Pharmacological and neurochemical differences between acute and tardive vacuous chewing movements induced by haloperidol

Lute onset vacuous chewing movements (VCMs) from chronic neuroleptic treatment have been used as a rat model of tardive dyskinesia (TD). Early onset VCMs have also been observed, raising questions about the validity of this model. To assess the relationship between these two types of VCMs, pharmacological and neurochemical properties of early and late onset VCMs were compared, “Acute” VCMs were induced by daily intraperitoneal injections for 1–21 days. “Tardive” VCMs were induced by intramuscular injections of haloperidol decanoate every 3 weeks for 30 weeks followed by a 24-week withdrawal period. Suppression was attempted for both types of VCMs using several doses of intraperitoneal haloperidol. Striatonigral activation was assessed by measuring mRNA expression levels of the neuropeptides dynorphin and substance P using in situ hybridization histochemistry. Enkephalin mRNA was also measured as an index of striatopallidal activation. The results indicate that acute VCMs cannot be suppressed with increased doses of haloperidol and are associated with reduced dynorphin and substance P. This profile is similar to that seen with an animal model of parkinsonism. Tardive VCMs, in contrast, were markedly suppressed by haloperidol. They have previously been shown to be associated with increased striatonigral activation as indicated by increased dynorphin mRNA. Enkephalin mRNA was elevated following both short and long term treatment. Although superficially similar, acute and tardive VCMs appear to have different pharmacological and neurochemical profiles, suggesting they are related to acute extrapyramidal side effects and tardive dyskinesia, respectively.     

Endorphins and food intake: kappa opioid receptor agonists and hyperphagia

Evidence from studies which utilise either opiate receptor agonists and antagonists strongly indicate a role for endorphinergic mechanisms in the control of feeding responses. Two means by which these compounds may exert an effect on feeding can be singled-out. Firstly, emerging evidence suggests that the process of achieving satiety (terminating a meal, or choice of a commodity) may be accelerated following treatments with opiate receptor antagonists. Secondly, the preference for highly palatable solutions (sweet solutions have received most attention) in two-bottle tests is blocked after injection of opiate receptor antagonists. This finding has been interpreted in terms of the abolition of the reward or incentive quality associated with the particularly attractive flavour. These two mechanisms of action may represent two aspects of a single, fundamental process. Following an introduction to rat urination model of in vivo kappa agonist activity, the consistent effect of several kappa agonists (including the highly selective U-50,488H) to stimulate food consumption is described. Recognising that members of the dynorphin group of endogenous opioid peptides are kappa receptor ligands, some with a high degree of selectivity, and the evidence the dynorphins and neo-endorphins produce hyperphagia in rats is particularly interesting. Such lines of evidence lead to the hypothesis that peptides of the dynorphin group may act endogenously to promote the expression of normal feeding behaviour.     

A model of chronic pain in the rat: high-resolution neuroanatomical approach identifies alterations in multiple opioid systems in the periaqueductal grey

Inoculation of the tail base of rats with Mycobacterium butyricum led to an arthritic swelling and inflammation of the limbs which displayed a hyperalgesia to noxious pressure: these effects peaked at 3 weeks postinoculation. In vitro autoradiography of coronal sections of rat brain was used for a parallel determination of binding to mu-, delta- and kappa-opioid binding sites. In only two regions, the dorsomedial and dorsolateral parts of the periaqueductal grey (PAG), was a significant change seen: this comprised an increase in binding to kappa-sites, whereas mu- and delta-sites therein were unaffected. This region was analysed for opioid peptides derived from each of the three opioid peptide families known. While no change was seen in levels of immunoreactive (ir)-dynorphin1-17 A (DYN) and ir-Met-enkephalin, a decrease was detected in those of ir-beta-endorphin (beta-EP): this change was restricted to the PAG. These data demonstrate a highly localized and selective influence of chronic arthritic pain upon multiple opioid systems in the PAG of the rat, a structure playing a key role in the control of pain and in the expression of the antinociceptive actions of opioids. The data suggest a possible significance of PAG pools of beta-EP and kappa-receptors in the response to and modulation of chronic pain.     

Effect of chronic treatment with morphine, midazolam and both together on dynorphin(1–13) levels in the rat

We have recently reported that midazolam, a benzodiazepine receptor agonist that is also a short acting anesthetic and analgesic drug, can produce analgesia and decrease morphine tolerance and dependence in the rat by interacting with the opioidergic system. This study was designed to investigate the chronic effect of midazolam and/or morphine on the levels of dynorphin(1–13) in the pituitary gland, different brain regions, spinal cord and peripheral tissues of the rat. Four sets of animals were used: (I) saline-saline; (II) midazolam (0.03, 0.3 or 3.0 mg/kg, body wt., i.p.)-saline; (III) saline-morphine (10.0 mg/kg, body wt., s.c.); and (IV) midazolam-morphine (0.03, 0.3 or 3.0 mg/kg midazolam+10.0 mg/kg morphine) groups. The first saline or midazolam injection was given i.p. and after 30 min, the second injection of saline or morphine was given s.c. daily for 11 days. Animals were sacrificed on the 11th day, 60 min after the last injection and dynorphin(1–13) was measured in indicated tissues by radioimmunoassay method. The midazolam treated animals showed a significant decrease in dynorphin(1–13) levels in the cortex, cerebellum, cervical region of spinal cord, heart and adrenals, and a significant increase in the hypothalamus, striatum and lumbar region of the spinal cord. The morphine treated animals showed a significant decrease in dynorphin(1–13) levels in the pituitary gland, hypothalamus, hippocampus, striatum, cerebellum, pons, medulla, kidneys, adrenals and spleen, and a significant increase only in the lumbar region of the spinal cord. When both drugs were injected together there was no effect on pituitary gland, kidneys and spleen. These drugs antagonize each other's effect on dynorphin(1–13) in the hypothalamus, striatum, cerebellum, pons, medulla and heart. However, the midazolam-morphine combination significantly increases dynorphin(1–13) levels in the hippocampus, cortex, midbrain, cervical and lumbar regions of the spinal cord, and adrenals. These results suggest the involvement of dynorphin(1–13) in the inhibition of morphine-induced tolerance and dependence by midazolam in the rat. These results may also help us in understanding the intrinsic mechanisms involved in narcotic tolerance and dependence.© 1997 Elsevier Science B.V. All rights reserved.     

血浆和脑脊液中强啡肽—A含量变化与脑外伤的关系

３３例急性脑外伤病人伤后２４ｈ内和伤后第５天测定了血浆和脑脊液中Ｄｙｎ—Ａ含量。对照组（ｎ＝１３）血浆和脑脊液中Ｄｙｎ—Ａ含量分别为９３８．７７±３１６．６７ｐｇ／ｍｌ和７７．０８±３２．６５Ｐｇ／ｍｌ；中型脑外伤组为１８７０．３２±５７３．１２ｐｇ／ｍｌ和１８６．３２±５６．３４ｐｇ／ｍｌ，重型脑外伤组为２０３５．１３±６７５．４７ｐｇ／ｍｌ和２２７．５８±１１５．７７ｐｇ／ｍｌ，均明显高于对照组（Ｐ＜０．０１）。随着病情的好转Ｄｙｎ—Ａ含量亦随之降低，提示Ｄｙｎ—Ａ参与脑外伤的发病过程，其血浆和脑脊液中Ｄｙｎ—Ａ含量的变化对判断脑外伤病情的轻重和估价预后，有重要意义。     

Release of dynorphin-like immunoreactivity from rat anterior pituitary gland in vitro

Summary Rat anterior pituitary quarters were incubated in vitro and the release of dynorphin A_1–13-like immunoreactivity (Dyn A_1–13-IR) into the incubation medium was studied. An elevation of the potassium concentration of the incubation medium to 40 mmol/l increased the release of Dyn A_1–13-IR in a calcium-dependent manner. Addition of luteinizing hormone-releasing hormone (LHRH) stimulated the release of Dyn A_1–13-IR in a dose-dependent manner. The LHRH-induced release of Dyn A_1–13-IR was almost completely prevented by omission of calcium ions from the incubation medium or by addition of the LHRH-antagonistd-pGlu¹,d-Phe²,d-Trp^3,6-LHRH. This is the first demonstration that dynorphin-like immunoreactivity can be released from the rat adenohypophysis through calcium-dependent mechanisms by both high potassium concentration and receptor-mediated stimulation.This study was supported by the Deutsche Forschungsgemeinschaft (Kn 220/1-1)     

表达前强啡肽基因的Ad5型腺病毒载体的构建及鉴定

目的 构建且鉴定含前强啡肽基因(prodynorphin)的血清5型腺病毒载体(Ad5).方法 应用分子生物学方法 将前强啡肽基因序列克隆入腺病毒穿梭质粒pDC316-PDP,后者与骨架质粒共转染HEK293细胞,包装得到含前强啡肽转基因的腺病毒Ad5-PDP.用聚合酶链反应(PCR)方法 对转基因病毒进行鉴定,TCID50法测定病毒滴度.结果 PCR法证实转基因正确插入了Ad5型病毒基因组内,且没有野生型病毒污染,病毒滴度为1×1012v.p./mL.PCR鉴定Ad5-PDP重组成功.结论 获得的Ad5-PDP滴度高,感染性好,可以用于转基因治疗的实验研究.     

Stress and opioids: Role of opioids in modulating stress-related behavior and effect of stress on morphine conditioned place preference

Research studies have defined the important role of endogenous opioids in modulating stress-associated behavior. The release of β-endorphins in the amygdala in response to stress helps to cope with a stressor by inhibiting the over-activation of HPA axis. Administration of mu opioid agonists reduces the risk of developing post-traumatic stress disorder (PTSD) following a traumatic event by inhibiting fear-related memory consolidation. Similarly, the release of endogenous enkephalin and nociceptin in the basolateral amygdala and the nucleus accumbens tends to produce the anti-stress effects. An increase in dynorphin levels during prolonged exposure to stress may produce learned helplessness, dysphoria and depression. Stress also influences morphine-induced conditioned place preference (CPP) depending upon the intensity and duration of the stressor. Acute stress inhibits morphine CPP, while chronic stress potentiates CPP. The development of dysphoria due to increased dynorphin levels may contribute to chronic stress-induced potentiation of morphine CPP. The activation of ERK/cyclic AMP responsive element-binding (CREB) signaling in the mesocorticolimbic area, glucocorticoid receptors in the basolateral amygdala, and norepinephrine and galanin system in the nucleus accumbens may decrease the acute stress-induced inhibition of morphine CPP. The increase in dopamine levels in the nucleus accumbens and augmentation of GABAergic transmission in the median prefrontal cortex may contribute in potentiating morphine CPP. Stress exposure reinstates the extinct morphine CPP by activating the orexin receptors in the nucleus accumbens, decreasing the oxytocin levels in the lateral septum and amygdala, and altering the GABAergic transmission (activation of GABA_A and inactivation of GABA_B receptors). The present review describes these varied interactions between opioids and stress along with the possible mechanism.     

Effects of corticotropin-releasing hormone receptor antagonists on the ethanol-induced increase of dynorphin A1-8 release in the rat central amygdala

Neurons in the central amygdala (CeA) co-express dynorphin and corticotropin-releasing hormone (CRH). Moreover, the activity of both the CRH and dynorphin systems in CeA is altered by alcohol treatments, effects suggesting interactions between the CRH and dynorphin systems. Thus, the objectives of the present study were to investigate the effects of (1) activating CRH receptors (CRHRs) by microinjection of CRH in CeA and (2) blocking CRHRs by local microinjections of CRHR antagonists in the CeA on the alcohol-induced changes in the extracellular concentrations of dynorphin A1-8 with in vivo microdialysis experiments. Microdialysis probes with a microinjection port were implanted in the CeA of alcohol-naïve Sprague–Dawley rats. Microinjections of CRH or antalarmin, a CRH receptor type 1 (CRHR1) antagonist, or anti-sauvagine-30, a CRH receptor type 2 (CRHR2) antagonist, at the level of CeA were followed by an intraperitoneal injection of either saline or 2.8 g ethanol/kg body weight. The content of dynorphin A1-8 was determined in dialyzate samples obtained prior to and following the various treatments using a specific radioimmunoassay. Activation of CRHRs in CeA induced an increase in the extracellular concentrations of dynorphin A1-8. Moreover, acute alcohol administration increased the extracellular concentrations of dynorphin A1-8 in CeA, an effect that was attenuated by blocking CRHR2 with anti-sauvagine-30 microinjection but not blocking CRHR1 with antalarmin microinjection. Therefore, the findings suggest an interaction between the CRH and dynorphin A1-8 systems at the level of CeA in response to acute alcohol exposure.     

重组前强啡肽基因35型腺病毒载体的构建

目的 构建含前强啡肽(PDP)基因的重组35型腺病毒载体(Ad5/F35).方法 以pUC57-PDP重组质粒为模板扩增PDP基因,将回收的聚合酶链反应(PCR)产物片段克隆入pDC316载体,获得重组质粒pDC316-PDP.骨架质粒pBHG-fiberS/35和穿梭质粒pDC316-PDP共转染293细胞,同源重组产生Ad5/F35-PDP.经PCR鉴定目的 基因的表达.结果 PCR表明Ad5/F35-PDP质粒构建正确.结论 获得的Ad5/F35-PDP可以用于转基因治疗的实验研究.