The activation of supraspinal GPR40/FFA1 receptor signalling regulates the descending pain control system

BACKGROUND AND PURPOSE

The ω-3 polyunsaturated fatty acids exert antinociceptive effects in inflammatory and neuropathic pain; however, the underlying mechanisms remain unclear. Docosahexaenoic acid-induced antinociception may be mediated by the orphan GPR40, now identified as the free fatty acid receptor 1 (FFA1 receptor). Here, we examined the involvement of supraspinal FFA1 receptor signalling in the regulation of inhibitory pain control systems consisting of serotonergic and noradrenergic neurons.

EXPERIMENTAL APPROACH

Formalin-induced pain behaviours were measured in mice. Antinociception induced by FFA1 receptor agonists was examined by intrathecal injections of a catecholaminergic toxin, 5-HT lowering drug or these antagonists. The expression of FFA1 receptor protein and c-Fos was estimated by immunohistochemistry, and the levels of noradrenaline and 5-HT in the spinal cord were measured by LC-MS/MS.

KEY RESULTS

FFA1 receptors colocalized with NeuN (a neuron marker) in the medulla oblongata and with tryptophan hydroxylase (TPH; a serotonergic neuron marker) and dopamine β-hydroxylase (DBH; a noradrenergic neuron marker). A single i.c.v. injection of GW9508, a FFA1 receptor agonist, increased the number of c-Fos-positive cells and the number of neurons double-labelled for c-Fos and TPH and/or DBH. It decreased formalin-induced pain behaviour. This effect was inhibited by pretreatment with 6-hydroxydopamine, DL-p-chlorophenylalanine, yohimbine or WAY100635. Furthermore, GW9508 facilitated the release of noradrenaline and 5-HT in the spinal cord. In addition, GW1100, a FFA1 receptor antagonist, significantly increased formalin-induced pain-related behaviour.

CONCLUSION AND IMPLICATIONS

Activation of the FFA1 receptor signalling pathway may play an important role in the regulation of the descending pain control system.

Induction and repression of beta-xylanase of Thermomyces lanuginosus TISTR 3465

The effect of carbon sources on the production of beta-xylanase by Thermomyces lanuginosus TISTR 3465 was investigated. Xylan showed the highest inductive effect on the enzyme formation whereas xylobiose and xylooligosaccharides resulted in lesser effect. beta-Xylanase was also produced at low level with xylose as well as other sugars tested. Xylan concentration at 15 g L(-1) gave the maximum inductive effect on beta-xylanase formation, whereas xylooligosaccharides and xylose were effective at a lower concentration of 2.5 g L(-1). High concentrations of these sugars significantly repressed the enzyme formation. Crude enzyme from the supernatants, without and with other sugars produced a single xylanase band on non-denaturing PAGE gels. However, an intense xylanase activity band was observed from the supernatant of media with xylan, xylobiose and xylooligosaccharides as the carbon sources. An intense protein band of 24.9 kDa from the culture filtrate of xylan medium was observed. Xylan increased beta-xylanase production by the fungus 16-fold when it was added to the xylose medium after cultivation for 3 days. In contrast, addition of xylose to the xylan medium decreased beta-xylanase production 3-fold. A distinct appearance and disappearance of a 24.9 kDa protein and the activity band coincided with an increase and decrease of xylanase activity, respectively. This indicated the synthesis of xylanase by this strain was most induced by xylan. Moreover, the level of xylanase induction has no related to amino acid sequence of the enzyme.

Over-expression system for secretory phospholipase D by Streptomyces lividans

The structural gene for phospholipase D (PLD) of an actinomycete, Streptoverticillium cinnamoneum, together with its promoter region was introduced into Streptomyces lividans using a shuttle vector-pUC702-for Escherichia coli and S. lividans. The transformant was found to secrete a large amount of PLD (about 2.0x10(4) U/l, 42 mg/l) when cultured in a jar fermentor. Both an initial glucose concentration of 17.5 g/l and the feeding of carbon and nitrogen sources are effective for efficient secretion of PLD; under these culture conditions, the amount of PLD secreted reached a maximum level (about 5.5x10(4) U/l, 118 mg/l) after about 60 h. In contrast to the original producer, Stv. cinnamoneum, which secretes only a small amount of PLD (about 1.1x10(3) U/l, 2 mg/l) along with other extracellular proteins, this heterologous expression system is markedly more efficient in production of secretory PLD.

[Retrospective evaluation of PSA density for selection of biopsy candidates with prostate specific antigen in the gray zone]

PURPOSE

We examined the usefulness of prostate specific antigen density (PSAD) for selection of biopsy candidate with prostate specific antigen levels between 4.1 and 10.0 ng./ml. in prostate cancer screening retrospectively.

MATERIALS AND METHODS

The screening was conducted on male candidates in Natori city, aged 55 years or older, for 6 years from 1994 through 1999. We could analyze serum PSA levels and PSA density in 118 men with PSA levels between 4.1 and 10.0 ng./ml. All of 118 men underwent ultrasound guided systematic prostate biopsy regardless of findings of digital rectal examination and transrectal ultrasound. Prostate volume was estimated by transrectal ultrasound measurements using the prolate ellipse formula (pi/6 x length x width x height). PSAD was calculated by dividing serum PSA level by prostate volume. Serum PSA levels were determined by Tandem-R assay.

RESULTS

In 118 men, twenty-five men had prostate cancer. There was no significant difference in mean PSA between those with prostate cancer and those without prostate cancer, but the difference was significant in the mean PSA density (mean 0.26 and 0.16, respectively, p < 0.0001). Receiver operating characteristic curves for PSA and PSAD demonstrated superior benefit for PSAD in 118 men. A sensitivity, a specificity, a positive predictive value and a negative predictive value of PSAD cut-off of 0.15 were 88%, 52.7%, 33.3% and 94.2%. PSAD cut-off of 0.18 showed the highest sum of sensitivity and specificity, which gave a sensitivity of 80%, a specificity of 72%, a positive predictive value of 43.5% and a negative predictive value of 93.1%. PSAD cut-off of 0.15 would seem to be preferable to cut-off of 0.18 because of less cancer missing.

CONCLUSIONS

Although further studies are needed to determine optimal cut-off value to be used in clinical practice, PASD seems to be useful for the selection of biopsy candidates with PSA levels of 4.1 to 10.0 ng./ml. in the prostate cancer screening.

Neurosteroids stimulate G protein-coupled sigma receptors in mouse brain synaptic membrane

Dehydroepiandrosterone, its sulfate (DHEAS) and pregnenolone sulfate, representative neurosteroids as well as (+)-pentazocine concentration-dependently stimulated the [35S]GTPgammaS binding in synaptic membranes of mouse prefrontal cortex. These stimulations were blocked by NE-100, a sigma-receptor antagonist, and by progesterone, another type of neurosteroid. The DHEAS-induced stimulation was blocked by the pertussis toxin (PTX)-treatment, and completely recovered by reconstitution of PTX-treated membranes with recombinant G(i1), but not with G(oA). DHEAS also stimulated the [35S]GTPgammaS binding in the coronal sections of mouse brain in NE-100- or progesterone-reversible manner. These findings suggest that some neurosteroids may act on metabotropic sigma receptors, and this study may be the first to show the coupling of neurosteroid binding site and G(i).

Changes of tissue factor-dependent coagulant activity mediated by adhesion between polymorphonuclear leukocytes and endothelial cells

The purpose of this study was to examine whether polymorphonuclear leukocytes (PMNs) facilitate a tissue factor, a physiologic initiator of coagulation in endothelial cells, -dependent coagulant activity (TF activity). The TF activity in bovine endothelial cells (BAECs) was significantly increased in a concentration-dependent manner by PMNs (1 x 10(5) - 1 x 10(7) cells/ml) without affecting the treatment of N-formyl-methionyl-leucyl-phenylalanine, a selective activator of PMNs, and the addition of PMNs finally resulted in cell damage as evaluated by the lactate dehydrogenase leakage method. In the same conditions, an increase of adhesion between PMNs and BAECs was also observed in a time-dependent manner. However, since direct adhesion of PMNs to BAECs was impossible by using the transwell, PMNs failed to induce any changes in the TF activity. Hence, the change of TF activity found here might be closely related to the PMNs adhesion to BAECs. Indeed, anti-intercellular adhesion molecule-1 (anti-ICAM-1) antibody blocked the increase of TF activity in BAECs. These findings suggest that PMNs could increase TF activity in endothelial cells, which is triggered by adhesion to endothelial cells through ICAM-1.

Climbazole is a new potent inducer of rat hepatic cytochrome P450

We examined the effect of climbazole on the induction of rat hepatic microsomal cytochrome P450 (P450), and compared the induction potency with other N-substituted azole drugs such as clorimazole. We found that climbazole is found to be a potent inducer of rat hepatic microsomal P450 as clorimazole. Induced level of P450 by climbazole was almost similar in extent to clorimazole when compared with other imidazole drugs in a dose- and time-dependent manner. Parallel to the increase in P450, climbazole increased aminopyrine and erythromycin N-demethylase, ethoxycoumarin O-deethylase, and androstenedione 16 beta- and 15 alpha/6 beta hydroxylase activities; however, clorimazole did not induce aminopyrine N-demethylase activity irrespective of its marked increase in P450 content. Immunoblot analyses revealed that climbazole induced CYP2B1, 3A2 and 4A1. The present findings indicate that climbazole is a new potent inducer of hepatic microsomal P450 and drug-metabolizing enzymes like clorimazole, but it may have some differential mechanism(s) for these enzymes' induction in rat liver.

Further evidence for a role of NMDA receptors in the locus coeruleus in the expression of withdrawal syndrome from opioids

To examine a role of N-methyl-D-aspartate (NMDA) receptors in the locus coeruleus (LC) in the expression of the withdrawal signs from opioids, rats were continuously infused with morphine (a mu-opioid agonist, 26 nmol/microl per h) or butorphanol (a mu/delta/kappa-mixed opioid agonist, 26 nmol/microl per h) intracerebroventricularly (i.c.v.) through osmotic minipumps for 3 days. An LC injection of NMDA (0.1 and 1 nmol/5 microl) induced withdrawal signs in opioid-dependent animals. However, it did not precipitate any abnormal behaviors in saline-treated control rats. The expression of the withdrawal signs precipitated by NMDA (1 nmol/5 microl), glutamate (10 nmol/5 microl), or naloxone (an opioid antagonist, 24 nmol/5 microl) was completely blocked by pretreatment with a NMDA antagonist, MK-801 (5-methyl-10,11-dihydro-5H-dibenzo[a,d]cycloheptan-5,10-imine), 0.1 mg/kg, i.p. In animals that had been infused with opioids in the same manner, naloxone (48 nmol/5 microl, i.c.v.) precipitated withdrawal signs and increased extracellular glutamate levels in the LC of opioid-dependent rats measured by in vivo microdialysis method. Pretreatment with MK-801, however, did not affect the increases of glutamate levels in the LC. These results further demonstrate that the expression of opioid withdrawal induced by an expeditious release of glutamate in the LC region of opioid-dependent animals might be mainly mediated by the postsynaptic NMDA receptors.

Effect of 4-(4-chlorobenzyl)pyridine on rat hepatic microsomal cytochrome P450 and drug-metabolizing enzymes in vivo and in vitro

The effect of 4-(4-chlorobenzyl)pyridine (4-CBP) on rat hepatic microsomal cytochrome P450 (P450) and its molecular species (CYP2B1, 2E1, 3A2, 2C11, and 2C12), and on drug-metabolizing enzyme activities were examined in vivo and in vitro. Treatment of rats with 4-CBP resulted in the induction of P450 and drug-metabolizing enzymes in a dose-dependent manner, but it was markedly inhibitory at higher dose levels. Immunoblot analyses revealed that 4-CBP induces both CYP2B1 and 2E1; however, both were decreased by increasing the dose of 4-CBP. The in vitro inhibitory experiment revealed that 4-CBP strongly inhibited benzphetamine N-demethylase activity, but not dimethylnitrosamine N-demethylase activity. The present findings provide information on the induction and inhibition effect of chlorinated benzylpyridine on hepatic microsomal P450s and drug-metabolizing enzymes in vivo and in vitro.

[Pharmacological and physiological effects of ginseng on actions induced by opioids and psychostimulants]

Pharmacological and physiological effects of ginseng on actions induced by opioids and psychostimulants were summarized. Analgesic effects of opioids, such as morphine and U-50,488H, were blocked by ginseng in a non-opioid dependent manner. Furthermore, ginseng inhibited the tolerance to and dependence on morphine, and prevented the suppressive effect on the development of morphine tolerance caused by co-exposure to foot-shock stress, but not psychological stress. On the other hand, behavioral sensitization (reverse tolerance to ambulation-accelerating effect) to morphine, methamphetamine (MAP) and cocaine was also inhibited by ginseng. Interestingly, ginseng also inhibited the appearance of the recurrent phenomenon (reappearance of the sensitized state was observed at the time of readministration of MAP and cocaine even after a 30-day discontinuation of drug administration) of the effect of MAP and cocaine. The conditioned place preference of MAP and cocaine was completely blocked by ginseng. These findings provide evidence that ginseng may be useful clinically for the prevention of abuse and dependence of opioids and psychostimulants.

Cloning and high expression of catalase gene from bacillus sp. TE124

An efficient expression system for producing catalase in Bacillus was developed. A catalase was purified from Bacillus sp. TE124 and the catalase gene was cloned by plaque hybridization with a probe constructed from the N-terminal amino acid sequence of the enzyme. The gene, containing an open reading frame of 1452 bp, was subcloned into pHY300PLK for self-cloning into the organism. As a result, the production of catalase increased 20-fold over that of the parent strain.

The role of glutamate in the locus coeruleus during opioid withdrawal and effects of H-7, a protein kinase inhibitor, on the action of glutamate in rats

To investigate the role of glutamate in the locus coeruleus (LC) during opioid withdrawal, rats were continuously infused with morphine (a mu-opioid receptor agonist, 26 nmol/microl/h) or butorphanol (a mu/delta/kappa-mixed opioid receptor agonist, 26 nmol/microl/h) intracerebroventricularly (i.c.v.) via osmotic minipumps for 3 days. A direct LC injection of glutamate (1 or 10 nmol/5 microl) or naloxone (an opioid receptor antagonist, 24 nmol/5 microl) induced withdrawal signs in morphine- or butorphanol-dependent animals. However, these agents failed to precipitate any withdrawal signs in saline-treated control animals. On the other hand, the expression of withdrawal signs precipitated by the administration of glutamate or naloxone in opioid-dependent animals was completely blocked by concomitant infusion with 1 or 10 nmol/microl/h of an inhibitor of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase and protein kinase C, H-7 [1-(5-isoquinolinesulfonyl)-2-methylpiperazine]. In animals that had been infused with opioids in the same manner, i.c.v. injection of naloxone (48 nmol/5 microl) precipitated withdrawal signs and increased extracellular fluid levels of glutamate in the LC of morphine- or butorphanol-dependent rats measured by in vivo microdialysis method. However, concomitant infusion with H-7 inhibited the increases of glutamate levels in the LC. These results strongly suggest that an expeditious release of glutamate in the LC region plays an important role in the expression of physical dependence on opioids. Furthermore, the action on glutamate release might be increased by the enhancement of cAMP-dependent protein kinase and/or protein kinase C activity.

[On the role of glutamate within the locus coeruleus during the development of opioid dependence and on the expression of withdrawal from dependence on opioids]

The development of dependence with repeated use and the expression of withdrawal syndrome are characteristic features of all the opioids represented by morphine. Although many studies regarding several neurotransmitters and receptors have been conducted to define the mechanism involved in the development of dependence on opioids, the definitive evidence has still not been presented. Hyperactivity of noradrenergic neurons within the locus coeruleus has been proposed to play a critical role in the physiological and behavioral responses that comprise opioid withdrawal. Furthermore, much recent interest has been focused on the putative involvement of glutamate within the locus coeruleus, as one member of the excitatory amino acid neurotransmitter family, in the development of dependence on opioids, since several results obtained from a variety of molecular biological, electrophysiological, biochemical, and behavioral studies indicate that glutamate and its receptors participate in both the withdrawal-associated increase in neuronal activity of locus coeruleus and the expression of opioid withdrawal behaviors. Therefore the present review will evaluate a recent trend regarding the role of glutamate within the locus coeruleus during the development of opioid dependence and on the expression of withdrawal from dependence on opioids.

Opioid analgesic-induced apoptosis and caspase-independent cell death in human lung carcinoma A549 cells

We characterized anticancer effects of opioid analgesics that are clinically used for cancer patients for pain relief. Treatment with 100 microM buprenorphine, a representative analgesic, induced cell death of human carcinomas, such as A549 (squamous epithelial cell of lung cancer), MCF-7 (breast cancer) and N417 (small cell of lung cancer), but not in KATO III (gastric cancer) cells as evaluated by alamar blue assay. Among 18 clinically utilized and related analgesics, buprenorphine and loperamide showed potent inhibition of cell viability. However, these anti-cancer effects were not affected by opioid receptor antagonists nor by pertussis toxin. Buprenorphine-induced cell death occurred as early as 1 h after the addition, and its T1/2 of cell viability inhibition was 3 h. The cell death manifested the characteristics of apoptosis, such as DNA-laddering and nuclear fragmentation, which were sensitive to a caspase inhibitor, Z-Asp-CH2-DCB. The nuclear fragmentation was independent of cell cycle phase specificity. The activity of caspase-3-like protease which is known to be closely related to apoptotic DNA laddering was markedly enhanced by buprenorphine. However, the inhibition of cell viability by buprenorphine was not affected by the caspase inhibitor. These findings suggest that some opioid analgesics induce typical apoptotic features sensitive to the caspase inhibitor, while also inhibition of cell viability insensitive to the inhibitor.

Sex-related effect of hemin on cytochrome P450 and drug-metabolizing enzymes in rat liver

We examined the effect of hemin on rat hepatic microsomal cytochrome P450 (P450) and its molecular species (P450 2E1, 3A2, 2C11 and 2C12) under the induction of heme oxygenase activity in male and female rats. Hemin produced an inverse relationship between the induction of heme oxygenase activity and the decrease of P450 content in a dose-dependent manner. A time course study revealed that hemin produced a significant decrease in total P450 content in male rats to about 37% that of the controls at 24 hr after its administration. Western and Northern blot analyses revealed that the increase in both heme oxygenase-1 (HO-1) protein and HO-1 mRNA reached a maximum at 24 hr and returned to control levels within 120 hr in both sexes. With respect to P450-dependent monooxygenase activities, we found that there was a significant decrease of aniline p-hydroxylase activity to about 30% of the control animals, but not in erythromycin N-demethylase activity at various time intervals. Immunoblot analysis revealed that P450 2E1 in male rat liver was dramatically decreased at 24 hr to about 20% of the controls, but not P450 3A2. Parallel to the decrease of androstenedione 16 alpha-hydroxylase activity, there was a marked decrease of P450 2C11 or 2C12 in male or female rats, respectively, at 72 hr after the treatment; however, hemin did not decrease androstenedione 16 alpha-hydroxylase activity in phenobarbital-pretreated rat liver. These findings suggest that hemin predominantly affects constitutively expressed isozymes rather than inducible P450 species in rat liver.

A protein kinase inhibitor, H-7, blocks naloxone-precipitated changes in dopamine and its metabolites in the brains of opioid-dependent rats

The influence of an inhibitor of cAMP-dependent protein kinase and protein kinase C, H-7 [1-(5-isoquinolinesulfonyl)-2-methylpiperazine], on naloxone (an opioid receptor antagonist)-precipitated withdrawal signs and changes in levels of dopamine (DA) and its metabolites in morphine- or butorphanol-dependent rats was investigated. Animals were infused continuously with morphine (a mu-opioid receptor agonist) or butorphanol (a mu/delta/kappa mixed opioid receptor agonist) for 3 days. Naloxone precipitated withdrawal syndrome and decreased the levels of DA in the cortex, striatum, and midbrain; 3, 4-dihydroxyphenylacetic acid (DOPAC) in the cortex, striatum, limbic areas, and midbrain; and homovanilic acid (HVA) in the striatum, limbic areas, and midbrain regions. In animals rendered dependent on butorphanol, the results obtained were similar to those of morphine-dependent rats except for the changes in DOPAC levels. Concomitant infusion of H-7 and opioid blocked both the expression of withdrawal signs and the decreases in DA, DOPAC, and HVA levels in a dose-dependent manner. These results suggest that the enhancement of cAMP-dependent protein kinase and/or protein kinase C activity accompanying the increase of DA neuron activity during continuous infusion of opioids leads to an abrupt reduction in levels of DA and its metabolites precipitated by naloxone, which is intimately involved in the expression of physical dependence on opioids.

Differential property of antigenic characterization between piroxicam and ampiroxicam in contact hypersensitivity

Piroxicam (PXM; a non-steroidal anti-inflammatory drug) has been reported to induce photosensitivity. In our previous report, however, ultraviolet-A (UVA)-irradiated or non-irradiated PXM did not induce any reactions in the in vivo model of contact hypersensitivity, while positive patch testing was shown by ampiroxicam (APX; a prodrug of PXM). The purpose of the present study was to clarify the influence of protein on the antigenicity of PXM using this model. Animals sensitized by UVA-irradiated 1% APX showed positive patch testing (open application) in UVA-irradiated 1% APX, while they were negative in challenge by UVA-irradiated PXM with or without 5% human serum albumin (HSA). Although animals sensitized by 1% thiosalicylate (TOS), which is thought to be an active hapten of PXM, were cross-reacted with UVA-irradiated 1% APX, they failed to react with UVA-irradiated 1% PXM with or without HSA. On the other hand, intra-dermal testing (intra-dermal application) in UVA-irradiated 0.1% PXM with 5% HSA was positive in animals sensitized by UVA-irradiated 1% APX, while 5% HSA alone, 0.1% PXM with 5% HSA and UVA-irradiated 0.1% PXM did not induce any reactions under this condition. Furthermore, concentration of PXM in the presence of HSA was reduced by UVA-irradiation in a time dependent manner, while the degradation of PXM was not observed in the absence of HSA. Finally, PXM almost disappeared at 120 min after the initiation of UVA-irradiation. The degradation of PXM irradiated by UVA was dependent on the concentration of HSA at the range of 0 to 4%. Hence, these results suggest that the presence of protein is necessary for the induction of the antigenic activity of PXM and the antigenic characterization of PXM is different from that of APX in contact hypersensitivity.

Concurrent induction of rat hepatic microsomal cytochrome P450 and haem oxygenase by 2,2'-dipyridyl ketone: comparison with the effect of 2,2'-dipyridyl amine

1. The effect of 2,2'-dipyridyl ketone and 2,2'-dipyridyl amine on the induction of hepatic microsomal cytochrome P450 (P450) and heme oxygenase was compared, and their effects on five different P450 isoforms (P4501A1, 3A2, 2B1, 2E1 and 2C11) in rat were examined. 2. Treatment of rat with 2,2'-dipyridyL amine resulted in the marked induction of haem oxygenase to about seven-fold of the controls with a decrease in p450 content. 2,2'-Dipyridyl ketone produced concomitant induction of both P450 and haem oxygenase activity in a dose- and time-dependent manner without showing any sex differences. 3. Immunoblot analysis revealed that 2,2'-dipyridyl ketone slightly increased CYP2E1 and CYP3A2 at low doses, but not at high dose levels. There was no effect on P4502C11. P4502B1 was induced by the treatment with 2,2'-dipyridyl ketone in a dose-dependent manner. 4. These results indicate that dipyridyl compounds having different bridges between two aromatic moieties act as differential inducers of hepatic microsomal P450s and haem oxygenase.

A novel effect of polymorphonuclear leukocytes in the facilitation of angiogenesis

The purpose of this study was to examine whether the adhesion of polymorphonuclear leukocytes (PMNs) to endothelial cells and/or reactive oxygen species (ROS) released from PMNs are responsible for inducing angiogenesis. Angiogenesis was assessed by tube formation using endothelial cells obtained from bovine thoracic aorta (BAECs) grown on a layer of collagen type I. Addition of PMNs to BAECs weakly induced angiogenesis. The angiogenesis induced by PMNs alone was further enhanced by treatment of the PMNs with N-formyl-methionyl-leucyl-phenylalanine (FMLP), a selective activator of PMN. The involvement of PMN adhesion to BAECs via adhesion molecules in angiogenesis was investigated by using monoclonal antibodies against E-selectin and intercellular adhesion molecule-1 (ICAM-1). These antibodies blocked both the PMN adhesion to BAECs and the enhancement of angiogenesis induced by FMLP-treated PMNs. Furthermore, the enhancement of angiogenesis by FMLP-treated PMNs was blocked by catalase, a scavenging enzyme of H2O2, but not by superoxide dismutase (SOD). These results suggest that PMNs induce angiogenesis in vitro, and that the mechanism of stimulation of angiogenesis by PMNs may involve the adherence of PMNs to endothelial cells via E-selectin and ICAM-1, and H2O2, but not superoxide. Thus, activated PMNs in pathological states may not only induce tissue injury, but may also function as regulators of angiogenesis.

Antigenic characterization in ampiroxicam-induced photosensitivity using an in vivo model of contact hypersensitivity

Ampiroxicam (APX), a prodrug of piroxicam (PXM), has been reported to induce photosensitivity. Antigenic characterization of these photosensitivities, however, is still insufficient. The purpose of the present study was to elucidate further mechanism of photosenstivity induced by APX and PXM using an in vivo model of contact hypersensitivity in guinea pigs. Animals sensitized with ultraviolet-A (UVA)-irradiated 1% APX showed positive reaction in the patch testing to UVA-irradiated 1% APX and 1% thiosalicylate (TOS), while they were negative in challenge with UVA-irradiated 1% PXM, non-irradiated APX and PXM, whereas none of UVA-irradiated or non-irradiated APX and PXM showed positive patch test reaction in animals sensitized with UVA-irradiated 1% PXM or control vehicles. Animals sensitized with 1% TOS were successfully challenged by 1% TOS and cross-reacted with UVA-irradiated 1% APX; however, they failed to react with UVA-irradiated PXM, non-irradiated APX and PXM. Indeed, the in vitro study revealed that the concentration of APX was easily reduced by the increase of UVA irradiation dose, as compared with that of PXM. Interestingly, absorption spectrum of UVA-irradiated APX was similar to that of TOS, which is thought to be an active hapten of PXM. In the present study, we succeeded in the development of a novel animal model reflecting the clinical observations. Furthermore, these results suggested that contact hypersensitivity induced by UVA-irradiated APX is developed by photoproducts of APX itself, but not by the biotransformation of APX to PXM.

Cloning, expression, and chromosomal mapping of a human ganglioside sialidase

Here we report the cDNA sequence of a human ganglioside sialidase. The cDNA was isolated from a human brain cDNA library by screening with a 240 bp probe generated by polymerase chain reaction using primers based on the sequences of rat cytosolic and bovine membrane sialidases which we previously cloned. The 3.0 kb cDNA encodes an open reading frame of 436 amino acids containing a putative transmenbrane domain and an Arg-Ile-Pro and three Asp-box sequences characteristic of sialidases and showing overall 83% and 39% identities to the bovine and rat enzymes, respectively. Northern blot analysis revealed high expression in skeletal muscle and testis, but low level in kidney, placenta, lung, and digestive organs. Transient expression of the cDNA in COS-1 cells resulted in a 130-fold increase in sialidase activity compared to the control level, and the activity was found to be almost specific for gangliosides. Fluorescent in situ hybridization allowed the human sialidase gene localized to chromosome 11 at q 13.5.

Selective coupling of mouse brain metabotropic sigma receptor with recombinant Gi1

Various sigma (sigma) ligands including (+)-pentazocine stimulated [35S]GTPgammaS binding in synaptic membranes from the mouse cerebellum. The (+)-pentazocine-stimulated [35S]GTPgammaS binding was blocked by the treatment of membranes with pertussis toxin (PTX), but completely recovered by the reconstitution of PTX-treated membranes with recombinant Gi1, but not with GoA. These findings suggest that metabotropic sigma receptors are selectively coupled to Gi1 protein.

The significance of resections for residual masses after chemotherapy in metastatic testicular tumors

BACKGROUND

After chemotherapy for metastatic testicular tumors, masses may remain, often in the metastatic sites. This study analyses the role of resections for the residual masses.

METHODS

Seventy-seven patients with advanced (stage II, III) testicular tumors were treated. Of these, 38 patients, including eight with seminoma and 30 patients with non-seminomatous germ cell tumors, underwent resection of residual masses after chemotherapy and have been followed for a median of 41.5 months (range 2-138) after the resection.

RESULTS

Residual masses were necrosis/fibrosis in 19 patients, mature teratoma in 11 and cancer in eight. The ratio of cancer in stage III (41.2%) was significantly higher than that in stage II (4.8%). Ten of 38 (26.3%) patients experienced recurrences in sites other than the resected sites, and five of 10 patients have died of cancer. Most recurrences (80%) occurred within two years. Recurrences after resection were detected in 4.8% of stage II patients, 52.9% of stage III, 16.7% of necrosis/fibrosis and mature teratoma, and 62.5% of cancer. The survival rate of patients with cancer was significantly lower in spite of adjuvant chemotherapy after surgery.

CONCLUSIONS

Resection for residual masses after chemotherapy in metastatic testicular tumors was useful in confirming the tissue and in controlling the metastatic sites. Recurrences were often found in patients with cancer in the residual mass and the prognosis of patients with cancer was poor, therefore the development of more effective therapy for patients with cancer is required to improve the prognosis.

Molecular cloning and characterization of a plasma membrane-associated sialidase specific for gangliosides

Gangliosides are plasma membrane components thought to play important roles in cell surface interactions, cell differentiation, and transmembrane signaling. A mammalian sialidase located in plasma membranes is unique in specifically hydrolyzing gangliosides, suggesting crucial roles in regulation of cell surface functions. Here we describe the cloning and expression of a cDNA for the ganglioside sialidase, isolated from a bovine brain cDNA library based on the amino acid sequence of the purified enzyme from bovine brain. This cDNA encodes a 428-amino acid protein containing a putative transmembrane domain and the three Asp boxes characteristic of sialidases and sharing 19-38% sequence identity with other sialidases. Northern blot and polymerase chain reaction analyses revealed a general distribution of the gene in mammalian species, including man, and the mouse. In COS-7 cells transiently expressing the sialidase, the activity was found to be 40-fold that of the control level with ganglioside substrates in the presence of Triton X-100, and the hydrolysis was almost specific to gangliosides other than GM1 and GM2, both alpha2-->3 and alpha2-->8 sialyl linkages being susceptible. The major subcellular localization of the expressed sialidase was assessed to be plasma membrane by Percoll density gradient centrifugation of cell homogenates and by immunofluorescence staining of the transfected COS-7 cells. Analysis of the membrane topology by protease protection assay suggested that this sialidase has a type I membrane orientation with its amino terminus facing to the extracytoplasmic side and lacking a signal sequence.

Purification, characterization, and sequence determination of phospholipase D secreted by Streptoverticillium cinnamoneum

Phospholipase D (PLD), secreted into the culture medium of an actinomycete, Streptoverticillium cinnamoneum, has been purified to homogeneity and characterized. The Stv. cinnamoneum PLD efficiently catalyzes both the hydrolysis and transphosphatidylation of various phospholipids, including phosphatidylethanolamine (PE), phosphatidylcholine (PC), and phosphatidylserine (PS). However, the substrate specificity differs between the two reactions; PE serves as the most preferred substrate for the hydrolysis, but PC and PS are better substrates than PE for the transphosphatidylation. In addition, the transphosphatidylation but not the hydrolysis of PE and PC is markedly activated on the addition of metal ions, especially Al3+. Nucleotide and amino acid sequence determination of the Stv. cinnamoneum PLD revealed the presence of common structural motifs identified in all PLD sequences from various species.

[Public health nurses' disaster responses for intractable neurological patients at home]

OBJECTIVE

This paper describes the 1995 Hanshin-Awaji Earthquake experience of the local public health nurses. The purpose of the study was to identify problems regarding assistance of intractable neurological patients at home during and after the earthquake and to discuss ways to improve future local disaster responses by public health nurses for those patients.

METHODS

Approximately 2 hours of a group interview of public health nurses from 2 public health centers in Kobe City was conducted in August, 1996. Interview data was collected via audio-tape and transcribed. The data was organized according to phases of the earthquake. The acute phase of the earthquake disaster ended within 72 hours. The data was then analyzed to identify problems in assisting intractable neurological home patients in order to discuss disaster responses by public health nurses.

RESULTS

There was a delay in confirming the safety of and providing needed assistance for intractable neurological patients at home by public health nurses. During the first 3 days after the earthquake, the majority of public health nurses were unable to commute to work due to the shutdown of transportation systems. In addition, nurses, who were able to come to work, were preoccupied with treating earthquake casualties and distributing medical supplies. Other factors associated with the delay included the following: lack of a registration list for intractable neurological patients at home; lack of close contacts between public health nurses and patients, and between public health nurses and patient support groups; and sparing nurses for guiding volunteers and for coordinating between shelters and hospitals.

CONCLUSION

Measures to improve future disaster responses are as follows: a) teaching patients and their families how to safeguard against disaster; b) preparing registration lists; c) establishing support networks and cooperating with network members; and d) upon disaster, assigning some nurses to assess the needs of patients.

Enhancement of tissue factor following ischemic-reperfusion injury in rats

To evaluate the involvement of tissue factor (TF) in blood coagulation reflecting injury of the blood vessels induced by reperfusion following ischemic treatment in rat abdominal blood vessels in vivo, both TF expression and prothrombin time (PTT), which is used as a marker of coagulation, were measured after ischemic-reperfusion treatment. TF expression was significantly increased at 0 and 5 min after reperfusion following a 30 min period of vessel ligation, while the PTT was significantly shortened at 5 and 10 min. On the other hand, the change of TF expression and PTT were not detected in the animals ligated vessel for 15 min. These results suggest that TF plays an important role in the injury after reperfusion following ischemia.

In vivo signal transduction of tetrodotoxin-sensitive nociceptive responses by substance P given into the planta of the mouse hind limb

1. We developed a simple and sensitive peripheral analgesic test in mice. 2. Substance P (SP) given into the planta (i.pl.) of the mouse hind limb produced a flexor response. The flexor response was dependent on SP doses (0.1-100 pmol, i.pl.). When SP (10 pmol) was given every 5 min, there were stable flexor responses. These nociceptive responses were completely abolished by CP-96,345, a neurokinin 1 receptor antagonist. 3. SP-induced responses were also blocked by several signal transduction-related compounds, such as tetrodotoxin, EGTA, and U73122, a selective phospholipase C inhibitor. 4. These findings suggest that SP depolarizes peripheral nerve endings, possibly through inositol trisphosphate (Ins P3)-gated Ca2+ influx, followed by induction of action potentials in the peripheral axons of primary afferent neurons.

Antiamnesic action of cromakalim, a potassium channel opener, in mice treated with hypoxia- and cerebral ischemia-type stress stimuli

1. The amnesia induced by various stress stimuli through hypoxia and cerebral ischemia was evaluated by the shortening of the response latency in a step-through task in mice. 2. The hypoxia-induced amnesia was reduced by cromakalim, a K+ channel opener (KCO), given 10 min before or immediately after the hypoxic treatment. 3. Similarly, the ischemia-induced amnesia was also reduced by cromakalim given 30 min before the occlusion. 4. In ischemic-induced amnesic mice, pyknotic cells, indicating the condensation of chromatin, were observed histochemically at the dentate gyrus granule cells in hippocampal regions 96 hr after ischemic treatment. In addition, cromakalim inhibited the induction of pyknotic cells. 5. These results suggest that KCOs might produce prophylactically neuroprotective effects against hypoxia- and cerebral ischemia-induced amnesia.

Lack of tolerance in peripheral opioid analgesia in mice

We recently developed a sensitive peripheral analgesic test in mice. Bradykinin, a representative pain-producing substance, when given subcutaneously through a polyethylene tube into the plantar of the limb connected to a transducer, induced a flexor reflex response, in a dose dependent manner. When morphine, a mu-opioid receptor agonist, was added to the plantar through another polyethylene tube, bradykinin-induced responses were completely abolished in a naloxone-reversible manner. These peripheral analgesic effects were also observed with DAMGO, another mu-opioid receptor agonist, and U-69,593, a kappa-opioid receptor agonist, but not DSLET, a delta-opioid receptor agonist. When morphine was given subcutaneously to the back, a potent analgesia in the tail pinch test was observed. Repeated administrations of morphine once per day for 5 days showed a marked tolerance or reduction in morphine analgesia on the 6th day, while there was no significant reduction in the peripheral analgesia of morphine. These findings suggest that tolerance to morphine analgesia is mediated through synaptic plasticity in the central nervous system, but not through a receptor desensitization at the level of the single cell.

Attempts to classify dependence-liable drugs by using a simple drug-discrimination test in mice

1. In a simple discrimination test using a two-compartment shuttle box with mice, we examined the action properties of dependence-liable drugs. In mice trained to discriminate morphine from saline, neither methamphetamine (MAP) nor cocaine (COCA) was generalized to the discriminative stimulus effects of morphine. 2. Similarly, in mice trained to discriminate MAP from saline, COCA, which is known to have neuronal mechanisms in common with MAP, was generalized to the stimulus effects of MAP, but morphine was not. 3. Dihydroetorphine (DHE), which has receptor mechanisms in common with morphine, was generalized to the discriminative stimulus effects of morphine, whereas it was not generalized to the effects of MAP. Thus, the present discrimination test might be useful for the first screening of compounds with unknown neuronal mechanisms, particularly for classification into groups having separate neuropharmacological mechanisms in common.

Pharmacological and physiological effects of ginseng on actions induced by opioids and psychostimulants

Pharmacological and physiological effects of ginseng on actions induced by opioids and psychostimulants are summarized. Analgesic effects of opioids, such as morphine and U-50, 488H, were blocked by ginseng in a nonopioid dependent manner. Furthermore, ginseng inhibited the tolerance to and dependence on morphine, and eliminated the suppressive effect of the development of morphine tolerance by coexposure to footshock stress, but not psychological stress. On the other hand, behavior sensitization (reverse tolerance to their ambulation-accelerating effect) to morphine, methamphetamine and cocaine was also inhibited by ginseng. Interestingly, ginseng also inhibited the appearance of the recurrent phenomenon (reappearance of the sensitized state was observed at the time of readministration of methamphetamine and cocaine even after a 30-day discontinuation of drug administration) of the effect of methamphetamine and cocaine. The conditioned place preference of methamphetamine and cocaine was completely blocked by ginseng. These findings provide evidence that ginseng may be useful clinically for the prevention of abuse and dependence of opioids and psychostimulants.

Partial loss of tolerance liability to morphine analgesia in mice lacking the nociceptin receptor gene

In mice lacking the nociceptin (or orphanin FQ) receptor gene, when 10 mg/kg of morphine was subcutaneously given, a potent analgesia in the tail pinch test was observed. The analgesic effect of morphine was equivalent among wild-type, heterozygous and homozygous mutant mice. When morphine was given to such mice in a dose of 10 mg/kg once per day for 5 days, wild-type and heterozygous mice showed marked tolerance or reduction in the morphine analgesia on the 5th day, while homozygous mice showed only 50% reduction in the peripheral analgesia of morphine. These findings suggest that nociceptin or its receptor plays important roles in the in vivo mechanism for the development of morphine tolerance.

Characterization of nociceptin-stimulated in situ [35S]GTPgammaS binding in comparison with opioid agonist-stimulated ones in brain regions of the mice

We studied the characterization of receptor-mediated G protein activity by nociceptin throughout brain regions, using in situ GTPgammaS binding autoradiography. Nociceptin-stimulated GTPgammaS binding was markedly observed in amygdala, hippocampal pyramidal cell layers, temporal and entorhinal cortex, infralimbic organ, anterior olfactory nucleus, and rostral part of thalamus. These nociceptin-stimulated activities were not affected by naloxone, naltrindol nor norbinaltorphimine which completely blocked mu-, delta- or kappa-opioid agonist-stimulated GTPgammaS binding, respectively. In addition, the distribution of nociceptin-stimulated activities throughout brain regions was found to be different from such opioid receptor-mediated ones.

Suppression of pulmonary metastasis in murine B16 melanoma cells by transfection of a sialidase cDNA

A cytosolic sialidase cDNA was transfected into a highly metastatic and invasive cell line, B16-BL6, derived from the murine B16 melanoma. Stable transfection of a cytosolic sialidase expression vector yielded 4 transfectants with high content of the exogenous sialidase protein as well as enzyme activity. These transfectants exhibited markedly decreased experimental pulmonary metastasis, invasiveness in collagen gels and cell motility on colloidal gold-coated glass plates but no change in cell attachment to fibronectin, collagen type VI or laminin. To cast light on the underlying mechanisms, cellular constituents of the transfectants were analyzed. Sialidase over-expression did not lead to any significant changes in cell surface carbohydrates or intracellular glycoproteins, as revealed by lectin flow cytometry and lectin blotting, respectively. Thin layer chromatography of intracellular glycolipids, however, revealed decreased ganglioside GM3 and increased lactosylceramide as major changes.

Peripheral non-opioid analgesic effects of kyotorphin in mice

Bradykinin (BK) given into the plantar (i.pl.) of the mouse hind-limb produced a flexor response. The flexor responses were dependent on BK doses (0.02-20 pmol, i.pl.), and were completely abolished by Hoe140, a B2-type BK receptor antagonist. Kyotorphin, an analgesic neuropeptide which shows enkephalin release in brain slices, produced a dose-dependent reduction of the BK-induced nociceptive responses in ranges of 10 pmol to 1 nmol (i.pl.). Such analgesic effects of kyotorphin were reversed by leucine-arginine, a specific kyotorphin receptor antagonist, but not by naloxone. The kyotorphin-analgesia was also abolished by pertussis toxin (PTX) pretreatment. These results suggest that peripheral analgesic effects of kyotorphin are mediated through mechanisms of kyotorphin specific receptor and PTX-sensitive Gi/Go, and that the enkephalin release is not necessary for this analgesia.

Sigma ligands stimulate GTPase activity in mouse prefrontal membranes: evidence for the existence of metabotropic sigma receptor

We studied effects of various sigma ligands on GTPase activity in mouse prefrontal membranes. Some representative sigma agonists, such as (+)-pentazocine, SA4503 and (+)-3-PPP, stimulated the GTPase activity in a concentration-dependent manner in ranges of 10 nM to 10 microM. Maximal effect was almost 10% increase to the control without treatment of drugs. However, another representative agonist, (+)-SKF10,047 showed only a partial activity with maximal effect 5% at 1 microM. NE-100, a representative antagonist, showed no effect at concentrations not more than 100 nM, while it did stimulate GTPase activity at 1 and 10 microM. Furthermore, these stimulative effects of both (+)-pentazocine and SA4503 on GTPase activity were significantly antagonized by NE-100 at 100 nM, suggesting that NE-100 possesses agonist-antagonist property. These findings suggest the possibility that there exist metabotropic sigma receptors.

Glutamate in opioid dependence

The present review will concentrate on a discussion of recent investigations which implicate a critical linkage of three facets of the central nervous system mediation of opioid dependence, as evidenced by expression of acutely-precipitated withdrawal events. These are the kappa-opioid receptor subtype, the glutamatergic neuronal system and a specific brain locus, the locus coeruleus. The impetus for this line of investigation derives from a recognition that opioid analgesics, such as butorphanol (Stadol), exhibit a markedly different profile of activity at opioid receptors than does morphine yet have abuse liability and cause dependence readily. Emphasis will be placed on demonstration of a rodent model in which butorphanol administration induces dependence through a unique (in comparison with morphine) activation of the kappa-opioid receptor. The use of in vivo microdialysis techniques clearly identifies, in this model, that acutely-precipitated withdrawal from dependence on butorphanol results in focal increases in extracellular levels of glutamate within the locus coeruleus, and that the withdrawal syndrome can be mimicked by intracerebroventricular administration of exogenous glutamate, acting through the N-methyl-D-aspartate glutamate receptor subtype. The data confirm the participation of glutamate as a general phenomenon in opioid dependence, identify the locus coeruleus as a primary site for glutamatergic mediation of dependence, and suggest novel aspects to the neuropharmacology of opioid dependence with respect to the role of the kappa-opioid receptor.

Dual effects of NMDA-induced intracellular Ca2+ elevations on cGMP levels in cultured cerebellar granule neurons

1. Cyclic GMP (cGMP) levels were markedly elevated by N-methyl-D-aspartate (NMDA) within 1-3 min of incubation, then gradually decreased with incubation time. 2. The NMDA-induced intracellular Ca2+ elevations showed maximal levels just after adding NMDA and were maintained for 60 min. 3. NMDA did not show augmentation of cGMP elevation with sodium nitroprusside (SNP), rather it decreased the SNP-induced cGMP elevation after exposure for 60 min. 4. The NMDA-induced elevation of cGMP was remarkably augmented with the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX, 1mM), after 60 min of incubation.

A potent mu-opioid receptor agonist, dihydroetorphine, fails to produce the conditioned place preference in mice

Reinforcing effects of dihydroetorphine (DHE) and morphine were evaluated by the conditioned place preference paradigm. Both DHE and morphine produced an antinociceptive effect in a dose-dependent manner. On the other hand, DHE (0.1, 1, 3 and 10 micrograms/kg, i.p.) failed to induce the conditioned preference, while morphine (0.1, 1, 3 and 10 mg/kg, i.p.) caused a dose-dependent preference for the drug-paired place. Thus, these characteristic properties of DHE make it attractive for development as a novel potent analgesic compound that has less dependence liability.

The effect of ginseng extract on locomotor sensitization and conditioned place preference induced by methamphetamine and cocaine in mice

Repeated i.p. injections of 2 mg/kg methamphetamine (MA) or 20 mg/kg cocaine at 48-h intervals induced reverse tolerance to their ambulation-enhancing effects (behavioral sensitization). Furthermore, the reappearance of the sensitized state was observed at the time of readministration of MA or cocaine even after a 30-day discontinuation of drug administration. A concomitant injection of ginseng extract (GE), 200 mg/kg, i.p., suppressed the development of reverse tolerance and the reappearance of sensitization to MA and cocaine. Conditioned place preference to MA (1, 2, and 4 mg/kg, i.p.) and cocaine (1, 4, 10, and 20 mg/kg, i.p.), was completely blocked by GE, 200 mg/kg, i.p. combined treatment with MA of cocaine. Meanwhile, spontaneous motor activity and place preference were not affected by GE alone. These results provide evidence that GE may be useful clinically for the prevention of adverse actions of MA and cocaine.

Inhibition of endothelium-dependent relaxation by hemoglobin in rabbit aortic strips: comparison between acellular hemoglobin derivatives and cellular hemoglobins

Hemoglobin (Hb)-based artificial oxygen carriers are supposed to induce vasoconstriction through the inactivation of endothelium-derived relaxing factor (EDRF). We examined the vasoconstrictive activity of acellular Hb and cellular Hb solutions in rabbit aortic strips. Unmodified Hb, pyridoxalated Hb, bovine unmodified Hb, haptoglobin-Hb complex (Hp-Hb), and polyoxyethylene glycol-conjugated Hb (PEG-Hb) were used as acellular Hbs having different molecular masses. Cellular Hbs included liposome-encapsulated Hb and red blood cells (RBC). In the first experiment, Hb (10 ng/ml to 1 mg/ml) was cumulatively added to the tissues in which steady-state relaxation was evoked by acetylcholine (ACh) after precontraction induced by phenylephrine. Although all Hb solutions induced a dose-dependent reversal of ACh-induced relaxation, the most potent vasoconstrictive effect was noted with acellular Hbs, and their contractile activities were almost the same independent of molecular mass. On the other hand, liposome-Hb and RBC showed reduced potencies in this order. These results indicate the importance of cellularity as the major factor determining Hb-related EDRF inactivation. In another experiment, the tissues were exposed to Hb at 0.01, 0.1, or 1 mg/ml for 30 min and ACh-induced relaxation was recorded after the complete removal of Hb in an organ bath chamber. Exposure to unmodified Hb at > 0.1-mg/ml concentrations significantly reduced the ACh-induced relaxation, whereas the relaxation was not affected by PEG-Hb, Hp-Hb, liposome-Hb, or RBC. These results suggest that unmodified Hb might be persistently associated with tissues and thereby inhibit ACh-induced relaxation. From these findings, we propose two attributes of Hb-related inhibition of endothelium-dependent relaxation: Acellular Hbs inhibit EDRF more efficiently in the luminal space than cellular Hbs, and unmodified Hb can also inhibit it adluminally and/or adventitially.

Naloxone-precipitated changes in biogenic amines and their metabolites in various brain regions of butorphanol-dependent rats

Influence of a naloxone (an opioid receptor antagonist) challenge (5 mg/kg, IP) on levels of biogenic amines and their metabolites in various brain regions of rats infused continuously with butorphanol (a mu/delta/kappa mixed opioid receptor agonist; 26 nmol/microliter/h) or morphine (a mu-opioid receptor agonist; 26 nmol/microliter/h) was investigated using high-performance liquid chromatography with electrochemical detection (HPLC-ED). Naloxone precipitated a withdrawal syndrome and decreased the levels of: dopamine (DA) in the cortex and striatum, 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum, homovanilic acid (HVA) in the striatum, limbic, midbrain, and pons/medulla regions in butorphanol-dependent rats. However, the levels of norepinephrine (NE), serotonin (5-hydroxytryptamine; 5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) in the regions studied were not affected by naloxone-precipitated withdrawal. In addition, naloxone increased the HVA/DA ratio in the cortex, while this ratio was reduced in the limbic, midbrain, and pons/medulla. The reduction of 5-HIAA/5-HT ratio was also detected in the limbic area. In the animals rendered dependent on morphine, the results obtained were similar to those of butorphanol-dependent rats except for changes of 5-HIAA levels in some brain regions. These results suggest that an alteration of dopaminergic neuron activity following a reduction of DA and its metabolites in specific brain regions (e.g., striatum, limbic, midbrain, and pons/medulla) play an important role in the expression of the opioid withdrawal syndrome.

Inhibitory effects of diltiazem, an L-type Ca2+ channel blocker, on naloxone-increased glutamate levels in the locus coeruleus of opioid-dependent rats

To investigate the effects of diltiazem, an L-type Ca2+ channel blocker, on naloxone-precipitated withdrawal and elevations of glutamate levels in the locus coeruleus (LC) of opioid-dependent rats, animals were continuously infused with 26 nmol/microliter/h of morphine or butorphanol intracerebroventricularly (i.c.v.) via osmotic minipumps for 3 days. I.c.v. injection of naloxone (an opioid-receptor antagonist, 48 nmol/5 microliters) precipitated withdrawal signs and increased extracellular fluid levels of glutamate in the LC of morphine- or butorphanol-dependent rats measured by in vivo microdialysis. Meanwhile, concomitant infusion of opioids with diltiazem (10 or 100 nmol/microliter/h) inhibited the withdrawal signs and prevented the elevations of glutamate levels in the LC. These results suggest that an expeditious release of glutamate in the LC region regulated by L-type Ca2+ channels mediated system plays a role in the expression of withdrawal signs from opioids.