Elucidation of the mechanisms of exercise-induced hypoalgesia and pain prolongation due to physical stress and the restriction of movement

Persistent pain signals cause brain dysfunction and can further prolong pain. In addition, the physical restriction of movement (e.g., by a cast) can cause stress and prolong pain. Recently, it has been recognized that exercise therapy including rehabilitation is effective for alleviating chronic pain. On the other hand, physical stress and the restriction of movement can prolong pain. In this review, we discuss the neural circuits involved in the control of pain prolongation and the mechanisms of exercise-induced hypoalgesia (EIH). We also discuss the importance of the mesolimbic dopaminergic network in these phenomena.

Unexpected Rearrangement Reactions of the 14-Aminonaltrexone Skeleton

The reaction of 14-aminonaltrexone with acetic anhydride was found to produce a range of different novel compounds between the free compound and its hydrochloride. The hydrochloride produced a compound with an acetylacetone moiety, whereas the free form produced a compound with a pyranopyridine moiety. Efforts to isolate reaction intermediates and density functional theory calculations have elucidated those formation mechanisms with both bearing the novel morphinan-type skeleton. Furthermore, a derivative with the acetylacetone moiety showed binding to opioid receptors.

Design and Synthesis of Orexin 1 Receptor-Selective Agonists

Orexins are a family of neuropeptides that regulate various physiological events, such as sleep/wakefulness as well as emotional and feeding behavior, and that act on two G-protein-coupled receptors, i.e., orexin 1 (OX₁R) and orexin 2 receptors (OX₂R). Since the discovery that dysfunction of the orexin/OX₂R system causes the sleep disorder narcolepsy, several OX₂R-selective and OX_1/2R dual agonists have been disclosed. However, an OX₁R-selective agonist has not yet been reported, despite the importance of the biological function of OX₁R. Herein, we report the discovery of a potent OX₁R-selective agonist, (R,E)-3-(4-methoxy-3-(N-(8-(2-(3-methoxyphenyl)-N-methylacetamido)-5,6,7,8-tetrahydronaphthalen-2-yl)sulfamoyl)phenyl)-N-(pyridin-4-yl)acrylamide [(R)-YNT-3708; EC₅₀ = 7.48 nM for OX₁R; OX₂R/OX₁R EC₅₀ ratio = 22.5]. The OX₁R-selective agonist (R)-YNT-3708 exhibited antinociceptive and reinforcing effects through the activation of OX₁R in mice.

Design and synthesis of novel orexin 2 receptor agonists with a 1,3,5‑trioxazatriquinane skeleton

A novel series of 1,3,5‑trioxazatriquinane with multiple effective residues (TriMER) derivatives with amino-methylene side chains was designed and synthesized based on the docking-simulation results between orexin receptors (OXRs) and TriMER-type OXR antagonists. In vitro screening against orexin receptors identified six TriMER derivatives with a cis side-chain configuration, and, among these, 20d and 28d showed full agonist activity against OX₂R at a concentration of 10 µM. To determine the absolute stereochemistry of these hit compounds, we also conducted the first asymmetric synthesis of a 1,3,5‑trioxazatriquinane skeleton using a Katsuki-Sharpless asymmetric epoxidation as the key reaction and obtained a set of the individual stereoisomers. After evaluating their activity, (+)-20d (EC₅₀ = 3.87 μM for OX₂R) and (+)-28d (EC₅₀ = 1.62 μM for OX₂R) were determined as eutomers for OX₂R agonist activity. Our results provide a new class of skeleton consisting of an (R)-1,3,5‑trioxazatriquinane core with flexible methylene linkers and hydrophobic substituents at the terminals of the side chains via carbamates/sulfonamides as OX₂R agonists.

OX2R-selective orexin agonism is sufficient to ameliorate cataplexy and sleep/wake fragmentation without inducing drug-seeking behavior in mouse model of narcolepsy

Acquired loss of hypothalamic orexin (hypocretin)-producing neurons causes the chronic sleep disorder narcolepsy-cataplexy. Orexin replacement therapy using orexin receptor agonists is expected as a mechanistic treatment for narcolepsy. Orexins act on two receptor subtypes, OX1R and OX2R, the latter being more strongly implicated in sleep/wake regulation. However, it has been unclear whether the activation of only OX2R, or both OX1R and OX2R, is required to replace the endogenous orexin functions in the brain. In the present study, we examined whether the selective activation of OX2R is sufficient to rescue the phenotype of cataplexy and sleep/wake fragmentation in orexin knockout mice. Intracerebroventricular [Ala¹¹, _D-Leu¹⁵]-orexin-B, a peptidic OX2R-selective agonist, selectively activated OX2R-expressing histaminergic neurons in vivo, whereas intracerebroventricular orexin-A, an OX1R/OX2R non-selective agonist, additionally activated OX1R-positive noradrenergic neurons in vivo. Administration of [Ala¹¹, _D-Leu¹⁵]-orexin-B extended wake time, reduced state transition frequency between wake and NREM sleep, and reduced the number of cataplexy-like episodes, to the same degree as compared with orexin-A. Furthermore, intracerebroventricular orexin-A but not [Ala¹¹, _D-Leu¹⁵]-orexin-B induced drug-seeking behaviors in a dose-dependent manner in wild-type mice, suggesting that OX2R-selective agonism has a lower propensity for reinforcing/drug-seeking effects. Collectively, these findings provide a proof-of-concept for safer mechanistic treatment of narcolepsy-cataplexy through OX2R-selective agonism.

Essential structure of orexin 1 receptor antagonist YNT-707: Conversion of the 16-cyclopropylmethyl group to the 16-sulfonamide group in D-nor-nalfurafine derivatives

The five-membered D-ring nalfurafine (D-nor-nalfurafine) derivatives with a 16-sulfonamide group were synthesized. Conversion of the 16-cyclopropylmethyl group to the 16-benzenesulfonamide group in the D-nor-nalfurafine derivatives drastically improved the orexin 1 receptor (OX₁R) antagonist activities. The intramolecular hydrogen bond between the 14-hydroxy and the 16-sulfonamide groups may play an important role in increasing the probability that the 6-amide group would be located at the lower side of the C-ring, leading to an active conformation for OX₁R. The assay results and the conformational analyses of the 14-OH, 14-H, and 14-dehydrated D-nor-nalfurafine derivatives suggested that the 14- and 16-substituents of the D-nor-nalfurafine derivatives had a greater effect on the affinities for the OX₁R than did the 14- and 17-substituents of nalfurafine derivatives.

Synthesis of unnatural morphinan compounds to induce itch-like behaviors in mice: Towards the development of MRGPRX2 selective ligands

Mas-related G protein-coupled receptor X2 (MRGPRX2) mediates the itch response in neurons and is involved in atopic dermatitis (AD)-associated inflammation and itch. Potent and MRGPRX2-selective ligands are essential to an understanding of the detailed function of the receptor and to develop new therapeutic agents for its related diseases. (+)-TAN-67 (1), the enantiomer of the δ-opioid receptor (DOR) selective ligand (-)-TAN-67 (1), has been reported to activate MRGPRX2, although (+)-1 also interacts with DOR, which prevents investigators from interrogating the function of MRGPRX2. Here, we have succeeded in developing a novel unnatural morphinan compound (+)-2a by a transformation based on the structure of (+)-1, which removes the DOR binding affinity. (+)-2a activated both human MRGPRX2 and the mouse orthologue Mrgprb2 in in vitro experiments and induced itch-like behaviors in mice to the same extent as (+)-1. The (+)-2a-induced itch response in mice was suppressed by administration of the tripeptide QWF, an MRGPRX2/Mrgprb2 antagonist, or the antipruritic drug nalfurafine. Together, (+)-2a serves as a useful tool to elucidate the itch-related function/action of MRGPRX2 and its mouse orthologue Mrgprb2.

Design and synthesis of novel orexin 2 receptor agonists based on naphthalene skeleton

A novel series of naphthalene derivatives were designed and synthesized based on the strategy focusing on the restriction of the flexible bond rotation of OX₂R selective agonist YNT-185 (1) and their agonist activities against orexin receptors were evaluated. The 1,7-naphthalene derivatives showed superior agonist activity than 2,7-naphthalene derivatives, suggesting that the bent form of 1 would be favorable for the agonist activity. The conformational analysis of 1,7-naphthalene derivatives indicated that the twisting of the amide unit out from the naphthalene plane is important for the enhancement of activity. The introduction of a methyl group on the 2-position of 1,7-naphthalene ring effectively increased the activity, which led to the discovery of the potent OX₂R agonist 28c (EC₅₀ = 9.21 nM for OX₂R, 148 nM for OX₁R). The structure-activity relationship results were well supported by a comparison of the docking simulation results of the most potent derivative 28c with an active state of agonist-bound OX₂R cryo-EM SPA structure. These results suggested important information for understanding the active conformation and orientation of pharmacophores in the orexin receptor agonists, which is expected as a chemotherapeutic agent for the treatment of narcolepsy.

Effect of removal of the 14-hydroxy group on the affinity of the 4,5-epoxymorphinan derivatives for orexin and opioid receptors

To investigate the contribution of hydrogen bonding between the 14-hydroxy group and the 6-amide chain on the binding affinity of nalfurafine toward KOR and OX₁R, we prepared the 14-H and 14-dehydrated nalfurafine and their five-membered D-ring nalfurafine (D-nor-nalfurafine) derivatives. The 14-H and 14-dehydrated nalfurafine derivatives showed almost the same affinity for KOR as nalfurafine and more potent affinity for OX₁R. On the other hand, 14-H and 14-dehydrated D-nor-nalfurafine derivatives showed weak affinity for KOR and almost no affinity for OX₁R. The conformational analyses suggested that the 6-amide chains of the nalfurafine derivatives are mainly oriented just at or downward from the C-ring, while those of the D-nor-nalfurafine derivatives were mainly oriented toward the upper side of the C-ring even in the absence of the 14-hydroxy group. We postulated that the ion-dipole interaction between the 6-amide and the 16-nitrogen might stabilize the upwardly oriented 6-amide group. These results suggested that the 14-hydroxy group and the ion-dipole interaction would play important roles in the orientation of the 6-amide group, which might control the affinity between KOR and OX₁R.

Discovery of attenuation effect of orexin 1 receptor to aversion of nalfurafine: Synthesis and evaluation of D-nor-nalfurafine derivatives and analyses of the three active conformations of nalfurafine

The D-nor-nalfurafine derivatives, which were synthesized by contraction of the six-membered D-ring in nalfurafine (1), had no affinity for orexin 1 receptors (OX₁Rs). The 17N-lone electron pair in 1 oriented toward the axial direction, while that of D-nor-derivatives was directed in the equatorial configuration. The axial lone electron pair can form a hydrogen bond with the 14-hydroxy group, which could push the 6-amide side chain toward the downward direction with respect to the C-ring. The resulting conformation would be an active conformation for binding with OX₁R. The dual affinities of 1 for OX₁R and κ opioid receptor (KOR) led us to elucidate the mechanism by which only 1 showed no aversion but U-50488H. Actually, 1 selectively induced severe aversion in OX₁R knockout mice, but not in wild-type mice. These results well support that OX₁R suppresses the aversion of 1. This is the elucidation of long period puzzle which 1 showed no aversion in KOR.

Structure-Activity Relationship between Thiol Group-Trapping Ability of Morphinan Compounds with a Michael Acceptor and Anti-Plasmodium falciparum Activities

7-Benzylidenenaltrexone (BNTX) and most of its derivatives showed in vitro antimalarial activities against chloroquine-resistant and -sensitive Plasmodium falciparum strains (K1 and FCR3, respectively). In addition, the time-dependent changes of the addition reactions of the BNTX derivatives with 1-propanethiol were examined by ¹H-NMR experiments to estimate their thiol group-trapping ability. The relative chemical reactivity of the BNTX derivatives to trap the thiol group of 1-propanethiol was correlated highly with the antimalarial activity. Therefore, the measurements of the thiol group-trapping ability of the BNTX derivatives with a Michael acceptor is expected to become an alternative method for in vitro malarial activity and related assays.

Essential structure of orexin 1 receptor antagonist YNT-707, part V: Structure-activity relationship study of the substituents on the 17-amino group

The morphinan-type orexin 1 receptor (OX₁R) antagonists such as YNT-707 (2) and YNT-1310 (3) show potent and extremely high selective antagonistic activity against OX₁R. In the course of our studies of the essential structure of 2, we identified new scaffolds by simplification of the morphinan skeleton. However, the new chemical entities carrying the D-ring removed scaffold showed insufficient activity. To improve the activity of these derivatives, we investigated the effect of substituents mainly focused on the 17-nitrogen group. The 17-N-substituted derivatives, as well as the cyclic derivatives, were synthesized and examined the OX₁R antagonistic activity. The assay results showed the interesting relationship between the OX₁R antagonistic activity and the substituents on the 17-nitrogen: the antagonistic activity was increased as the bulkiness of 17-substituents increased. Finally, the 17-N-Boc derivative 14a showed the most potent OX₁R antagonistic activity (K_i = 14.8 nM).

Favorskii-Type Rearrangement of the 4,5-Epoxymorphinan Skeleton

The aldol condensation of naltrexone with various aryl aldehydes gives the corresponding 7-benzylidenenaltrexone derivatives in high yields. However, novel C-ring-contracted morphinan compounds were produced when 2-pyridinecarboxaldehyde or its related analogues were used as a coupling partner. The key structural feature was the existence of the tetrahydrofuran ring (4,5-epoxy ring, E-ring) of the morphinan skeleton. The time-resolved in situ IR spectroscopy of the reaction system indicated the short-lived absorption of the distorted cyclopropanone intermediate.

Defining the molecular response to trastuzumab, pertuzumab and combination therapy in ovarian cancer

BACKGROUND

Trastuzumab and pertuzumab target the Human Epidermal growth factor Receptor 2 (HER2). Combination therapy has been shown to provide enhanced antitumour activity; however, the downstream signalling to explain how these drugs mediate their response is not clearly understood.

METHODS

Transcriptome profiling was performed after 4 days of trastuzumab, pertuzumab and combination treatment in human ovarian cancer in vivo. Signalling pathways identified were validated and investigated in primary ovarian xenografts at the protein level and across a timeseries.

RESULTS

A greater number and variety of genes were differentially expressed by the combination of antibody therapies compared with either treatment alone. Protein levels of cyclin-dependent kinase inhibitors p21 and p27 were increased in response to both agents and further by the combination; pERK signalling was inhibited by all treatments; but only pertuzumab inhibited pAkt signalling. The expression of proliferation, apoptosis, cell division and cell-cycle markers was distinct in a panel of primary ovarian cancer xenografts, suggesting the heterogeneity of response in ovarian cancer and a need to establish predictive biomarkers.

CONCLUSION

This first comprehensive study of the molecular response to trastuzumab, pertuzumab and combined therapy in vivo highlights both common and distinct downstream effects to agents used alone or in combination, suggesting that complementary pathways may be involved.

Phase II trial of preoperative chemotherapy for breast cancer: Japan Breast Cancer Research Network (JBCRN)-02 trial

BACKGROUND

Neoadjuvant chemotherapy (NAC) is one of the main strategies for patients with locally advanced breast cancer. In our previous study, biological markers such as estrogen receptor (ER), progesterone receptor (PgR), and HER2 were essential predictors of the effectiveness of NAC to help individualize treatment. This study examined the effect of NAC on the disease-free survival (DFS) of breast cancer patients. Furthermore, the study was expanded by adding Ki-67 as a biological marker, and examined the correlation between Ki-67 and the prognosis.

PATIENTS AND METHODS

Between September 2005 and September 2007, 43 patients with breast cancer received NAC and surgery. Four cycles of DC (doxorubicin: 60 mg/m(2) and cyclophosphamide: 500 mg/m(2)) were administered intravenously (i.v.) on day 1 every 21 days, followed by 12 cycles of paclitaxel i.v. (80 mg/m(2)) every 7 days, prior to surgery. The primary endpoint was the pathological complete response (pCR) rate and the secondary endpoint was DFS; the pCR rate was estimated for each groups stratified by the presence or absence of different factors (PcR, ER/PgR, and Ki-67).

RESULTS

The clinical response (cCR+cPR) rate was 81.0%, and the pCR rate was 25.6%. The pCR rate was 75, 50, 9 and 0% in HER2(+)/ER(-), HER2(+)/ER(+), HER2(-)/ER(-), and HER2(-)/ER(+) patients, respectively. The 4-year DFS rate was estimated at 78% for all patients. The HER2 status was an independent predictor of pathological complete response (pCR). The DFS rate of patients with lower Ki-67 values (<15%) was higher than that of patients with higher Ki-67 values (≥15%). The treatment-related adverse events were manageable: the majority were mild, but five patients experienced grade 3 (neutropenia and sensory neuropathy) adverse events.

CONCLUSION

DC followed by weekly paclitaxel is an active and manageable preoperative regimen for breast cancer patients. HER2 overexpression may be a good predictive marker of pCR, and the Ki-67 value after NAC may be a prognostic factor for DFS.

Synapse- and subtype-specific modulation of synaptic transmission by nicotinic acetylcholine receptors in the ventrobasal thalamus

The rodent thalamic ventrobasal complex (VB) which is a subdivision of somatosensory thalamus receives two excitatory inputs through the medial lemniscal synapse, which is a sensory afferent synapse, and the corticothalamic synapse from layer VI of the somatosensory cortex. In addition, the VB also receives cholinergic inputs from the brain stem, and nicotinic acetylcholine receptors (nAChRs) are highly expressed in the VB. Little is known, however, how acetylcholine (ACh) modulates synaptic transmission at the medial lemniscal and corticothalamic synapses in the VB. Furthermore, it remains unclear which subtype of nAChRs contributes to VB synaptic transmission. We report here that the activation of nAChRs presynaptically depressed corticothalamic synaptic transmission, whereas it did not affect medial lemniscal synaptic transmission in juvenile mice. This presynaptic modulation was mediated by the activation of nAChRs that contained α4 and β2 subunit, but not by α7 nAChRs. Moreover, galanthamine, an allosteric modulator of α4β2α5 nAChR, enhanced the ACh-induced depression of corticothalamic excitatory postsynaptic currents (EPSCs), indicating that α4β2α5 nAChRs at corticothalamic axon terminals specifically contribute to the depression of corticothalamic synaptic transmission.

Efficacy of S-1 in patients with capecitabine-resistant breast cancer-Japan Breast Cancer Research Network (JBCRN) 04-1 trial

BACKGROUND

S-1 is an orally administered fluorinated pyrimidine with high activity in metastatic breast carcinoma (MBC) and in chemotherapy-pretreated metastatic breast carcinoma.

PATIENTS AND METHODS

Forty patients with MBC who did not respond to capecitabine-based chemo-therapy and then received S-1 were identified from our data base of records between 2006 and 2008. The clinico-pathological data and outcomes of these patients were then reviewed.

RESULTS

The overall response rate was 27.8%. The median survival was 19.2 months, and the median time to disease progression was 6.2 months. The most common treatment-related adverse events (all grades) were hand-foot syndrome (15%), nausea (15%), vomiting (7.5%), disorder of taste (7.5%), and diarrhea (5%). However, the majority were mild to moderate in intensity, and only one patient experienced grade 3 (according to the National Cancer Institute of Canada Common Toxicity criteria) adverse events. Myelosuppression and alopecia were rare, and there were no reported treatment-related deaths.

CONCLUSION

The results of the current study demonstrate that S-1 is an effective and well-tolerated treatment in patients with capecitabine-resistant MBC. In addition, it is a convenient, orally administered drug, which makes it an attractive agent for use in outpatient treatment.

Phase II study of AC (doxorubicin and cyclophosphamide) followed by weekly paclitaxel as neoadjuvant chemotherapy in operable patients with primary breast cancer

e11587

Background: The objective of this multi center Phase II clinical study prove the benefit of neoadjuvant combination therapy using anthracycline based AC therapy (doxorubicin and cyclophosphamide), which is useful as a standard therapy, followed by weekly PTX(paclitaxel) in patients with early stage breast cancer. Methods: Forty-seven patients with operable breast cancer were enrolled to the study. Patients received four cycles of AC followed by weekly PTX. The primary endpoint was disease free survival (DFS) stratified by the absence of presence of Quasi-pCR (QpCR: absence of invasive tumor or only focal residual tumor cells). Secondary endpoints were predictors for QpCR, clinical response, breast conservation rate, and safety. The planned sample size was 25. Results: Of 43 assessable patients, 25.6% achieved QpCR. With 28.6 months median follow-up, DFS was estimated at 72% for all patients. 3 year DFS for patients with QpCR was 80% vs. 72% without QpCR. HER2 status and response to AC were independent predictors of QpCR. The overall clinical response was 79%; 58% of patients achieved breast conservation. Nausea was the most common adverse event, observed in 62.8% and 33.3% of patients during AC and PTX respectively. The second common adverse event was peripheral neuritis, observed in 9.3% and 57.1% of patients during AC and PTX respectively. Conclusions: Despite the small sample size, these data shows that AC followed PTX is a highly active neoadjuvant therapy for women with early stage breast cancer.

No significant financial relationships to disclose.

[Effects of fasudil on neuropathic pain-like state in mice]

The aim of the present study was to investigate the role of protein kinases within the spinal cord in the development of a neuropathic pain-like state induced by partial sciatic nerve ligation in mice. Thermal hyperalgesia induced by nerve ligation in mice was markedly suppressed by either repeated intrathecal (i.t.) pre-treatment or post-treatment with the selective protein kinase (PKC) inhibitor RO-32-0432 and the selective Rho kinase inhibitor Y-27632. In contrast, sciatic nerve ligation-induced thermal hyperalgesia was not observed by repeated i.t. pre-treatment with the selective PKA inhibitor KT5720. Interestingly, thermal hyperalgesia induced by nerve ligation in mice was significantly suppressed by repeated i.t. post-treatment with fasudil, which possesses the inhibitory effect of several protein kinases including PKC and Rho kinase. Collectively, these findings suggest that a long-lasting activation of PKC and RhoA/Rho kinase pathways in the spinal cord may be responsible for the development of thermal hyperalgesia induced by nerve ligation in mice. The present data raise the fascinating possibility that i.t. or epidural administration with fasudil may be useful for the treatment of neuropathic pain.

Role of spinal voltage-dependent calcium channel α2δ-1 subunit in the expression of a neuropathic pain-like state in mice

The present study was undertaken to investigate the role of spinal voltage-dependent calcium channel alpha(2)delta-1 subunit in the expression of a neuropathic pain-like state induced by partial sciatic nerve ligation in mice. In cultured spinal neurons, gabapentin (GBP), which displays the inhibitory effect of alpha(2)delta-1 subunit, suppressed the extracellular Ca(2+) influx induced by KCl, whereas it failed to inhibit the intracellular Ca(2+) release induced by inositol-1,4,5-triphosphate. Seven days after sciatic nerve ligation, the protein level of alpha(2)delta-1 subunit in the ipsilateral spinal cord was clearly increased compared to that observed in sham-operated mice. In addition, the mRNA level of alpha(2)delta-1 subunit was significantly increased in the dorsal root ganglion, but not in the spinal cord, of nerve-ligated mice. Under these conditions, a marked decrease in the latency of paw-withdrawal against a thermal stimulation and tactile stimulation, induced by sciatic nerve ligation was abolished by repeated intrathecal (i.t.) treatment with GBP. Additionally, the persistent reduction in the nociceptive threshold by i.t. treatment with GBP at the early stage of the neuropathic pain-like state was maintained for 7 days even after GBP withdrawal. It is of interest to note that a single i.t. post-injection of GBP showed a marked and transient inhibitory effect on the developed neuropathic pain-like state, whereas repeated i.t. post-treatment with GBP produced a persistent inhibitory effect during the treatment. In conclusion, we propose here that the neuropathic pain-like state with sciatic nerve ligation is associated with the increased level of the alpha(2)delta-1 subunit of Ca(2+) channels at the sensory nerve terminal in the spinal dorsal horn of mice. Furthermore, the present data provide evidence that the neuropathic pain may be effectively controlled by repeated treatment with GBP at the early stage.

Implication of protein kinase C in the orexin-induced elevation of extracellular dopamine levels and its rewarding effect

In the present study, we investigated the role of orexinergic systems in the activation of midbrain dopamine neurons. In an in vitro study, exposure to either orexin A or orexin B under superfusion conditions produced a transient increase in the intracellular Ca(2+) concentration through the phospholipase C (PLC)/protein kinase C (PKC) pathway via G(q11)alpha or Gbetagamma subunits in midbrain cultured neurons, which were shown to be tyrosine hydroxylase (TH)-positive cells, but not in purified midbrain astrocytes. Here we show that in vivo injection with a selective PKC inhibitor chelerythrine chloride or 2-{8-[(dimethylamino)methyl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-3-yl}-3-1-methyl-1H-indol-3-ylmaleimide HCl (Ro-32-0432) into the ventral tegmental area (VTA) significantly suppressed the place preference and increased levels of dopamine in the nucleus accumbens (NAcc) induced by intra-VTA injection of orexins. These results strongly support the idea that activation of the orexin-containing neuron in the VTA leads to the direct activation of mesolimbic dopamine neurons through the activation of the PLC/PKC pathway via G(q11)alpha or Gbetagamma-subunit activation, which could be associated with the development of its rewarding effect.

Chronic pain-induced astrocyte activation in the cingulate cortex with no change in neural or glial differentiation from neural stem cells in mice

Pain pathways terminate in discrete brain areas that monitor the sensory and affective qualities of the initiating stimulus and show remarkable plasticity. Here, we found that chronic pain by sciatic nerve ligation caused a dramatic increase in glial fibrillary acidic protein (GFAP)-like immunoreactivity (IR), which is located in the dendritic astrocytes, with its expanding distribution in the cingulate cortex (CG) of mice. The branched GFAP-like IR in the CG of nerve-ligated mice was overlapped with S100beta-like IR, which is highly limited to the cell body of astrocytes, whereas there was no difference of S100beta-like IR between sham-operated and nerve-ligated mice. The number of BrdU-positive cells on the CG was not changed by sciatic nerve ligation. Furthermore, subventricular zone (SVZ)-derived neural stem cells marked by pEGFP-C1 did not migrate toward the CG after sciatic nerve ligation. In the behavioral assay, the thermal hyperalgesia observed on the ipsirateral side in nerve-ligated mice was significantly suppressed by a single pre-microinjection of a glial-modulating agent propentofylline into the CG 24 h before nerve ligation. These results suggest that chronic painful stimuli induces astrocyte activation in the CG, whereas they do not affect the cell proliferation/differentiation from neural stem cells in the CG and the migration of neural stem cells from the SVZ area. The astrocyte activation in the CG may, at least in part, contribute to the development of a chronic pain-like state following sciatic nerve ligation in mice.

Direct evidence of astrocytic modulation in the development of rewarding effects induced by drugs of abuse

Long-term exposure to pyschostimulants and opioids induced neuronal plasticity. Accumulating evidence suggests that astrocytes actively participate in synaptic plasticity. We show here that a glial modulator propentofylline (PPF) dramatically diminished the activation of astrocytes induced by drugs of abuse, such as methamphetamine (METH) and morphine (MRP). In vivo treatment with PPF also suppressed both METH- and MRP-induced rewarding effects. On the other hand, intra-nucleus accumbens (N.Acc.) administration of astrocyte-conditioned medium (ACM) aggravated the development of rewarding effects induced by METH and MRP via the Janus kinase/signal transducers and activators of transcription (Jak/STAT) pathway, which modulates astrogliosis and/or astrogliogenesis. Furthermore, ACM, but not METH itself, clearly induced the differentiation of multipotent neuronal stem cells into glial fibrillary acidic protein-positive astrocytes, and this effect was reversed by cotreatment with the Jak/STAT inhibitor AG490. Intra-cingulate cortex (CG) administration of ACM also enhanced the rewarding effect induced by METH and MRP. In contrast to ACM, intra-N.Acc. administration of microglia-conditioned medium failed to affect the rewarding effects of METH and MRP in mice. These findings suggest that astrocyte-, but not microglia-, related soluble factors could amplify the development of rewarding effect of METH and MRP in the N.Acc. and CG. The present study provides direct evidence that astrocytes may, at least in part, contribute to the synaptic plasticity induced by drugs of abuse during the development of rewarding effects induced by psychostimulants and opioids.

Chronic pain-induced emotional dysfunction is associated with astrogliosis due to cortical delta-opioid receptor dysfunction

It has been widely recognized that chronic pain could cause physiological changes at supraspinal levels. The delta-opioidergic system is involved in antinociception, emotionality, immune response and neuron-glia communication. In this study, we show that mice with chronic pain exhibit anxiety-like behavior and an increase of astrocytes in the cingulate cortex due to the dysfunction of cortical delta-opioid receptor systems. Using neural stem cells cultured from the mouse embryonic forebrain, astrocyte differentiation was clearly observed following long-term exposure to the selective delta-opioid receptor antagonist, naltrindole. We also found that micro-injection of either activated astrocyte or astrocyte-conditioned medium into the cingulate cortex of mice aggravated the expression of anxiety-like behavior. Our results indicate that the chronic pain process promotes astrogliosis in the cingulate cortex through the dysfunction of cortical delta-opioid receptors. This phenomenon may lead to emotional disorders including aggravated anxiety under chronic pain-like state.

Chronic pain induces anxiety with concomitant changes in opioidergic function in the amygdala

Clinically, it has been reported that chronic pain induces depression, anxiety, and reduced quality of life. The endogenous opioid system has been implicated in nociception, anxiety, and stress. The present study was undertaken to investigate whether chronic pain could induce anxiogenic effects and changes in the opioidergic function in the amygdala in mice. We found that either injection of complete Freund's adjuvant (CFA) or neuropathic pain induced by sciatic nerve ligation produced a significant anxiogenic effect at 4 weeks after the injection or surgery. Under these conditions, the selective mu-opioid receptor agonist [D-Ala2,N-MePhe4,Gly5-ol]-enkephalin (DAMGO)- and the selective delta-opioid receptor agonist (+)-4-[(alphaR)-alpha-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80)-stimulated [35S]GTPgammaS binding in membranes of the amygdala was significantly suppressed by CFA injection or nerve ligation. CFA injection was associated with a significant increase in the kappa-opioid receptor agonist 2-(3,4-dichlorophenyl)-N-methyl-N-[(1S)-1-phenyl-2-(1-pyrrolidinyl)ethyl]acetamide hydrochloride (ICI199,441)-stimulated [35S]GTPgammaS binding in membranes of the amygdala. The intracerebroventricular administration and microinjection of a selective mu-opioid receptor antagonist, a selective delta-opioid receptor antagonist, and the endogenous kappa-opioid receptor ligand dynorphin A caused a significant anxiogenic effect in mice. We also found that thermal hyperalgesia induced by sciatic nerve ligation was reversed at 8 weeks after surgery. In the light-dark test, the time spent in the lit compartment was not changed at 8 weeks after surgery. Collectively, the present data constitute the first evidence that chronic pain has an anxiogenic effect in mice. This phenomenon may be associated with changes in opioidergic function in the amygdala.

Direct involvement of orexinergic systems in the activation of the mesolimbic dopamine pathway and related behaviors induced by morphine

In this study, we investigated the role of orexinergic systems in dopamine-related behaviors induced by the mu-opioid receptor agonist morphine in rodents. Extensive coexpression of tyrosine hydroxylase with orexin receptors was observed in the mouse ventral tegmental area (VTA). The levels of dopamine and its major metabolites in the nucleus accumbens were markedly increased by the microinjection of orexin A and orexin B into the VTA. The subcutaneous morphine-induced place preference and hyperlocomotion observed in wild-type mice were abolished in mice that lacked the prepro-orexin gene. An intra-VTA injection of a selective orexin receptor antagonist SB334867A [1-(2-methylbenzoxazol-6-yl)-3-[1.5]naphthyridin-4-yl urea] significantly suppressed the morphine-induced place preference in rats. Furthermore, the increased level of dialysate dopamine produced by morphine in the mouse brain was significantly decreased by deletion of the prepro-orexin gene. These findings provide new evidence that orexin-containing neurons in the VTA are directly implicated in the rewarding effect and hyperlocomotion induced by morphine through activation of the mesolimbic dopamine pathway in rodents.

Protease-activated receptor-1 and platelet-derived growth factor in spinal cord neurons are implicated in neuropathic pain after nerve injury

Recently, it has been reported that both thrombin-sensitive protease-activated receptor 1 (PAR-1) and platelet-derived growth factor (PDGF) are present not only in platelets, but also in the CNS, which indicates that they have various physiological functions. In this study, we evaluated whether PAR-1/PDGF in the spinal cord could contribute to the development of a neuropathic pain-like state in mice. Thermal hyperalgesia and tactile allodynia induced by sciatic nerve ligation were significantly suppressed by repeated intrathecal injection of hirudin, which is characterized as a specific and potent thrombin inhibitor. Furthermore, a single intrathecal injection of thrombin produced long-lasting hyperalgesia and allodynia, and these effects were also inhibited by hirudin in normal mice. In nerveligated mice, the increase in the binding of [35S]GTPgammaS to membranes of the spinal cord induced by thrombin and PAR-1-like immunoreactivity (IR) in the spinal cord were each greater than those in sham-operated mice. Thermal hyperalgesia and tactile allodynia induced by sciatic nerve ligation were also suppressed by repeated intrathecal injection of either the PDGF alpha receptor (PDGFRalpha)/Fc chimera protein or the PDGFR-dependent tyrosine kinase inhibitor AG17 [(3,5-di-tert-butyl-4-hydroxybenzylidene)-malononitrile]. Moreover, thermal hyperalgesia and tactile allodynia induced by thrombin in normal mice were virtually eliminated by intrathecal pretreatment with PDGFRalpha/Fc. In immunohistochemical studies, PAR-1-like IR-positive cells in the spinal dorsal horn were mostly colocated on PDGF-like IR-positive neuronal cells. These data provide novel evidence that PAR-1 and PDGF-A-mediated signaling pathway within spinal cord neurons may be directly implicated in neuropathic pain after nerve injury in mice.

Age-related emotionality is associated with cortical delta-opioid receptor dysfunction-dependent astrogliosis

Multiple changes occur in the aging brain, leading to age-related emotional disorders. A growing body of recent evidence suggests that the cortical delta-opioid receptor system plays a critical role in anxiety- and depressive-like behaviors in the rodent. In this study, we show that aging mice promoted anxiety-like behaviors as characterized by both the light-dark and elevated plus-maze tests, and they exhibit an increase in astrocytes in the cingulate cortex due to the dysfunction of cortical delta-opioid receptor systems. As well as aging mice, mice with a dysfunction of the delta-opioid receptor system induced by chronic treatment with the selective delta-opioid receptor antagonist naltrindole, revealed astrogliosis in the cingulate cortex, which was associated with anxiety. We also found that the microinjection of cultured astrocytes into the cingulate cortex of young mice enhanced the expression of anxiety-like behavior. Our results indicate that the aging process promotes astrogliosis in the cingulate cortex through the dysfunction of cortical delta-opioid receptors. This phenomenon may lead to emotional disorders including aggravated anxiety during normal aging.

Involvement of mitogen-stimulated p70-S6 kinase in the development of sensitization to the methamphetamine-induced rewarding effect in rats

The neural plasticity associated with behavioral sensitization following repeated administration of a psychostimulant methamphetamine (METH) is thought to require synthesis of new proteins. The aim of the present study was to investigate the role of p70-S6 kinase (p70-S6K) phosphorylation, which contributes to the selective translation of a unique family of mRNA, in mediating both the METH-induced rewarding effect and its sensitization. An intra-nucleus accumbens (N.Acc.) pre-injection with 0.025 pmol/rat of a selective p70-S6K inhibitor rapamycin failed to affect the METH-induced conditioned place preference. However, this treatment clearly abolished the development of sensitization of the METH-induced conditioned place preference. Consistent with the behavioral assay, the level of the immunoreactivity of phosporylated-p70-S6K was not changed in the cytosolic fraction of the N.Acc. obtained from rats that had revealed the METH-induced rewarding effect. In contrast, the immunoreactivities in the cytosolic preparation for Western blotting and immunohistochemical density of phosphorylated-p70-S6K were significantly increased in the N.Acc. obtained from METH-sensitized rats as compared with those with chronic saline treatment. However, the immunoreactivities of phosphorylated-extracellular signal-regulated kinase and phosphorylated-ribosomal S6 protein were not significantly altered in the N.Acc. under the same condition. The present data provide evidence for the change in the translation rate, which can be regulated by S6K phosphorylation, in the N.Acc. during the development of sensitization to METH-induced rewarding effects in rats.

Implication of cyclin-dependent kinase 5 in the development of psychological dependence on and behavioral sensitization to morphine

In the present study, we investigated the role of cyclin-dependent kinase 5 (cdk5) in the brain dynamics changed by repeated in vivo treatment with morphine. The level of phosphorylated-cdk5 was significantly increased in the cingulate cortex of mice showing the morphine-induced rewarding effect. Under these conditions, roscovitine, a cdk5 inhibitor, given intracerebroventricularly (i.c.v.) caused a dose-dependent and significant inhibition of the morphine-induced rewarding effect. In addition, the dose-response effect of the morphine-induced rewarding effect was dramatically attenuated in cdk5 heterozygous (+/-) knockout mice. Furthermore, the development of behavioral sensitization by intermittent administration of morphine was virtually abolished in cdk5 (+/-) mice. These findings suggest that the induction and/or activation of cdk5 are implicated in the development of psychological dependence on morphine.

Implications of protein kinase C in the nucleus accumbens in the development of sensitization to methamphetamine in rats

Repeated treatment with methamphetamine leads to an enhancement in the methamphetamine-induced dopamine release and its related behaviors. This phenomenon is called sensitization or reverse tolerance. Protein kinase C (PKC) controls numerous signaling cascades by virtue of its ability to phosphorylate target proteins that include other kinases. The purpose of study was then to investigate the implication of PKC in the development of sensitization to the rewarding effect and to the extracellular dopamine release induced by methamphetamine in rats. The conditioned place preference paradigm and in vivo microdialysis assay were performed in the present study. An intra-nucleus accumbens injection of a selective PKC inhibitor chelerythrine chloride abolished the enhancement of the methamphetamine-induced place preference following repeated treatment with methamphetamine. Furthermore, intra-nucleus accumbens injection of chelerythrine chloride blocked the development of sensitization to dopamine release and to the decrease in the major dopamine metabolites, 3'4-dihydroxyphenylacetic acid and homovanillic acid, in the nucleus accumbens induced by repeated methamphetamine treatment. Under these conditions, the immunoreactivity of the cytosolic phosphorylated conventional- or classic-type PKC in the limbic forebrain region including the nucleus accumbens was slightly, but significantly increased in methamphetamine-sensitized rats. The present data provide evidence for the implication of PKC in the nucleus accumbens in the development of sensitization to the methamphetamine-induced rewarding effect, dopamine release and inhibition of dopamine metabolism/re-uptake in rats.

Concise synthesis of ciguatoxin ABC-ring fragments and surface plasmon resonance study of the interaction of their BSA conjugates with monoclonal antibodies

Monoclonal antibodies (mAbs), 4H2 and 6H7, were prepared previously using a protein conjugate of a 1:1 epimeric mixture of the synthetic ABC-ring fragments of ciguatoxin (CTX), 3 and 4. Here, the interactions of these mAbs with the fragments of CTX and CTX3C, 3 and 5, were investigated by surface plasmon resonance (SPR) spectroscopy in an attempt to clarify an antigenic determinant. Compared with the previous synthesis, the fragment 3 possessing the 2S configuration was synthesized from tri-O-acetyl-D-glucal much more effectively. The mAb 4H2 was already known to show a dose-dependent binding to the bovine serum albumin (BSA) conjugate of 3, but not to that of 5. The present SPR study of 4H2 demonstrates that the A-ring side chain of 3 plays a decisive role as an epitope. Therefore, SPR can effectively replace the ELISA method for the analysis of mAbs.

T7 RNA polymerase activation and improvement of the transcriptional sequencing by polyamines

We examined the possibility to improve the effectiveness of the in vitro transcription system using T7 RNA polymerase by coexistence with organic bases. The effect of the additives was evaluated by measuring the amount of RNA products in comparison with that of the control system (without additive). We found that four commercial bases and a series of ethylated polyamine analogues newly designed were active enhancers in the following activation order, 1,8-bis(ethylamino)octane > 1,8-octanediamine > 1,5-bis(ethylamino)pentane > cadaverine > 1,8-bis(ethylamino)-4-azaoctane > spermidine 1,18-bis(ethylamino)-5,14-diazaoctadecane > agmatine. It was shown that RNA products were corresponding, only in the presence of active enhancers, to the full length size of the template DNA, and that sequencing signals were enhanced by the presence of active enhancers with high fidelity so that the transcriptional sequencing was further refined to be a highly sensitive sequencing method from a small amount of linear dsDNA. These results suggest that T7 RNA polymerase was activated by the specific binding of the polyamine additive to produce RNA transcripts with fidelity to the template DNA. Therefore, it is expected that the transcriptional sequencing in the presence of active enhancers might be a powerful and sensitive method, in place of the prevalent DNA amplification method, for genomic science projects and clinical and practical gene diagnoses.

Widely Tunable Continuous-Wave CR(3+):LiSrAlF(6) Ring Laser from 800 to 936 nm

We report on a widely tunable, diode-pumped, continuous-wave, single-frequency Cr(3+):LiSrAlF(6) laser with a novel double-ring cavity configuration. The optical diode and the tuning element were located in the ring subcavity to decrease their insertion loss. Using an 1800-lines/mm grating as the tuning element, we obtained a laser emission of 20-mW output power at 870 nm and a tuning range of from 800 to 936 nm. When we used a 1200-lines/mm grating with a higher diffraction efficiency, the laser had a slightly wider tuning range of from 800 to 938 nm. However, the output power decreased at this tuning range.

[Three dimensional architecture of the microvascular systems of the skin in wound healing processes of normal and streptozotocin-induced diabetic rats]

Fine vascular architectures in the wound healing process of streptozotocin (STZ)-induced diabetic rat skin were studied by scanning electron microscope with newly designed high pressure resin injection method. In the normal rat skin, the new method successfully demonstrated the hitherto unknown subepidermal fine capillary network which continuously surrounded the pillosebaceous tissues. In wound healing processes after combined resection of skin and fascia, vascular regeneration occurred from both the border and the base of the lesion. The new vasculatures from the border of dermis demonstrated concentric array of loops extending toward the center of the lesion. The direct budding emerged from the capillary network of the exposed muscle surface. Subepidermal vasculatures of the intact back skin of STZ-induced diabetic rats showed coarse and poorer network pattern. Increased number of anastomoses between arterioles and venules, insufficiently dilated arterioles distal to the A-V shunt were the other findings which may imply the increased shunt blood flow and consequent poor peripheral dermal circulation.