环孢霉素A对大鼠单个核细胞雄激素和雌激素受体的影响及意义

研究了环孢霉素Ａ（ＣａＡ）、环磷酰胺（ＣＴＸ）及甲基强的松龙（ＭＰ）对大鼠单个核细胞（ＭＮＬ）雄激素受体（ＡＲ）及雌激素受体（ＥＲ）的影响。结果表明：静注ＣｓＡ２０ｍｇ／ｋｇ，ＥＲ明显降低，３ｈ作用达高峰，持续低水平达８ｈ；而ＡＲ无明显影响。静注ＣａＡ１００ｍｇ／ｋｇ用ＣＴＡ和ＭＰ使ＡＲ、ＥＲ均明显降低。而ＣＴＸ和ＭＰ使ＥＲ降低，也使ＡＲ降低，故ＣｓＡ免疫抑制作用优于ＣＴＸ和ＭＰ。     

牛磺酸对缺血大鼠心肌线粒体Ca^2＋—Mg^2＋—ATP酶活性与MDA …

目的和方法：用Ｗｉｓｔａｒ大鼠皮下注射异丙肾上腺素（ＩＳＰ,５ｍｇ／ｋｇ）诱导心肌缺血模型。观测心肌线粒体（Ｍｉｔ）中丙二醛（ＭＤＡ）含量、Ｃａ＾２＋－Ｍｇ＾２＋－ＡＴＰ酶和Ｃａ＾２＋－Ｍｇ＾２＋－ＡＴＰ酶和Ｃａ＾２＋－ＡＴＰ酶活性及牛磺酸（Ｔａｕ）的影响。结果：缺血组大鼠心肌Ｍｉｔ中ＭＤＡ升高８７．８３％、Ｃａ＾２＋－Ｍｇ＾２＋－ＡＴＰ酶和Ｃａ＾２＋－ＡＴＰ酶活性分别降低３７．５６％和５０．２０     

牛磺酸对缺血大鼠心肌线粒体Ca2+-Mg2+-ATP酶活性与MDA含量影响

目的和方法：用Ｗｉｓｔａｒ大鼠皮下注射异丙肾上腺素（ＩＳＰ,５ｍｇ／ｋｇ）诱导心肌缺血模型。观测心肌线粒体（Ｍｉｔ）中丙二醛（ＭＤＡ）含量、Ｃａ２＋－Ｍｇ２＋－ＡＴＰ酶和Ｃａ２＋－ＡＴＰ酶活性及牛磺酸（Ｔａｕ）的影响。结果：缺血组大鼠心肌Ｍｉｔ中ＭＤＡ升高８７８３％、Ｃａ２＋－Ｍｇ２＋－ＡＴＰ酶和Ｃａ２＋－ＡＴＰ酶活性分别降低３７５６％和５０２０％（Ｐ＜０．０１）。Ｃａ２＋－Ｍｇ２＋－ＡＴＰ酶活性与ＭＤＡ含量也呈显著负相关（ｒ＝－０．８７,Ｐ＜０．０１）。Ｃａ２＋－ＡＴＰ酶活性与ＭＤＡ含量也呈显著负相关（ｒ＝－０７９,Ｐ＜０．０１）。在注射异丙肾上腺素（ＩＳＰ）前３０ｍｉｎ腹腔注射Ｔａｕ（２００ｍｇ／ｋｇ）则Ｍｉｔ中ＭＤＡ含量、Ｃａ２＋－Ｍｇ２＋－ＡＴＰ酶和Ｃａ２＋－ＡＴＰ酶活性均未见显著异常改变。结论：Ｔａｕ可能通过抑制ＭＤＡ的生成实现其保护Ｃａ２＋－ＡＴＰ酶和Ｃａ２＋－Ｍｇ２＋－ＡＴＰ酶活性的作用。     

实验性心律失常与性激素的关系

目的和方法：通过动物实验探讨心律失常发病是否有性别差异以及性激素对心律失常的影响。结果：乌头碱（Ａｃｏ）诱发心律失常有性别差异，即雌鼠心律失常持续时间较雄鼠长，尤以雌鼠动情期更突出（Ｐ＜００１），并证实造成这种差异可能与血浆雌激素水平有关。外源性Ｅ２（６０μｇ／ｋｇｉｖ）：（１）能明显缩短由Ａｃｏ诱发的雄大鼠心律失常持续时间（６８６±１８．２）ｍｉｎｖｓ（４７．１±１９．６）ｍｉｎ，Ｐ＜０．０５；（２）提高哇巴因（Ｏｕａ）致雄豚鼠ＶＰ、ＶＦ的剂量（１０７．５±１０．４）μｇ／ｋｇｖｓ（１２１．３±９．９）μｇ／ｋｇ，Ｐ＜０．０５；（１５１．３±１４．６）μｇ／ｋｇｖｓ（１６７．５±１１．７）μｇ／ｋｇ，Ｐ＜００５。（３）缩短由肾上腺素（Ａｄ）诱发的雄兔心律失常持续时间（２６２±５４）ｓｖｓ（１４５±２２）ｓ，Ｐ＜００１。说明外源性Ｅ２可对抗某些雄性动物实验性心律失常     

阿托品减轻大鼠脑缺血后再灌流损害机制的初步探讨

为探讨乙酰胆碱（ａｃｅｔｙｌｃｈｏｌｉｎｅ，Ａｃｈ）在神经元缺血性损害中的作用和机制，本实验观察了Ａｃｈ能Ｍ受体拮抗剂阿托品对大鼠脑缺血再灌注损害的影响，发现阿托品（２５ｍｇ／ｋｇ，ｂｗ，ｉｐ）可明显减轻大鼠前脑缺血后再灌流所致海马ＣＡ１区神经元迟发性损害，减小大鼠大脑中动脉阻塞后再灌流损害范围，而对局部皮质血流变化无影响，表明阿托品对缺血脑组织的保护作用不是由于改善了局部脑血流，提示Ａｃｈ参与神     

西红花提取物对大鼠血小板聚集、软脑膜血流量和离体兔主动脉条的作用

经实验证明西红花提取物ＸＨＨ－１的小鼠灌胃ＬＤ５０大于１０ｇ／ｋｇ，毒性很小。ＸＨＨ－１的五个浓度（０．５、１、２、３、４ｍｇ／ｍｌＰＲＰ）均能显著地对抗由ＡＤＰ引起的大鼠体外血小板聚集，并缩短血小板最大聚集时间。ＸＨＨ－１浓度为４、８、１２ｍｇ／ｍｌ时，对ＫＣｌ引起的离体兔主动脉血管平滑肌的抑制作用与对照组相比都有非常显著的统计学意义。大鼠静注１０ｍｇ／ｋｇＸＨＨ－１后１０ｍｉｎ，软脑膜血流量增加５４％，２０ｍｉｎ时仍维持在相近水平，灌胃给药２５０ｍｇ／ｋｇ后３０ｍｉｎ。软脑膜血流量同给药前相比增加了３９％，至６０ｍｉｎ仍维持这一水平，均有显著统计学差异。     

维生素A对胸腺凋亡有关基因的影响

为观察营养缺乏及补充维生素Ａ（ＶＡ）对胸腺细胞凋亡有关基因的影响，采用原位杂交及免疫组化的方法观察了胸腺组织ｂｃｌ－２ｍＲＮＡ，Ｆａｓ及Ｂａｘ蛋白的表达。结果表明营养缺乏的大鼠胸腺细胞ｂｃｌ－２ｍＲＮＡ的表达明显降低，而Ｆａｓ及Ｂａｘ蛋白的表达则明显增强；补充ＶＡ后大鼠胸腺ｂｃｌ－２ｍＲＮＡ的表达明显增强，Ｂａｘ蛋白的表达明显降低，而Ｆａｓ蛋白的表达无明显变化。本结果表明：营养缺乏时胸腺细胞凋亡增加导致免疫功能降低，补充ＶＡ可抑制细胞凋亡，可能是通过促进ｂｃｌ－２ｍＲＮＡ的表达，抑制Ｂａｘ蛋白的表达而起作用     

肝细胞提取物对肝癌细胞（BEL—7402）凋亡相关基因表达的影响

肝细胞提取物经ＨＰＬＣ，ＦＰＬＣ进一步分离纯化，得到了单一色谱峰，激光飞行时间质谱仪测分子量为４．０２０ｋＤ该单一组分（Ｓ４）对ＢＥＬ－７４０２肝癌细胞有增殖回落作用，半数抑制浓度（ＩＣ５０）为７．５８ｍｇ／Ｌ。对ＢＥＬ－７４０２细胞的基因表达影响研究，Ｓ４对Ｐ５３，Ｆａｓ表达有增强作用，而抑制Ｂｃｌ－２，ｃ－ｍｙｃ的表达，Ｓｏｕｔｈｅｒｍｂｌｏｔ技术表明，Ｓ４可抑制Ｂｃｌ－２的ｍＲＮＡ转录，提示     

分枝杆菌多糖对小鼠骨髓造血祖细胞GMCFU的影响

对分枝杆菌多糖（Ｍｙｃｏｂａｃｔｅｒｉａｌｐｏｌｙｓａｃｃｈａｒｉｄｅｓ，ＭＰＳ）促进小鼠骨髓造血祖细胞形成ＧＭＣＦＵ的量效关系进行了实验研究。结果表明，给予不同剂量的ＭＰＳ使ＧＭＣＦＵ提高的水平在一定剂量范围内（０．６～１．０ｍｇ／ｋｇ）随剂量增加而升高，剂量大于１．２ｍｇ／ｋｇ时不再继续升高。共进行３批试验，重复性好（Ｐ＞０．０５）。说明ＭＰＳ的升白作用具有一定的量效关系     

不同年龄大鼠斜角带核水平支神经元内TrkA和ChAT的表达——免疫组织化学研究

目的 了解大鼠基底前脑斜角带核水平支神经元内酪氨酸激酶Ａ（ｔｙｒｏｓｉｎｅ ｋｉｎａｓｅ,Ａ,ＴｒｋＡ）、胆碱乙酰化转移酶（ｃｈｏｌｉｎｅ ａｃｅｔｙｌｔｒａｎｓｆｅｒａｓｅ,ＣｈＡＴ）样阳性神经元的生后发育规律及两乾的相互关系。方法 用免疫组织化学方法结合图像分析仪检测大鼠基底前脑斜角带核水平支ＴｒｋＡ、ＣｈＡＴ样阳性神经元的数量、面积和灰度值。结果 ＴｒｋＡ、ＣｈＡＴ分布于基底前脑神经元。生后１ｄ可见ＴｒｋＡ表达,但生后５ｄ才出现ＣｈＡＴ表达。生后２０ｄＴｒｋＡ、ＣｈＡＴ表达至高峰;生后３０ｄ下调,成年时维持相对较高水平。老年鼠ＴｒｋＡ、ＣｈＡＴ样阳性神经元出现萎缩、数量也分别减少３９．７％、３３．３％;胞体平均面积分别减少１５．７％、１２．８％;平均灰度值分别减少２９．９％、９．９％。同时,不同年龄大鼠Ｔ     

银杏内酯B对帕金森病模型大鼠的保护作用

目的 探究银杏内酯B（ginkgolide B,GB）对帕金森病（Parkinson's disease,PD）模型大鼠的保护作用。 方法 采用脑内定位注射6-OHDA建立大鼠PD模型,随机分为Sham组、模型组、美多芭组（20 mg/kg）和GB低、中、高剂量组（15、30、60 mg/kg）,另将大鼠随机分为Sham组、Model组、GB 60 mg/kg组、LY294002组和（GB 60 mg/kg+LY294002）组,旋转实验检测大鼠行为学,试剂盒检测MDA、SOD、GSH水平,ELISA检测IL-6、IL-1β、TNF-α水平,Western blot检测大鼠黑质和纹状体组织PI3K/Akt信号通路蛋白表达情况。 结果 治疗后,美多芭组和GB中、高剂量组大鼠旋转圈数明显少于模型组（P<0.05）,MDA和IL-6、IL-1β、TNF-α水平明显低于模型组（P<0.05）,SOD、GSH水平、p-PI3K、p-Akt蛋白表达明显高于模型组（P<0.05）;与LY294002组比较,（GB 60 mg/kg+LY294002）组大鼠p-PI3K、p-Akt蛋白表达明显上调（P<0.05）,MDA和IL-6、IL-1β、TNF-α水平明显降低（P<0.05）,SOD、GSH水平明显升高（P<0.05）。 结论 高剂量GB可改善PD大鼠行为学,增强抗氧化应激能力,减轻炎性损伤,起到一定保护作用,其机制可能与调节PI3K/Akt信号通路有关。     

Lipopolysaccharide reduces sodium intake and sodium excretion in dehydrated rats

The objective of this study was to find out if lipopolysaccharide (LPS) administered intraperitoneally affects sodium and water intake and renal excretion in dehydrated rats. LPS (0.3-5 mg/kg b.w.) inhibited 0.3 M NaCl intake induced by subcutaneous injection of the diuretic furosemide (FURO, 10 mg/kg b.w.) combined with the angiotensin converting enzyme inhibitor, captopril (CAP, 5 mg/kg b.w.). Only the highest doses of LPS (2.5 and 5 mg/kg) inhibited water intake induced by FURO/CAP. LPS (0.6 mg/kg) reduced urinary volume and sodium excretion, but had no effect on mean arterial pressure or heart rate of rats treated with FURO/CAP. LPS (0.3-5.0 mg/kg) abolished intracellular thirst and reduced by 50% the urine sodium concentration of rats that received 2 ml of 2 M NaCl by gavage. LPS (0.3-5.0 mg/kg) also reduced thirst in rats treated with FURO alone (10 mg/rat sc). The results suggest that LPS has a preferential, but not exclusive, inhibitory effect on sodium intake and on intracellular thirst. The inhibition of hydro-mineral intake and the antinatriuresis caused by LPS in dehydrated rats may contribute to the multiple effects of the endotoxin on fluid and electrolyte balance and be part of the strategy to cope with infections.     

Dietary protein modulates circadian changes in core body temperature and metabolic rate in rats

We assessed the contribution of dietary protein to circadian changes in core body temperature (Tb) and metabolic rate in freely moving rats. Daily changes in rat intraperitoneal temperature, locomotor activity (LMA), whole-body oxygen consumption (VO2), and carbon dioxide production (VCO2) were measured before and during 4 days of consuming a 20% protein diet (20% P), a protein-free diet (0% P), or a pair-fed 20% P diet (20% P-R). Changes in Tb did not significantly differ between the 20% P and 20% P-R groups throughout the study. The Tb in the 0% P group remained elevated during the dark (D) phase throughout the study, but VO2, VCO2, and LMA increased late in the study when compared with the 20% P-R group almost in accordance with elevated Tb. By contrast, during the light (L) phase in the 0% P group, Tb became elevated early in the study and thereafter declined with a tendency to accompany significantly lower VO2 and VCO2 when compared with the 20% P group, but not the 20% P-R group. The respiratory quotient (RQ) in the 0% P group declined throughout the D phase and during the early L phase. By contrast, RQ in the 20% P-R group consistently decreased from the late D phase to the end of the L phase. Our findings suggest that dietary protein contributes to the maintenance of daily oscillations in Tb with modulating metabolic rates during the D phase. However, the underlying mechanisms of Tb control during the L phase remain obscure.     

Acute Effects of the Anti-Inflammatory Cyclooxygenase-2 Selective Inhibitor, Flosulide, on Renal Plasma Flow and Glomerular Filtration Rate in Rats

Nephrotoxicity of nonsteroidal anti-inflammatory drugs is associated with other risk factors (volume-depletion) and may be secondary to functional changes mediated by the inhibition of renal cyclooxygenases. Acute anti-inflammatory doses of flosulide and indomethacin were determined on carrageenan paw edema and its effects on renal plasma flow (RPF) and glomerular filtration rate (GFR) were studied in normovolemic and hypovolemic rats. In normovolemic rats, flosulide increased RPF and GFR (25 mg/kg) and indomethacin (5–10 mg/kg) was without effect. Volume-depleted rats were obtained by oral furosemide (32 mg/kg), urinary eicosanoids were determined. After furosemide, plasma volume, RPF and GFR and PGE₂ decreased. Treatment of hypovolemic rats with flosulide (5–25 mg/kg) or indomethacin 10 mg/kg reduced RPF and GFR. Flosulide at 5 mg/kg reduced 6-keto-PGF₁ whereas at 25 mg/kg and after indomethacin at 10 mg/kg a fall in 6-keto-PGF₁ and TXB₂ appeared. Our data suggest that acute COX-2 selective inhibition may alter renal function.     

Further antinociceptive effects of myricitrin in chemical models of overt nociception in mice

The present work explored the antinociceptive effects of the flavonoid myricitrin in models of overt nociception triggered by intraplantar injection of chemical algogens into the hind paw of mice. The nociception induced by bradykinin (3 nmol/paw i.pl.) was abolished by prior treatment with myricitrin (10–100 mg/kg, i.p.) with ID₅₀ of 12.4 (8.5–18.1) mg/kg. In sharp contrast, myricitrin failed to affect the nociception elicited by prostaglandin E₂ (3 nmol/paw i.pl.). Cinnamaldehyde (10 nmol/paw i.pl.)-induced nociception was reduced by myricitrin (100 mg/kg, i.p.) and camphor (7.6 mg/kg, s.c.) in 43 ± 10% and 57 ± 8%, respectively. Myricitrin (30–100 mg/kg, i.p.) and amiloride (100 mg/kg, i.p.) inhibited nociceptive responses induced by acidified saline (pH 5/paw i.pl.), with ID₅₀ of 22.0 (16.1–30.0) mg/kg and inhibition of 71 ± 6% and 64 ± 5%, respectively. Moreover, myricitrin (10–30 mg/kg, i.p.) and ruthenium red (3 mg/kg, i.p.) significantly reduced the nociception induced by menthol (1.2 μmol/paw i.pl.) with the mean ID₅₀ of 2.4 (1.5–3.7) mg/kg and inhibition of 95 ± 3% and 51 ± 7%, respectively. In addition, myricitrin administration (30 and 100 mg/kg, i.p.) markedly reduced menthol-induced mechanical allodynia. However, myricitrin (100 mg/kg, i.p.) prevented (only in time of 60 min) cold allodynia induced by menthol. Collectively, the present results extend prior data and show that myricitrin promotes potent antinociception, an action that is likely mediated by an inhibition of the activation of nociceptors by bradykinin and TRPs agonist (i.e. cinnamaldehyde, acidified saline and menthol), probably via inhibition of PKC pathways. Thus, myricitrin could constitute an attractive molecule of interest for the development of new analgesic drugs.     

Effect of an Na+/H+ exchange inhibitor,SM-20550, on ischemic preconditioning in rabbits

The effects of SM-20550 [N-(aminoiminomethyl)-1,4-dimethyl-1H-indole-2-carboxamide methanesulfonic acid], an Na+/H+ exchange inhibitor, on ischemic preconditioning (IPC) were studied in a rabbit model of myocardial ischemia and reperfusion injury. Anesthetized rabbits underwent occlusion of the coronary artery (30 min) followed by reperfusion (5 h). In SM-20550-treated animals, SM-20550 was intravenously administered at 0.03 mg/kg or 0.1 mg/kg before ischemia (30 min). Treatment with SM-20550 at 0.03 mg/kg had a nonsignificant tendency to reduce infarct size (18%). In contrast, 0.1 mg/kg of SM-20550 significantly reduced infarct size by 62%. In animals with IPC, the condition was induced by 2 or 5 min of ischemia and 10 min of reperfusion prior to sustained ischemia (30 min). Although 5 min of IPC significantly reduced infarct size by 72%, 2 min of IPC reduced infarct size by only 27%, which was not significant. The combination of 5 min of IPC and 0.1 mg/kg of SM-20550 significantly reduced infarct size by 78%. This reduction in infarct size was similar to that produced by 0.1 mg/kg SM-20550 or 5 min of IPC alone. Moreover, the combination of 2 min of IPC and 0.03 mg/kg of SM-20550 significantly reduced infarct size by 64%, although neither 0.03 mg/kg SM-20550 nor 2 min of IPC alone reduced infarct size significantly. These results indicate that an Na+/H+ exchange inhibitor SM-20550, does not antagonize the cardioprotective effect of IPC. SM-20550 and IPC appeared to act synergistically to exert a combined cardioprotective effect.     

The role of beta-1-adrenoceptors in the renin release response to graded renal sympathetic nerve stimulation

The contribution of beta-adrenoceptor activation to renin release was examined in anaesthetized dogs using renal nerve stimulation (RNS) at different discharge rates in the presence of i.v. beta-adrenoceptor blockade. The animals were divided into 2 groups, which received either low or high level of RNS, defined by the frequency of stimulation producing decrease in renal blood flow of 5 and 50%, respectively. Low level RNS increased renin release tenfold. The renin release response was almost abolished by 0.5 mg/kg of metoprolol ordl-propranolol but unaffected by 0.5 mg/kg ofd-propranolol. The increase in renin release to high level RNS was equally reduced by 33% by 0.5 mg/kg and 2.0 mg/kg of metoprolol.dl-propranolol, 0.5 mg/kg, reduced the renin release response to about the same extent, 44%, while 2.0 mg/kg reduced it somewhat more, 59%. This was probably due to its membrane stabilizing properties asd-propranolol, 2.0 mg/kg and lidocaine 2.0 mg/kg+0.1 mgxkg^–1xmin^–1, also reduced the renin release response. These data suggest that the renin release response to low level RNS is almost completely mediated by beta-adrenoceptors which are of the beta-1 subtype. High level RNS results in a renin release, which is only partly mediated by beta-1-adrenoceptors. The remainder is apparently related to other mechanisms activated by high level RNS and is probably a consequence of the associated renal vasoconstriction.     

Immunomodulatory effect of candesartan on indomethacin-induced gastric ulcer in rats

Non steroidal anti-inflammatory drugs (NSAIDs) induce gastric mucosal lesions in part by induction of oxidative stress as well as the activation of inflammatory cells and the production of proinflammatory cytokines. In this study, we examined the protective effect of candesartan (2 and 5?mg/kg) on indomethacin-induced gastric mucosa damage. Pretreatment with candesartan for 10 days reduced significantly the ulcer index induced by indomethacin injection. The preventive index of 2?mg/kg (76.74%) was higher than that of 5?mg/kg (65.11%). Both doses of candesartan were able to reduce significantly the stomach malondialdehyde content compared to indomethacin-treated group. Myeloperoxidase, tumor necrosis factor-α, cytokine-induced neutrophil chemoattractant gastric levels were significantly reduced by 2?mg/kg of candesartan more than 5?mg/kg. The Th1 cytokine interferon γ was also significantly reduced by both doses of candesartan compared to indomethacin injected group. On the other hand, indomethacin significant decreased the anti-inflammatory cytokine IL-10 gastric level. Pretreatment with candesartan (2 and 5?mg/kg) reversed this effect. In conclusion, the present study indicates that pretreatment with candesartan, can protect against the stomach injury induced by indomethacin through its antioxidant and immunomodulatory effects.     

Depression by nicotine of pain-related nociceptive activity in the rat thalamus and spinal cord

Summary To assess the possible role of nicotinergic control in nociception and pain, experiments were carried out on rats under urethane anesthesia in which nociceptive activity was elicited by electrical stimulation of afferent C fibers in the sural nerve and recorded from single neurones in the thalamus and from ascending axons in the spinal cord. Intravenous administration of nicotine (0.01–0.5 mg/kg) depressed the nociceptive activity evoked in the thalamus and the spinal cord in a dose-dependent way. The maximum depression in thalamus and spinal cord was 40% of control activity and obtained at a dose of 0.025 mg/kg. Likewise, local administration of nicotine to the spinal cord by intrathecal injection (5, 10, and 30 g) reduced the nociceptive activity evoked in neurones of the thalamus and in ascending axons of the spinal cord, the maximum of the depression being 40% of control activity. The depressant effect of nicotine (0.05 mg/kg) was reduced by mecamylamine (1 mg/kg) but not by atropine (0.5 mg/kg). It is concluded that the antinociceptive effect of nicotine is due to a specific action of the alcaloid at the spinal level.     

Differential role of mu, delta and kappa opioid receptors in ethanol-mediated locomotor activation and ethanol intake in preweanling rats

The opioid system modulates ethanol intake and reinforcement in adult and preweanling rodents. While adult heterogeneous rats normally do not show ethanol-mediated locomotor stimulation, preweanling rats show it quite clearly. We recently observed that naloxone, a non-specific opioid antagonist, attenuated ethanol-induced locomotor activation in preweanling rats. In the present study we tested the role of specific opioid receptors (mu, delta and kappa) in ethanol-mediated locomotor stimulation and ethanol intake. In Experiment 1 13-day-old rats received naloxonazine (mu antagonist: 0, 7.5 or 15 mg/kg), naltrindole (delta antagonist: 0, 2 or 4 mg/kg) or nor-binaltorphimine (kappa antagonist: 0, 2, 4 or 8 mg/kg) before an intragastric administration of ethanol (0 or 2.5 g/kg), and subsequent locomotor activity assessment. In Experiment 2, the same opioid antagonists were administered on postnatal days 13 and 14 before consumption of ethanol (6%), saccharin (0.05%) or distilled water. In Experiment 1 only naloxonazine reduced ethanol-mediated locomotor stimulation. None of the opioid antagonists affected locomotor activity in water controls. In Experiment 2 naloxonazine and naltrindole suppressed ingestion of all the solutions tested. Similar to what has been reported in adult rodents, mu-opioid receptors seem to modulate ethanol-activating effects during early ontogeny. Hence, there seems to be a partial overlap of neurochemical mechanisms involved in the rewarding and stimulating effects of ethanol in preweanling rats. Mu-receptor antagonists reduced both ethanol-induced activity and ethanol intake, but it is unclear whether the latter effect is specific to ethanol or only a reflection of an effect on consummatory behavior generally, since mu and delta receptor antagonists also suppressed ingestion of water and sacccharin.