Mice lacking rhes show altered morphine analgesia, tolerance, and dependence

Nitric oxide (NO) is an important messenger in the central nervous system to mediate male copulatory behavior. EGb 761, a standardized extract of Gingko biloba, has been reported to facilitate male copulation in rats. The present study is to determine the effects of neuronal nitric oxide synthase (nNOS) in the medial preoptic area (MPOA) on copulation in male rats following EGb 761 treatment. Adult male rats were treated with 50mg/kg of EGb 761 or distilled water by oral gavage for 14 consecutive days. The animals were sacrificed approximately 14h after the last behavioral test and MPOA brain tissues were collected for nNOS immunohistochemistry. EGb 761 treatment for 14 days significantly increased the intromission frequency compared to the vehicle-treated controls on day 14. An increase in ejaculation frequency was also seen in the EGb 761-treated group compared to the vehicle-treated controls on day 14 and to the same group on day 0. However, EGb 761 treatment did not influence the number of nNOS-immunoreactive cells in the MPOA. These results suggest that enhanced male copulatory performance in sexually experienced rats administered EGb 761 may not be related to central nNOS activity in the MPOA.     

Neuropeptide modulation of opiate and ethanol tolerance and dependence

Evidence exists to suggest that there are neurochemical responses common to the development of tolerance to and dependence on a variety of psychoactive drugs. Experimental data indicates that pituitary peptides such as corticotropin and vasopressin, in addition to the endorphins, influence the development of physical dependence on either morphine or ethanol. If these findings are supported by further investigations with human subjects, various manipulations of pituitary-adrenal function, such as the administration of corticotropin and vasopressin analogs or drugs such as dexamethasone, may prove to be of clinical utility.     

Mice lacking C1q or C3 show accelerated rejection of minor H disparate skin grafts and resistance to induction of tolerance

Complement activation is known to have deleterious effects on organ transplantation. On the other hand, the complement system is also known to have an important role in regulating immune responses. The balance between these two opposing effects is critical in the context of transplantation. Here, we report that female mice deficient in C1q (C1qa^?/?) or C3 (C3^?/?) reject male syngeneic grafts (HY incompatible) at an accelerated rate compared with WT mice. Intranasal HY peptide administration, which induces tolerance to syngeneic male grafts in WT mice, fails to induce tolerance in C1qa^?/? or C3^?/? mice. The rejection of the male grafts correlated with the presence of HY D^bUty‐specific CD8⁺ T cells. Consistent with this, peptide‐treated C1qa^?/? and C3^?/? female mice rejecting male grafts exhibited more antigen‐specific CD8⁺IFN‐γ⁺ and CD8⁺IL‐10⁺ cells compared with WT females. This suggests that accumulation of IFN‐γ‐ and IL‐10‐producing T cells may play a key role in mediating the ongoing inflammatory process and graft rejection. Interestingly, within the tolerized male skin grafts of peptide‐treated WT mice, IFN‐γ, C1q and C3 mRNA levels were higher compared to control female grafts. These results suggest that C1q and C3 facilitate the induction of intranasal tolerance.     

Effects of the fruit essential oil of Cuminum cyminum Linn. (Apiaceae) on acquisition and expression of morphine tolerance and dependence in mice

The problem of morphine tolerance and dependence is a universal phenomenon threatening social health everywhere the world. The major objective of this paper was to investigate the effects of fruit essential oil (FEO) of Cuminum cyminum on acquisition and expression of morphine tolerance and dependence in mice. Animals were rendered dependent on morphine using the well-established method in which was morphine (50, 50, 75 mg/kg; s.c.) injected three times daily for 3 days. In experimental groups, administration of FEO (0.001, 0.01, 0.1, 0.5, 1 and 2%; 5 ml/kg; i.p.) or Tween-80 (5 ml/kg; i.p.) was performed 60 min prior to each morphine injection (for acquisition) or the last injection of morphine on test day (for expression). Morphine tolerance was measured by tail-flick before and after administration of a single dose of morphine (50 mg/kg; s.c.) in test day (4th day). Morphine dependence was also evaluated by counting the number of jumps after injection of naloxone (5 mg/kg; i.p.) on the test day. The results showed that Cumin FEO, only at the dose of 2%, significantly attenuated the development of morphine tolerance (P < 0.01) and dependence (P < 0.05) while it could be significantly effective on expression of morphine tolerance (1 and 2%) and dependence (0.5, 1 and 2%) in a dose-dependent manner. Solely Cumin FEO injection (0.001–2%) did not show any analgesic effect. In conclusion, the essential oil of Cuminum cyminum seems to ameliorate the morphine tolerance and dependence in mice.     

Striatum specific protein, Rhes regulates AKT pathway

The Rhes/RASD2 GTPase complex is involved in dopamine D1/D2 receptor-mediated signaling and behavior. This GTP binding protein belongs to the RAS superfamily, along with Dexras1/RASD1, and is primarily expressed in the striatum. RASDs differ from typical small GTPases as they have an extended C-terminal tail of roughly 7 kDa. Previously, it has been shown that dopamine depletion reduces Rhes mRNA expression in the brain. Here we show that Rhes interacts with p85, the regulatory subunit of PI3K. Specifically, the C-terminal unique tail region of Rhes is responsible for this interaction. The interaction between p85 and the C-terminal region of Rhes is enhanced upon growth factor treatment in vitro, while AKT translocation to the membrane is facilitated in the presence of Rhes or the Rhes-p85 complex. These findings suggest that Rhes is a novel striatal regulator of the AKT-mediated pathway in the striatum.     

Anti-morphine antibody contributes to the development of morphine tolerance in rats

Previous studies have shown that tolerance to the antinociceptive effect of morphine develops after a prolonged exposure, but its mechanisms remain unclear. In the present study, we examined whether anti-morphine antibody produced by chronic morphine exposure would contribute to the development of morphine antinociceptive tolerance in rats. Our results showed that anti-morphine antibody was present in rats rendered tolerance to antinociception after intrathecal morphine exposure for seven consecutive days. Superfusion of anti-morphine antibody onto spinal cord slice dose-dependently produced an inward excitatory current in spinal cord dorsal horn neurons using whole-cell patch-clamp recording, which surpassed morphine-induced outward inhibiting current. Co-administration of morphine with a monoclonal antibody (2.4G₂) against Fc receptors for seven days significantly attenuated the production of anti-morphine antibody as well as the behavioral manifestation of morphine tolerance in same rats. These results indicate that anti-morphine antibody produced by morphine exposure may contribute to the development of morphine tolerance possibly through counteracting the inhibitory morphine effect on spinal cord dorsal horn neurons.     

Limbic oxytocin and arginine8-vasopressin in morphine tolerance and dependence

Summary Immunoreactive oxytocin (OXT) and arginine⁸-vasopressin (AVP) levels were measured in limbic areas of the mouse brain (hippocampus, amygdala and basal forebrain). Peptides were measured by radioimmunoassay (RIA). Acute morphine treatment caused a naloxone-reversible increase in OXT content in all three brain regions. The AVP contents of the same brain areas, on the other hand, were not affected by acute morphine treatment. In mice rendered tolerant to/dependent on morphine with subcutaneous morphine pellets, the OXT levels in the limbic brain structures were in the control range (basal forebrain and amygdala) or even decreased (hippocampus). In the latter brain structure of the tolerant animals, the AVP content was also decreased. Naloxone-precipitated withdrawal syndrome in the tolerant/dependent animals resulted in abrupt increases in the OXT and AVP levels of the hippocampus and in the OXT content of the basal forebrain structures.     

Epinephrine inhibits analgesic tolerance to intrathecal administrated morphine and increases the expression of calcium-calmodulin-dependent protein kinase IIalpha

Activation of hypothalamic-pituitary-adrenal (HPA) axis inhibits development of morphine tolerance. Also, the expression of CaMKIIalpha is increased following chronic administration of morphine. In the current study, we tried to examine the effect of epinephrine, on the development of morphine tolerance; and also evaluate the expression of CaMKIIalpha as a molecular index for tolerance development. Analgesic tolerance was induced by intrathecal (i.t.) injection of morphine 15 microg/rat, twice a day for 5 days. To study the effect of epinephrine on development or reversal of morphine tolerance, epinephrine was administrated 20 min before morphine injections. Analgesia was assessed using tail flick test. Gene expression assays were done using RT-PCR. Following 5 days of combined administration of morphine and epinephrine (2, 5 or 10 microg/rat), in day 6, morphine produced potent analgesia. Administration of saline and morphine during days 1-5, caused reduced analgesic effect of morphine on day 6. After tolerance induction during 5 days, co-administration of epinephrine and morphine for another 5 days, significantly reversed the tolerance. Both morphine and epinephrine increased the expression of CaMKIIalpha. The expression of CaMKIIalpha was highly increased following combined administration of epinephrine and morphine. Our results showed the inhibition and reversal of analgesic tolerance to local administrated morphine by epinephrine. We observed the increased expression of CaMKIIalpha without development of morphine tolerance in animals treated with combined epinephrine and morphine.     

Evaluation of morphine analgesia and motor coordination in mice following cortex-specific knockout of the N-methyl-D-aspartate NR1-subunit

Studies have shown that N-methyl-d-aspartate (NMDA) receptors play a critical role in morphine analgesia and motoric processes at different levels of the central nervous system. In this study, we used cortex-specific NR1 knockout (KO) mice (C57BL/6 strain) to elucidate the role of cortical NMDA receptors in morphine analgesia and motor coordination. On post-natal day 20, mice (CTL and KO) received vehicle (saline) or morphine (10mg/kg) and paw withdrawal latency (PWL) to a noxious thermal stimulus was measured. On post-natal day 21, motor coordination was measured using the rotating pole test. No differences in KO mice were found with respect to PWL following administration of saline or morphine (p>0.05). However, sex-dependent differences were found in motor coordination, with male KO mice showing a greater motor impairment in the rotating pole test than female KO mice (p<0.05). The present results demonstrate that NMDA receptors are involved in both the analgesic effects of morphine and motor coordination, with the existence of sex-related differences in motor coordination.     

Non-myeloablative mixed chimerism approaches and tolerance, a split decision

Stable mixed chimerism has been considered the most robust tolerance strategy. However, rejection of solid donor tissues by chimeras has been observed, a state termed split tolerance. Since new non-myeloablative mixed chimerism approaches are being actively pursued, we sought to determine whether they lead to full tolerance or split tolerance and to define the mechanisms involved. Fully mismatched mixed chimeras generated by induction with various lymphocyte-depleting antibodies along with either low-dose irradiation or busulfan and temporary sirolimus, maintained stable mixed chimerism but nevertheless rejected donor skin grafts. Generation of stable mixed chimerism using antibody targeting CD40L, but not depleting antibodies to CD4 and CD8, could prevent split tolerance when skin grafts were given together with donor bone marrow. Minor antigen matching abrogated the ability of effector T cells to reject donor skin grafts. A CFSE killing assay indicated that chimeras were both directly and indirectly tolerant of donor hematopoietic cell antigens, suggesting that minor mismatches triggered a tissue-specific response. Thus, split tolerance due to tissue-restricted polymorphic antigens prevents full tolerance in a number of non-myeloablative mixed chimerism protocols and a 'tolerizing' agent is required to overcome split tolerance. A model of the requirements for split tolerance is presented.     

Microglia show altered morphology and reduced arborization in human brain during aging and Alzheimer's disease

Changes in microglia function are involved in Alzheimer's disease (AD) for which ageing is the major risk factor. We evaluated microglial cell process morphologies and their gray matter coverage (arborized area) during ageing and in the presence and absence of AD pathology in autopsied human neocortex. Microglial cell processes were reduced in length, showed less branching and reduced arborized area with aging (case range 52–98 years). This occurred during normal ageing and without microglia dystrophy or changes in cell density. There was a larger reduction in process length and arborized area in AD compared to aged‐matched control microglia. In AD cases, on average, 49%–64% of microglia had discontinuous and/or punctate Iba1 labeled processes instead of continuous Iba1 distribution. Up to 16% of aged‐matched control microglia displayed discontinuous or punctate features. There was no change in the density of microglial cell bodies in gray matter during ageing or AD. This demonstrates that human microglia show progressive cell process retraction without cell loss during ageing. Additional changes in microglia occur with AD including Iba1 protein puncta and discontinuity. We suggest that reduced microglial arborized area may be an aging‐related correlate of AD in humans. These variations in microglial cells during ageing and in AD could reflect changes in neural‐glial interactions which are emerging as key to mechanisms involved in ageing and neurodegenerative disease.     

环氧化酶2抑制剂帕瑞昔布、塞来昔布在TKA围手术期多模式镇痛中的效果研究

目的：比较两种选择性环氧化酶2（COX-2）抑制剂帕瑞昔布、塞来昔布在全膝关节置换围手术期多模式镇痛中的镇痛效果。方法选择2013年1月至2014年3月首都医科大学附属北京友谊医院收治的80例行单侧全膝关节置换术（TKA）患者,随机分为塞来昔布组、帕瑞昔布组,每组40例。两组患者均进行超前镇痛及患者自控静脉镇痛,塞来昔布组在术后6 h口服塞来昔布200 mg,此后1次／12 h,200 mg／次,连续3 d;帕瑞昔布组在同时期采用肌肉注射帕瑞昔布40 mg,此后1次／12h,40mg／次,连续3d10观察术后6h、12h、1d、2d、3d两组患者静息及活动时视觉模拟量表（VAS）评分,术后第3天记录患者患侧关节最大主动、被动活动度;术后每天记录患者引流量,至引流管拔除;术后1、2、3d记录患者睡眠满意度评分;记录术后3d内患者恶心、呕吐、瘙痒、眩晕、尿潴留、呼吸抑制等不良反应的发生例数。VAS评分、伤口引流量、膝关节活动度、睡眠满意度,采用配对t检验进行统计学分析;药物不良反应的发生情况,采用χ2检验进行统计学分析。结果术后6 h、12 h、1d、2d、3d两组患者静息时VAS评分比较差异均无统计学意义（P＞0．05）,术后6h、12h、1d、2d、3 d活动时的 VAS 评分帕瑞昔布组均小于塞来昔布组,两组比较差异有统计学意义（t ＝－5．586、－6．643、－6．729、－5．414、－4．718,均P＜0．05）;术后第3天帕瑞昔布组、塞来昔布组的膝关节主动活动度分别为（78．75±7．32）°和（74．50±6．87）°,两组比较差异有统计学意义（t ＝2．978,P＝0．005）;被动活动度分别为（96．13±6．04）°、（92．88±5．98）°,两组比较差异有统计学意义（t ＝2．458,P＝0．019）;术后1、2d帕瑞昔布组与塞来昔布组的伤口引流量比较,差异无统计学意义（t＝0．191、0．401,P＝0．850、0     

Concomitant airway expression of granulocyte-macrophage colony-stimulating factor and decorin, a natural inhibitor of transforming growth factor-beta, breaks established inhalation tolerance

We previously showed that granulocyte-macrophage colony-stimulating factor (GM-CSF) breaks tolerance induction. The objective of this study was to determine whether GM-CSF breaks established inhalation tolerance. To induce tolerance, BALB/c mice were exposed to aerosolized ovalbumin (OVA) for 10 consecutive days. A control group was exposed to saline. Subsequently, tolerant and control animals were exposed to OVA in a GM-CSF-enriched airway microenvironment. Tolerant animals, unlike control animals, did not develop airway and peripheral blood eosinophilia, had diminished levels of OVA-specific IgE, and reduced airway hyper-responsiveness. While tolerant animals did not express IL-4, IL-5 and IL-13, levels of the regulatory cytokines IL-10, IFN-gamma and transfoming growth factor (TGF)-beta were similar between tolerant and non-tolerant animals. Lung CD4+ T cells were activated according to CD69, CD25 and T1/ST2 expression, but systemic responses characterized by splenocyte proliferation and Th2 effector function were dramatically reduced. Concurrent expression of GM-CSF and decorin, a natural inhibitor of TGF-beta, reversed eosinophilic unresponsiveness. Our study suggests that the breakdown of tolerance and, by extension, the emergence of eosinophilic inflammation, requires two signals: one that triggers sensitization and one that interferes with negative regulation. Moreover, our study shows that dysregulated expression of an extracellular matrix protein may break established tolerance and lead to eosinophilic airway inflammation.     

Effects of an odor paired with illness on startle,freezing, and analgesia in rats

The data reported in this experiment provide the first systematic exploration of the effectiveness of an odor previously paired with an aversive reinforcer other than shock on eliciting various behavioral expressions of fear in the rat. Specifically, we measured potentiation of the acoustic startle response, freezing, and analgesia in the presence of an odor previously paired with an illness-inducing agent (lithium chloride; LiCl). We found that this odor elicited freezing and analgesia, but failed to potentiate the startle response. The results are discussed in terms of (1). potential threshold differences for various expressions of learned fear and (2). the possibility that the content of the learning established by odor-shock pairings differ from those established by odor-illness pairings.     

Chimerism and tetragametic chimerism in humans: implications in autoimmunity, allorecognition and tolerance

The presence of cells or tissues from two individuals, chimeras, or the presence of cells and tissues that include the gonads, tetragametic chimerism can be detected by the analysis of cytogenetics and analysis of polymorphic genetic markers, using patterns of pedigree inheritance. These methodologies include determination of sex chromosomes, major histocompatibility complex (MHC) polymorphisms and panels of short tandem repeats (STRs) that include mitochondrial DNA markers. Studies routinely involve cases of temporal chimerism in blood transfusion, or following allotransplantation to measure the outcome of the organ, lymphopoietic tissues or bone marrow grafts. Demonstration of persistent chimerism is usually discovered in cases of inter-sexuality due to fusion of fraternal twins or in cases of fusion of embryos with demonstrable allogeneic monoclonality of blood which, excluded maternity or paternity when blood alone is used as the source of DNA. In single pregnancies it is possible to produce two kinds of microchimerism: feto-maternal and materno-fetal, but in cases of fraternal twin pregnancies it is possible to identify three different kinds which are related to cases of vanishing twins that can be identified during pregnancy by imaging procedures; (1) hematopoietic, (2) gonadal, and (3) freemartins when the twins have different sex and the individual born is a female with either gonadal or both gonadal and hematopoietic tissues. Fraternal twin pregnancies can also produce fusion of embryos. Such cases could be of different sex presenting with inter-sexuality or in same sex twins. One of such cases, the best studied, showed evidence of chimerism and tetragametism. In this regard, the case was studied because of disputed maternity of two of her three children. All tissues studied, except for the blood, demonstrated four genetic components but only two in her blood of four possible showed allogeneic monoclonality consistent with the interpretation that her blood originated from one hematopoietic stem cell. Also, microchimerism, due to traffic of cells via materno-fetal or feto-maternal has been prompted by reports of their potential association with the development of autoimmune disorders including systemic lupus erythematosus (SLE) and systemic sclerosis, and in allotransplantation. In addition, their relevance of chimerism in the positive and negative selection of T cells in the thymus has not been addressed. T lymphocytes play a central role in controlling the acquired immune response and furthermore serve as crucial effector cells through antigen specific cytotoxic activity and the production of soluble mediators. Central tolerance is established by the repertoire selection of immature T lymphocytes in the thymus, avoiding the generation of autoreactive T cells. Expression of chimeric antigens in the thymus could modify the generation of specific T cell clones in chimeric subjects and these mechanisms could be important in the induction of central tolerance against foreign antigens important in allo-transplantation. In this review, we discuss the genetics of chimerism and tetragametism and its potential role in thymic selection and the relevance in allotransplantation and autoimmune disorders. This review is dedicated to the memory of Robert A. Good, MD, PhD, an outstanding physician and scientist, one discoverer of the functions of the Thymus in immunobiology and the pioneer of human bone marrow allotransplantation. Presented at the First Robert A Good Society Symposium, St. Petersburg, FL 2006.     

Current practices of mobilization,analgesia, relaxants and sedation in Indian ICUs: A survey conducted by the Indian Society of Critical Care Medicine

Background and Aim:

Use of sedation, analgesia and neuromuscular blocking agents is widely practiced in Intensive Care Units (ICUs). Our aim is to study the current practice patterns related to mobilization, analgesia, relaxants and sedation (MARS) to help in standardizing best practices in these areas in the ICU.

Materials and Methods:

A web-based nationwide survey involving physicians of the Indian Society of Critical Care Medicine (ISCCM) and the Indian Society of Anesthesiologists (ISA) was carried out. A questionnaire included questions on demographics, assessment scales for delirium, sedation and pain, as also the pharmacological agents and the practice methods.

Results:

Most ICUs function in a semi-closed model. Midazolam (94.99%) and Fentanyl (47.04%) were the most common sedative and analgesic agents used, respectively. Vecuronium was the preferred neuromuscular agent. Monitoring of sedation, analgesia and delirium in the ICU. Ramsay''s Sedation Scale (56.1%) and Visual Analogue Scale (48.07%) were the preferred sedation and pain scales, respectively. CAM (Confusion Assessment Method)-ICU was the most preferred method of delirium assessment. Haloperidol was the most commonly used agent for delirium. Majority of the respondents were aware of the benefit of early mobilization, but lack of support staff and safety concerns were the main obstacles to its implementation.

Conclusion:

The results of the survey suggest that compliance with existing guidelines is low. Benzodiazepines still remain the predominant ICU sedative. The recommended practice of giving analgesia before sedation is almost non-existent. Delirium remains an underrecognized entity. Monitoring of sedation levels, analgesia and delirium is low and validated and recommended scales for the same are rarely used. Although awareness of the benefits of early mobilization are high, the implementation is low.     

Relationship between MUC5AC and altered expression of MLH1 protein in mucinous and non-mucinous colorectal carcinomas

The main purpose of this study was to examine the expression of mucins and mismatch repair proteins in colorectal carcinomas. The immunohistochemical distribution of apomucins MUC2, MUC5AC, and the expression of MLH1 and MSH2 proteins were examined in 76 mucinous and 60 non-mucinous colorectal carcinomas. MUC2 was noted in all mucinous carcinomas, whereas MUC5AC was present in 41 cases only (54%). In non-mucinous carcinomas, MUC2 was expressed in 61.7% of the tumors; by contrast, MUC5AC was present in 20% of the cases. The expression level of apomucins was significantly different in mucinous and non-mucinous lesions (p<0.001). Twenty-seven (35.5%) of the mucinous carcinomas showed no MLH1 expression, whereas 11 (18.3%) of the non-mucinous tumors did. This difference was statistically significant (p<0.005). Altered expression of MSH2 protein was never observed. The lack of MLH1 expression was considerably more frequent in carcinomas with secretion of MUC5AC (p<0.005). Our study has demonstrated this close relationship by immunohistochemical methods. In summary, our data show: (1) differences in the expression of mucins between mucinous and non-mucinous tumors; (2) a high frequency of altered MLH1 protein expression (35.5%) in mucinous carcinomas; (3) a significant relationship between the presence of MUC5AC and the altered expression of MLH1 protein in colorectal carcinomas.     

Maternal-fetal tolerance is maintained despite transgene-driven trophoblast expression of MHC class I,and defects in Fas and its ligand

During mammalian pregnancy, one or more semiallogeneic fetuses gestate in direct contact with the maternal circulation and uterine tissue. However, a damaging maternal immune response is not normally provoked. We studied two possible mechanisms for this maternal-fetal tolerance, alone and in combination. First, we directly tested the hypothesis that the striking absence of MHC class I molecules on most placenta trophoblasts protects the fetus from maternal immune attack, by creating transgenic mice which express L^d in giant cell trophoblasts. Second, because Fas ligand (FasL) may contribute to immune privilege, we tested whether functional FasL expression by the fetus, or Fas expression by the mother, contributes to successful reproduction in a fully allogeneic breeding. Our data indicate that neither abnormal expression of MHC class I in giant cells, nor disruption of the Fas-FasL system, nor a combination of these two defects, has an adverse effect on pregnancy outcome. These results suggest that during healthy allogeneic pregnancy, down-regulation of MHC class I and expression of FasL on placenta are not critical events, and other factors must prevent a harmful maternal immune response.     

Effect of KEPI (Ppp1r14c) deletion on morphine analgesia and tolerance in mice of different genetic backgrounds: when a knockout is near a relevant quantitative trait locus

We previously identified KEPI as a morphine-regulated gene using subtractive hybridization and differential display PCR. Upon phosphorylation by protein kinase C, KEPI becomes a powerful inhibitor of protein phosphatase 1. To gain insights into KEPI functions, we created KEPI knockout (KO) mice on mixed 129S6×C57BL/6 genetic backgrounds. KEPI maps onto mouse chromosome 10 close to the locus that contains the μ-opioid receptor (Oprm1) and provides a major quantitative trait locus for morphine effects. Analysis of single nucleotide polymorphisms in and near the Oprm1 locus identified a doubly-recombinant mouse with C57BL/6 markers within 1 Mb on either side of the KEPI deletion. This strategy minimized the amount of 129S6 DNA surrounding the transgene and documented the C57BL/6 origin of the Oprm1 gene in this founder and its offspring. Recombinant KEPIKO mice displayed (a) normal analgesic responses and normal locomotion after initial morphine treatments, (b) accelerated development of tolerance to analgesic effects of morphine, (c) elevated activity of protein phosphatase 1 in thalamus, (d) attenuated morphine reward as assessed by conditioned place preference. These data support roles for KEPI action in adaptive responses to repeated administration of morphine that include analgesic tolerance and drug reward.