mRNA In Striatum Research Articles

Effect of scalp acupuncture stimulation on expression of pentraxin 3 in striatum in acute ische-mic cerebrovascular disease rats

To observe the influence of scalp-acupuncture on the expression of pentraxin 3 (PTX3), Interleukin (IL)-1β, zonula occludens-1(ZO-1) mRNA and Occludin mRNA in striatum in acute ischemic cerebrovascular disease (AICD) rats, so as to investigate its mechanisms underlying improvement of AICD. Forty-eight male SD rats were randomly allocated to control, model, IL-1Ra and IL-1Ra+scalp-acupuncture groups (n=12 rats in each group). The AICD model was established by occlusion of the middle cerebral artery (MCAO). Rats of the IL-1Ra group and IL-1Ra+scalp-acupuncture group received intraperitoneal injection of IL-1Ra (0.05 mg·kg-1·d-1), once daily for 6 days. Scalp acupuncture stimulation was applied to bilateral "Dingnieqianxiexian" (MS6) once daily for 6 days for rats in IL-1Ra+scalp-acupuncture group. Before and after intervention, the neurologic deficit score (NDS) was evalua-ted according to Longa's method. The expression of striatum PTX3 and IL-1β was detected by immunohistochemistry, and ZO-1 mRNA and Occludin mRNA in the striatum tissue were detected by fluorescence quantitative real-time PCR. The Evans Blue (EB) tracer method was used to monitor the degree of blood-brain barrier (BBB) damage. Following modeling, the NDS, EB content and the expression of PTX3 and IL-1β in the striatum tissue were significantly increased, and the ZO-1 mRNA and Occludin mRNA expression was considerably decreased in the model group compared with the control group (P<0.05). After the interventions and compared with the model group, the NDS, EB content in both IL-1Ra and IL-1Ra+scalp acupuncture groups, and PTX3 in the IL-1Ra group were significantly down-regulated (P<0.05), while the striatum ZO-1 mRNA and Occludin mRNA expression in both IL-1Ra and IL-1Ra+scalp acupuncture groups, and PTX3 in the IL-1Ra+scalp acupuncture group were obviously up-regulated (P<0.05), and the expression of IL-1β was obviously down-regulated in the IL-1Ra+scalp acupuncture group (P<0.05) rather than in the IL-1Ra group (P>0.05). The effects of scalp acupuncture combined with IL-1Ra were obviously superior to that of IL-1Ra in down-regulating NDS, EB content and IL-1β expression level, and in up-regulating PTX3, ZO-1 mRNA and Occludin mRNA expression levels (P<0.05). Scalp acupuncture can improve neurological function and reduce the degree of BBB injury in AICD rats, which may be associated with its function in up-regulating the expression of PTX3 and in promoting the expression of ZO-1 mRNA and Occludin mRNA.

H3K4 dimethylation at FosB promoter in the striatum of chronic stressed rats promotes morphine-induced conditioned place preference.

Expression of FosB gene in striatum is essential in addiction establishment. Activated glucocorticoid receptors (GRs) induce FosB gene expression in response to stressor. Therefore, elevation of FosB expression in striatum serves as one mechanism by which stress increases risk for addiction. In this study, adult male Sprague-Dawley rats were used to investigate whether chronic stress result in histone modifications at FosB gene promoter in striatum and how these histone modifications affect FosB expression and the establishment of addiction behavior after administration of drugs of abuse. Animals were randomly assigned to three groups: Electric foot shock (EFS) group received 7-day EFS to induce chronic stress; electric foot shock plus mifepristone (EFS + Mif) group were injected with mifepristone, a nonspecific GRs antagonist, before EFS; control group did not receive any EFS. All groups then received 2-day conditioned place preference (CPP) training with morphine (5 mg/kg body weight) to test vulnerability to drug addiction. Before and after morphine administration, FosB mRNA in striatum was quantified by real-time RT-PCR. Levels of histone H3/H4 acetylation and histone H3K4 dimethylation at FosB promoter in striatum after morphine administration were measured by using chromatin immunoprecipitation (ChIP) plus real-time PCR. EFS group had stronger place preference to morphine and had significantly higher level of FosB mRNA in striatum than the other two groups. H3K4 dimethylation was 2.6-fold higher in EFS group than control group, while no statistical difference in H3/H4 acetylation. Mifepristone administration before EFS decreased histone H3K4 dimethylation and FosB mRNA in striatum, and also diminished morphine-induced conditioned place preference. Altogether, increased level of H3K4 dimethylation at FosB promoter in striatum is partially dependent on the activation of GR and responsible for the elevated level of morphine-induced FosB mRNA in chronic stressed animals.

RGS4 is involved in the generation of abnormal involuntary movements in the unilateral 6-OHDA-lesioned rat model of Parkinson's disease

Regulators of G-protein signalling (RGS) proteins are implicated in striatal G-protein coupled receptor (GPCR) sensitisation in the pathophysiology of l-DOPA-induced abnormal involuntary movements (AIMs), also known as dyskinesia (LID), in Parkinson's disease (PD). In this study, we investigated RGS protein subtype 4 in the expression of AIMs in the unilateral 6-hydroxydopamine (6-OHDA)-lesioned rat model of LID. The effects of RGS4 antisense brain infusion on the behavioural and molecular correlates of l-DOPA priming in 6-OHDA-lesioned rats were assessed. In situ hybridisation revealed that repeated l-DOPA/benserazide treatment caused an elevation of RGS4 mRNA levels in the striatum, predominantly in the lateral regions. The increased expression of RGS4 mRNA in the rostral striatum was found to positively correlate with the behavioural (AIM scores) and molecular (pre-proenkephalin B, PPE-B expression) markers of LID. We found that suppressing the elevation of RGS4 mRNA in the striatum by continuous infusion of RGS4 antisense oligonucleotides, via implanted osmotic mini-pumps, during l-DOPA priming, reduced the induction of AIMs. Moreover, ex vivo analyses of the rostral dorsolateral striatum showed that RGS4 antisense infusion attenuated l-DOPA-induced elevations of PPE-B mRNA and dopamine-stimulated [35S]GTPγS binding, a marker used for measuring dopamine receptor super-sensitivity. Taken together, these data suggest that (i) RGS4 proteins play an important pathophysiological role in the development and expression of LID and (ii) suppressing the elevation of RGS4 mRNA levels in l-DOPA priming attenuates the associated pathological changes in LID, dampening its physiological expression. Thus, modulating RGS4 proteins could prove beneficial in the treatment of dyskinesia in PD.

Alteration of striatal tetrahydrobiopterin in iron-induced unilateral model of Parkinson's disease.

It has been suggested that transition metal ions such as iron can produce an oxidative injuries to nigrostriatal dopaminergic neurons, like Parkinson's disease (PD) and subsequent compensative increase of tetrahydrobiopterin (BH4) during the disease progression induces the aggravation of dopaminergic neurodegeneration in striatum. It had been established that the direct administration of BH4 into neuron would induce the neuronal toxicity in vitro. To elucidate a role of BH4 in pathogenesis in the PD in vivo, we assessed the changes of dopamine (DA) and BH4 at striatum in unilateral intranigral iron infused PD rat model. The ipsistriatal DA and BH4 levels were significantly increased at 0.5 to 1 d and were continually depleting during 2 to 7 d after intranigral iron infusion. The turnover rate of BH4 was higher than that of DA in early phase. However, the expression level of GTP-cyclohydrolase I mRNA in striatum was steadily increased after iron administration. These results suggest that the accumulation of intranigral iron leads to generation of oxidative stress which damage to dopaminergic neurons and causes increased release of BH4 in the dopaminergic neuron. The degenerating dopaminergic neurons decrease the synthesis and release of both BH4 and DA in vivo that are relevance to the progression of PD. Based on these data, we propose that the increase of BH4 can deteriorate the disease progression in early phase of PD, and the inhibition of BH4 increase could be a strategy for PD treatment.

Treadmill pre-training suppresses the release of glutamate resulting from cerebral ischemia in rats

This study was designed to investigate the neuroprotective effect of treadmill pre-training against the over-release of glutamate resulting from cerebral ischemia. Sprague-Dawley rats underwent 2 weeks of treadmill run-training before cerebral ischemia was performed by middle cerebral artery occlusion. The level of glutamate in brain extracellular fluid was detected before, during and after ischemia/reperfusion. The expression of metabotropic glutamate receptor-1 (mGluR1) mRNA in striatum was examined after ischemia for 80 min and reperfusion for 240 min. Neurological defect score and brain infarction volumes were measured. The treadmill pre-training significantly suppressed the release of glutamate, and reduced the expression of mGluR1 mRNA at 59% (P < 0.01) and 62% (P < 0.05), respectively, as compared with the ischemia group. The neurological defect score and infarction volume were significantly improved by 75% (P < 0.01) and 74% (P < 0.01), respectively, in the pre-training group, as compared to the ischemia group. Treadmill pre-training has a significant neuroprotective function against ischemia/reperfusion injury, by suppressing glutamate release resulting from cerebral ischemia, and this effect may be mediated by downregulation of mGluR1.

Effects of Ningdong granule on the dopamine system of Tourette's syndrome rat models

Ethnopharmacological relevance Ningdong Granula (NDG) is a traditional Chinese medicine (TCM) preparation for the treatment of Tourette's syndrome (TS). Aim of the study To explore the effects of NDG on stereotyped behavior, homovanillic acid (HVA) in sera, dopamin (DA) and dopamin D2 receptor (DRD2) in striatum in TS rats. Materials and methods Sixty-four rats were randomly divided into control group and three experimental groups. TS rat models were induced by intraperitoneal injection ( i.p.) of Apomorphine (Apo, 2 mg/kg) in the experimental groups. After Apo i.p., rats were intragastrically injected ( i.g.) with NDG at 370 mg/kg (NDG + Apo group), haloperidol (Hal) at 1.0 mg/kg (Hal + Apo group), and normal saline (0.9%) at 10 ml/kg (control group and Apo group), respectively, once a day for 12 weeks. The behaviors of the rats were observed and recorded each day. After 12 weeks, all rats were sacrificed and sera and striatum were collected. The levels of HVA in sera, DA in striatum were examined by ELISA, and the expression of DRD2 mRNA in striatum was measured by RT-PCR. Results NDG could increase the HVA content in sera ( P < 0.05), meanwhile downregulate the expression of DRD2 mRNA in striatum ( P < 0.05), and inhibit the stereotyped behaviors induced by Apo ( P < 0.01) in TS rats, the same effects with Hal. NDG could also reduce the DA content in striatum ( P < 0.01), while Hal could not. Conclusions NDG could effectively inhibit the stereotyped behaviors in TS rats, and the mechanisms may be related to the suppression of DA system by increasing the content of HVA in sera, decrease the content of DA and repressing the expression of DRD2 mRNA in striatum.

Cotreatment with the kappa opioid agonist U69593 enhances locomotor sensitization to the D2/D3 dopamine agonist quinpirole and alters dopamine D2 receptor and prodynorphin mRNA expression in rats

The repeated coadministration of the kappa opioid receptor agonist U69593 with the D2/D3 dopamine (DA) agonist quinpirole (QNP) potentiates locomotor sensitization induced by QNP. Behavioral evidence has implicated both pre- and postsynaptic changes as being involved in this augmentation. The objectives of this study were to obtain supporting molecular evidence of pre- and/or postsynaptic alterations in the DA system with U69593/QNP cotreatment and to examine the relationship of such changes to locomotor sensitization. Gene expression of D1 and D2 receptors (D1R and D2R), the DA transporter, as well as the endogenous opioid prodynorphin (DYN), in the basal ganglia was examined by in situ hybridization in rats after one or ten drug injections. After one injection, changes that were specific to U69593/QNP cotreatment were decreased D1R and D2R messenger RNA (mRNA) in the nucleus accumbens (Acb) shell and increased DYN mRNA in the dorsal striatum (STR). After ten injections, U69593/QNP-specific changes were decreased D2R mRNA in substantia nigra (SN) and increased DYN mRNA in STR and Acb core. Only in U69593/QNP rats was the sensitized locomotor performance on injection ten positively correlated with DYN mRNA levels in Acb and STR. Distinct alterations of D2R and DYN mRNA levels in SN and Acb/STR, respectively, strengthen the evidence implicating pre- and postsynaptic changes in augmented locomotor sensitization to U69593/QNP cotreatment. It is suggested that repeated U69593/QNP cotreatment may augment locomotor sensitization to QNP by activating D1R-expressing DYN neurons and attenuating presynaptic D2R function.

Mild postnatal manipulation reduces proenkephalin mRNA in the striatum in developing mice and increases morphine conditioned place preference in adulthood

Stressful events during certain neonatal periods may increase the vulnerability of an individual to develop psychopathology and/or drug dependence later in life. Therefore, in the present study, we assessed activity levels, emotionality, sensitivity to the effects of morphine, as well as expression of proenkephalin and prodynorphin in several brain regions in 35 and 90-day-old male mice, subjected to postnatal manipulation consisting in brief exposures to clean bedding (CB). In comparison with controls, CB mice showed reduced emotionality expressed as percentage of time in open arms of the elevated plus maze both at 35 days of life and in adulthood. Increased nociceptive threshold was also present in both time points measured. Conversely, higher locomotor activity was recorded in 35 days of life but not in adulthood. Analysis of film autoradiograms revealed no changes in prodynorphin mRNA level, but statistically significant decrease in the level of proenkephalin mRNA in striatum in young CB mice in comparison with young controls; no difference was observed between adult CB and control animals. CB adult mice also showed hypersensitivity to the rewarding effect of morphine in comparison with controls in the place preference test. In conclusion, our results revealed that in the critical period of development the effects of manipulation were evident, not only on behavioral responses but also on the neurochemical markers considered in the present research. Postnatal manipulation could induce changes in the dynamic neuronal processes occurring during development with long-term behavioral effects.

Effect of antisense FosB and CREB on the expression of prodynorphin gene in rats with Levodopa-induced dyskinesias

The effects of antisense FosB and CREB intra-striatum injection on the expression of prodynorphin (PDyn) gene in striatal neurons of Levodopa-induced dyskinesias (LID) rats with Parkinson disease (PD) were explored. PD model in rats was established by 6-OHDA microinjection stereotaxically. The rats were treated with chronic intermittent Levodopa celiac injection for 28 days to get the LID rats. Antisense FosB and cAMP response element-binding protein (CREB) were injected into striatum of all rats respectively. In situ hybridization was used to measure the changes in the expression of PDyn mRNA in striatum and behavior changes were observed. The results showed after administration of antisense FosB, abnormal involuntary movement (AIM) was decreased and the expression of PDyn mRNA in striatum was increased in LID rats as compared with sense FosB group (P<0.01, respectively). As compared with the control group, the expression of PDyn mRNA in striatum was decreased by antisense CREB-treated LID group (P<0.01) and compared with sense CREB treated LID group, antisense CREB-treated LID group showed no changes in AIM scores and the expressions of PDyn mRNA (both P>0.05). In conclusion, FosB protein, which replaced the CREG, could regulate the expression of PDyn mRNA and play critical role in the pathogenesis of LID.

Multiple High Doses of Methamphetamine Increase the Number of Preproneuropeptide Y mRNA-Expressing Neurons in the Striatum of Rat via a Dopamine D1 Receptor-Dependent Mechanism

Neuropeptide Y (NPY) is a neuropeptide that may be involved with emotional regulation and drug addiction and may act as a neuroprotective agent during toxic insults, such as is associated with multiple, high doses of methamphetamine (METH). The purpose of the present study was to elucidate the nature of METH-induced changes in the NPY system by examining the effect of multiple, high doses of METH on preproNPY (ppNPY) mRNA expression in the striatum and the role that dopamine (DA) D1 and D2 receptors might play in these changes. Rats were administered five injections of 10 mg/kg METH at 6-h intervals, along with the D1 receptor antagonist 7-chloro-8-hydoxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benazepine hydrochloride (SCH22390) or the D2 receptor antagonist eticlopride, and they were sacrificed 3 h after the last dose of METH. The number of neurons expressing ppNPY mRNA in striatum was examined using in situ hybridization histochemistry. An acute dose of METH as well as multiple, high doses of METH increased the number of neurons expressing ppNPY mRNA in all regions of striatum examined. There was no change in the number of prosomatostatin (pSOM) mRNA-containing neurons. The increase in the number of ppNPY mRNA-expressing neurons was abolished by pretreatment with SCH22390. Eticlopride alone increased the number of ppNPY mRNA-expressing neurons in striatum, and METH treatment did not further increase the number. These findings suggest that exposure to multiple, high doses of METH increases the number of neurons expressing detectable levels of ppNPY mRNA and that this phenomenon is dependent on DA D1-receptor activation.

Rhes, the Ras homolog enriched in striatum, is reduced under conditions of dopamine supersensitivity

Striatal dopamine receptors become supersensitive when dopaminergic input is removed through either surgical denervation or pharmacological depletion. Although alterations such as increased D2 receptor binding and increased receptor-G protein coupling have been described in supersensitive striatal tissue, their roles in the mechanism of supersensitivity remain uncertain. The Ras Homolog Enriched in Striatum (Rhes) is expressed in brain areas that receive dopaminergic input, and here we test whether alterations in its expression accompany treatments that promote dopamine receptor supersensitivity in rats. Removal of dopamine input to the striatum by surgical denervation with 6-hydroxydopamine resulted in a decrease in rhes mRNA expression throughout striatum, as measured with quantitative in situ hybridization. The decrease was detected as early as two weeks and as late as seven months after surgery. Furthermore, a decrease in rhes mRNA was evident after repeated or acute reserpine treatment. Chronic daily injection of rats with the D2 antagonist eticlopride, which is known to up-regulate D2 receptors without inducing profound receptor supersensitivity, did not alter the expression of rhes mRNA in striatum. Thus, changes in rhes mRNA expression are strictly correlated with receptor supersensitivity, perhaps as a result of continuous removal of dopaminergic input. These findings suggest that rhes mRNA expression is maintained by dopamine and may play a role in determining normal dopamine receptor sensitivity.

Induction of Type 2 Iodothyronine Deiodinase in Astrocytes after Transient Focal Cerebral Ischemia in the Rat

This study investigated the expression of deiodinases of thyroid hormones in the rat brain after transient occlusion of the middle cerebral artery. The activity of type 2 deiodinase (D2), which catalyzes the deiodination of thyroxine into the more active thyroid hormone 3,5,3'-triiodothyronine, was strongly increased by cerebral ischemia at 6 and 24 hours in the striatum and at 24 hours in the cerebral cortex. The activity of type 3 deiodinase, which catalyzes the inactivation of thyroid hormones, was not affected by ischemia. In situ hybridization showed, as soon as 6 hours, an upregulation of the expression of D2 mRNA in the ipsilateral striatum, which disappeared at 24 hours. In the ipsilateral cortex, the induction of D2 mRNA started at 6 hours, was increased at 24 hours and finally declined at 72 hours. These results were confirmed by reverse transcription-PCR for D2 mRNA in the striatum and cerebral cortex. The upregulation of D2 mRNA after ischemia was mainly localized in astrocytic cell bodies. These results show that D2 is rapidly induced in astrocytes after ischemic stroke. Future work will include the exploration of the role of the upregulation of this enzyme, responsible for local 3,5,3'-triiodothyronine production as a neuroprotective mechanism in the brain.

Neuronal expression of cAMP-specific phosphodiesterase 7B mRNA in the rat brain

cAMP plays an important role as second messenger molecule controlling multiple cellular processes in the brain. cAMP levels depend critically on the phosphodiesterases (PDE) activity, enzymes responsible for the clearance of intracellular cAMP. We have examined the regional distribution and cellular localization of mRNA coding for the cAMP-specific phosphodiesterase 7B (PDE7B) in rat brain by in situ hybridization histochemistry. PDE7B mRNA is specifically distributed in rat brain, preferentially in neuronal cell populations. The highest levels of hybridization are observed in olfactory tubercle, islands of Calleja, dentate gyrus, caudate-putamen and some thalamic nuclei. Positive hybridization signals are also detected in other areas, such as cerebral cortex, Purkinje cells of the cerebellum and area postrema. By double in situ hybridization histochemistry, we found that 74% and 79% of the cells expressing PDE7B mRNA in striatum and olfactory tubercle, respectively, were GABAergic cells (expressing glutamic acid decarboxylase mRNA), in contrast with the lack of expression in the few cholinergic cells (expressing choline acetyltransferase mRNA) present in those two areas (around 0.4% in olfactory tubercle). In the thalamic nuclei, a majority of cells containing PDE7B mRNA also expresses a glutamatergic marker (76.7% express vesicular glutamate transporter vGluT1 and 76% express vGluT2 mRNAs). Almost all PDE7B expressing cells in dentate gyrus (93%) were glutamatergic. These results offer a neuroanatomical and neurochemical base that will support the search for specific functions for cAMP dependent PDEs and for the development of specific PDE7 inhibitors.

Quantitative analyses of GFRα-1 and GFRα-2 mRNAs and tyrosine hydroxylase protein in the nigrostriatal system reveal bilateral compensatory changes following unilateral 6-OHDA lesions in the rat

Copy numbers of mRNAs for GFRα-1 and GFRα-2, the preferred receptors for glial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) were determined by real-time quantitative RT-PCR (QRT-PCR). Receptor expression was assessed in striatum (ST) and substantia nigra (SN) of normal rats and rats acutely or progressively lesioned by 6-OHDA injected into the medial forebrain bundle or ST, respectively. GFRα-1 mRNA was clearly detected in normal ST. In normal SN, significantly higher expression of both receptors was observed. At 4 weeks after acute lesion, GFRα-2 mRNA was markedly decreased in SN bilaterally, whereas GFRα-1 mRNA in SN and ST was not affected. A progressive lesion resulted in a progressive decrease of GFRα1 mRNA in ST bilaterally. In SN, levels of GFRα-1 mRNA were not significantly affected by a progressive lesion, whereas GFRα-2 mRNA was markedly decreased bilaterally. Quantitative western blotting standardized against tyrosine hydroxylase (TH) protein from PC12 cells revealed the expected decrease in TH protein in lesioned SN, but also significant increases in TH protein in contralateral, unlesioned SNs at 4 weeks after both acute and progressive lesions. These data suggest that previously unrecognized compensatory changes in the nigrostriatal system occur in response to unilateral dopamine depletion. Since the changes observed in receptor expression did not always parallel loss of dopamine neurons, cells in addition to the nigral dopamine neurons appear to be affected by a 6-OHDA insult and are potential targets for the neurotrophic factors, GDNF and NTN.

Distinct effects of methamphetamine and cocaine on preprodynorphin messenger RNA in rat striatal patch and matrix.

We and others previously reported that equimolar doses of methamphetamine and cocaine differentially increase preprodynorphin mRNA in striatum: methamphetamine causes a patchy increase, whereas cocaine produces a more homogenous one. The current study directly examined whether this effect reflects differential induction in the patch-matrix division of striatum, as identified by micro opioid receptor immunohistochemistry. In addition, we determined whether doses of cocaine (30 mg/kg) and methamphetamine (2 mg/kg) that produced equivalent increases in extracellular dopamine differentially affected preprodynorphin mRNA expression in striatum of male, Sprague-Dawley rats. In both experiments, methamphetamine and cocaine differentially affected preprodynorphin mRNA in striatum after 3 h. The high, equimolar dose of methamphetamine selectively increased preprodynorphin mRNA in the patch division of rostral striatum, whereas cocaine increased preprodynorphin mRNA throughout patch and matrix divisions of striatum. In contrast, a dose of methamphetamine (2.0 mg/kg) that caused an increase in extracellular dopamine similar to that produced by 30 mg/kg cocaine did not significantly affect preprodynorphin mRNA in any region of striatum. These data provide further evidence that cocaine and amphetamines exert distinct effects on the patch-matrix division of striatum and suggest further that the post-synaptic consequences of elevated extracellular dopamine produced by methamphetamine and cocaine are distinct.

Chronic treatment with certain antipsychotic drugs preserves upregulation of regulator of G-protein signalling 2 mRNA in rat striatum as opposed to c-fos mRNA

Quantitative in situ hybridization on rat coronal brain sections with radiolabelled oligonucleotide probes was performed to investigate the effects of antipsychotic drugs on mRNA levels of regulator of G-protein signalling (RGS) 2 and c-fos. This study demonstrated a similar increase of RGS2 mRNA level in the striatum upon both a single and a 21-day treatment with either haloperidol (2 mg/kg) or risperidone (7.5 mg/kg) in contrast to clozapine (20 mg/kg). Otherwise, the acute c-fos mRNA induction in the striatum was abolished by 74 to 89% upon chronic treatment with either haloperidol or risperidone. In conclusion, the induction of RGS2 mRNA in the striatum, in contrast to the immediate early gene c-fos mRNA, is preserved upon chronic treatment with haloperidol and risperidone.

Cocaine and Methamphetamine Differentially Affect Opioid Peptide mRNA Expression in the Striatum

In general, administration of methamphetamine and cocaine alters preprodynorphin and preproenkephalin mRNA levels in striatum. However, no study has directly compared the effects of these stimulants on opioid peptides in striatum. This study used in situ hybridization to compare directly the effects of cocaine and methamphetamine on preprodynorphin and preproenkephalin mRNAs in distinct striatal regions. Male Sprague-Dawley rats received a single administration of 15 mg/kg methamphetamine or 30 mg/kg cocaine and were killed 30 min or 3 h later. Methamphetamine and cocaine differentially affected preprodynorphin mRNA in striatum after 3 h. Densitometric analysis of film autoradiograms revealed that cocaine, but not methamphetamine, significantly increased preprodynorphin. This effect was seen throughout rostral striatum and dorsally in caudal striatum. However, specific analysis of "patches" in which preprodynorphin expression is high revealed a significantly greater effect of methamphetamine versus cocaine. In contrast, both cocaine and methamphetamine had similar effects on preproenkephalin mRNA, decreasing levels after 30 min in rostral striatum and in the core of nucleus accumbens. These data suggest that methamphetamine and cocaine have distinct postsynaptic consequences on striatal neurons.

Effect of nicotine use and withdrawal on brain preproenkephalin A mRNA

Although the effect of nicotine on brain neurotransmitters and behavior has been studied, the mechanism(s) by which nicotine contributes to tobacco use remains unclear. One transmitter that may relate to long-term nicotine use and its withdrawal is enkephalin, a five-amino acid opioid peptide derived from the proenkephalin A family. In the present study we determined the effect of acute and chronic nicotine treatment and its withdrawal on preproenkephalin A mRNA levels (PPE mRNA) in specific rat brain regions using Northern blot analysis. Acute treatment with nicotine produced a significant increase in PPE mRNA in striatum and hippocampus. Chronic treatment with nicotine caused a significant decrease in PPE mRNA in these brain regions. In both striatum and hippocampus there was a rebound increase in PPE mRNA 24 h after nicotine cessation which approached the saline level 7 days later. Nicotine withdrawal 24 h following nicotine cessation, caused a significant increase in PPE mRNA in both brain regions. These effects of nicotine were blocked by pretreating rats with the nicotinic antagonist, mecamylamine. These data strongly suggest that brain opioid system(s) are involved in mediating nicotinic responses and its withdrawal and may have clinical implications in treating nicotine addiction.

Regional differences in the ability of caffeine to affect haloperidol-induced striatal c -fos mRNA expression in the rat

By using in situ hybridisation we examined the acute effects of caffeine on haloperidol-induced c- fos mRNA in rat striatum. A homogenous induction of striatal c- fos mRNA was found 30 min after injection of haloperidol (1 mg kg −1). At this timepoint caffeine (40 mg kg −1) did not affect c- fos mRNA in striatum but caused a significant increase of this gene in the somatosensory cortex. When caffeine was injected together with haloperidol c- fos mRNA was reduced in the medial part of the striatum, but enhanced in the caudal part. Similar region-specific effects of caffeine were observed on c- fos mRNA induced by the selective dopamine D 2 antagonist raclopride (0.5 mg kg −1). Both haloperidol and raclopride counteracted caffeine-induced c- fos mRNA expression in somatosensory cortex. By contrast no significant interactions between caffeine and the dopamine D 1 antagonist SCH 23 390 (0.5 mg kg −1) on striatal c- fos mRNA expression were observed. The present data show that caffeine modulates c- fos mRNA induced by dopamine D 2 receptor antagonism differentially in sensorimotor and limbic-related areas of striatum. It is suggested that this could depend upon a different action of caffeine on the cortical inputs to these two parts of the striatum.

The effect of in vivo ethanol consumption on cyclic AMP and δ-opioid receptors in mouse striatum

In this study the effect of in vivo ethanol consumption on cyclic AMP (cAMP) and [ d-Ala 2, d-Leu 5]enkephalin (DADLE) inhibition of forskolin-stimulated cAMP production was examined in mouse striatum. Effects of ethanol on striatal δ-opioid receptor (DOR) density and mRNA were also examined. Mice had unlimited access to 7% (v/v) ethanol alone or water for 1 or 7 days and were then sacrificed and striatum removed for analysis. There was no difference in basal cAMP formation between water and ethanol-treated mouse striatum following 7 day treatment, and a small, but statistically significant increase in basal cAMP in the ethanol group following 1 day treatment. Both 1 day and 7 day ethanol treatment did not significantly alter the percentage increase in cAMP following treatment with 10 μM forskolin. There was a significant effect of ethanol treatment on the maximum inhibitory effect of DADLE on forskolin-stimulated cAMP formation following both 1 and 7 day ethanol treatment. The DADLE IC 50 was unaffected by ethanol treatment. Saturation binding studies ([ 3H]Deltorphin II) indicated no effect of ethanol on B max or K d in striatum. Similarly, no difference between water and ethanol-treated was observed for DOR mRNA in striatum. These data indicate that ethanol consumption can alter opioid regulation of cAMP formation. However, this effect is not related to changes in any δ-opioid receptor parameters that were examined.