Regulatory neuropeptides (ghrelin,obestatin and nesfatin-1) levels in serum and reproductive tissues of female and male rats with fructose-induced metabolic syndrome

Although, the exact mechanisms underlying the development of the metabolic syndrome (MetS) are not still completely understood, obesity, circulated peptide hormone levels and their interaction with genetic factors are considered largely responsible. The purpose of this study is to explore how the levels of ghrelin, obestatin (OBS) and NUCB2/nesfatin-1 (NES)/NUCB2 change in serum and the reproductive tissues of female and male rats with fructose-induced metabolic syndrome, and whether the levels of each hormone is correlated with the hormones involved with fertility. Experiments were conducted on 5-week-old Sprague–Dawley male and female rats assigned to either a control group or a MetS group. Controls were fed standard rat food and water ad libitum, while the MetS group was fed standard food with 10% (v/v) fructose solution added to their drinking water for 12 weeks with a 12/12 h photoperiod circle. Then, all animals were sacrificed after a one night fast. Peptides levels in the serum and reproductive tissues of rats were studied using the ELISA method while the immunoreactivity of reproductive system peptide hormones were shown by immunohistochemical staining method. Furthermore, the other biochemical parameters were measured using Konelab-60 equipment and infertility hormones were measured with Immulite2000. Fasting serum insulin, glucose, triglyceride, alanine aminotransferase (ALT), gamma glutamyl transpeptidase (GGT), low-density lipoprotein cholesterol (LDL-C), and total cholesterol (TC) levels were statistically significantly higher, and the amount of high density lipoprotein cholesterol (HDL-C) was significantly lower, in the MetS groups. Serum and tissue supernatant NES levels were significantly higher in the rats with MetS than the control group. Ghrelin, OBS and NES were expressed in the cytoplasm, concentrated around the apical parts of the epithelial cells in the reproductive tissues of the rats. The amounts of ghrelin were lower in the reproductive tissues of the animals with MetS, while NES levels in the same tissues increased. Obestatin also decreased, though not in the seminal glands.     

Lithium levels in blood platelets,serum, red blood cells and brain regions in rats given acute or chronic lithium salt treatments

Experiments were carried out on rats given lithium (1–4 mmol/kg/day) to determine the relationship between the Li level in blood platelets compared to serum, red blood cells and brain regions. In acute studies, the time course of the platelet Li content resembled the changes in the Li level in serum more than in red blood cells and brain. Inchronic studies, the correlations between the Li level in platelets and the Li levels in serum, red blood cells and brain regions ranged from 0.81 to 0.86 and were lower than the correlations between the Li levels in serum and in red blood cells and brain regions. The findings suggest that there may be differences in the membrane transport of Li in blood platelets compared to red blood cells and brain.     

Kainic acid induced hippocampal seizures in rats: comparisons of acute and chronic seizures using intrahippocampal versus systemic injections

Hyppocampal epilepsy is a recently defined syndrome occurring in 65% of all temporal lobe epilepsies as defined by: 1) electrographic (EEG) onset in the hippocampus (HC) prior to EEG seizures elsewhere, 2) post-resection hippocampal sclerosis and mossy fiber synaptic reorganizations and 3) relief of typical complex partial seizures after surgical resection of the hyppocampus. We used intrahippocampal kainic acid injections V² in rats at different developmental ages (postnatal 7 through adult) to develop long term spontaneous HC EEG spikes, EEG seizures, and behavioral seizures. Split-screen video/EEG monitoring demonstrated that this intrahippocampal kainic acid model produced progressive development of: 1) ipsilateral interictal spikes, 2) later polyspike complexes, 3) bilaterally-asynchronous EEG spiking, 4) unilateral HC EEG seizure onsets with occasional secondarily generalized spread to apposite HC and motor cortex to elicit complex partial seizures, and 5) in all seizing rats there was mossy fiber synaptic reorganization, even when injected at age 7 days. These results indicate that the intrahippocampal kainic acid injection model is similar to human hippocampal epilepsy.Supported by NIH Grants NS 02808, NS 31655 (T.L.B.); K08 NS 1603 (G.W.M.); and Fogarty Fellowship TWO 4959 (J.P.L.).     

Timecourse and corticosterone sensitivity of the brain, pituitary, and serum interleukin-1β protein response to acute stress

Activation of peripheral immune cells leads to increases of interleukin-1β (IL-1β) mRNA, immunoreactivity, and protein levels in brain and pituitary. Furthermore, IL-1β in brain plays a role in mediating many of the behavioral, physiological, and endocrine adjustments induced by immune activation. A similarity between the consequences of immune activation and exposure to stressors has often been noted, but the potential relationship between stress and brain IL-1β has received very little attention. A prior report indicated that exposure to inescapable tailshocks (IS) raised levels of brain IL-1β protein 2 h after IS, but only in adrenalectomized (and basal corticosterone replaced) subjects. The studies reported here explore this issue in more detail. A more careful examination revealed that IL-1β protein levels in hypothalamus were elevated by IS in intact subjects, although adrenalectomy, ADX (with basal corticosterone replacement) exaggerated this effect. IL-1β protein increases were already present immediately after the stress session, both in the hypothalamus and in other brain regions in adrenalectomized subjects, and no longer present 24 h later. Furthermore, IS elevated levels of IL-1β protein in the pituitary, and did so in both intact and adrenalectomized subjects. IS also produced increased blood levels of IL-1β, but only in adrenalectomized subjects. Finally, the administration of corticosterone in an amount that led to blood levels in adrenalectomized subjects that match those produced by IS, inhibited the IS-induced rise in IL-1β in hypothalamus and pituitary, but not in other brain regions or blood.     

Effect of phenobarbital on carbamazepine and its major metabolites in serum, different brain areas, and urine after acute and chronic administration to rats

The influence of coadministration of phenobarbital (PB) on disposition of carbamazepine (CBZ) and carbamazepine-10,11-epoxide (CBZ-E) in serum and in discrete areas of rat brain, together with its effects on urinary excretion of CBZ, CBZ-E, and trans-10,11-dihydro-10,11-dihydroxycarbamazepine (CBZ-DIOL) were investigated after both acute and chronic administration. Acute coadministration of PB resulted in increased serum CBZ levels, whereas serum CBZ-E levels were initially lower and then higher. In daily urinary excretion, a reduction in both CBZ-E/CBZ ratio and CBZ-DIOL/CBZ ratio was observed. Chronic (30 day) coadministration of PB led to a decrease in serum CBZ levels after the first hour, whereas serum CBZ-E levels were initially higher and then lower. In daily urinary excretion, a decrease in CBZ-E/CBZ ratio and an increase in CBZ-DIOL/CBZ ratio were noted. These results are consistent with an inhibitory interaction and a metabolic induction on both CBZ epoxidation and CBZ-E metabolism in acute and chronic administration, respectively. However, effects on CBZ epoxidation were preferential. In the various brain areas, the effects observed were similar to those noted in serum. In addition, a relevant increase in brain/serum CBZ ratios was observed with chronic coadministration of PB.     

运动对大鼠慢性颞叶癫痫模型痫性发作和脑内强啡肽A1-17含量及分布的影响

目的　探讨有氧运动对痫性活动的影响状况及其可能的机制。方法　 Wistar大鼠经匹罗卡品化学点燃成功 45 d后 ,将存活鼠 (致痫鼠 )随机分为运动组和安静组。分别监测两组动物在有氧运动中及随后 1h这一时间段内其痫性发作频次。运动阶段 (45 d)结束后 ,应用免疫细胞化学的方法研究运动对内源性抗痫物质—强啡肽A1 - 1 7含量及分布的影响。结果　两组之间平均痫性发作频次对比 ,无显著差异 (P>0 .0 5 )。运动组较安静组在海马结构、内嗅皮质、扣带回及额叶眶部等皮质脑区中 ,强啡肽 A1 - 1 7的密度和免疫反应强度显著增加 (P<0 .0 0 1)。结论　运动并不能被看作一种癫痫发作的诱发因素。脑内强啡肽 A1 - 1 7在运动中释放增多 ,其神经元的神经化学可塑性变化可能体现了内阿片肽强啡肽 A1 - 1 7促使兴奋 /抑制神经传递恢复平衡的一种倾向     

Effects of developmental stress and lead (Pb) on corticosterone after chronic and acute stress, brain monoamines, and blood Pb levels in rats

Despite restrictions, exposure to lead (Pb) continues. Moreover, exposure varies and is often higher in lower socioeconomic status (SES) families and remains a significant risk to cognitive development. Stress is another risk factor. Lower SES may be a proxy for stress in humans. When stress and Pb co-occur, risk may be increased. A few previous experiments have combined Pb with intermittent or acute stress but not with chronic stress. To determine if chronic developmental stress affects outcome in combination with Pb, we tested such effects on growth, organ weight, brain monoamines, and response to an acute stressor. Sprague Dawley rats were gavaged with Pb acetate (1 or 10 mg/kg) or vehicle every other day from postnatal day (P)4-29 and reared in standard or barren cages. Subsets were analyzed at different ages (P11, 19, 29). Chronic stress did not alter blood Pb levels but altered HPA axis response during early development whereas Pb did not. Pb treatment and rearing each altered organ-to-body weight ratios, most notably of thymus weights. Both Pb and rearing resulted in age- and region-dependent changes in serotonin and norepinephrine levels and in dopamine and serotonin turnover. The model introduced here may be useful for investigating the interaction of Pb and chronic developmental stress.     

Impairments of exploration and memory after systemic or prelimbic D1-receptor antagonism in rats

D1-receptor antagonism is known to impair rodent memory but also inhibits spontaneous exploration of stimuli to be remembered. Hypo-exploration could contribute to impaired memory by influencing event processing. In order to explore this effect, the D1 receptor antagonist, SCH23390, was administered to rats via routes that either did or did not affect spontaneous exploration: systemic or prelimbic administration, respectively. Effects were tested in spatial and non-spatial memory tasks selected for their requirements for self-initiated exploration of stimuli to be remembered in order to examine the effects on memory: cross-maze and object recognition task. Systemic administration reduced spatial exploration in cross-maze as well as in an open field test, and also reduced object exploration. Spatial (hippocampus-dependent) short-term memory was inhibited in the cross-maze and non-spatial short-term object retention was also impaired. In contrast to these systemic effects, bilateral injections of SCH23390 into the prelimbic cortices altered neither spatial nor object exploration, but did inhibit short-term memory in both cross-maze and object recognition task. Therefore, the inhibiting effects of SCH23390 on both spatial and non-spatial memory were not mediated indirectly via reduced exploration of stimuli to be remembered, but through antagonism of a prelimbic D1-R function that is directly involved in memory formation. Finally, a cooperative regulation of spatial exploration between D1-R and mGlu5 was indicated by a synergistic effect of the antagonists SCH23390 and MPEP.     

Serotonin levels and turnover in different brain areas of isolated aggressive or non-aggressive strains of mice

After eight weeks of individual housing DBA/2 but not C57 B1/6 (C57) mice showed high levels of aggressive responses in comparison with grouped mice. Social isolation did not modify serotonin (5-HT) levels in either strain of mice, while it produced a decrease of turnover rate in amygdala, lateral hypothalamus and pons in C57 mice and in lateral hypothalamus and pons of DBA mice. When isolated mice of both C57 and DBA strains are compared, no differences in turnover rate in amygdala and pons are evident, while isolated DBA mice show significant lower turnover values in lateral hypothalamus in comparison with isolated C57 mice. A possible suggestion emerging from our results is that aggressive responses exhibited by isolated DBA mice but not by isolated C57 mice may be related to lower 5-HT turnover rate in lateral hypothalamus.     

脑出血大鼠脑组织ICAM-1的表达与脑含水量的变化及药物对其影响

目的探讨脑出血后血肿周围脑组织炎性损伤的病理发展过程。方法健康Wister大鼠72只随机分成脑出血模型组、假手术组、麝香组,分别于3h、24h、72h、7d取血肿周围脑组织检测细胞间黏附因子-1(ICAM-1)的表达及出血侧脑组织含水量的测定。结果与假手术组比较,脑出血组ICAM-1从3h起即有表达,72h达高峰,持续7d仍有表达(P<0.05)。脑含水量在24h后明显增加(P<0.01),7d时与假手术组无显著性差异。结论ICAM-1在血肿周围的高表达推测是脑出血后水肿形成和缺血性损伤的主要原因之一。减少ICAM-1的表达和脑含水量推测是复方麝香注射液的药理机制。     

急性颅脑损伤患者血清ET-1、SE-CAD及镁离子的动态变化与意义

目的探讨急性颅脑损伤（aTBI）患者血清血清内皮素-1（ET-1）、可溶性上皮钙黏蛋白（SE-CAD）及镁离子的动态变化及其意义。方法将100例aTBI患者分为轻、中型组（GCS 9~15分,66例）和重型组（GCS〈8分34例）,另将40例健康体检者作为对照组。测定血清ET-1、SE-CAD及镁离子的水平,比较各组ET-1、SE-CAD及镁离子水平的变化。结果轻、中型组和重型组伤后24 h内血清ET-1、SE-CAD明显高于对照组（P〈0.05）,而镁离子水平明显低于对照组（P〈0.05）。重型组伤后24 h内血清ET-1、SE-CAD明显高于轻、中型组（P〈0.05）,而镁离子水平明显低于轻、中型组（P〈0.05）。重型组治疗后血清ET-1、SE-CAD较治疗前明显增高（P〈0.05）,而镁离子水平较治疗前明显降低（P〈0.05）。结论 ET-1、SE-CAD及镁离子可能参与aTBI后颅内的病理生理变化,其对判定伤情及预后具有重要的临床参考价值。     

急性脑梗死患者血清HMGB1、OPG和MIF水平的变化及PAS三联疗法的干预作用

目的 探讨急性脑梗死患者血清高迁移率族蛋白BI( HMGB1)、骨保护素(OPG)及巨噬细胞移动抑制因子(MIF)水平的变化以及普罗布考、阿司匹林、他汀类药物(PAS)三联疗法对其干预作用.方法 选择150例急性脑梗死患者,根据颈动脉超声检查结果分为颈动脉稳定斑块组(50例)和颈动脉易损斑块组(100例).将稳定斑块组作为对照组,易损斑块组抽血检查后按随机数字法分为AS组50例(阿司匹林100 mg/d,阿托伐他汀20 mg/d,口服)和PAS组50例(阿司匹林100 mg/d,阿托伐他汀20 mg/d,普罗布考0.25/次,2次／d,口服).比较治疗前和治疗后4周血清HMGB1、OPG和MIF水平.结果 治疗前,易损斑块组中两亚组血清HMGB1、OPG和MIF含量均明显高于稳定斑块组,差异有显著统计学意义(均P＜0.01);两亚组中血清HMGB1、OPG和MIF含量差异无统计学意义(均P＞0.05).治疗后4周,PAS组中血清HMGB1,OPG和MIF含量均明显低于AS组,且各指标下降幅度均高于AS组,差异有显著统计学意义(均P＜0.01).结论 血清HMGB1、OPG和MIF均参与脑梗死患者动脉粥样硬化的进程,可作为评估颈动脉粥样硬化斑块不稳定性的预测因子,PAS三联疗法可有效降低其血清浓度,具有更强的抗炎作用,可提高易损斑块的稳定性.     

血清sTREM-1、IL-12及IL-33水平对创伤性脑损伤严重程度和预后评估的价值

目的探讨血清可溶性髓样细胞触发受体-1（sTREM-1）、白介素-12（IL-12）及白介素-33（IL-33）水平对创伤性脑损伤（TBI）严重程度和预后评估的价值。 方法选取儋州市人民医院神经外科自2016年1月至2019年12月收治的142例TBI患者,根据治疗后28 d的预后情况将患者分为存活组（107例）和死亡组（35例）,依据GCS评分将患者分为轻中度组87例（GCS 13~15分10例,9~12分77例）和重度组55例（GCS 3~8分）。比较各组第1、3、5天血清sTREM-1、IL-12及IL-33水平变化。采用受试者工作特征（ROC）曲线分析血清sTREM-1、IL-12及IL-33水平,预测TBI患者死亡的价值。 结果死亡组GCS评分明显低于存活组,差异有统计学意义（P<0.05）。死亡组第1、3、5天血清sTREM-1、IL-12及IL-33水平均明显高于存活组,差异有统计学意义（P<0.05）。重度组第1、3、5天血清sTREM-1、IL-12及IL-33水平均明显高于轻中度组,差异有统计学意义（P<0.05）。ROC曲线显示,第3天sTREM-1、IL-12及IL-33联合预测TBI患者死亡的曲线下面积（0.933,95%CI：0.875~0.994）最大,其敏感度和特异度为95.4%和88.0%。 结论血清sTREM-1、IL-12及IL-33水平升高与TBI患者的病情严重程度相关,第3天采用3项联合检测对预测TBI患者预后有较好的价值。     

重组人促红细胞生成素对急性脑缺血大鼠Nrf2及HO-1表达的影响

目的 研究重组人促红细胞生成素(rhEPO)对急性脑缺血大鼠脑组织中核因子E2相关性因子2(Nrf2)及血红素加氧酶1(HO-1)表达的影响,探讨rhEPO的抗氧化作用机制. 方法 将36只雄性SD大鼠按随机数字表法分为假手术组、模型组、rhEPO组,后两组采用线栓法制备大鼠永久性局灶性脑缺血模型.rhEPO组在造模成功2h后腹腔注射rhEPO 5000 IU/kg,假手术组和模型组给予等量生理盐水.缺血24 h后处死大鼠取脑,采用免疫组化染色和Western blotting检测脑组织中Nrt2及HO-1的表达. 结果 免疫组化染色结果显示,假手术组Nrf2及HO-1均只有少量阳性表达,模型组和rhEPO组Nrf2及HO-1阳性表达细胞数均较假手术组明显增多,且rhEPO组阳性表达细胞数亦明显多于模型组,差异均有统计学意义(P＜0.05);阳性表达细胞主要为缺血区的神经元和星形胶质细胞.Western blotting结果也显示Nrt2及HO-1表达按假手术组、模型组、rhEPO组顺序依次增强,组间两两比较差异均有统计学意义(P＜0.05). 结论 急性脑缺血后脑组织中Keap1 -Nrf2/ARE抗氧化系统可被激活,rhEPO通过激活该抗氧化系统从而发挥脑保护作用.     

Effects of acute and chronic administration of MK-801 on c-Fos protein expression in mice brain regions implicated in schizophrenia with or without clozapine

This study investigated the effects of acute and chronic administration of the non-competitive NMDA receptor antagonists MK-801 on c-Fos protein expression in different brain regions of mice with or without clozapine. MK-801 (0.6 mg/kg) acute administration produced a significant increase in the expression of c-Fos protein in the layers III–IV of posterior cingulate and retrosplenial (PC/RS) cortex, which was consistent with the previous reports. Moreover, we presented a new finding that MK-801 (0.6 mg/kg) chronic administration for 8 days produced a significant increase of c-Fos protein expression in the PC/RS cortex, prefrontal cortex (PFC) and hypothalamus of mice. Among that, c-Fos protein expression in the PC/RS cortex of mice was most significant. Compared to acute administration, we found that MK-801 chronic administration significantly increased the expression of c-Fos protein in the PC/RS cortex, PFC and hypothalamus. Furthermore, pretreatment of mice with clozapine significantly decreased the expression of c-Fos protein induced by MK-801 acute and chronic administration. These results suggest that c-Fos protein, the marker of neuronal activation, might play an important role in the chronic pathophysiological process of schizophrenic model induced by NMDA receptor antagonist.     

Chlorine conductance of the GABAA receptor of synaptoneurosomes from the brain cortex of WAG/Rij rats with absence epilepsy and wistar rats at an early period in the development of nonconvulsive or tonic-clonic kindling

We have studied muscimol-induced ³⁶Cl^? conductivity in synaptoneurosomes prepared from the frontal and somatosensory cortex of rats with three types of epileptic activity: tonic-clonic pentylenetetrazole kindling in Wistar rats, nonconvulsive absence pentylenetetrazole kindling in Wistar rats, and a genetic model of epilepsy in WAG/Rij rats. We used two concentrations of muscimol: 30 and 100 μM. The occurrence of kindling prior to tonic-clonic seizures in the Wistar rats was considerably decreased in the muscimol-induced ³⁶Cl^? conductivity as compared to the control. Development of nonconvulsive kindling considerably increased the ³⁶Cl^? conductance into the neocortical synaptoneurosomes. The control WAG/Rij rats demonstrated a significant increase in the ³⁶Cl^? conductance into neocortical synaptoneurosomes as compared to the control Wistar rats. The decrease in muscimol-induced ³⁶Cl^? conductivity after development of tonic-clonic kindling was in agreement with a large volume of literature data regarding the decrease in the activity of GABA_A receptor during tonic-clonic kindling. The high level of muscimol-induced ³⁶Cl^? conductivity in the neocortical synaptoneurosomes of the WAG/Rij rats supported the concept that absence epilepsy was induced by hyperpolarization. The high level of ³⁶Cl^? conductivity during nonconvulsive pentylenetetrazole-induced kindling suggested that the activity of the GABA_A receptor was similar in the genetic and drug-induced models of the absence epilepsy.     

强化他汀治疗对脑梗死患者血清HMGB1 IL-17A和S-100A12水平的影响

目的观察脑梗死患者血清HMGB1、IL-17A和S-100A12水平的变化,并探讨瑞舒伐他汀钙治疗对脑梗死的脑保护作用机制。方法采用随机、对照、单盲法的前瞻性研究。根据颈动脉彩超检查结果,将卒中单元中符合纳入标准的280例急性脑梗死患者分为稳定斑块组100例和易损斑块组180例,后者按照随机数字法分为低剂量治疗组(A组,瑞舒伐他汀片,5 mg/晚,口服)和高剂量治疗组(B组,瑞舒伐他汀片,20 mg/晚,口服)各90例。检测发病第1天(治疗前)、第3天、第7天、第14天血清HMGB1、IL-17A和S-100A12水平;治疗前、治疗后第3天、治疗后1 w、2 w和3 w神经功能缺损采用NIHSS评分评定。结果发病第1天,易损斑块组(A组和B组)患者血清HMGB1、IL-17A和S-100A12水平高于稳定斑块组,且于第3天均达峰值,继之出现缓慢下降。在发病第7天、第14天B组血清HMGB1、IL-17A和S-100A12含量均明显低于A组(均P0.01)。治疗后第3天,A组和B组患者NIHSS评分较治疗前明显增加,达峰值(均P0.01)。治疗后2 w和3 w,B组患者NIHSS评分低于A组(均P0.01)。易损斑块组患者血清S-100A12水平与NIHSS评分呈正相关(发病第1天,分别r1=0.856,发病第3天,r1=0.870,均P0.01)。此外,血清HMGB1和IL-17A水平呈显著正相关(发病第1天,r=0.972,发病第3天,r=0.975,均P0.01)。结论血清S-100A12浓度可作为评估脑梗死后神经功能损伤严重程度的血清学指标,可作为评估颈动脉斑块易损性的血清学指标,HMGB1和IL-17A可能参与了脑梗死后急性期炎性反应过程。采取高强度他汀治疗具有减轻脑梗死后继发炎症反应、保护脑细胞和提高患者神经功能的作用。     

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.