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.