Role of dopamine D2 and D3 receptors in mediating the U-50,488H discriminative cue: comparison with methamphetamine and cocaine

Substitutions of the dopamine D(2) or D(3) receptor agonists for the discriminative stimulus effect induced by U-50,488H, methamphetamine (METH) and cocaine in rats were examined. The D(2) receptor agonist R-propylnorapomorphine [(-)-NPA] failed to substitute for U-50,488H cue, while the D(3) receptor-preferred agonist (+/-)-7-hydroxy-dipropylaminotetralin hydrobromide (7-OH-DPAT) produced dose-related increases in drug-appropriate responding up to 0.03 mg/kg, which fully substituted. At doses greater than 0.03 mg/kg of 7-OH-DPAT, there was a dose-dependent decrease in the percentage of responses on the U-50,488H-appropriate lever. Furthermore (-)-NPA and 7-OH-DPAT at high doses substituted for the discriminative stimulus effect induced by both METH and cocaine, indicating that 7-OH-DPAT at high doses may interact with D(2) receptors. These results suggest that the stimulation of D(2) receptor may be critical for the production of the discriminative stimulus effect induced by METH and cocaine, whereas the stimulation of D(3) receptor may contribute to the production of the U-50,488H cue.

Ligand directed signaling differences between rodent and human κ-opioid receptors

KOR activation of Gβγ dependent signaling results in analgesia, whereas the dysphoric effects of KOR agonists are mediated by a different pathway involving G protein receptor kinase and non-visual arrestin. Based on this distinction, a partial KOR agonist that does not efficiently activate arrestin-dependent biased signaling may produce analgesia without dysphoria. No KOR-selective partial agonists are currently available, and preclinical assessment is complicated by sequence differences between rodent (r) and human (h) KOR. In this study, we compared the signaling initiated by the available partial agonists. Pentazocine was significantly more potent at activating p38 MAPK in hKOR than rKOR expressed in HEK293 cells but equally potent at arrestin-independent activation of ERK1/2 in hKOR and rKOR. Similarly, butorphanol increased phospho-p38-ir in hKOR-expressing cells but did not activate p38 in rKOR-HEK293. Like pentazocine, butorphanol was equally efficacious at activating ERK1/2 in rKOR and hKOR. In contrast, levorphanol, nalorphine, and U50,488 did not distinguish between hKOR and rKOR in p38 MAPK activation. Consistent with its low potency at p38 activation, pentazocine did not produce conditioned place aversion in mice. hKOR lacks the Ser-369 phosphorylation site in rKOR required for G protein receptor kinase/arrestin-dependent p38 activation, but mutation of the Ser-358 to asparagine in hKOR blocked p38 activation without affecting the acute arrestin-independent activation of ERK1/2. This study shows that hKOR activates p38 MAPK through a phosphorylation and arrestin-dependent mechanism; however, activation differs between hKOR and rKOR for some ligands. These functional selectivity differences have important implications for preclinical screening of partial KOR agonists.

Selective p38α MAPK deletion in serotonergic neurons produces stress resilience in models of depression and addiction

Maladaptive responses to stress adversely affect human behavior, yet the signaling mechanisms underlying stress-responsive behaviors remain poorly understood. Using a conditional gene knockout approach, the α isoform of p38 mitogen-activated protein kinase (MAPK) was selectively inactivated by AAV1-Cre-recombinase infection in specific brain regions or by promoter-driven excision of p38α MAPK in serotonergic neurons (by Slc6a4-Cre or ePet1-Cre) or astrocytes (by Gfap-CreERT2). Social defeat stress produced social avoidance (a model of depression-like behaviors) and reinstatement of cocaine preference (a measure of addiction risk) in wild-type mice, but not in mice having p38α MAPK selectively deleted in serotonin-producing neurons of the dorsal raphe nucleus. Stress-induced activation of p38α MAPK translocated the serotonin transporter to the plasma membrane and increased the rate of transmitter uptake at serotonergic nerve terminals. These findings suggest that stress initiates a cascade of molecular and cellular events in which p38α MAPK induces a hyposerotonergic state underlying depression-like and drug-seeking behaviors.

Duration of action of a broad range of selective κ-opioid receptor antagonists is positively correlated with c-Jun N-terminal kinase-1 activation

The κ-opioid receptor is a widely expressed G-protein-coupled receptor that has been implicated in biological responses to pain, stress, anxiety, and depression, and its potential as a therapeutic target in these syndromes is becoming increasingly apparent. However, the prototypical selective κ-opioid antagonists have very long durations of action that have been attributed to c-Jun N-terminal kinase (JNK) 1 activation in vivo. To test generality of this proposed noncompetitive mechanism, we used C57BL/6 wild type mice to determine the durations of antagonist action of novel κ-opioid receptor ligands and examined their efficacies for JNK1 activation compared with conventional competitive antagonists. Of the 12 compounds tested, 5 had long durations of action that positively correlated with JNK activation: RTI-5989-97 [(3S)-7-hydroxy-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-(2-methylpropyl]-2-methyl-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide], RTI-5989-194 [(3R)-7-hydroxy-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-(2-methylbutyl]-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide], RTI-5989-241 [(3R)-7-hydroxy-N-[(1S)-1-{[(3R,4R)-4-(3-methoxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxamide)], nor-binaltorphimine (nor-BNI); and (3R)-7-hydroxy-N-((1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic). Seven had short durations of action and did not increase phospho-JNK-ir: RTI-5989-212[(3R)-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-(2-methylpropyl]-7-methoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxamide], RTI-5989-240 [(3R)-7-hydroxy-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethylpiperidin-1-yl]methyl}-(2-methylpropyl]-3-methyl-1,2,3,4-tetrahydroisoquinoline-3-carboxamide], JSPA0658 [(S)-3-fluoro-4-(4-((2-(3,5-dimethylphenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide], JSPA071B [(S)-3-fluoro-4-(4-((2-(3,5-bis(trifluoromethyl)phenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide]. PF-4455242 [2-methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine], PF-4455242 [2-methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine], FP3FBZ [(S)-3-fluoro-4-(4-((2-(3-fluorophenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide], and naloxone. After long-acting antagonist treatment, pJNK-ir did not increase in mice lacking the κ-opioid receptor; increased pJNK-ir returned to baseline by 48 h after treatment; and a second challenge with nor-BNI 72 h after the first did not increase pJNK-ir. Long-lasting antagonism and increased phospho-JNK-ir were not seen in animals lacking the JNK1 isoform. These results support the hypothesis that the duration of action of small molecule κ-opioid receptor antagonists in vivo is determined by their efficacy in activating JNK1 and that persistent inactivation of the κ-receptor does not require sustained JNK activation.

Morphine modulation of thrombospondin levels in astrocytes and its implications for neurite outgrowth and synapse formation

Opioid receptor signaling via EGF receptor (EGFR) transactivation and ERK/MAPK phosphorylation initiates diverse cellular responses that are cell type-dependent. In astrocytes, multiple μ opioid receptor-mediated mechanisms of ERK activation exist that are temporally distinctive and feature different outcomes. Upon discovering that chronic opiate treatment of rats down-regulates thrombospondin 1 (TSP1) expression in the nucleus accumbens and cortex, we investigated the mechanism of action of this modulation in astrocytes. TSP1 is synthesized in astrocytes and is released into the extracellular matrix where it is known to play a role in synapse formation and neurite outgrowth. Acute morphine (hours) reduced TSP1 levels in astrocytes. Chronic (days) opioids repressed TSP1 gene expression and reduced its protein levels by μ opioid receptor and ERK-dependent mechanisms in astrocytes. Morphine also depleted TSP1 levels stimulated by TGFβ1 and abolished ERK activation induced by this factor. Chronic morphine treatment of astrocyte-neuron co-cultures reduced neurite outgrowth and synapse formation. Therefore, inhibitory actions of morphine were detected after both acute and chronic treatments. An acute mechanism of morphine signaling to ERK that entails depletion of TSP1 levels was suggested by inhibition of morphine activation of ERK by a function-blocking TSP1 antibody. This raises the novel possibility that acute morphine uses TSP1 as a source of EGF-like ligands to activate EGFR. Chronic morphine inhibition of TSP1 is reminiscent of the negative effect of μ opioids on EGFR-induced astrocyte proliferation via a phospho-ERK feedback inhibition mechanism. Both of these variations of classical EGFR transactivation may enable opiates to diminish neurite outgrowth and synapse formation.

Inhibition of EGF-induced ERK/MAP kinase-mediated astrocyte proliferation by mu opioids: integration of G protein and beta-arrestin 2-dependent pathways

Although micro, kappa, and delta opioids activate extracellular signal-regulated kinase (ERK)/mitogen-activated protein (MAP) kinase, the mechanisms involved in their signaling pathways and the cellular responses that ensue differ. Here we focused on the mechanisms by which micro opioids rapidly (min) activate ERK and their slower (h) actions to inhibit epidermal growth factor (EGF)-induced ERK-mediated astrocyte proliferation. The micro-opioid agonists ([d-ala(2), mephe(4), gly-ol(5)] enkephalin and morphine) promoted the phosphorylation of ERK/MAP kinase within 5 min via G(i/o) protein, calmodulin (CaM), and beta-arrestin2-dependent signaling pathways in immortalized and primary astrocytes. This was based on the attenuation of the micro-opioid activation of ERK by pertussis toxin (PTX), the CaM antagonist, W-7, and siRNA silencing of beta-arrestin2. All three pathways were shown to activate ERK via an EGF receptor transactivation-mediated mechanism. This was disclosed by abolishment of micro-opioid-induced ERK phosphorylation with the EGF receptor-specific tyrosine phosphorylation inhibitor, AG1478, and micro-opioid-induced reduction of EGF receptor tyrosine phosphorylation by PTX, and beta-arrestin2 targeting siRNA in the present studies and formerly by CaM antisense. Long-term (h) treatment of primary astrocytes with [d-ala(2),mephe(4),gly-ol(5)] enkephalin or morphine, attenuated EGF-induced ERK phosphorylation and proliferation (as measured by 5'-bromo-2'-deoxy-uridine labeling). PTX and beta-arrestin2 siRNA but not W-7 reversed the micro-opioid inhibition. Unexpectedly, beta-arrestin-2 siRNA diminished both EGF-induced ERK activation and primary astrocyte proliferation suggesting that this adaptor protein plays a novel role in EGF signaling as well as in the opioid receptor phase of this pathway. The results lend insight into the integration of the different micro-opioid signaling pathways to ERK and their cellular responses.

Implication of activated astrocytes in the development of drug dependence: differences between methamphetamine and morphine

Astrocytes are a subpopulation of glial cells that directly affect neuronal function. This review focuses on the potential functional roles of astrocytes in the development of behavioral sensitization and rewarding effects induced by chronic treatment with drugs of abuse. In vitro treatment of cortical neuron/glia cocultures with either methamphetamine or morphine caused activation of astrocytes via protein kinase C (PKC). Purified cortical astrocytes were markedly activated by methamphetamine, whereas morphine had no such effect. Methamphetamine, but not morphine, caused a long-lasting astrocytic activation in cortical neuron/glia cocultures. Morphine-induced behavioral sensitization, assessed as hyperlocomotion, was reversed by 2 months of withdrawal from intermittent morphine administration, whereas behavioral sensitization to methamphetamine-induced hyperlocomotion was maintained even after 2 months of withdrawal. In vivo treatment with methamphetamine, which was associated with behavioral sensitization, caused PKC-dependent astrocytic activation in the mouse cingulate cortex and nucleus accumbens. Furthermore, the glial modulator propentofylline dramatically diminished the activation of astrocytes and the rewarding effect induced by methamphetamine and morphine. On the other hand, intra-nucleus accumbens and intra-cingulate cortex administration of astrocyte-conditioned medium aggravated the development of rewarding effects induced by methamphetamine and morphine. Furthermore, astrocyte-conditioned medium, but not methamphetamine itself, clearly induced differentiation of neural stem cells into astrocytes. These findings provide direct evidence that astrocytes may, at least in part, contribute to the development of the rewarding effects induced by drugs of abuse in the nucleus accumbens and cingulate cortex.

Kappa opioids promote the proliferation of astrocytes via Gbetagamma and beta-arrestin 2-dependent MAPK-mediated pathways

GTP binding regulatory protein (G protein)-coupled receptors can activate MAPK pathways via G protein-dependent and -independent mechanisms. However, the physiological outcomes correlated with the cellular signaling events are not as well characterized. In this study, we examine the involvement of G protein and beta-arrestin 2 pathways in kappa opioid receptor-induced, extracellular signal-regulated kinase 1/2 (ERK1/2)-mediated proliferation of both immortalized and primary astrocyte cultures. As different agonists induce different cellular signaling pathways, we tested the prototypic kappa agonist, U69593 as well as the structurally distinct, non-nitrogenous agonist, C(2)-methoxymethyl salvinorin B (MOM-Sal-B). In immortalized astrocytes, U69593, activated ERK1/2 by a rapid (min) initial stimulation that was sustained over 2 h and increased proliferation. Sequestration of activated Gbetagamma subunits attenuated U69593 stimulation of ERK1/2 and suppressed proliferation in these cells. Furthermore, small interfering RNA silencing of beta-arrestin 2 diminished sustained ERK activation induced by U69593. In contrast, MOM-Sal-B induced only the early phase of ERK1/2 phosphorylation and did not affect proliferation of immortalized astrocytes. In primary astrocytes, U69593 produced the same effects as seen in immortalized astrocytes. MOM-Sal-B elicited sustained ERK1/2 activation which was correlated with increased primary astrocyte proliferation. Proliferative actions of both agonists were abolished by either inhibition of ERK1/2, Gbetagamma subunits or beta-arrestin 2, suggesting that both G protein-dependent and -independent ERK pathways are required for this outcome.

[Behavioral analysis of chronic exposure to diphenylarsinic and associated influence on central nervous systems]

It has been clinically reported that chronic exposure to diphenylarsinic acid (DPAA) induced prominent cerebellar symptoms in apartment building residents in Kamisu, Japan. The aim of the present study was then to investigate the effect of chronic treatment with DPAA on the central motor impairment in mice. In the present study, we found that chronic in vivo exposure to a high dose of DPAA induced motor impairment in adult mice. This impairment was reversed by withdrawal following chronic DPAA treatment. The [35S]GTPgammaS binding assay showed the down-regulation of the dopamine receptor function in the striatum in adult mice treated with DPAA. We also found that neonatal exposure to a low dose of DPAA induced motor learning impairment in mice. Furthermore, treatment with an extremely low dose of DPAA caused the activation of caspase-3, the increase in glial fibrillary acidic protein-like immunoreactivity (IR) and the reduction in levels of myelin-associated glycoprotein-IR in mouse cerebellum neuron/glia co-cultures. In addition, we found that neonatal exposure to a low dose of DPAA induced anxiogenic behavior in a plus maze in mice. Taken together, these results suggest that chronic treatment with DPAA may induce motor impairment in adult mice. Moreover, neonatal exposure to DPAA leads to the irreversible motor impairment associated with abnormalities in the cerebellum.

Lack of development of behavioral sensitization to methylphenidate in mice: Correlation with reversible astrocytic activation

Methamphetamine is a powerfully addictive psychostimulant that dramatically affects the mammalian central nervous system. Methylphenidate has been shown to have psychostimulus effects similar to methamphetamine. In the present study, we compared several effects of methylphenidate to those of methamphetamine. The subcutaneous administration of either methamphetamine or methylphenidate increased extracellular dopamine levels in the nucleus accumbens of mice. Interestingly, methamphetamine, but not methylphenidate, also increased the extracellular serotonin levels in this area. Further, repeated treatment with methamphetamine induced the development of sensitization to hyperlocomotion, whereas methylphenidate failed to induce behavioral sensitization. Moreover, in vitro treatment with methamphetamine, but not methylphenidate, caused long-lasting astrocytic activation in limbic neuron/glia co-cultures. These findings suggest that, unlike methamphetamine, methylphenidate shows a lack of development of behavioral sensitization to its hyperlocomotion and induces reversible astrocytic activation.

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.

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.

Role of delta-opioid receptor function in neurogenesis and neuroprotection

The present study was undertaken to evaluate the implication of delta-opioid receptor function in neurogenesis and neuroprotection. We found that the stimulation of delta-opioid receptors by the selective delta-opioid receptor agonist SNC80 [(+)-4-[(alphaR)-alpha-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide] (10 nm) promoted neural differentiation from multipotent neural stem cells obtained from embryonic C3H mouse forebrains. In contrast, either a selective micro-opioid receptor agonist, [D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO), or a specific kappa-opioid receptor agonist, (-)-trans-(1S,2S)-U-50488 hydrochloride (U50,488H), had no such effect. In addition to neural differentiation, the increase in cleaved caspase 3-like immunoreactivity induced by H2O2 (3 microm) was suppressed by treatment with SNC80 in cortical neuron/glia co-cultures. These effects of SNC80 were abolished by a Trk-dependent tyrosine kinase inhibitor: (8R*,9S*,11S*)-(-)-9-hydroxy-9-methoxycarbonyl-8-methyl-2,3,9,10-tetrahydro-8,11-epoxy-1H,8H,11H-2,7b,11a-triazadibenzo(a,g)cycloocta(cde)trinden-1-one (K-252a). The SNC80-induced neural differentiation was also inhibited by treatment with the protein kinase C (PKC) inhibitor, phosphatidylinositol 3-kinase (PI3K) inhibitor, mitogen-activated protein kinase kinase (MEK) inhibitor or Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitor. These findings raise the possibility that delta-opioid receptors play a crucial role in neurogenesis and neuroprotection, mainly through the activation of Trk-dependent tyrosine kinase, which could be linked to PI3K, PKC, CaMKII and MEK.

Dynamic changes in dopaminergic neurotransmission induced by a low concentration of bisphenol-A in neurones and astrocytes

One of the most common chemicals that behaves as an endocrine disruptor is the compound 4,4'-isopronylidenediphenol, called bisphenol-A (BPA). We previously reported that prenatal and postnatal exposure to BPA potentiated central dopaminergic neurotransmission, resulting in supersensitivity to psychostimulant-induced pharmacological actions. Many recent findings have supported the idea that astrocytes, which are a subpopulation of glial cells, play a critical role in neuronal transmission in the central nervous system. The present study aimed to investigate the role of neurone-astrocyte communication in the enhancement of dopaminergic neurotransmission induced by BPA. We found that treatment of mouse purified astrocytes and neurone/glia cocultures with BPA in vitro caused the activation of astrocytes, as detected by a stellate morphology and an increase in levels of glial fibrillary acidic protein. A low concentration of BPA significantly enhanced the Ca2+ responses to dopamine in both neurones and astrocytes. Furthermore, a high concentration of BPA markedly induced the activation of caspase-3, which is a marker of neuronal apoptotic cell death in mouse midbrain neurone/glia cocultures. By contrast, treatment with 17beta-oestradiol (E2) had no such effects. Prenatal and neonatal exposure to BPA led to an enhancement of the dopamine-dependent rewarding effect induced by morphine. These findings provide evidence that BPA alters dopamine responsiveness in neurones and astrocytes and that, at least in part, it may contribute to potentiate the development of psychological dependence on drugs of abuse.

Role of neuronal NR2B subunit-containing NMDA receptor-mediated Ca2+ influx and astrocytic activation in cultured mouse cortical neurons and astrocytes

The excitatory neurotransmitter glutamate has been shown to mediate such bidirectional communication between neurons and astrocytes. In the present study, we determined the role of N-methyl-D-aspartate (NMDA) receptors on glutamate-evoked Ca(2+) influx into neurons and astrocytes. Either a nonselective NMDA receptor antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801) or selective NR2B subunit-containing NMDA receptor antagonists ifenprodil and (R,S)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-piperid inepropanol (Ro25-6981) significantly inhibited the glutamate-evoked Ca(2+) influx into neurons, but not into astrocytes. Furthermore, we investigated whether NR2B subunit-containing NMDA receptor antagonists could suppress the astrocytic activation, as detected by glial fibrillary acidic protein (GFAP; as a specific marker of astrocyte)-like immunoreactivities in mouse cortical astrocytes. Here, we demonstrated that the increases in the level of GFAP-like immunoreactivities induced by glutamate were markedly suppressed by cotreatment with ifenprodil in cortical neuron/glia cocultures, but not in purified astrocytes. These results suggest that NR2B subunit-containing NMDA receptor plays a critical role in not only glutamate-evoked Ca(2+) influx into neurons, but also glutamate-induced astrocytic activation. Thus, glutamate-mediated pathway via NR2B subunit-containing NMDA receptor may, at least in part, contribute to neuron-to-astrocyte signaling.

Direct evidence for spinal cord microglia in the development of a neuropathic pain-like state in mice

The present study was undertaken to further investigate the role of glial cells in the development of the neuropathic pain-like state induced by sciatic nerve ligation in mice. At 7 days after sciatic nerve ligation, the immunoreactivities (IRs) of the specific astrocyte marker glial fibrillary acidic protein (GFAP) and the specific microglial marker OX-42, but not the specific oligodendrocyte marker O4, were increased on the ipsilateral side of the spinal cord dorsal horn in nerve-ligated mice compared with that on the contralateral side. Furthermore, a single intrathecal injection of activated spinal cord microglia, but not astrocytes, caused thermal hyperalgesia in naive mice. Furthermore, 5-bromo-2'-deoxyuridine (BrdU)-positive cells on the ipsilateral dorsal horn of the spinal cord were significantly increased at 7 days after nerve ligation and were highly co-localized with another microglia marker, ionized calcium-binding adaptor molecule 1 (Iba1), but neither with GFAP nor a specific neural nuclei marker, NeuN, in the spinal dorsal horn of nerve-ligated mice. The present data strongly support the idea that spinal cord astrocytes and microglia are activated under the neuropathic pain-like state, and that the proliferated and activated microglia directly contribute to the development of a neuropathic pain-like state in mice.

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.

[Role of astrocytes in rewarding effects of drugs of abuse]

There are two categories of cells in the central nervous system; neurons and adjacent glial cells including astrocytes, microglia and oligodendrocytes. Accumulating evidence suggests that astrocytes actively participate in synaptic plasticity. On the other hand, long-term exposure to drugs of abuse could induce neuronal plasticity. Astrocytes undergo a process of prolifiration, morphological change, and enhancement of glial fibrillary acidic protein expression, termed activation of astrocytes. Recently, we demonstrated a dramatic increase in reactive astrocytes in the dorsal horn of the spinal cord following repeated in vivo treatment with morphine. We also found that in vivo treatment with morphine, which was associated with the rewarding effect, caused a robust astrocytic activation in the cingulate cortex. These data suggest that astrocytes may contribute to the synaptic plasticity induced by morphine during the development of dependence and tolerance. Therefore, this review focuses on several aspects of astrocytic response and discusses possible roles of astrocytes in the development of dependence and tolerance induced by morphine. We also report here that protein kinase C, Janus kinase/signal transducer and activator of transcription pathway, cyclin-dependent kinase 5 and tyrosine kinase cascade are directly involved in the neuron-glia communication during the development of synaptic plasticity induced by chronic morphine treatment.

mu-Opioid receptor internalization-dependent and -independent mechanisms of the development of tolerance to mu-opioid receptor agonists: Comparison between etorphine and morphine

A growing body of evidences suggests that receptor desensitization is implicated in the development of tolerance to opioids, which is generally regulated by protein kinases and receptor trafficking proteins. In the present study, we demonstrated that repeated s.c. treatment with etorphine, but not morphine, produced a significant increase in protein levels of G protein-coupled receptor kinase 2, dynamin II, beta-arrestin 2 and phosphorylated-conventional protein kinase C in membranes of the mouse spinal cord, suggesting that the etorphine-induced mu-opioid receptor desensitization may result from G protein-coupled receptor kinase 2/dynaminII/beta-arrestin2-dependent phosphorylation of mu-opioid receptors. Unlike etorphine, morphine failed to change the levels of these trafficking proteins. Furthermore, we found that the level of glial fibrillary acidic protein in the mouse spinal cord was clearly increased by chronic in vivo and in vitro treatment with morphine, whereas no such effect was noted by etorphine. In the behavioral study, intraperitoneal pretreatment with the glial-modulating agent propentofylline suppressed the development of tolerance to morphine-induced antinociception. In addition, intrathecal injection of astrocytes and astrocyte-conditioned medium mixture, which were obtained from cultured astrocytes of the newborn mouse spinal cord, aggravated the development of tolerance to morphine. In contrast, these agents failed to affect the development of tolerance induced by etorphine. These findings provide direct evidence for the distinct mechanisms between etorphine and morphine on the development of tolerance to spinal antinociception. These findings raise the possibility that the increased astroglia response produced by chronic morphine could be associated with the lack of mu-opioid receptor internalization.

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.

Glutamatergic neurotransmission and protein kinase C play a role in neuron-glia communication during the development of methamphetamine-induced psychological dependence

Methamphetamine (METH) is a strongly addictive psychostimulant that dramatically affects the central nervous system (CNS). On the other hand, protein kinase C (PKC) plays a major role in cellular regulatory and signalling processes that involve protein phosphorylation. The purpose of this study was to investigate the role of neuronal and astrocytic PKC in changes in the central glutamatergic system induced by METH. We show here that in vitro treatment with METH caused the phosphorylation of both neuronal and astrocytic PKC and the activation of astrocytes in cortical neuron/glia co-cultures. Treatment of cortical neuron/glia co-cultures with either the PKC activator phorbol 12,13-dibutyrate (PDBu) or glutamate also caused the PKC-dependent activation of astrocytes. The PKC inhibitor chelerythrine suppressed the Ca2+ responses to glutamate in both cortical neurons and astrocytes. Moreover, a low concentration of PDBu significantly enhanced the Ca2+ responses to glutamate, but not to dopamine, in both cortical neurons and astrocytes. Notably, treatment with METH also enhanced the Ca2+ responses to glutamate in cortical neurons. The activation of astrocytes induced by METH was also reversed by co-treatment with glutamate receptor antagonists (ifenprodil, DNQX or MPEP) in cortical neuron/glia co-cultures. In the conditioned place preference paradigm, intracerebroventricular administration of glutamate receptor antagonists (ifenprodil, DNQX or MPEP) attenuated the METH-induced rewarding effect. These findings provide evidence that the changes in PKC-dependent neuronal and astrocytic glutamatergic transmission induced by METH may, at least in part, contribute to the development of psychological dependence on METH.

Long-lasting change in brain dynamics induced by methamphetamine: enhancement of protein kinase C-dependent astrocytic response and behavioral sensitization

It is well known that long-term exposure to psychostimulants induces neuronal plasticity. Recently, accumulating evidence suggests that astrocytes may actively participate in synaptic plasticity. In this study, we found that in vitro treatment of cortical neuron/glia co-cultures with either methamphetamine (METH) or morphine (MRP) caused the activation of astrocytes via protein kinase C (PKC). Purified astrocytes were markedly activated by METH, whereas MRP had no such effect. METH, but not MRP, caused a long-lasting astrocytic activation in cortical neuron/glia co-cultures. Furthermore, MRP-induced behavioral sensitization to hyper-locomotion was reversed by 2 months of withdrawal following intermitted MRP administration, whereas behavioral sensitization to METH-induced hyper-locomotion was maintained even after 2 months of withdrawal. Consistent with this cell culture study, in vivo treatment with METH, which was associated with behavioral sensitization, caused a PKC-dependent astrocytic activation in the cingulate cortex and nucleus accumbens of mice. These findings provide direct evidence that METH induces a long-lasting astrocytic activation and behavioral sensitization through the stimulation of PKC in the rodent brain. In contrast, MRP produced a reversible activation of astrocytes via neuronal PKC and a reversibility of behavioral sensitization. This information can break through the definition of drugs of abuse and the misleading of concept that morphine produces a long-lasting neurotoxicity.

Involvement of spinal metabotropic glutamate receptor 5 in the development of tolerance to morphine-induced antinociception

It is well known that prolonged exposure to morphine results in tolerance to morphine-induced antinociception. In the present study, we found that either intrathecal (i.t.) or subcutaneous (s.c.) injection of the selective metabotropic glutamate receptor 5 (mGluR5) antagonist, methyl-6-(phenylethynyl)-pyridine hydrochloride (MPEP), attenuated the development of tolerance to morphine-induced antinociception. Using the receptor binding assay, we found here that the number of mGluR5 in the mouse spinal cord was significantly increased by repeated treatment with morphine. Furthermore, repeated treatment with morphine produced a significant increase in the level of mGluR5 immunoreactivity in the dorsal horn of the mouse spinal cord. Double-labeling experiments showed that the increased mGluR5 was predominantly expressed in the neurons and sparsely expressed in the processes of astrocytes following repeated treatment with morphine. Consistent with these results, the response of Ca2+ to the selective group I mGluR agonist, 3,5-dihydroxyphenylglycine (DHPG), in cultured spinal cord neurons was potently enhanced by 3 days of in vitro treatment with morphine. These findings support the idea that the increased mGluR5 following repeated treatment with morphine leads to enhanced neuronal excitability and synaptic transmission in the dorsal horn of the spinal cord and, in turn, suppresses the morphine-induced antinociception in mice.

Direct evidence for the involvement of brain‐derived neurotrophic factor in the development of a neuropathic pain‐like state in mice

Thermal hyperalgesia and tactile allodynia induced by sciatic nerve ligation were completely suppressed by repeated intrathecal (i.t.) injection of a TrkB/Fc chimera protein, which sequesters endogenous brain-derived neurotrophic factor (BDNF). In addition, BDNF heterozygous (+/-) knockout mice exhibited a significant suppression of nerve ligation-induced thermal hyperalgesia and tactile allodynia compared with wild-type mice. After nerve ligation, BDNF-like immunoreactivity on the superficial laminae of the ipsilateral side of the spinal dorsal horn was clearly increased compared with that of the contralateral side. It should be noted that a single i.t. injection of BDNF produced a long-lasting thermal hyperalgesia and tactile allodynia in normal mice, and these responses were abolished by i.t. pre-treatment with either a Trk-dependent tyrosine kinase inhibitor K-252a or a selective protein kinase C (PKC) inhibitor Ro-32-0432. Supporting these findings, we demonstrated here for the first time that the increase in intracellular Ca2+ concentration by application of BDNF in cultured mouse spinal neurons was abolished by pre-treatment with either K-252a or Ro-32-0432. Taken together, these findings suggest that the binding of spinally released BDNF to TrkB by nerve ligation may activate PKC within the spinal cord, resulting in the development of a neuropathic pain-like state in mice.

[The functional change in the 5-HT1A receptor induced by stress and the role of the 5-HT1A receptor in neuroprotection]

Mice exposed to various stresses, especially restrained-stress, revealed the anxiogenic effect detected by the light-dark test. Under this condition, a remarkable decrease in [35S]GTPgammaS binding to membranes from the prefrontal cortex, amygdala and hypothalamus of restrained-stress mice stimulated by the selective 5-HT1A receptor agonist 5-carboxamidotriptamine (5-CT) was clearly observed, whereas a significant increase in [35S]GTPgammaS binding stimulated by the 5-HT1A receptor agonist was clearly observed in the dorsal raphe nuclei (DRN) of restrained-stress mice. The immunohistochemical study showed a drastic reduction in phosphorylated-CREB-like immunoreactivity in the DRN of restrained-stress mice. Furthermore, we found a drastic reduction in myelin-associated glycoprotein (MAG)-like immunoreactivity (MAG-IR) in the DRN, amygdala and hypothalamus, indicating the direct suppression of synaptic transmission in these regions. It has been accepted that GSK3beta in the Wnt signal pathway plays an important role in various neuronal functions including apoptosis, clustering of synapsin I and early growth and axonal remodeling. In the present study, the increase in protein levels of GSK3beta and phosphorylated-GSK3beta to cytosol fractions of the amygdala was noted in restrained-stress mice. Taken together, these results suggest that restrained stress may directly affect the 5-HT1A receptor-regulated synaptic transmission in the brain, leading to the expression of the anxiogenic effect in mice. It is well known that various stresses induce intracellular oxidative stress. The present study was then undertaken to investigate the effect of the stimulation of 5-HT1A receptors on oxidative stress. Treatment with H2O2 caused the activation of caspase-3-positive cells and the reduction in levels of MAG-IR in the limbic neuron/glia cocultures as compared to medium alone. The stimulation of 5-HT1A receptor by 5-CT produced a dramatic protection against H2O2-triggered activation of caspase-3 and reduction in levels of MAG-IR. These results suggest that 5-HT1A receptors were involved in the modulation of anxiety and the understanding of molecular mechanisms of 5-HT1A receptor-related cascades may pave the way for new therapeutic strategies for affective disorders.

Behavioral sensitization to the discriminative stimulus effects of methamphetamine in rats

Sensitization to the discriminative stimulus effects of psychostimulants is not fully understood. Therefore, the present study was designed to investigate the development of sensitization to the discriminative stimulus of methamphetamine in rats. A dose-response curve for methamphetamine and a generalization test for cocaine were recorded in rats trained to discriminate between 1.0 mg/kg methamphetamine and saline. A significant leftward shift of the dose-response curve for methamphetamine and of the dose-generalization curve for cocaine was observed following repeated administration of methamphetamine (2.0 mg/kg) instead of saline. These findings suggest that repeated administration of methamphetamine can produce behavioral sensitization to the discriminative stimulus effects of methamphetamine in rats.

Enhancement of dopamine-induced signaling responses in the forebrain of mice lacking dopamine D3 receptor

It is well known that the dopamine D(3) receptor plays a critical role in several psychological disorders, such as drug dependence. The present study was designed to investigate the influence of lacking dopamine D(3) receptors in dopamine-induced G-protein activation and Ca(2+) influx in the mouse forebrain. The deletion of dopamine D(3) receptor gene caused the enhancement of dopamine-induced G-protein activation in the limbic forebrain of dopamine D(3) receptor knockout (D(3)KO) mice. Furthermore, the dopamine-induced Ca(2+) influx was enhanced in the coculture of neuron/glia cells obtained from the forebrain of D(3)KO mice. The present data provide direct evidence that a deletion of central dopamine D(3) receptor enhances the dopamine D(1)/D(2) receptor-mediated intracellular signaling.

A putative sigma1 receptor antagonist NE-100 attenuates the discriminative stimulus effects of ketamine in rats

Ketamine, one of the dissociative anaesthetic agents, has been shown to produce psychotomimetic effects. It has been well documented that activation of sigma receptors is responsible for the pathogenesis of some psychiatric disorders. In the present study, the effects of NE-100, a putative sigma(1) receptor antagonist, was investigated in rats trained to discriminate between ketamine (5 mg/kg, i.p.) from saline under a fixed-ratio 10 food-reinforced procedure. Here we report for the first time that NE-100 (1 mg/kg) produced a shift to the right in the dose-response curve for ketamine's discriminative stimulus effects. These results suggest that the sigma(1) receptor is, at least in part, involved in the discriminative stimulus effects of ketamine.

A gene encoding endo-1,4-beta-glucanase from Bacillus sp. 22-28

Clones of a gene encoding an endo-1,4-beta-glucanase (EC 3.2.1.4) were obtained from Bacillus sp. 22-28, and the nucleotides were sequenced. A recombinant plasmid, pMK5, included a complete ORF of 2352 bp that encoded 783 amino acid residues. Another plasmid, pM3, which showed enzymatic activity in E. coli JM109, was also obtained, and it included an incomplete ORF of 1873 bp, which lacked the original stop codon and 479 bp of the C-terminal region. The enzymes purified from both of the two types of transformants have shown almost the same properties in comparison with that of the wild type Bacillus sp. 22-28.

A case of pulmonary arteriovenous malformation in a patient with brain abscess successfully treated with video-assisted thoracoscopic resection

A 45-year-old women was admitted to the hospital with a brain abscess due to asymptomatic pulmonary arteriovenous malformation (PAVM). The brain abscess was removed by craniotomy and excision following antibiotic therapy. The stapled wedge excision of the lung with the PAVM was successful under video-assisted thoracoscopic surgery.

Central nervous system disorders and possible brain type carnitine palmitoyltransferase II deficiency

We describe two male infants with central nervous system disorders, i.e. infantile spasms in one and athetotic quadriplegia in the other, and with recurrent attacks of high plasma creatine kinase levels induced by viral infections. Although carnitine palmitoyltransferase I (CPT I) activity in biopsied muscle was normal in both cases, that of carnitine palmitoyltransferase II (CPT II) was decreased to 37% and 25% of the control value, respectively. Meanwhile, to determine whether or not and how CPT exists in the central nervous system (CNS), we studied animal brain tissues. CPT activity was demonstrated in almost all regions, especially in the brainstem, cerebellum and spinal cord. Although CPT deficiency can be classified into hepatic (CPT I) and muscular (CPT II) presentations, these data suggest that another symptomatology of CPT II deficiency with CNS involvement (brain type?) might exist.

Developmental studies of dystrophin-positive fibers in mdx, and DRP localization

Dystrophin positive fibers (DPFs) were observed in about 1% of the total muscle fibers in 1-year-old mice. Some of these fibers were found to have positive staining with all six antibodies, while others showed a negative reaction with specific antibodies. These results suggest that the most likely mechanism giving rise to these DPFs is a second site mutation which prepares in-frame deletion. A study of the frequency of DPF during development showed single and scattered DPFs in younger mice, which gradually increased in number and began to form small groups with age. DRP was observed constantly on the neuromuscular junctions in both control and mdx muscle, and surface membrane of immature muscle fibers such as regenerating fibers in mdx and newborn muscle during 2 weeks of age in control and mdx.

Dystrophin and a dystrophin-related protein in intrafusal muscle fibers, and neuromuscular and myotendinous junctions

To determine whether or not and how dystrophin exists in neuromuscular junctions (NMJs) and myotendinous junctions (MTJs), we studied the mid-belly and peripheral portions of control and mdx muscles, immunohistochemically and immunoelectrophoretically, using six kinds of polyclonal antibodies, and an antibody against a dystrophin-related protein (DRP). In controls these regions and the polar region of intrafusal muscle fibers showed a rather clearer immunohistochemical dystrophin reaction than those of extrafusal muscle fibers with all antibodies used. In the muscles of mdx mice NMJs only showed a positive dystrophin reaction with the c-terminal antibody, that is, no reaction with the other five antibodies, and MTJs in mdx showed a positive reaction with the c-terminal antibody and a faint to negative reaction with the other five antibodies. In biopsied human muscles NMJs and MTJs also showed a clear reaction with all ten antibodies, i.e., six polyclonal and four monoclonal ones. Although an immunohistochemical DRP reaction was clearly seen at NMJs, only a faint or no reaction was seen on MTJs and on intrafusal muscle fibers in both mouse and human materials. Western blot analysis of control mouse muscle for dystrophin showed a clearer band for the peripheral portion, which contains many MTJs, than for the mid-belly portion. These data suggest that dystrophin really exists on MTJs, and that dystrophin and DRP exist on NMJs in mouse and human muscles.

[MR evaluation of wallerian degeneration of the pyramidal tract]

This study is based on 135 magnetic resonance (MR) exams of 110 patients with wallerian degeneration of the pyramidal tract shown on MR images acquired on a mid field imaging scanner. The MR findings of wallerian degeneration were abnormal signal band along the course of the pyramidal tract and ipsilateral brain stem shrinkage. In all 110 cases an abnormal signal band was seen on T2-weighted spin-echo images, that is, a hypointense band in four exams between 30 days and 116 days after onset of symptoms, and hyperintense bands in 122 exams. The hyperintense signal on T2-weighted images was shown in most cases after 200 days from the onset. In one case a signal of the pyramidal tract showed a hyperintense band at 7 days, hypointense at 30 days, and hyperintense again at 123 days after onset. Sequential MR exams of another case showed gradual narrowing of the hyperintense signal band and progression of the ipsilateral brainstem shrinkage. The narrowing of the pyramidal tract and the ipsilateral brain stem shrinkage tended to be shown after 6 months from onset.(ABSTRACT TRUNCATED AT 250 WORDS)

Dystrophin: localization and presumed function

To determine the localization and functional significance of dystrophin, we studied various tissues from almost the entire body of control and mdx mice, and control rats, using polyclonal antibodies against dystrophin. We observed a dystrophin reaction in synaptic regions such as neuromuscular junctions, the equatorial region of intrafusal muscle fibers, the outer plexiform layer of the retina, the myoepithelial cell layer of salivary and sweat glands, tactile nerve endings, and neurons in the brain. These dystrophin-positive regions reportedly contain actin filaments as a common characteristic, which is compatible with the dystrophin cDNA sequence. Dystrophin was absent in these regions in mdx mice. These results suggest that dystrophin plays an important physiological and/or structural role in cell motility as a trigger for propagating contractile force in, for example, the conduction system, with some relationship between actin filaments.

Dystrophin in control and mdx retina

To determine whether or not dystrophin really exists in the outer plexiform layer (OPL) of the retina, we studied control and mdx mice, using four kinds of polyclonal antibodies (DMDP-II, 60 kd, 30 kd and DMDP-IV) against dystrophin. Although control OPL showed a positive immunohistochemical reaction with all four antibodies, mdx OPL showed a positive reaction with DMDP-II and DMDP-IV, a negative reaction with 60 kd and 30 kd antibodies. Immunoblot analysis showed the positive band compatible with the immunohistochemical reaction.

Vascular alterations in Fukuyama type congenital muscular dystrophy

Blood vessels in muscle biopsy specimens from 6 Fukuyama type congenital muscular dystrophy (FCMD) patients were examined by electron microscopy and compared with ones in non-diagnostic biopsy specimens from age-matched controls and patients with childhood neuromuscular disorders. The most striking feature was the blister-like swelling of vascular endothelial cells in the biopsied muscle specimens from 5 of the 6 patients with FCMD. Morphometric analysis of capillaries in biopsied muscles showed the extremely greater capillary, endothelial and pericyte areas in the FCMD patients than in controls. These phenomena are quite similar to those found in Duchenne muscular dystrophy (DMD) at the preclinical stage and suggest an as yet undetermined process in blood vessels in FCMD as well as DMD. An immunohistochemical study involving dystrophin antibodies showed positive staining in FCMD.

Age-related changes in distribution of cytochrome P-450 in the hepatic lobule of the rat

The effect of age on distribution of the phenobarbital-inducible forms of cytochrome P-450 IIBI and IIB2 in the hepatic lobule was investigated immunohistochemically by the avidin-biotin-peroxidase complex (ABC) method in male rats of various ages pretreated with phenobarbital. Exposure of liver sections to anti-cytochrome P-450 serum resulted in intense immunostaining in centrilobular hepatocytes but produced staining of weaker intensity in periportal cells in phenobarbital-treated rats, while in livers of nontreated animals, no significant immunoreactivity was detectable. Difference in the intensity of immunostaining between the centrilobular cells and the periportal ones was statistically significant in the liver of 3 and 13 month rats. By contrast, in the 30 month rat liver, intensity of immunostaining was greatly reduced in both the centrilobular and the periportal cells; no significant difference was detected in the intensity of staining between these cells. Throughout the three age-groups, a significant decrease with age was evident in the content of the immunoreactive cytochrome P-450 isozymes IIB1 and IIB2 in both the centrilobular cells and the periportal ones. The results show that the administration of phenobarbital causes an increase in the content of these cytochrome P-450 isozymes in greater amount in the centrilobular hepatocytes than in the periportal cells in the liver lobule and that the content of cytochrome P-450 isozymes induced by the phenobarbital administration decreases with age in male rats.

Possible systemic smooth muscle layer dysfunction due to a deficiency of dystrophin in Duchenne muscular dystrophy

The localization of dystrophin was examined immunohistochemically in various tissues from mice and rats as well as from biopsied human muscle specimens, using polyclonal antibodies against dystrophin. Although dystrophin was completely absent in biopsied muscle specimens from 3 male DMD patients, it was faintly observed in the surface membrane of almost all muscle fibers examined in a female DMD patient. In all controls, human and animal, a strong dystrophin reaction was observed in the surface membrane of intrafusal muscle fibers and at the neuromuscular junctions, rather than in the surface membrane of skeletal and cardiac muscle fibers. In addition, dystrophin was clearly localized in the surface membrane of smooth muscle fibers in the viscera, bronchial system, ureter, and tunica media of blood vessels, including arteries and veins, in all examined animal tissues. In mdx mice, dystrophin was absent in almost all muscle and smooth muscle fibers in various tissues and blood vessels. These results suggested a possible systemic dysfunction of smooth muscle layers, especially those of blood vessels, as well as skeletal muscle fibers, due to a deficiency of dystrophin in Duchenne muscular dystrophy.

Immunohistochemical dystrophin reaction in synaptic regions

To investigate the functional significance of dystrophin, we studied various tissues of control and mdx mice, and rats immunohistochemically, using anti-dystrophin antibodies. In control animals, we observed the immunohistochemical localization of dystrophin in synaptic regions such as neuromuscular junctions, the cornea and outer plexiform layer of the retina, the taste buds and neurons in the brain, as well as on the surface membrane of skeletal, cardiac and smooth muscle fibers. In mdx mice, dystrophin was absent from the surface membrane of muscle fibers and the outer plexiform layer of the retina. These results suggest that dystrophin plays an important physiological and/or structural role in the conduction system.