TOM40 mediates the effect of TSPO on postpartum depression partially through regulating calcium homeostasis in microglia

AIMS

To assess the effect of the translocator protein 18 kDa (TSPO) on postpartum depression and explore its mechanism.

METHODS

Postpartum depression (PPD) mouse model was established, and flow cytometry, immunofluorescence, Western blot analysis, real-time quantitative PCR, adeno-associated virus (AAV), co-immunoprecipitation-mass spectrometry and immunofluorescence co-staining were used to detect the effect of TSPO ligand ZBD-2 on PPD mice.

RESULTS

ZBD-2 inhibits the overactivation of microglia in the hippocampus and amygdala of PPD model mice. ZBD-2 not only inhibited the inflammation but also repressed the burst of reactive oxygen species (ROS) and mitochondrial ROS (mtROS). Meanwhile, ZBD-2 protects mitochondria from LPS-induced damages through inhibiting the influx of calcium. ZBD-2 modulated the calcium influx by increasing the level of translocase of the outer mitochondrial membrane 40 (TOM40) and reducing the interaction of TSPO and TOM40. In addition, the effect of ZBD-2 was partially dependent on anti-oxidative process. Knockdown of TOM40 by adeno-associated virus (AAV) in the hippocampus or amygdala dramatically reduced the effect of ZBD-2 on PPD, indicating that TOM40 mediates the effect of ZBD-2 on PPD.

CONCLUSIONS

TOM40 is required for the effect of ZBD-2 on treating anxiety and depression in PPD mice. This study reveals the role of microglia TSPO in PPD development and provides the new therapeutic strategy for PPD.

Tanshinone IIA improves contextual fear- and anxiety-like behaviors in mice via the CREB/BDNF/TrkB signaling pathway

Posttraumatic stress disorder (PTSD) is one of the most common psychiatric diseases, which is characterized by the typical symptoms such as re-experience, avoidance, and hyperarousal. However, there are few drugs for PTSD treatment. In this study, conditioned fear and single-prolonged stress were employed to establish PTSD mouse model, and we investigated the effects of Tanshinone IIA (TanIIA), a natural product isolated from traditional Chinese herbal Salvia miltiorrhiza, as well as the underlying mechanisms in mice. The results showed that the double stress exposure induced obvious PTSD-like symptoms, and TanIIA administration significantly decreased freezing time in contextual fear test and relieved anxiety-like behavior in open field and elevated plus maze tests. Moreover, TanIIA increased the spine density and upregulated synaptic plasticity-related proteins as well as activated CREB/BDNF/TrkB signaling pathway in the hippocampus. Blockage of CREB remarkably abolished the effects of TanIIA in PTSD model mice and reversed the upregulations of p-CREB, BDNF, TrkB, and synaptic plasticity-related protein induced by TanIIA. The molecular docking simulation indicated that TanIIA could interact with the CREB-binding protein. These findings indicate that TanIIA ameliorates PTSD-like behaviors in mice by activating the CREB/BDNF/TrkB pathway, which provides a basis for PTSD treatment.

Association of thymosin β4 expression with clinicopathological parameters and clinical outcomes of bladder cancer patients

The clinical significance of thymosin β4 (Tβ4) expression in bladder transitional cell carcinoma (BTCC) remains unclear. The present study assessed the relationship between the expression of Tβ4 protein and the clinicopathological features, as well as the prognosis of bladder cancer patients. Tβ4 protein expression in 24 normal bladder and 138 primary BTCC tissue specimens was detected by immunohistochemistry, and the association of this expression with BTCC clinicopathological features and recurrence as well as patient survival was analyzed. Tβ4 expression was significantly stronger in BTCC patients than in normal volunteers. The expression of Tβ4 was significantly associated with differentiation capability, tumor stage and lymph node metastasis (P = 0.025, 0.043, and 0.039, respectively). Moreover, Tβ4 expression was positively correlated with integrin-linked kinase (ILK) and β-catenin expression (P = 0.042, 0.031, respectively) and inversely correlated with E-cadherin expression (P = 0.022). In the present cohort of bladder cancer patients, Tβ4 expression was found to be a predictor of poor survival (P < 0.05); however, high Tβ4 expression exhibited unfavorable prognostic value for recurrence. These data suggested that Tβ4 is correlated with the pathogenesis of BTCC. In addition, the patients with higher Tβ4 expression had a shorter survival.

Mechanical properties for irradiated face-centred cubic nanocrystalline metals

In this paper, a self-consistent plasticity theory is proposed to model the mechanical behaviours of irradiated face-centred cubic nanocrystalline metals. At the grain level, a tensorial crystal model with both irradiation and grain size effects is applied for the grain interior (GI), whereas both grain boundary (GB) sliding with irradiation effect and GB diffusion are considered in modelling the behaviours of GBs. The elastic-viscoplastic self-consistent method with considering grain size distribution is developed to transit the microscopic behaviour of individual grains to the macroscopic properties of nanocrystals (NCs). The proposed theory is applied to model the mechanical properties of irradiated NC copper, and the feasibility and efficiency have been validated by comparing with experimental data. Numerical results show that: (i) irradiation-induced defects can lead to irradiation hardening in the GIs, but the hardening effect decreases with the grain size due to the increasing absorption of defects by GBs. Meanwhile, the absorbed defects would make the GBs softer than the unirradiated case. (ii) There exists a critical grain size for irradiated NC metals, which separates the grain size into the irradiation hardening dominant region (above the critical size) and irradiation softening dominant region (below the critical size). (iii) The distribution of grain size has a significant influence on the mechanical behaviours of both irradiated and unirradiated NCs. The proposed model can offer a valid theoretical foundation to study the irradiation effect on NC materials.

Soybean phytoalexin, glyceollin, prevents accumulation of aflatoxin B1 in cultures ofAspergillus flavus

The soybean phytoalexin, glyceollin, suppresses the accumulation of aflatoxin B1 in cultures ofAspergillus flavus. At concentrations of 6.25μg/ ml and 62.5μg/ml, glyceollin causes 70% and 95% decreases in the maximum observed levels of aflatoxin B1, respectively. In contrast to the dramatic effect on aflatoxin B1 levels, these concentrations have little effect on fungal growth. For example, at 62.5μg/ml in liquid culture, glyceollin causes a barely discernible lag in the beginning of growth and a 11.5% decrease in maximum fungal mass. When the same concentration of glyceollin is added to the colony margin on semisolid medium, an inhibition zone is formed and then overgrown in one day. Glyceollin appears to act by inhibiting aflatoxin B1 synthesis, since the rate of aflatoxin B1 breakdown is not increased in fungal cultures that have been grown in the presence of glyceollin. Glyceollin does accumulate in viable soybean seeds that have been infected withAspergillus flavus. Such seeds accumulate aflatoxin B1 at one-third the rate of non-glyceollin-producing, nonviable seeds. These results suggest that the synthesis of glyceollin in infected seeds may explain, at least in part, why aflatoxin contamination of soybeans is not a common problem.

Ambivalent role of gallated catechins in glucose tolerance in humans: a novel insight into non-absorbable gallated catechin-derived inhibitors of glucose absorption

Prolonged postprandial hyperglycemia is a detrimental factor for type 2 diabetes and obesity. The benefit of green tea extract (GTE) consumption still requires confirmation. We report the effects of circulating green tea catechins on blood glucose and insulin levels. Oral glucose loading 1 h after GTE ingestion in humans led to higher blood glucose and insulin levels than in control subjects. Gallated catechins were required for these effects, although within the intestinal lumen they have been known to decrease glucose and cholesterol absorption. Treatment with epigallocatechin-3-gallate hindered 2-deoxyglucose uptake into liver, fat, pancreatic beta-cell, and skeletal muscle cell lines. The glucose intolerance was ameliorated by gallated catechin-deficient GTE or GTE mixed with polyethylene glycol, which was used as an inhibitor of intestinal absorption of gallated catechins. These findings may suggest that the gallated catechin when it is in the circulation elevates blood glucose level by blocking normal glucose uptake into the tissues, resulting in secondary hyperinsulinemia, whereas it decreases glucose entry into the circulation when they are inside the intestinal lumen. These findings encourage the development of non-absorbable derivatives of gallated catechins for preventative treatment of type 2 diabetes and obesity, which would specifically induce only the positive luminal effect.

Cyclin-dependent kinase-5 prevents neuronal apoptosis through ERK-mediated upregulation of Bcl-2

Cyclin-dependent kinase-5 (Cdk5) is required for neuronal survival, but its targets in the apoptotic pathways remain unknown. Here, we show that Cdk5 kinase activity prevents neuronal apoptosis through the upregulation of Bcl-2. Treatment of SH-SY5Y cells with retinoid acid (RA) and brain-derived neurotrophic factor (BDNF) generates differentiated neuron-like cells. DNA damage triggers apoptosis in the undifferentiated cells through mitochondrial pathway; however, RA/BDNF treatment results in Bcl-2 upregulation and inhibition of the mitochondrial pathway in the differentiated cells. RA/BDNF treatment activates Cdk5-mediated PI3K/Akt and ERK pathways. Inhibition of Cdk5 inhibits PI3K/Akt and ERK phosphorylation and Bcl-2 expression, and thus sensitizes the differentiated cells to DNA-damage. Inhibition of ERK, but not PI3K/Akt, abrogates Cdk5-medidated Bcl-2 upregulation and the protection of the differentiated cells. This study suggests that ERK-mediated Bcl-2 upregulation contributes to BDNF-induced Cdk5-mediated neuronal survival.

Persistent autoregulatory disturbance after angioplasty for cerebral vasospasm. A case report

SUMMARY

Hyperdynamic therapy, consisting of hypervolemia, haemodilution, and hypertension, is an established treatment for cerebral vasospasm following subarachnoid haemorrhage. Angioplasty has emerged as an additional, effective treatment for symptomatic vasospasm. Loss of autoregulation, however, can occur despite effective angioplasty, underscoring the need for treatment with hyperdynamic therapy in combination with angioplasty. A 43-year-old woman underwent endovascular coiling of a ruptured left posterior communicating artery aneurysm. The patient went on to develop symptomatic vasospasm and was treated with hyperdynamic therapy and angioplasty. Autoregulation was assessed with xenon CT cerebral blood flow (CBF) measurement. An initial CBF study was obtained when the patient received dopamine and dobutamine infusions to maintain systolic blood pressure at 160 mmHg. The vasopressor drips were then temporarily held for twenty minutes, allowing the patient's systolic blood pressure to drop to 140 mmHg, and a repeat CBF study was obtained. Several days after angioplasty, CBF decreased significantly when the patient was taken off vasopressors, indicating impaired autoregulation. Hyperdynamic therapy was continued, and another CBF study one week later showed a return of autoregulation and normalization of CBF without induced hypertension. Autoregulation is disturbed during vasospasm. Although angioplasty can improve large artery blood flow during vasospasm, hyperdynamic therapy is also needed to maintain cerebral perfusion, particularly in the face of impaired autoregulation. Quantitative CBF measurement permits the maintenance of optimal CBF and monitoring of response to therapy.

Adeno-associated viral glutamate decarboxylase expression in the lateral nucleus of the rat hypothalamus reduces feeding behavior

In vivo gene transfer of glutamate decarboxylase (GAD) has been explored as a means of inducing or increasing the production of the inhibitory amino-acid neurotransmitter, GABA. This strategy has been applied to neuroprotection, seizure prevention, and neuromodulation. In the present experiment, AAV2 was used to transfer the genes for green fluorescence protein (GFP) and GAD65 into the lateral nucleus of the rat hypothalamus. Microinjection of 500 nl of AAV2 resulted in transduction of a 0.25+/-0.04 mm(3) with targeting errors of X=0.48 mm, Y=0.18 mm, Z=0.37 mm using standard stereotactic technique. Pre- and postinjection food and water consumption, urine and feces production, and weight were recorded. In comparison with rAAVCAGGFP- and PBS-injected animals, rats treated with rAAVCAGGAD65 demonstrated reduced weight gain (P<0.014) and transiently reduced daily food consumption (P<0.007) during the postoperative period. No changes in water consumption or waste production were recorded. Effective GAD65 gene transfer was confirmed with in situ hybridization using a probe to the woodchuck post-transcriptional regulatory element sequence included in the vector. These findings suggest that increased GABA production in lateral nucleus of the hypothalamus induced by GAD65 gene transfer may reduce weight gain through reduced feeding.

Characterization of antidepressant-like effects of p-synephrine stereoisomers

We previously reported that p-synephrine has antidepressant-like activity in the murine models of forced swimming and tail suspension. In the present study, we characterized antidepressant-like effects of p-synephrine stereoisomers in both in vivo and in vitro systems. In the tail suspension test, S-(+)-p-synephrine (3 mg/kg, p.o.) reduced the duration of immobility, while R-(-)-p-synephrine (0.3-3 mg/kg, p.o.) had no effect. S-(+)-p-synephrine (0.3, 1 and 3 mg/kg, p.o.) and R-(-)-p-synephrine (1 mg/ kg and 3 mg/kg, p.o.) significantly reversed the reserpine (2.5 mg/kg, i.p.)-induced hypothermia. S-(+)-p-synephrine was more effective than R-(-)-p-synephrine in inhibition of both [3H]noradrenaline uptake in rat cerebral cortical slices (maximal inhibition 85.7 +/- 7.8% vs. 59.8 +/- 4.3%; EC50 5.8 +/- 0.7 microM vs. 13.5 +/- 1.2 microM) and [3H]nisoxetine binding (Ki 4.5 +/- 0.5 microM vs. 8.2 +/- 0.7 microM). In contrast, R-(-)-p-synephrine was more effective than S-(+)-p-synephrine in stimulation of [3H]noradrenaline release from rat cerebral cortical slices (maximal stimulation 23.9 +/- 1.8% vs. 20.1 +/- 1.7%; EC50 8.2 +/- 0.6 microM vs. EC50 12.3 +/- 0.9 microM). The stimulatory effect of R-(-)-p-synephrine on [3H]noradrenaline release was inhibited by nisoxetine (100 nM), but tetrodotoxin (1 microM) and elimination of extracellular calcium had no effect. It is suggested that S-(+)-p-synephrine has more effective antidepressant-like activity than R-(-)-p-synephrine.

ATP modulation of ATP-sensitive potassium channel ATP sensitivity varies with the type of SUR subunit

ATP-sensitive potassium (K(ATP)) channels comprise Kir and SUR subunits. Using recombinant K(ATP) channels expressed in Xenopus oocytes, we observed that MgATP (100 microm) block of Kir6.2/SUR2A currents gradually declined with time, whereas inhibition of Kir6.2/SUR1 or Kir6.2DeltaC36 currents did not change. The decline in Kir6.2/SUR2A ATP sensitivity was not observed in Mg(2+) free solution and was blocked by the phosphatidylinositol (PI) 3-kinase inhibitors LY 294002 (10 microm) and wortmannin (100 microm), and by neomycin (100 microm). These results suggest that a MgATP-dependent synthesis of membrane phospholipids produces a secondary decrease in the ATP sensitivity of Kir6.2/SUR2A. Direct application of the phospholipids PI 4,5-bisphosphate and PI 3,4,5-trisphosphate in the presence of 100 microm MgATP activated all three types of channel, but the response was faster for Kir6.2/SUR2A. Chimeric studies indicate that the different responses of Kir6.2/SUR2A and Kir6.2/SUR1 are mediated by the first six transmembrane domains of SUR. The MgATP-dependent loss of ATP sensitivity of Kir6.2/SUR2A was enhanced by the actin filament disrupter cytochalasin and blocked by phalloidin (which stabilizes the cytoskeleton). Phalloidin did not block the effect of PI 3,4,5-trisphosphate. This suggests that MgATP may cause disruption of the cytoskeleton, leading to enhanced membrane phospholipid levels (or better targeting to the K(ATP) channel) and thus to decreased channel ATP sensitivity.

Central beta-amyloid peptide-induced peripheral interleukin-6 responses in mice

beta-Amyloid peptides (Abetas) share with lipopolysaccharide, a potent pro-inflammatory agent, the property of stimulating glial cells or macrophages to induce various inflammatory mediators. We recently reported that central administration of lipopolysaccharide induces peripheral interleukin-6 responses via both the central and peripheral norepinephrine system. In this study, the effect of intracerebroventricular injection of various synthetic Abetas on plasma interleukin-6 levels was examined in mice. Abeta(1-42) dose-dependently increased plasma interleukin-6 levels: 'aged' Abeta(1-42) was more effective than fresh, whereas Abeta(42-1) had no effect. 'Aged' Abeta(1-42) (205 pmol/mouse i.c.v.)-induced plasma interleukin-6 peaked at 2 h post injection, which is earlier than the peak time of the Abeta(1-42)-induced brain interleukin-6, tumor necrosis factor-alpha and interleukin-1beta levels, which was 4, 4 and 24 h, respectively. Among various peripheral organs, Abeta(1-42) (205 pmol/mouse i.c.v.) significantly increased interleukin-6 mRNA expression in lymph nodes and liver. Abeta(1-42) (205 pmol/mouse i.c.v.) significantly increased norepinephrine turnover in both hypothalamus and spleen. Either central or peripheral norepinephrine depletion effectively inhibited the Abeta(1-42)-induced peripheral interleukin-6 response. Pretreatment with prazosin (alpha(1)-adrenergic antagonist), yohimbine (alpha(2)-adrenergic antagonist), and ICI-118,551 (beta(2)-adrenergic antagonist), but not with betaxolol (beta(1)-adrenergic antagonist), inhibited Abeta(1-42)-induced plasma interleukin-6 levels. These results demonstrate that centrally administered Abeta(1-42) effectively induces the systemic interleukin-6 response which is mediated, in part, by central Abeta(1-42)-induced activation of the central and the peripheral norepinephrine systems.

Effect of melatonin on the regulation of proenkephalin and prodynorphin mRNA levels induced by kainic acid in the rat hippocampus

The in vivo short-term effect of melatonin on kainic acid (KA)-induced proenkephalin (proENK) or prodynorphin (proDYN) mRNA, and on AP-1 protein levels in the rat hippocampus, were studied. Melatonin (5 mg/kg) or saline was administered intraperitoneally (i.p.) to rats 30 min prior to and immediately after i.p. injection of KA (10 mg/kg). Rats were sacrificed 1 and 3 h after KA injection. The proENK and proDYN mRNA levels were significantly increased 3 h after KA administration. The elevations of both proENK and proDYN mRNA levels induced by KA were significantly inhibited by the preadministration with melatonin. The increases of proENK and proDYN mRNA levels induced by KA were well-correlated with the increases of c-Fos, Fra-2, FosB, c-Jun, and JunB protein levels, which were significantly increased 3 h after KA administration and effectively inhibited by administration with melatonin. In an electrophoretic mobility shift assay, both AP-1 and ENKCRE-2 DNA binding activities were increased by KA, which were also attenuated by the administration of melatonin. In addition, cross-competition studies revealed that AP-1 or ENKCRE-2 DNA binding activity was effectively reduced by the 50x unlabeled cross-competitor. Therefore, these data suggest that melatonin has an inhibitory role in KA-induced gene expression, such as proENK and proDYN mRNA expression, and this may be due to a reduction of KA-induced AP-1 or ENKCRE-2 DNA binding activity.

Increased plasma corticosterone, aggressiveness and brain monoamine changes induced by central injection of pertussis toxin

The effects of intracerebroventricular (i.c.v.) injection of pertussis toxin, a specific inhibitor of G(i)/G(o) proteins, on plasma corticosterone levels, aggressiveness, and hypothalamic and hippocampal monoamines and their metabolites levels were examined in mice. Plasma corticosterone level was markedly increased at 3 h after pertussis toxin injection (0.03 and 0.2 microg/mouse), peaked at 6 h and was still increased for up to 6 days after injection. Mice injected with pertussis toxin (0.2 microg/mouse) did not show weight gain between day 0 and day 6 after injection. In addition, pertussis toxin (0.2 microg/mouse) induced a progressive increase in aggressiveness, i.e. a decrease in attack latency and an increase in number of attacks, on day 1 and 6 after injection. Brain monoamines and their metabolites levels were changed on day 1 and 6 after pertussis toxin injection (0.2 microg/mouse): in the hypothalamus, levels of dopamine and 3,4-dihydroxyphenylacetic acid were increased, norepinephrine level decreased, and 5-hydroxyindole acetic acid (5-HIAA) level was markedly increased, with no changes in 5-hydroxytryptamine (5-HT) level, whereas in the hippocampus, 5-HT level was significantly decreased, with no changes in 5-HIAA and catecholamines. These results suggest that signal transduction through G(i)/G(o) proteins in the brain is involved in the modulation of hypothalamo-pituitary-adrenal axis, aggressiveness, and monoamine levels in vivo.

Inhibition of brain protein kinase C attenuates immobilization stress-induced plasma corticosterone levels in mice

To evaluate the involvement of brain protein kinase C (PKC) in the stress-induced activation of hypothalamic-pituitary-adrenal (HPA) axis, we examined the effects of PKC inhibitors administered intracerebroventricularly (i.c.v.) on the immobilization stress-induced plasma corticosterone levels in mice. Calphostin C (a pan-specific PKC inhibitor) injected i.c.v. decreased the immobilization stress-induced plasma corticosterone level: maximal inhibition of 35% was attained at a dose of 100 pmol. Gö 6976 (an alpha and beta1 PKC isotype-selective inhibitor) was less effective than Calphostin C: maximal inhibition of 17% was attained at a dose of 30 pmol. Phorbol 12-myristate 13-acetate (a general PKC activator) injected i.c.v. at doses of 16 and 48 pmol increased the plasma corticosterone levels in a dose-dependent manner. The present study demonstrates the involvement of PKC in the brain in the regulation of the immobilization stress-induced stimulation of HPA axis in vivo.

Involvement of dynorphin in immobilization stress-induced antinociception in the mouse

The effect of antiserum against [Met(5)]-enkephalin, [Leu(5)]-enkephalin, beta-endorphin, or dynorphin A-(1-13) administered intracerebroventricularly (i.c.v.) or intrathecally (i. t.) on immobilization-induced antinociception was studied in ICR mice. Antinociception was assessed by the tail-flick assay. Immobilization of the mouse increased inhibition of the tail-flick response at least 1 h. The i.c.v. or i.t. injection with antiserum against dynorphin A-(1-13) at the dose of 200 microg significantly attenuated immobilization-induced inhibition of the tail-flick response. However, antiserum against [Met(5)]-enkephalin, [Leu(5)]-enkephalin, or beta-endorphin did not affect the immobilization stress-induced antinociception. Furthermore, i.c.v. or i.t. injection with nor-binaltorphimine (Nor-BNI; from 1 to 20 microg) effectively inhibited immobilization stress-induced inhibition of the tail-flick response in a dose-dependent manner. However, beta-FNA (from 0.5 to 2 microg) or naltrindole (from 1 to 20 microg) administered i.c.v. or i.t. did not affect immobilization stress-induced antinociception. Our results suggest that supraspinally and spinally located dynorphin appears to be involved in the production of immobilization stress-induced antinociception via stimulating kappa-opioid receptors.

Regulation of c-fos gene expression by lipopolysaccharide and cycloheximide in C6 rat glioma cells

The effect of lipopolysaccharide (LPS) on the expression of immediate early genes, such as c-fos and c-jun, was examined in C6 rat glioma cells. LPS (1 microg/ml) alone did not affect c-fos mRNA level. LPS, however, transiently increased c-jun mRNA level. Cycloheximide (CHX, 20 microM), a protein synthesis inhibitor, alone caused increases of c-fos and c-jun mRNA levels. LPS showed a potentiating effect in the regulation of c-fos mRNA level, whereas LPS showed an additive action for the regulation of CHX-induced c-jun mRNA expression. To determine if CREB and mitogen-activated protein kinases (MAPKs) are involved in the regulation of c-fos mRNA expression by LPS and CHX, Western blot was carried out using the phosphorylated form of antibodies against ERK, JNK, p38, and CREB. LPS transiently increased the phosphorylation of p38-MAPK and CREB. In addition, LPS alone elevated phosphorylation of ERK (p44/p42) MAPK in a time-dependent manner. Furthermore, LPS plus CHX enhanced phosphorylation of ERK, p38, and CREB in a synergistic manner. Our results suggest that the phosphorylation of ERK, p38, and CREB may be involved in the regulation of synergistic c-fos mRNA expression induced by LPS plus CHX in C6 rat glioma cells.

Differential effects of cholera toxin and pertussis toxin on the c-fos and c-jun mRNA expression in rat C6 glioma cells

Cholera toxin (CTX) increased c-fos mRNA level whereas it down-regulated the c-jun mRNA level in rat C6 glioma cells. In contrast to the action of CTX, pertussis toxin (PTX) did not affect either c-fos or c-jun mRNA level. The elevated c-fos mRNA level induced by CTX was significantly inhibited by the co-treatment with dexamethasone (DEX). However, DEX did not affect CTX-induced down-regulation of c-jun mRNA level. Cycloheximide (CHX) increased c-fos and c-jun mRNA levels. CHX caused a super-induction of CTX-induced c-fos mRNA level. Our results suggest that CTX-, but not PTX-, sensitive G-proteins may play an important role for c-fos mRNA up-regulation and c-jun mRNA down-regulation. In addition, DEX appears to have a selective inhibitory action against c-fos mRNA expression regulated by CTX. Ongoing protein synthesis inhibition is required for the superinduction of c-fos, but not c-jun, mRNA induced by CTX.

Differential modulatory roles of cholera toxin and pertussis toxin in the regulation of pain responses induced by excitatory amino acids administered intrathecally in mice

The present study was designed to characterize the possible roles of spinally located cholera toxin (CTX)- and pertussis toxin (PTX)-sensitive G-proteins in excitatory amino acids induced pain response. Intrathecal (i.t.) injection of glutamate (20 microg), N-methyl-D-aspartic acid (NMDA; 60 ng), alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA; 13 ng), and kainic acid (12 ng) showed pain response. Pretreatment with CTX (0.05 and 0.5 microg, i.t.) attenuated pain response induced by glutamate, NMDA, AMPA and kainic acid administered i.t. in a dose-dependent manner. On the other hand, i.t. pretreatment with PTX further increased the pain response induced by glutamate, NMDA, AMPA and kainic acid administered i.t., especially at the dose of 0.5 microg. Our results suggest that, at the spinal cord level, CTX- and PTX-sensitive G-proteins appear to play opposite roles in modulating the pain response induced by spinally administered. Furthermore, CTX- and PTX-sensitive G-proteins appear to modulate pain response induced by stimuli of both NMDA and non-NMDA glutamate receptors.

Supraspinal NMDA and non-NMDA receptors are differentially involved in the production of antinociception by morphine and beta-endorphin administered intracerebroventricularly in the formalin pain model

Our previous studies have demonstrated that supraspinal glutamate receptors are differentially involved in the antinociception induced by morphine and beta-endorphin given intracerebroventricularly (i.c.v.) in the tail-flick and hot-plate tests. The formalin pain test was used in the present study. Injection of mice with formalin solution (2%, 10 microl) into the hindpaw intraplantarly produced the first (0-5 min) and second (20-40 min) phases of formalin responses. The formalin responses in the both phases were attenuated dose-dependently by morphine (0.125-1 microg) or beta-endorphin (0.125-1 microg) administered i.c.v. 5 min before. The antinociceptive effect of morphine was slightly more potent in the second phase whereas the effect of beta-endorphin was more pronounced in the first phase. MK-801 (0.1-1 microg), a non-competitive NMDA receptor antagonist, and CNQX (0.05-0.5 microg), a non-NMDA antagonist, given i.c.v., produced antinociceptive effect in the both phases, but only in a partial manner. Both MK-801 (0.05 microg) and CNQX (0.01 microg), at the dose which had no intrinsic effect, reversed the antinociceptive effect of beta-endorphin (1 microg) observed during the second, but not the first, phase partially but significantly. However, the antinociceptive effect of morphine (1 microg) was not affected by the same dose of MK-801 or CNQX given i.c.v. Our results indicate that, at the supraspinal level, both NMDA and non-NMDA receptors are involved in the production of antinociception induced by supraspinally administered beta-endorphin, but not morphine, in the formalin pain model.

Modulatory role of ginsenosides injected intrathecally or intracerebroventricularly in the production of antinociception induced by kappa-opioid receptor agonist administered intracerebroventricularly in the mouse

We examined the effects of ginseng total saponin and several ginsenosides injected intrathecally (i.t.) or intracerebroventricularly (i.c.v.) on the antinociception induced by U50, 488H (trans-3,4-dichloro-N-methyl-N-[2- (1-pyrrolidinyl)cyclohexyl]benzeocetamide; a kappa opioid receptor agonist) administered i.c.v. The tail-flick test was used as an analgesic assay. Total saponin fraction at doses of 0.1 to 20 micrograms, which when administered intrathecally (i.t.) or intracerebroventricularly (i.c.v.) alone did not affect the latencies of tail-flick threshold, attenuated dose-dependently the inhibition of the tail-flick response induced by U50, 488H (60 micrograms) administered i.c.v. The duration of antagonistic action of total saponin fraction against U50, 488H-induced antinociception lasted at least for 6 h. Various doses (from 0.1 to 1 microgram) of ginsenosides Rb1, Rb2, Rc, Rd, and Rg1, but not Re, injected i.t. dose-dependently attenuated antinociception induced by U50, 488H administered i.c.v. Furthermore, various doses (from 1 to 10 micrograms) of ginsenosides Rb2 and Re, but not Rb1, Rc, Rd, and Rg1, injected i.c.v. dose-dependently attenuated antinociception induced by U50, 488H administered i.c.v. In summary, ginsenosides Rb1, Rb2, Rc, Rd, and Rg1 administered spinally appear to be responsible for blocking the antinociception induced by U50, 488H administered supraspinally, whereas ginsenosides Rb2 and Re administered supraspinally appear to be responsible for blocking the antinociception induced by U50, 488H administered supraspinally.

Cycloheximide increases proenkephalin and tyrosine hydroxylase gene expression in rat adrenal medulla

The effect of cycloheximide (CHX; 5 mg/kg) on proenkephalin (proENK) and tyrosine hydroxylase (TH) mRNA expression in rat central and peripheral nervous systems was studied. CHX increased proENK and TH mRNA levels in the adrenal gland, but not in hippocampus, striatum, midbrain, brainstem, pituitary, and hypothalamus. The pretreatment with actinomycin D (0.5 mg/kg) significantly decreased CHX-induced proENK and TH mRNA expression, suggesting that the CHX-dependent increase of these mRNA levels may be caused by the increase of transcriptional activity rather than RNA stabilization. To investigate the factors involved in CHX-induced proENK and TH mRNA expression, the effect of CHX on activator protein-1 (AP-1), cAMP response element (CRE) binding protein (CREB), and glucocorticoid response element (GRE) was tested. In AP-1, the basal expression of Fra-2 and c-Jun proteins and AP-1 DNA binding activity in the adrenal medulla was higher than other tissues tested, but CHX reduced these protein levels and AP-1 DNA binding activity. In CREB, CHX time dependently increased the level of phospho-CREB without altering total CRE level and CRE DNA binding activity. Furthermore, phospho-CREB actively participated in CRE DNA binding activity. In GRE, although CHX increased plasma and adrenal corticosterone level, RU486 (10 mg/kg) reduced CHX-induced proENK, but not TH, mRNA level in a partial manner. These results suggest that the basal expression of proENK and TH mRNA transcription in the adrenal gland seems to be tonically inhibited by de novo protein synthesis. In addition, CHX-dependent increase of proENK and TH mRNA expression in the adrenal medulla is well correlated with phospho-CREB level, but not AP-1. Finally, glucocorticoid seems to be involved at least partially in CHX-dependent proENK, but not TH, mRNA expression in the adrenal medulla.

Modulatory effect of ginseng total saponin on dopamine release and tyrosine hydroxylase gene expression induced by nicotine in the rat

Several studies have demonstrated that behavioral activation induced by psychostimulants is prevented by ginseng total saponin (GTS), which has been known to act on the central dopaminergic system. In an attempt to investigate whether the effect of GTS is through its inhibitory action on the elevated dopaminergic transmission, we examined the effect of GTS on nicotine-induced dopamine (DA) release in the nucleus accumbens (NA) of freely moving rats using in vivo microdialysis. Systemic injection of nicotine (3 mg/kg; i.p.) produced a mild increase in extracellular DA of dialysates samples in the NA (132+/-13% over basal levels at the peak). GTS (100 mg/kg; i.p.) had no effect on resting levels of extracelluar DA. However, an increase in accumbens DA release produced by systemic nicotine was completely blocked by systemic pre-treatment with GTS (100 mg/kg; i.p.). In addition, the effect of GTS on nicotine-induced tyrosine hydroxylase (TH) and immediate early gene expression in ventral tegmental area (VTA) or NA regions was examined. A single injection of nicotine increased TH mRNA level at VTA region. GTS, which did not affect the basal TH mRNA expression, attenuated nicotine-induced TH mRNA expression. Nicotine slightly increased both c-fos and c-jun mRNA level and GTS, which did not affect the basal c-fos and c-jun mRNA expression, further enhanced nicotine-induced c-fos and c-jun mRNA level at both VTA and NA regions. Our results suggest that GTS may have an inhibitory action against nicotine-induced DA release in NA region and TH mRNA expression in VTA region. GTS may exert an potentiative effect on both c-fos and c-jun mRNA expression at NA region through inhibiting the release of DA in NA.

Central injection of nitric oxide synthase inhibitors increases peripheral interleukin-6 and serum amyloid A: involvement of adrenaline from adrenal medulla

1. Accumulating evidence suggests that plasma levels of interleukin-6 (IL-6), a major cytokine stimulating the synthesis of acute phase proteins, are intimately regulated by the central nervous system (CNS). 2. In the present study, effects of intracerebroventricular (i.c. v) injection of N(G)-nitro-L-arginine methyl ester (L-NAME) or 7-nitroindazole, nitric oxide synthase (NOS) inhibitors, on plasma IL-6 levels and peripheral IL-6 mRNA expression were examined in mice. 3. L-NAME (0.1 - 2 microg per mouse i.c.v.) and 7-nitroindazole (0.2 - 2 microg per mouse i.c.v.) induced a dose-dependent increase in plasma IL-6 levels and a subsequent increase in circulating serum amyloid A, a liver acute-phase protein. In contrast, an intraperitoneal (i.p.) injection of L-NAME up to the dose of 25 microg per mouse had no effect. 4. Pretreatment with yohimbine (alpha(2)-adrenergic antagonist; 1 mg kg(-1) i.p.), or ICI-118,551 (beta(2)-adrenergic antagonist; 2 mg kg(-1) i.p.), but not with prazosin (alpha(1)-adrenergic antagonist; 1 mg kg(-1) i.p.), nor betaxolol (beta(1)-adrenergic antagonist; 2 mg kg(-1) i.p.), significantly inhibited the central L-NAME-induced plasma IL-6 levels. 5. I.c.v. (50 microg per mouse) or i.p. (100 mg kg(-1)) pretreatment with 6-hydroxydopamine had no effect on central L-NAME-induced plasma IL-6 levels. However, intrathecal (i.t.) pretreatment with 6-hydroxydopamine (20 microg per mouse) markedly inhibited central L-NAME-induced plasma IL-6 levels. Both yohimbine (1.5 microg per mouse i.t.) and ICI-118,551 (1.5 microg per mouse i. t.) were effective in inhibition of central L-NAME-induced plasma IL-6 levels. 6. There was an elevation of base-line plasma IL-6 levels in adrenalectomized animals. The adrenalectomy-enhanced levels were not further increased by central L-NAME. 7. L-NAME (2 microg per mouse i.c.v.) induced an increase in IL-6 mRNA expression in liver, spleen, and lymph node. 8. These results suggest that NOS activity in the brain tonically down-regulates peripheral IL-6 by inhibiting adrenaline release from the adrenal medulla.

Stimulation of astrocyte-enriched culture with arachidonic acid increases proenkephalin mRNA: involvement of proto-oncoprotein and mitogen activated protein kinases

In astrocyte-enriched cultures, arachidonic acid (AA, 100 microM) significantly increased the proenkephalin (proENK) mRNA level (4. 9-fold at 8 h). In addition, AA also increased several AP-1 proteins, such as c-Fos, Fra-1, Fra-2, JunB, JunD, and c-Jun, or AP-1 and ENKCRE-2 DNA-binding activity. As well as AP-1 proteins and their DNA-binding activities, proENK mRNA level induced by AA was reduced by the pretreatment with 15 microM of cycloheximide (CHX; 1.6-fold). AA-dependent increase of proENK mRNA is not mediated by cyclooxygenase- or lipoxygenase-dependent metabolites, or free radicals, because the AA-induced increase of proENK mRNA levels was not affected by indomethacin (10 microM), nordihydroguaiaretic acid (10 microM), or N-acetylcysteine. However, as well as proto-oncoprotein levels, such as Fra-1, Fra-2, c-Jun, JunB, but not JunD, AA-induced increase of proENK mRNA was significantly reduced by the pretreatment with 10 microM of PD98059 (1.3-fold) or 10 microM of SB203580 (1.8-fold). These results strongly suggest that AA rather than one of its metabolites is involved in the increase of proENK mRNA. In addition, the activation of both the p38 and ERK pathways appears to be involved in the AA-induced increase of proENK mRNA via activating the expression of proto-oncoprotein, such as Fra-1, Fra-2, c-Jun, and JunB.

Differential potentiative effects of GABA receptor agonists in the production of antinociception induced by morphine and beta-endorphin administered intrathecally in the mouse

The effect of muscimol or baclofen injected intrathecally (i.t.) on the inhibition of the tail-flick response induced by morphine and beta-endorphin administered i.t. was studied in ICR mice. The i.t. injection of muscimol (100 ng) or baclofen (10 ng) alone did not affect the basal inhibition of the tail-flick response. Morphine (0.2 microg) and beta-endorphin (0.1 microg) caused only slight inhibition of the tail-flick response. Baclofen, but not muscimol, injected i.t. enhanced the inhibition of the tail-flick response induced by i.t. administered morphine. Both muscimol and baclofen injected i.t. significantly enhanced i.t. injected beta-endorphin-induced inhibition of the tail-flick response. Our results suggest that the GABA(B), but not GABA(A), receptors located in the spinal cord appear to be involved in enhancing the inhibition of the tail-flick response induced by morphine administered spinally. In addition, both GABA(A) and GABA(B) receptors are involved in enhancing the inhibition of the tail-flick response induced by beta-endorphin administered i.t.

Evidence of enhancement of malate-aspartate shuttle activity in beta cells of streptozotocin-induced non-insulin-dependent diabetic rats

Glucose-induced insulin secretion is selectively impaired in beta cells from animals with non-insulin-dependent diabetes mellitus (NIDDM). This study was performed to clarify whether the malate-aspartate shuttle among the glucose metabolic pathways is intact in beta cells of NIDDM rats. The insulin secretory capacity of the islets and the K(ATP) channel activity in single beta cells were measured in control and NIDDM rats injected with streptozotocin (STZ) during the neonatal period, using a radioimmunoassay and patch-clamp technique. The increase of insulin secretion induced by 11.1 mmol/L glucose or 10 mmol/L dihydroxyacetone (DHA) was significantly reduced in NIDDM islets, suggesting an impaired glycerol-phosphate shuttle. The application of glyceraldehyde (10 mmol/L) in NIDDM or control islets elicited an increase in insulin secretion, but the difference between the 2 groups was indistinguishable. On the contrary, the increase of insulin secretion and the inhibition of K(ATP) channel activity induced by aspartate, which preferentially participates in the malate-aspartate shuttle, were significantly greater in NIDDM versus the control. However, intracellularly applied aspartate in the inside-out mode did not inhibit K(ATP) channel activity. These findings show that malate-aspartate shuttle activity is potentiated in pancreatic beta cells of NIDDM rats, suggesting the development of a compensatory mechanism for the reduced activity of the glycerol-phosphate shuttle in NIDDM.

Differential modulation by baclofen on antinociception induced by morphine and beta-endorphin administered intracerebroventricularly in the formalin test

Our previous studies have demonstrated that supraspinal GABAergic receptors are differentially involved in the antinociception induced by morphine and beta-endorphin given intracerebroventricularly (i.c.v.) in the tail-flick and hot-plate tests. These two models employed a phasic, thermal nociceptive stimulus. The present study was designed to examine the possible involvement of supraspinal GABAergic receptors in opioid-induced antinociception in the formalin test. Morphine (1 microg) and beta-endorphin (1 microg) given i.c.v. displayed the almost complete inhibitory effects against the hyperalgesic response in both phases. Muscimol (75-100 ng) and baclofen (5-10 ng) injected i.c.v. produced the hypoalgesic response in the both phases. The hypoalgesic response induced by muscimol and baclofen observed during the second phase was more pronounced than that observed during the second phase. Baclofen (2.5 ng), at the dose which did not affect the hyperalgesic response, resulted in a significant reversal of the i.c.v. administered beta-endorphin-induced hypoalgesic response observed during the second, but not the first, phase. However, the hypoalgesic response induced by i.c.v. administered morphine was not changed by the same dose of muscimol or baclofen injected i.c.v. Our results indicate that, at the supraspinal level, GABA(B)receptors appear to be involved in the modulation of antinociception induced by supraspinally administered beta-endorphin, but not morphine, in the formalin test model.

Activation of adenylate cyclase results in down-regulation of c-jun mRNA expression in rat C6 glioma cells

To investigate the possible mechanisms involved in forskolin-induced c-jun mRNA decrease in rat C6 glioma cells, we examined effects of a PKA inhibitor (H-89), a L-type Ca2+ channel blocker (nimodipine), a calmodulin activation inhibitor (calmidazolium chloride) and a Ca2+/calmodulin-dependent protein kinase II inhibitor (KN-62) on forskolin-induced c-jun mRNA down-regulation. H-89 caused a reversal of forskolin-induced c-jun mRNA decrease. Furthermore, nimodipine, KN-62 and calmidazolium chloride partially blocked forskolin-induced c-jun mRNA down-regulation. Our results suggest that activation of adenylate cyclase appears to be involved in a down-regulation of c-jun mRNA expression through a PKA pathway. In addition, L-type calcium channels, calmodulin and Ca2+/calmodulin-dependent protein kinase II may be partially involved in c-jun mRNA down-regulation induced by forskolin.

Central injection of nicotine increases hepatic and splenic interleukin 6 (IL-6) mRNA expression and plasma IL-6 levels in mice: involvement of the peripheral sympathetic nervous system

Accumulating evidence suggests that plasma levels of interleukin 6 (IL-6), a major cytokine stimulating the synthesis of acute-phase proteins, are intimately regulated by the central nervous system. Nicotine, one of the major drugs abused by humans, has been shown to affect immunological functions. In the present study, effects of intracerebroventricular (i.c.v.) injection of nicotine on plasma IL-6 levels were investigated in mice. Nicotine administered i.c.v. dose-dependently increased plasma IL-6 levels; the lowest effective dose was 0.3 ng/mouse and the maximal effect was attained with the dose of 105 ng/mouse. The nicotine (105 ng/mouse, i.c.v.)-induced plasma IL-6 levels peaked at 3 h and approached basal levels 6 h after injection. Mecamylamine, a nicotinic receptor antagonist, blocked nicotine-induced plasma IL-6 levels. Depletion of peripheral norepinephrine with 6-hydroxydopamine [100 mg/kg, intraperitoneal (i. p.)] inhibited the nicotine-induced plasma IL-6 levels by 57%, whereas central norepinephrine depletion with 6-hydroxydopamine (50 microgram/mouse, i.c.v.) had no effect. Pretreatment with prazosin (alpha1-adrenergic antagonist; 1 mg/kg, i.p.), yohimbine (alpha2-adrenergic antagonist; 1 mg/kg, i.p.), and ICI-118,551 (beta2-adrenergic antagonist; 2 mg/kg, i.p.), but not with betaxolol (beta1-adrenergic antagonist; 2 mg/kg, i.p.), inhibited nicotine-induced plasma IL-6 levels. Among the peripheral organs, including the pituitary, adrenals, heart, lung, liver, spleen, and lymph nodes, nicotine (105 ng/mouse, i.c.v.) increased IL-6 mRNA expression only in the liver and spleen, which was inhibited by peripheral norepinephrine depletion. These results suggest that stimulation of central nicotinic receptors induces plasma IL-6 levels and IL-6 mRNA expression in the liver and spleen via the peripheral sympathetic nervous system, alpha1-, alpha2-, and beta2-adrenoreceptors being involved.

Blockade of the delayed rectifier K+ currents, IKr, in rabbit sinoatrial node cells by external divalent cations

We investigated the actions of various divalent cations on the delayed rectifier K+ currents (IKr) in rabbit sinoatrial node cells using the whole-cell voltage-clamp technique in isotonic K+ solutions. External divalent cations decreased the amplitude of currents, accelerated the time course of deactivation and shifted the activation to positive potentials in a dose-dependent manner. The concentrations for half-maximum inhibition of the steady-state currents (KM) obtained at 0 mV were 0.63, 1.36, 1.65 and 2.16 mM for Ni2+, Co2+, Mn2+ and Ba2+, respectively. The effect was voltage dependent (KM decreased e-fold for 12.2-16.8 mV hyperpolarization), but the dependence did not vary significantly among different cations. Acceleration of the time course of current deactivation by the increase of divalent cation concentration was well fitted by the voltage-dependent block model, and the binding rate constant (k1) was obtained. The binding rates for the ions took the following order: Ni2+ >Co2+ >Mn2+ >Ba2+. The degree of the shift of activation occurred in the same order: Ni2+ >Co2+ >Mn2+ >Ba2+. From these results, we conclude that IKr channels are non-selectively blocked by most divalent cations from the external side and that the binding site is located deep inside the channel, resulting in a steep voltage dependence of the blockade.

Effects of histamine receptor antagonists injected intrathecally on antinociception induced by opioids administered intracerebroventricularly in the mouse

The present study was designed to investigate the modulatory effects of blockade of spinal histamine receptors on antinociception induced by supraspinally administered mu-epsilon-, delta-, and kappa-opioid receptor agonists. The effects of intrathecal (i.t.) injections with cyproheptadine [a histamine-1 (H1) receptor antagonist], ranitidine (a H2 receptor antagonist), or thioperamide (a H3 receptor antagonist) injected i.t., on the antinociception induced by morphine (a mu-receptor antagonist), beta-endorphin (an epsilon-receptor agonist), D-Pen(2,5)-enkephalin (DPDPE, a delta-receptor agonist) or trans-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohxyl] benzeocetamide (U50,488H, a kappa-receptor agonist) injected intracerebroventricularly (i.c.v.) were studied. The antinociception was assayed using the tail-flick test. The i.t. injection of cyproheptadine (from 0.31 to 62 nmole), ranitidine (from 0.28 to 56 nmole), or thioperamide (from 0.24 to 48 nmole) alone did not show any antinociceptive effect. The i.t. pretreatment with cyproheptadine or thioperamide dose-dependently attenuated the inhibition of the tail-flick response induced by i.c.v. administered morphine (0.6 nmole), b-endorphin (0.03 nmole), DPDPE (1.5 nmole), and U50,488H (130 nmole). In addition, the i.t. pretreatment with ranitidine dose-dependently attenuated the inhibition of the tail-flick response induced by morphine, b-endorphin and U50,488H without affecting DPDPE-induced response. Our results suggest that spinal histamine H1 and H3 receptors may involved in the production of antinociception induced by supraspinally applied morphine, b-endorphin, DPDPE and U50,488H. Spinal H2 receptors appear to be involved in supraspinally administered morphine, b-endorphin- and U50,488H-induced antinociception but not DPDPE-induced antinociception.

Differential involvement of central and peripheral norepinephrine in the central lipopolysaccharide-induced interleukin-6 responses in mice

Intracerebroventricular injection of lipopolysaccharide (LPS) induces a marked increase in circulating interleukin (IL)-6 levels and in IL-6 mRNA expression in brain and peripheral organs. Recently, it was reported that intraperitoneal administration of alpha-adrenoceptor antagonists inhibits centrally injected LPS-induced increases in plasma IL-6 levels, suggesting the involvement of the norepinephrine (NE) system in the central LPS-induced IL-6 response. However, the localization (either central or peripheral) of NE involvement in the central LPS-induced IL-6 response has not been characterized. In the present study, mice were pretreated with 6-hydroxydopamine (6-OHDA) administered intracerebroventricularly or intraperitoneally to deplete central or peripheral stores of NE, respectively. Intracerebroventricular LPS (50 ng/mouse) markedly increased plasma IL-6 levels and IL-6 mRNA expression in choroid plexus, hypothalamus, pituitary, adrenals, heart, liver, spleen, and lymph nodes, but with minimal effect in lung, kidney, and testis, as revealed by RT-PCR. Pretreatment with intracerebroventricular 6-OHDA (50 microg/mouse) decreased the LPS-induced plasma IL-6 levels by 39% and the LPS-induced IL-6 mRNA expression in liver, spleen, and lymph nodes, but not in choroid plexus, hypothalamus, pituitary, adrenals, and heart. Pretreatment with intraperitoneal 6-OHDA (100 mg/kg) decreased the LPS-induced plasma IL-6 levels by 36% and the LPS-induced IL-6 mRNA expression in all the peripheral organs displaying increased IL-6 mRNA. Central LPS-induced increase in plasma corticosterone levels was decreased slightly by central but not by peripheral NE depletion. These results suggest that central NE and peripheral NE are differentially involved in the central LPS-induced IL-6 mRNA expression in peripheral organs.

Effects of ginsenosides injected intrathecally or intracerebroventricularly on antinociception induced by beta -endorphin administered intracerebroventricularly in the mouse

The effect of total saponin fraction of ginseng injected intrathecally (i.t.) or intracerebroventricularly (i.c.v.) on the antinociception induced by beta-endorphin administered i.c.v. was studied in ICR mice in the present study. The antinociception was assessed by the tail-flick test. Total saponin fraction at doses 0.1 to 1.0 microgram, which administered i.t. alone did not affect the latencies of tail-flick threshold, attenuated dose-dependently the inhibition of the tail-flick response induced by i.c.v. administered beta-endorphin (1 microgram). However, total saponin fraction at doses 1 to 20 microgram, which administered i.c.v. alone did not affect the latencies of the tail-flick response, did not affect i.c.v. administered beta-endorphiun (1 microgram)-induced antinociception. The duration of antagonistic action of total saponin fraction against beta-endorphin-induced antinociception lasted at least for 6 h. Various doses (from 0.1 to 1 microgram) of ginsenoside R(c), but not R(b2), R(d), Rg(1), R(b1)and R(e)injected i.t. dose-dependently attenuated antinociception induced by beta-endorphin administered i.c.v. Our results indicate that total saponin fraction injected spinally appears to have antagonistic action against the antinociception induced by supraspinally applied beta-endorphin. Ginsenoside R(c)appears to be responsible for blocking i.c.v. administered beta-endorphin-induced antinociception. On the other hand, total ginseng fraction, at supraspinal sites, may not exert an antagonistic action against the antinociception induced by supraspinally administered beta-endorphin.

Central GABAA and GABAB receptor modulation of basal and stress-induced plasma interleukin-6 levels in mice

To investigate the modulatory roles of central gamma-aminobutyric acid (GABA)A and GABAB receptors in the regulation of basal and stress-induced plasma interleukin-6 (IL-6) levels, we examined the effects of i.c.v. injection of GABA receptor agonists and antagonists on basal and restraint stress-induced plasma IL-6 levels in mice. Muscimol (20-200 ng), a GABAA receptor agonist, and baclofen (5-20 ng), a GABAB receptor agonist, injected i.c.v. did not affect the basal levels of plasma IL-6. In the restraint-stressed animals, muscimol and baclofen inhibited the stress-induced plasma IL-6 levels from the dose of 50 and 15 ng, respectively. 2-(3-Carboxyl)-3-amino-6-(4-methoxyphenyl)-pyridazinium bromide (SR-95,531; 0.3-10 ng), a GABAA receptor antagonist, and 2-hydroxysaclofen (1-10 microgram), a GABAB receptor antagonist, injected i.c.v. increased both the basal and the restraint stress-induced plasma IL-6 levels. The i.p. pretreatment of animals with 6-hydroxydopamine (100 mg/kg) for 3 days significantly inhibited SR-95,531 (3 ng i.c.v.)- but not 2-hydroxysaclofen (10 microg i.c.v.)-induced increase in the basal plasma IL-6 levels. These data suggest that central GABAA and GABAB receptors are involved in the suppressive modulation of basal and restraint stress-induced plasma IL-6 levels in mice.

Prostaglandin E2 increases proenkephalin mRNA level in rat astrocyte-enriched culture

The effect of prostaglandin E2 (PGE2) on proenkephalin (proENK) mRNA expression in primary cultured rat astrocytes was studied. The proENK mRNA level was significantly increased about 3.3-fold 4 h after PGE2 (10 microM) treatment and this increase was potentiated by the pre-treatment with cycloheximide (CHX; 15 microM) about 1.7-fold as much as PGE2 alone treated cells. The pretreatment with staurosporine (1 microM) completely inhibited the increase of PGE2-induced proENK mRNA level, although only a partial inhibition of PGE2-induced proENK mRNA level (approximately 1.5-fold) by H89 (10 microM) was observed. The increase of PGE2-induced proENK mRNA level was not affected by the pretreatment with PD98059 (1, 5, and 10 microM), omega-conotoxin GIVA (1 microM), nimodipine (1 microM), calmidazolium (1 microM), or KN-62 (1 microM). In addition to the proENK mRNA level, PGE2 also increased c-Fos (approximately 4.3-fold), Fra-1 ( approximately 3.8 fold), and Fra-2 (approximately 8.2-fold) protein levels at 4 h after drug treatment. However, c-Jun, JunB, and JunD protein levels were not affected by PGE2. Indeed, PGE2 failed to up-regulate c-jun mRNA expression as well as its protein product. Surprisingly, although three Jun proteins were not induced by PGE2, AP-1 and ENKCRE-2 DNA binding activities were increased by PGE2, (approximately 5 and approximately 2.8-fold, respectively) and which were effectively reduced by CHX (approximately 2.5 and 2-fold, respectively). In western blot analyses, PGE2 enhanced the phosphorylation of CREB (approximately 2.6-fold at 1 h), and CHX showed a potentiative effect on PGE2-induced CREB phosphorylation ( approximately 1.7 fold at 1 h) which is similar to the action on proENK mRNA regulation. Our results suggest that PGE2 increases proENK mRNA expression via activating serine/threonine protein kinase such as PKA, but not calcium/calmodulin dependent protein kinase and MAPK. In addition, phosphorylation of CREB rather than the increase of AP-1 may have a possible role at least early stage in PGE2-induced proENK mRNA level and CHX-evoked potentiation.

Postischemic hypothermia induced by eugenol protects hippocampal neurons from global ischemia in gerbils

We studied whether eugenol provides neuroprotection against delayed neuronal death in the hippocampal CA1 region following a 5 min occlusion of the common carotid arteries bilaterally under either free-regulating temperature (TF) or maintained temperature (TM, 37 degrees C) conditions in gerbils. Right after occlusion of the carotid arteries, we injected eugenol intraperitoneally at concentrations of either 50, 100, or 200 mg/kg. There was significant preservation of neuronal cells in the CA1 region in the eugenol-treated groups 7 days after the ischemic insult in the TF condition, with respective survival values of 26, 43, and 68%. In the TM condition, however, significant neuroprotection was only seen with eugenol concentrations of 100 and 200 mg/kg (32% and 52%, respectively). When the rectal temperature was maintained at 38 degrees C for 30 min after occlusion of the carotid arteries, no reduction in CA1 damage was observed with any dose of eugenol. These results suggest that eugenol may provide neuroprotection against ischemic damage by its hypothermic action.

Behavioral and neuropathologic changes induced by central injection of carboxyl-terminal fragment of beta-amyloid precursor protein in mice

Expression of the carboxyl-terminal fragment (CT) of the beta-amyloid precursor protein (APP) in transgenic animals has been linked with neurotoxicity. However, it remains to be clarified whether the neurotoxicity is caused by beta-amyloid proteins (A betas) derived from CT or by CT itself. To study the in vivo neurotoxicity of CT, mice were given a single intracerebroventricular injection of a recombinant 105-amino acid CT (CT105; 68.5-685 pmol, intracerebroventricularly), and changes in behavior and in brain histology were examined. Animals given CT105 (410 or 685 pmol, intracerebroventricularly) showed a dose-dependent impairment in the passive avoidance performance, whereas boiled CT105 had no effect. CT105 (685 pmol, intracerebroventricularly) induced reactive gliosis in neocortex and hippocampus and neurodegeneration in neocortex. These results indicate that centrally administered CT105 induces behavioral impairment and neuropathologic changes, suggesting a direct toxic effect of CT105 per se.

Brain-derived neurotrophic factor rapidly potentiates synaptic transmission through NMDA, but suppresses it through non-NMDA receptors in rat hippocampal neuron

Brain-derived neurotrophic factor (BDNF) rapidly enhances synaptic transmission among the hippocampal neurons. In order to examine which component of glutamate receptors participates in synaptic potentiation by BDNF, we have studied the effect of glutamate antagonists on excitatory postsynaptic currents (EPSCs) enhanced by BDNF, using cultured embryonic hippocampal neurons. In the presence of AP5, a N-methyl-D-aspartate (NMDA) antagonist, BDNF depressed the EPSCs. In contrast, BDNF enhanced the EPSCs in the presence of a non-NMDA antagonist CNQX. Our results suggest that BDNF acutely activates synaptic transmission via NMDA, but suppresses it via non-NMDA receptors in the hippocampus.

Inhibition of stress-induced plasma corticosterone levels by ginsenosides in mice: involvement of nitric oxide

Ginseng total saponins (GTS) injected intracerebroventricularly (i.c.v.) at doses of 0.1-1 microg inhibited the i.c.v. injection stress-induced plasma corticosterone levels in mice. The inhibitory action of GTS was blocked by co-administered N(G)-nitro-L-arginine methyl ester (L-NAME; 1.5 microg, i.c.v.), an inhibitor of nitric oxide synthase (NOS). Of the ginsenosides Rb1, Rb2, Rc, Rd, Re, Rf, Rg1, 20(S)-Rg3 and 20(R)-Rg3 injected i.c.v. at doses of 0.01-1 microg, 20(S)-Rg3 and Rc significantly inhibited the i.c.v. injection stress-induced plasma corticosterone levels. The inhibitory actions of 20(S)-Rg3 and Rc were blocked by co-administered L-NAME (1.5 microg, i.c.v.). These results suggest that GTS, 20(S)-Rg3 and Rc may inhibit the i.c.v. injection stress-induced hypothalamo-pituitary-adrenal response by inducing NO production in the brain.

Differential effects of adrenaline and noradrenaline on the hepatic expression of immediate early genes in mice

1. The effects of intraperitoneally (i.p.) administered noradrenaline and adrenaline on the hepatic expression of immediate early genes (IEGs) were studied in mice. 2. Intraperitoneal injections of various doses (0.2-2 mg kg(-1)) of noradrenaline and adrenaline dose-dependently induced hepatic c-fos and c-jun mRNA levels. The time-course study showed that there was an increase in c-fos and c-jun mRNA levels within 15 min, which reached a peak at 30 min, and returned to the basal levels 1-2 h after noradrenaline or adrenaline injection (2 mg kg(-1), i.p.). A Western blot assay revealed that c-Jun protein levels were maximally increased at 30 min and 1-2 h in noradrenaline- and adrenaline-treated mice, respectively. There was a slight increase in c-Fos protein, while 46-kDa Fra protein was prominently increased. Noradrenaline (2 mg kg(-1), i.p.) induced 46-kDa Fra within 15 min, which reached a maximum at 30 min and returned to the basal levels by 1 h. Adrenaline (2 mg kg(-1), i.p.) induced 46-kDa Fra at 30 min, which returned to the basal levels at 4 h. 3. Noradrenaline (2 mg kg(-1), i.p.)-induced increases in c-fos and c-jun mRNA expressions were inhibited by the pre-treatment with prazosin (alpha1-adrenergic antagonist; 0.5 mg kg(-1), i.p.), but not with yohimbine (alpha2-adrenoceptor antagonist; 1 mg kg(-1), i.p.) nor with propranolol (beta-adrenoceptor antagonist; 10 mg kg(-1), i.p.). Adrenaline (2 mg kg(-1), i.p.)-induced increases in c-fos and c-jun mRNA expressions were inhibited by the pre-treatment with prazosin or with propranolol, but not with yohimbine. Administration of ICI-118,551 (beta2-adrenoceptor antagonist; 2 mg kg(-1), i.p.), but not betaxolol (beta1-adrenoceptor antagonist; 2 mg kg(-1), i.p.), blocked adrenaline (2 mg kg(-1), i.p.)-induced increases in c-fos and c-jun mRNA expressions. 4. The results suggest that noradrenaline elicits the hepatic c-fos and c-jun mRNA responses by stimulating alpha1-adrenergic receptors, whereas in the case of adrenaline, this is elicited by stimulating both alpha1- and beta2-adrenergic receptors in mice. These catecholamine-induced hepatic IEG responses may be responsible for mediating some of the catecholamine actions in the liver.

The modulatory role of nitric oxide in the regulation of proenkephalin and prodynorphin gene expressions induced by kainic acid in rat hippocampus

The effect of L-arginine (L-ARG), a nitric oxide donor, or Nomega-nitro-L-arginine (L-NAME), a nitric oxide synthase inhibitor, on the regulation of kainic acid (KA)-induced proenkephalin (proENK) and prodynorphin (proDYN) mRNA expressions in rat hippocampus was studied. The proENK and proDYN mRNA levels were markedly increased 6 h after KA (10 mg/kg, i.p.) administration. The elevations of both proENK and proDYN mRNA levels induced by KA was effectively inhibited by pre-administration of L-ARG (400 mg/kg, i.p.), but was not affected by pre-treatment with L-NAME (200 mg/kg, i.p.). The blockade of KA-induced proENK and proDYN mRNA levels by the pre-treatment with L-ARG was well correlated with proto-oncoprotein levels, such as c-Fos, Fra-2, FosB, JunD, JunB, and c-Jun, as well as AP-1 and ENKCRE-2 DNA binding activities. The pre-administration with L-NAME further increased KA-induced c-jun and c-fos mRNA levels in addition to their protein product levels, although the pre-treatment with L-NAME did not affect KA-induced FosB, Fra-2, JunB, and JunD protein levels at 6 h after treatment. In addition, the pre-administration with L-NAME further increased the KA-induced AP-1 and ENKCRE-2 DNA binding activities. Our results suggest that L-ARG plays an important role in inhibiting KA-induced proENK or proDYN mRNA expression, and its inhibitory action may be mediated through reducing the proto-oncoprotein levels, such as c-Fos, Fra-2, FosB, c-Jun, JunD, and JunB. In addition, L-NAME potentiated the c-Fos or c-Jun gene expression, as well as AP-1 or ENKCRE-2 DNA binding activity. However, these increases did not show the potentiative effect on KA-induced increases of proENK and proDYN mRNA level.

Intracerebroventricular injection-induced increase in plasma corticosterone levels in the mouse: a stress model

The method of intracerebroventricular (i.c.v.) injection of drugs to conscious mice is a simple and useful technique for studying the central actions of drugs in mice. However, the use of this technique to dissect the central regulatory mechanisms of stress-activated hypothalamo-pituitary-adrenocortical (HPA) axis may produce confusing results difficult to interpret, because i.c.v. injection itself induces an increase in plasma corticosterone in mice due to the traumatic nature of the technique. Here we propose to use the i.c.v. injection itself as a stress stimulus in mice. An i.c.v. saline injection induced an increase in plasma corticosterone levels in mice, which reached a maximum of 38.0+/-1.9 microg/100 ml at 30 min after the i.c.v. injection. Alpha-helical corticotropin-releasing factor (CRF) 9-41, a CRF antagonist, injected i.c.v. (1, 3 microg), effectively inhibited the injection stress-induced rise in plasma corticosterone levels, suggesting the involvement of CRF in this response. This i.c.v. injection stress model permits the evaluation of the effects of drugs administered i.c.v. simultaneously.

The stimulation of rat astrocytes with phorbol-12-myristate-13-acetate increases the proenkephalin mRNA: involvement of proto-oncogenes

The effect of phorbol-12-myristate-13-acetate (PMA) on the regulation of proenkephalin (proENK) mRNA level, ENKCRE-2 or AP-1 DNA binding activity, and the mRNA and protein levels of proto-oncogenes (c-fos, fra-1, and c-jun) in primary cultured rat astrocytes were studied. The proENK mRNA level was elevated at 4 h after the treatment of PMA (2.5 microM) without altering the intracellular proENK protein level, and this increase was attenuated by pre-treatment with cycloheximide (CHX; 15 microM), a protein synthesis inhibitor. Both AP-1 and ENKCRE-2 DNA binding activities were markedly increased at 1-4 h by PMA treatment and these PMA-induced responses were inhibited by pre-treatment with CHX, showing that the increase of proENK mRNA level was well correlated with the AP-1 and ENKCRE-2 DNA binding activities. In contrast, although the phospho-CREBP level was also increased by PMA at 0.5-1 h, the pre-treatment with CHX further increased the PMA-induced phospho-CREBP level. In addition, PMA caused the induction of c-fos, c-jun and fra-1 mRNA level and, especially, PMA-induced increase of fra-1 mRNA level was further enhanced by CHX treatment at 4 h. Furthermore, western immunoblot assay showed that PMA caused induction of c-Fos, Fra-1, and c-Jun protein levels. PMA-induced increases of proto-oncoproteins levels were also inhibited by CHX treatment. The results suggest that newly synthesized AP-1 proteins, such as c-Fos, Fra-1, and c-Jun may play important roles in the regulation of PMA-induced proENK gene expression in cultured rat astrocytes. Phospho-CREB protein appears not to be involved in the regulation of PMA-induced proENK gene expression.

Phenidone blocks the increases of proenkephalin and prodynorphin gene expression induced by kainic acid in rat hippocampus: involvement of Fos-related antigene protein

To determine the possible role of cyclooxygenase/lipoxygenase pathway in the regulation of proenkephalin (proENK) and prodynorphin (proDYN) gene expression induced by kainic acid (KA) in rat hippocampus, the effects of esculetin, aspirin, or phenidone on the seizure activity, proENK and proDYN mRNA levels, and the level of fos-related antigene (Fra) protein induced by KA in rat hippocampus were studied. Esculetin (5 mg/kg), aspirin (15 mg/kg), or phenidone (50 mg/kg) was administered orally five times every 12 h before the injection of KA (10 mg/kg, i.p.). Seizure activity induced by KA was significantly attenuated by phenidone. However, neither esculetin nor aspirin affected KA-induced seizure activity. The proENK and proDYN mRNA levels were markedly increased 4 and 24 h after KA administration. The elevations of both proENK and proDYN mRNA levels induced by KA were inhibited by pre-administration with phenidone, but not with esculetin and aspirin. ProENK-like protein level increased by KA administration was also inhibited by pre-administration with phenidone, but not with esculetin and aspirin. The increases of proENK and proDYN mRNA levels induced by KA were well correlated with the increases of Fra protein level. Additionally, the induction of Fra protein was inhibited by pre-administration with phenidone, but not with esculetin and aspirin. The results suggest that blockade of both cyclooxygenase and lipoxygenase pathways appears to be responsible for increases of proENK and proDYN mRNA levels induced by KA via inhibiting the induction of Fra protein in rat hippocampus.

Effects of ginsenosides injected intrathecally or intracerebroventricularly on antinociception induced by morphine administrated intracerebroventricularly in the mouse

1. Total saponin fraction at doses of 0.1 to 1.0 microgram, which administered IT alone did not affect the latencies of the tail-flick threshold, dose dependently attenuated inhibition of the tail-flick response induced by ICV-administered morphine (2 micrograms). 2. Total saponin fraction at doses of 1 to 20 micrograms, which administered ICV alone did not affect the latencies of the tail-flick response, did not affect ICV-administered morphine-induced antinociception. 3. The duration of antagonistic action of the total saponin fraction against morphine-induced antinociception lasted for at least 6 hrs. 4. Various doses of ginsenosides Rb2, Rc, Rd and Rg1, but not Rb1 and Re, injected IT dose dependently attenuated antinociception induced by morphine administered ICV. 5. In summary, ginsenosides Rb2, Rc, Rd and Rg1 injected spinally appear to have antagonistic action against the antinociception induced by supraspinally applied morphine. On the other hand, the total ginseng fraction, at supraspinal sites, may not have an antagonistic action against the antinociception induced by morphine administered supraspinally.

Long-term oral administration of ginseng extract decreases serum gamma-globulin and IgG1 isotype in mice

Effects of long-term oral administration of ginseng extract on serum protein profile and immunoglobulin (Ig) isotypes were studied in mice. Ginseng extract was orally administered to healthy female mice for 52 days at doses of 30 and 150 mg/kg per day and serum protein electrophoretograms and Ig isotypes levels were evaluated. Serum level of gamma-globulin was decreased dose dependently to 82% (P < 0.05) and 56% (P < 0.01) of control values at the doses of 30 and 150 mg/kg per day, respectively. Levels of total protein, albumin, alpha2- and beta-globulin fractions, as well as the ratio of albumin to globulin (A/G) did not change significantly. However, the alpha1-globulin level increased by 24% (P < 0.05) at the doses of 30 and 150 mg/kg per day. Among the Ig isotypes, including IgG1, IgG2a, IgG2b, IgG3, IgM and IgA, serum IgG1 was dose dependently decreased to 68% (P < 0.05) of control values at the dose of 150 mg/kg per day without significant changes in other Ig isotypes. As IgG1 isotype is rarely cytotoxic and can act as a blocking antibody, it is suggested that the selective decrease in serum IgG1 induced by ginseng extract without changes in the cytotoxic antibodies such as IgG2a may be helpful for the prevention and inhibition of cancer.

Effects of intrathecal injection of nimodipine, omega-conotoxin GVIA, calmidazolium, and KN-62 on the antinociception induced by cold water swimming stress in the mouse

The present study was designed to determine if spinal calcium channels, calmodulin, and calcium/calmodulin-dependent protein kinase II were involved in the production of antinociception induced by cold water swimming stress (CWSS). The effects of intrathecal (i.t.) injection of nimodipine, omega-conotoxin GVIA, calmidazolium, or (S)-5-isoquinolinesulfonic acid, 4-[2-[(5-isoquinolinyl-sulfonyl)methylamino]-3-oxo-3-(4-phenyl-1-piperaz inyl)-propyl]phenyl ester (KN-62) on CWSS-induced antinociception were studied in ICR mice. The antinociception was assessed by the tail-flick test. CWSS produced inhibition of the tail-flick response. Various doses of nimodipine (10-40 ng), omega-conotoxin GVIA (5-40 ng), calmidazolium (10-40 ng), or KN-62 (5-40 ng) injected i.t. alone did not show any antinociceptive effect in the tail-flick test. I.t. pretreatment with omega-conotoxin GVIA, calmidazolium, or KN-62 dose dependently attenuated the CWSS-induced inhibition of the tail-flick response. However, i.t. pretreatment with nimodipine did not affect the inhibition of the tail-flick response induced by CWSS. Our results suggest that spinal N-type calcium channel, calmodulin and calcium/calmodulin-dependent protein kinase II may be involved in the production of antinociception induced by CWSS. On the other hand, CWSS-induced antinociception appears not to be mediated via the spinal L-type calcium channel.

Differential effects of omega-conotoxin GVIA, nimodipine, calmidazolium and KN-62 injected intrathecally on the antinociception induced by beta-endorphin, morphine and [D-Ala2,N-MePhe4,Gly-ol5]-enkephalin administered intracerebroventricularly in the mouse

We previously reported that beta-endorphin and morphine administered supraspinally produce antinociception by activating different descending pain-inhibitory systems. To determine the role of spinal calcium channels, calmodulin and calcium/calmodulin-dependent protein kinase II in the production of antinociception induced by morphine, [D-Ala2,N-MePhe4,Gly-ol5]-enkephalin (DAMGO) or beta-endorphin administered supraspinally, the effects of nimodipine (an L-type calcium channel blocker), omega-conotoxin GVIA (an N-type voltage-dependent calcium channel blocker), calmidazolium (a calmodulin antagonist) or KN-62 (a calcium/calmodulin-dependent protein kinase II inhibitor) injected intrathecally (i.t.) on the antinociception induced by morphine, DAMGO or beta-endorphin administered intracerebroventricularly (i.c.v.) were examined in the present study. Antinociception was assessed by the mouse tail-flick test. The i.t. injection of nimodipine (from 0.024 to 2.4 pmol), omega-conotoxin GVIA (from 0.0033 to 0.33 pmol), calmidazolium (from 0.0015 to 0.15 pmol) or KN-62 (from 0.0014 to 0.14 pmol) alone did not affect the basal tail-flick latencies. The i.t. pretreatment of mice with nimodipine, omega-conotoxin GVIA, calmidazolium or KN-62 dose dependently attenuated the inhibition of the tail-flick response induced by beta-endorphin administered i.c.v. However, the inhibition of the tail-flick response induced by morphine or DAMGO administered i.c.v. was not changed by i.t. pretreatment with nimodipine, omega-conotoxin GVIA, calmidazolium or KN-62. The results suggest that spinally located L- and N-type calcium channels, calmodulin and calcium/calmodulin-dependent protein kinase II may be involved in the modulation of antinociception induced by beta-endorphin, but not morphine and DAMGO, administered supraspinally.

Differential effects of adenosine receptor antagonists injected intrathecally on antinociception induced by morphine and beta-endorphin administered intracerebroventricularly in the mouse

A previous study reported that beta-endorphin and morphine administered supraspinally produce antinociception by activating different descending pain inhibitory systems. The present study was designed to investigate the blocking effects of A1 or A2 adenosine receptors in the spinal cord on antinociception induced by supraspinally administered mu- and epsilon-opioid receptor agonists. The effects of 1,3-dipropyl-8-(2-amino-4-chloro-phenyl)-xanthine (PACPX; an A1 adenosine receptor antagonist) or 3,7-dimethyl-1-propargylxanthine (DMPX; an A2 adenosine receptor antagonist) on the antinociception induced by morphine (a mu-opioid receptor agonist) or beta-endorphin (an epsilon-opioid receptor agonist) administered intracerebroventricularly (i.c.v.) were studied. The antinociception was assayed by the tail-flick test. DMPX at doses of 1-40 micrograms (which administered intrathecally alone did not affect the latencies of tail-flick thresholds), attenuated dose-dependently the inhibition of the tail-flick response induced by i.c.v. administered morphine (0.5 microgram) or beta-endorphin (1 microgram). PACPX at doses of 1-40 micrograms (which administered intrathecally alone did not affect the latencies of tail-flick thresholds), attenuated dose-dependently the inhibition of the tail-flick response induced by i.c.v. administered beta-endorphin but not morphine. These results suggest that A2 but not A1 adenosine receptors in the spinal cord may be involved in the antinociception induced by supraspinally administered morphine, while the antinociception induced by supraspinally administered beta-endorphin appears to be mediated by spinal A1 and A2 adenosine receptors. These results support the hypothesis that morphine and beta-endorphin administered supraspinally produce antinociception by different neuronal mechanisms.