chlorpheniramine (0.05-5 mg/kg, i.p.) dose-dependently and significantly decreased the duration of freezing behavior in both the elevated open-platform and conditioned fear tests. The anti-freezing effects of chlorpheniramine (5 mg/kg, i.p.) in these tests were inhibited by pretreatment with the non-selective antagonist at 5-HT receptors, methiothepin (0.01 mg/kg, s.c.). In addition, the local injection of chlorpheniramine (10-100 ng/mouse) and 5-HT (1-10 µg/mouse) into the medial part of the prefrontal cortex (mPFC) dose-dependently and significantly decreased the duration of freezing behavior in the elevated open-platform test. In a microdialysis study, chlorpheniramine (0.5 and 5 mg/kg, i.p.) dose-dependently and significantly increased the extracellular 5-HT level in the mPFC. In addition, the local perfusion of chlorpheniramine (10 and 30 µM), but not of the selective H1 receptor antagonist, cetirizine, into the mPFC markedly increased the extracellular 5-HT level in the mPFC. CONCLUSION: The anxiolytic-like effect of chlorpheniramine is produced, at least in part, by the facilitation of serotonergic neurotransmission in the PFC.

Effects of serotonergic anxiolytics on the freezing behavior in the elevated open-platform test in mice.

Freezing behavior is thought to be a sign of fear in animals. We examined whether the freezing behavior during the elevated open-platform stress, which is a psychological stressor without painful stimulus, is modulated by serotonergic neurotransmission and would be a useful marker for screening anxiolytic and/or antidepressant. Male ICR mice (6 - 8-week-old) were individually placed on an elevated open-platform and the duration of freezing behavior of mouse was measured for 10 min. Fluoxetine and citalopram, selective serotonin (5-HT) reuptake inhibitors, markedly decreased the duration of freezing. Fenfluramine, a 5-HT releaser, and 8-OH-DPAT, a potent 5-HT1A-receptor agonist, also significantly decreased the duration of freezing. In contrast, the 5-HT-synthesis inhibitor p-chlorophenylalanine significantly increased the duration of freezing. Diazepam, a benzodiazepine anxiolytic, had no effect on the duration of freezing at doses having no effect on locomotor activity. Imipramine and clomipramine, tricyclic antidepressants, also did not affect the duration of freezing. Reboxetine, a selective noradrenaline reuptake inhibitor, significantly increased the duration of freezing. These results indicate that the activation of serotonergic neurotransmission attenuates the fear-related behavior in the elevated open-platform test, while the activation of noradrenergic neurotransmission increases the fear-related behavior. In addition, this test is convenient for assaying anxiolytic drugs that affect serotonergic neurotransmission.

Involvement of dopamine D1 receptors and alpha1-adrenoceptors in the antidepressant-like effect of chlorpheniramine in the mouse tail suspension test.

It has been reported that chlorpheniramine, a classical antihistamine, has antidepressant-like effects in animal models of depression. In this study, we examined the involvement of dopaminergic (dopamine D(1) and dopamine D(2) receptors), noradrenergic (alpha(1)- and beta-adrenoceptors) and serotonergic (5-HT(1A) and 5-HT(2) receptors) receptors in the antidepressant-like effect of chlorpheniramine in the mouse tail suspension test. We also investigated the involvement of these monoamine receptors in the antidepressant-like effect of imipramine for comparison with the mechanisms of the effect of chlorpheniramine. Both imipramine and chlorpheniramine significantly reduced the duration of immobility in the tail suspension test without affecting spontaneous locomotor activity in mice. The anti-immobility effect of imipramine (30 mg/kg, i.p.) was significantly antagonized by the selective dopamine D(1) receptor antagonist SCH23390 but not by the other receptor antagonists. In contrast, the anti-immobility effect of chlorpheniramine was significantly inhibited by SCH23390 and the selective alpha(1)-adrenoceptor antagonist prazosin, but not by the other receptor antagonists. In conclusion, these results suggest that chlorpheniramine exerts an antidepressant-like effect in the mouse tail suspension test that is mediated by at least the activation of dopamine D(1) receptors and alpha(1)-adrenoceptors. In addition, the antidepressant-like effect of chlorpheniramine may be induced by several mechanisms that are different from those involved in the antidepressant-like effect of imipramine.

Diabetes attenuates psychological stress-elicited 5-HT secretion in the prefrontal cortex but not in the amygdala of mice.

It is well established that diabetes widely affects the functioning of the central nervous system. However, no in vivo study assessed the serotonin (5-HT)-releasing system in the prefrontal cortex (PFC) and amygdala--the crucial regions regulating emotion. We investigated the effects of streptozotocin (STZ)-induced diabetes on the levels of extracellular 5-HT in the PFC and amygdala by using an in vivo microdialysis technique in mice. In addition, the effects of psychological stress on 5-HT secretion were also examined. The basal and the selective 5-HT reuptake inhibitor citalopram (1 microM)-accumulated 5-HT levels remained unchanged in both the PFC and amygdala of diabetic mice. The elevated open platform stress-elicited 5-HT secretion was significantly decreased in the PFC of diabetic mice, and this blunted response was normalized by sub-chronic pretreatment with insulin (5 U/kg, s.c., twice daily). Diabetes had no significant effect on the KCl (100 mM)-stimulated 5-HT release in the PFC. In the amygdala, diabetes had no effect on the stress-elicited 5-HT secretion. Diabetic mice exhibited prolonged freezing as compared to the non-diabetic mice in the elevated open-platform test. In addition, insulin-treated diabetic mice showed the significant shorter duration of freezing than that in diabetic mice. In conclusion, our present findings indicate that diabetes attenuates the serotonergic response to stressful stimuli in a site-specific fashion. In addition, we suggest the possibility that the dysfunction of stress-elicited 5-HT release, but not basal 5-HT release, causes the increased expression of fear-related behavior in diabetic mice.

Antidepressant-like effect of leptin in streptozotocin-induced diabetic mice.

We previously reported that streptozotocin (STZ)-induced diabetic mice showed the depressive-like behavior in the tail suspension test. It has also been reported that leptin-deficient obese mice demonstrate the depressive-like behavior. Since STZ-induced diabetes causes a marked decrease in plasma leptin levels, it is possible that decrease in leptin levels and the depressive-like behavior may somehow be related. Therefore, we examined the effect of leptin on the depressive-like behavior of STZ-induced diabetic mice in the tail suspension test. The prolonged duration of immobility in diabetic mice was dose-dependently and significantly suppressed by single treatment with leptin (0.1-1 mg/kg, i.p.) without affecting on the locomotor activity. Leptin did not affect either the duration of immobility or the locomotor activity in non-diabetic mice. The anti-immobility effect of leptin (1 mg/kg, i.p.) in diabetic mice was significantly antagonized by the selective serotonin2 (5-HT2) receptor antagonist LY53,857 (0.03 mg/kg, s.c.), but not by the selective 5-HT1A receptor antagonist WAY-100635 (0.03 mg/kg, s.c.). Antagonists administered alone did not affect either the duration of immobility or the locomotor activity in diabetic mice. In conclusion, we suggest that leptin exerts the antidepressant-like effect in diabetic mice mediated by, at least in part, 5-HT2 receptors.

[Effect of streptozotocin-induced diabetes on the function of the central nervous system in rodents].

The prevalence of cognitive disorder, depression, and anxiety is about 2-fold higher in diabetic patients than in the general population. This higher prevalence is also observed in Japanese patients with diabetes. It has been reported that streptozotocin (STZ)-induced diabetic rodents demonstrate cognitive impairment, depressive-like behavior, and anxiety-like behavior. In addition, plasma corticosterone levels are significantly increased in STZ-induced diabetic rodents. Therefore, STZ-induced diabetic rodents demonstrate similar features as in patients with depression. In this review, we summarized the effect of STZ-induced diabetes on the function of the central nervous system in rodents and the similarity to the clinical features of several psychiatric disorders such as depression.

Involvement of diazepam-insensitive benzodiazepine receptors in the suppression of DOI-induced head-twitch responses in diabetic mice.

RATIONALE: We previously reported that the head-twitch responses induced by the 5-HT2 receptor agonist (+/-)-2,5-dimethoxy-4-iodoamphetamine (DOI) (DOI-HTRs) were decreased in streptozotocin-induced diabetic mice. OBJECTIVES: We examined the involvement of gamma-aminobutyric acid (GABA)/benzodiazepine system on the suppression of DOI-HTRs in diabetic mice. RESULTS: The benzodiazepine receptor antagonist flumazenil (0.1-1 mg/kg, i.v.) dose-dependently and significantly increased DOI-HTRs in diabetic mice to the same levels as in nondiabetic mice. However, flumazenil (0.1-1 mg/kg, i.v.) did not affect DOI-HTRs in nondiabetic mice. The benzodiazepine receptor agonist diazepam (0.1-1 mg/kg, i.p.) had no effect on DOI-HTRs in either nondiabetic or diabetic mice. The GABAA receptor antagonist bicuculline (0.1-1 mg/kg, i.p.) and the benzodiazepine receptor partial inverse agonist Ro 15-4513 (0.1-1 mg/kg, i.v.) dose-dependently and significantly suppressed DOI-HTRs in nondiabetic mice to the same levels as in diabetic mice. Ro 15-4513-induced reduction of DOI-HTRs in nondiabetic mice was completely antagonized by flumazenil (1 mg/kg, i.v.), but not diazepam (0.3 mg/kg, i.p.). CONCLUSIONS: We suggest that the abnormal diazepam-insensitive benzodiazepine receptor function partly underlies the suppression of DOI-HTRs in diabetic mice.

Effects of histamine H(1) receptor antagonists on depressive-like behavior in diabetic mice.

We previously reported that streptozotocin-induced diabetic mice showed depressive-like behavior in the tail suspension test. It is well known that the central histaminergic system regulates many physiological functions including emotional behaviors. In this study, we examined the role of the central histaminergic system in the diabetes-induced depressive-like behavior in the mouse tail suspension test. The histamine contents in the hypothalamus were significantly higher in diabetic mice than in non-diabetic mice. The histamine H(1) receptor antagonist chlorpheniramine (1-10 mg/kg, s.c.) dose-dependently and significantly reduced the duration of immobility in both non-diabetic and diabetic mice. In contrast, the selective histamine H(1) receptor antagonists epinastine (0.03-0.3 microg/mouse, i.c.v.) and cetirizine (0.01-0.1 microg/mouse, i.c.v.) dose-dependently and significantly suppressed the duration of immobility in diabetic mice, but not in non-diabetic mice. Spontaneous locomotor activity was not affected by histamine H(1) receptor antagonists in either non-diabetic or diabetic mice. In addition, the number and affinity of histamine H(1) receptors in the frontal cortex were not affected by diabetes. In conclusion, we suggest that the altered neuronal system mediated by the activation of histamine H(1) receptors is involved, at least in part, in the depressive-like behavior seen in diabetic mice.

Abnormal benzodiazepine receptor function in the depressive-like behavior of diabetic mice.

We previously reported that streptozotocin (STZ)-induced diabetic mice exhibited depressive-like behavior in the tail suspension test. In this study, we examined the involvement of benzodiazepine receptor functions in this diabetes-induced depressive-like behavior in mice. STZ-induced diabetes significantly increased the duration of immobility without affecting spontaneous locomotor activity. This increase was dose-dependently and significantly suppressed by a benzodiazepine receptor antagonist, flumazenil (0.1-1 mg/kg, i.v.). However, flumazenil (0.1-1 mg/kg, i.v.) did not affect the duration of immobility in non-diabetic mice. Furthermore, flumazenil (1 mg/kg, i.v.) had no significant effect on spontaneous locomotor activity in either non-diabetic or diabetic mice. The benzodiazepine receptor inverse agonist methyl beta-carboline-3-carboxylate (beta-CCM; 0.03-0.3 mg/kg, i.v.) dose-dependently and significantly increased the duration of immobility in non-diabetic mice, but not in diabetic mice. beta-CCM (0.3 mg/kg, i.v.) significantly suppressed spontaneous locomotor activity in non-diabetic mice, but not in diabetic mice. These results indicate that diabetic mice may have enhanced negative allosteric modulation by benzodiazepine receptor ligands, such as diazepam binding inhibitors, under stressful conditions, but not free-moving conditions, and this abnormal function of benzodiazepine receptors may cause, at least in part, the expression of depressive-like behavior in diabetic mice.

Effects of first- and second-generation histamine-H1-receptor antagonists on the pentobarbital-induced loss of the righting reflex in streptozotocin-induced diabetic mice.

The second-generation histamine-H(1)-receptor antagonists, such as epinastine and cetirizine, are used as non-sedating antihistamines for treating allergic symptoms due to their poor ability to penetrate blood-brain barrier. Because it has been reported that the blood-brain barrier system is disturbed in diabetes, it is possible that second-generation histamine-H(1)-receptor antagonists may easily penetrate the blood-brain barrier and cause potent sedation in diabetics. In the present study, we investigated the effects of first-generation (diphenhydramine) and second-generation (epinastine and cetirizine) histamine-H(1)-receptor antagonists on the duration of pentobarbital-induced loss of the righting reflex (LORR) in non-diabetic and diabetic mice. Systemic treatment with diphenhydramine (3 - 30 mg/kg, s.c.), and intracerebroventricular treatment with epinastine (0.03 - 0.3 microg/mouse) and cetirizine (0.03 - 0.3 microg/mouse) dose-dependently and significantly increased the duration of pentobarbital-induced LORR in both non-diabetic and diabetic mice. Although systemic treatment with epinastine (3 - 30 mg/kg, s.c.) and cetirizine (3 - 30 mg/kg, s.c.) did not affect the duration of pentobarbital-induced LORR in non-diabetic mice, these treatments significantly prolonged it in diabetic mice. Our results suggest that the systemic administration of second-generation histamine-H(1)-receptor antagonists may produce a central nervous system depressant effect in diabetes.

Diabetes inhibits the DOI-induced head-twitch response in mice.

RATIONALE: Clinical studies suggest that the prevalence of psychiatric disorders is higher in diabetic patients than in the general population. It has been reported that central serotonin(2A) (5-HT(2A)) receptors may be involved in the pathogenesis and treatment of psychiatric disorders. OBJECTIVES: We examined the effect of streptozotocin-induced diabetes on the function of central 5-HT(2A) receptors in mice. METHODS: Male ICR mice were rendered diabetic by an injection of streptozotocin (200 mg/kg, i.v.). The experiments were conducted 2 weeks after the injection of streptozotocin. To evaluate the central 5-HT(2A) receptor function, head-twitch responses were measured for 15 min immediately after the treatment with (+/-)-2,5-dimethoxy-4-iodoamphetamine (DOI) (0.1-1 mg/kg, s.c.), a selective 5-HT(2) receptor agonist. RESULTS: Significantly fewer head-twitch responses were induced by DOI in diabetic mice than in non-diabetic mice. The number and affinity of 5-HT(2A) receptors in the mouse frontal cortex were not affected by diabetes. The corticosterone response to DOI (1 mg/kg and 3 mg/kg, s.c.) was not different between non-diabetic and diabetic mice, although the baseline of plasma corticosterone levels was significantly higher in diabetic than in non-diabetic mice. CONCLUSIONS: Our results suggest that a neuronal network that causes head-twitch responses by triggering by the activation of 5-HT(2A) receptors may be altered by type-1 diabetes in mice.

[Diabetes attenuates the antidepressant-like effect mediated by the activation of 5-HT1A receptors in the mouse tail suspension test].

Several lines of evidence have indicated that the prevalence of psychiatric disorders in diabetic subjects is higher than that in the general population, however, little information is available on the effects of antidepressants in diabetes. In the present review, we summarized the effect of diabetes on the central serotonergic systems and the efficacy of serotonergic antidepressants. Streptozotocin-induced diabetic mice showed prolonged duration of immobility compared to non-diabetic mice in the tail suspension test. This behavioral change was unrelated to the transient increases in blood glucose concentrations or decreased body weights by diabetes. Fluoxetine, a selective serotonin (5-HT) reuptake inhibitor, reduced the duration of immobility in both non-diabetic and diabetic mice. However, a selective 5-HT1A receptor antagonist WAY-100635 reversed the antidepressant-like effect of fluoxetine only in non-diabetic mice. In addition, a 5-HT1A receptor agonist 8-OH-DPAT reduced the duration of immobility in non-diabetic mice, but not in diabetic mice. These results suggest a possibility that the antidepressant-like effect mediated by the activation of 5-HT1A receptors may be attenuated by diabetes.

Diabetes attenuates the antidepressant-like effect mediated by the activation of 5-HT1A receptor in the mouse tail suspension test.

Several lines of evidence have indicated that the prevalence of depression in diabetic subjects is higher than that in the general population, however, little information is available on the effects of antidepressants in diabetes. In the present study, the antidepressant-like effect mediated by the activation of 5-HT(1A) receptors was examined using the tail suspension test in streptozotocin-induced diabetic mice. Long-lasting increases in 5-HT turnover rates were observed in the diabetic mouse midbrain and frontal cortex, but not in the hippocampus. Duration of immobility was significantly longer in diabetic than in nondiabetic mice in the tail suspension test. The 5-HT(1A) receptor agonist (+/-)-8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) (3-30 microg/kg, i.p.) reduced the duration of immobility in nondiabetic mice, and this effect was completely antagonized by pretreatment with N-[2-[4-(2-methoxyphenil)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY-100635) (30 microg/kg, s.c.), a selective 5-HT(1A) receptor antagonist. In contrast, 8-OH-DPAT (3 microg/kg-3 mg/kg, i.p.) was ineffective in diabetic mice. The selective 5-HT reuptake inhibitor fluoxetine (3-56 mg/kg, i.p.) reduced the duration of immobility in both nondiabetic and diabetic mice. However, fluoxetine was less effective in diabetic mice than in nondiabetic mice. WAY-100635 (30 microg/kg, s.c.) reversed the suppression of the duration of immobility by fluoxetine (30 mg/kg, i.p.) in nondiabetic mice. On the other hand, the anti-immobility effect of fluoxetine (56 mg/kg, i.p.) was not antagonized by WAY-100635 (30 microg/kg, s.c.) in diabetic mice. The selective 5-HT(2) receptor antagonist 6-methyl-1-(1-methylethyl)-ergoline-8beta-carboxylic acid 2-hydroxy-1-methylpropyl ester (LY53,857) (30 microg/kg, s.c.) reversed the anti-immobility effect of fluoxetine in both nondiabetic and diabetic mice. Spontaneous locomotor activity in diabetic mice was not different from that in nondiabetic mice. 8-OH-DPAT (30 microg/kg, i.p.), but not fluoxetine, increased the spontaneous locomotor activity in both nondiabetic and diabetic mice. The number of 5-HT(1A) receptors in the mouse frontal cortex was unaffected by diabetes. Plasma corticosterone levels in diabetic mice were significantly higher than that in nondiabetic mice. These results suggest that the antidepressant-like effect mediated by 5-HT(1A) receptors may be attenuated by diabetes.