Mesenteric lymph reperfusion may exacerbate brain injury in a rat model of superior mesenteric artery occlusion shock

BACKGROUND:The intestinal lymphatic pathway and intestinal ischemia/reperfusion are mainly involved in mesenteric lymph duct ligation or drainage; moreover,intervention by reducing the lymph liquid reflux might relieve lung and other organ dysfunction induced by intestinal ischemia/reperfusion; however,research addressing mesenteric lymph reperfusion (MLR) and brain injury has not yet to be reported.OBJECTIVE:To observe the effect of MLR on brain tissue in a rat model of superior mesenteric artery occlusion (SMAO) shock,and to explore the molecular mechanism of MLR.DESIGN,TIME AND SETTING:A randomized,controlled,animal experiment at a neuro-pathophysiology level was performed at the Institute of Microcirculation,Hebei North University; Department of Pathophysiology,Basic Medical College; Department of Pathology,the First Hospital of Hebei North University between December 2007 and March 2009.MATERIALS:Adenosine triphosphate (ATP) standard was provided by the National Institute for the Control of Pharmaceutical and Biological Products; lactic acid (LA),superoxide dismutase (SOD),malonaldehyde (MDA),nitrogen monoxidum (NO),nitric oxide synthase (NOS),myeloperoxidase (MPO) and ATPase assay kits were provided by Nanjing Jiancheng Bioengineering Institute,China.METHODS:A total of 24 male Wistar rats were randomly divided into four groups.In the sham-surgery group (n = 6),both the mesenteric lymph duct and the superior mesenteric artery were not blocked; in the MLR group (n = 6),the mesenteric lymph duct was occluded for 1 hour followed by 2-hour reperfusion; in the SMAO group (n = 6),the superior mesenteric artery was occluded for 1 hour followed by 2-hour reperfusion; in the MLR + SMAO group (n = 6),both the mesenteric lymph duct and superior mesenteric artery were occluded for 1 hour followed by 2-hour reperfusion.MAIN OUTCOME MEASURES:Mean arterial blood pressure prior to and following ischemia/reperfusion; brain tissue morphology levels of LA,MDA,SOD,NO,NOS,MPO,ATPase and ATP following reperfusion.RESULTS:MLR did not cause changes in mean arterial blood pressure,brain tissue morphology,LA,MDA,NO,ATP,SOD,NOS,MPO and ATPase.However,SMAO caused a rapid decrease and gradual increase of mean arterial blood pressure.Neuronal necrosis,degeneration and swelling were observed in brain tissue.Contents of MDA,NO,LA and ATP as well as activities of NOS and MPO were significantly increased (P< 0.05),but activities of SOD and Na+-K+-ATPase were significantly decreased (P < 0.05).MLR aggravated neuronal damage in a rat model of SMAO shock.Following MLR,mean arterial blood pressure was significantly decreased (P < 0.05),contents of MDA and NO as well as activities of NOS and MPO were significantly increased (P <0.05),but activities of Ca2+-ATPase,Mg2+-ATPase and Ca2+-Mg2+-ATPase as well as ATP content were significantly decreased (P< 0.05).CONCLUSION:MLR aggravates brain injury in a rat model of SMAO shock,which correlates with oxygen-derived free radical injury,NO synthesis and release,sequestration of neutrophilic granulocytes,decreasing activity of cell membrane pumps and energy metabolism dysfunction.Pathogenesis of the intestinal lymphatic pathway should be thoroughly investigated to prevent ischemia/reperfusion injury.     

肠淋巴再灌注加重肠系膜上动脉闭塞性休克大鼠的脑损伤*

目的：观察肠淋巴再灌注（MLR）对肠系膜上动脉闭塞性（SMAO）休克大鼠脑组织形态学的影响；从氧自由基、一氧化氮、中性粒细胞、膜泵、能量代谢等方面揭示其机制。方法：24只Wistar雄性大鼠均分为4组：Sham组，仅麻醉与手术；MLR组，夹闭肠系膜淋巴管（ML）1h，再灌注2h；SMAO组，夹闭肠系膜上动脉（SMA）1h，再灌注2h；MLR+SMAO：夹闭ML和SMA1h，再灌注2h。于再灌注2h后，选择固定位置留取脑组织，制备病理切片，观察形态学；同时制备脑组织匀浆，用于检测LA、MDA、SOD、NO、NOS、MPO、ATPase及ATP。结果：Sham与MLR组大鼠脑组织结构基本正常；SMAO组大鼠可见神经元有坏死、变性，偶见肿胀；MLR+SMAO组神经元损伤情况较SMAO组重。MLR与Sham组脑组织匀浆各项指标均无统计学差异；SMAO与MLR+SMAO组脑匀浆MDA、NO、LA含量、NOS与MPO活性均显著高于MLR与Sham组，且MLR+SMAO组脑匀浆MDA、NO含量、NOS与MPO活性均显著高于SMAO组；SMAO组脑匀浆SOD、Na+- K+-ATPase活性显著低于Sham与MLR组、Mg2+-ATPase活性、ATP含量显著低于MLR组；MLR+SMAO组脑匀浆的SOD、Na+- K+-ATPase、Ca2+-ATPase、Mg2+-ATPase及Ca2+-Mg2+- ATPase活性均显著低于Sham与MLR组，且Ca2+-ATPase、Mg2+-ATPase及Ca2+-Mg2+-ATPase活性、ATP含量均显著低于SMAO组。结论：MLR加重SMAO休克大鼠的脑损伤，其机制可能与MLR加重或增加脑组织氧自由基损伤、NO合成与释放、中性粒细胞扣押、能量代谢障碍及降低脑组织细胞膜泵活性等因素有关。     

D-dimer as a marker for early diagnosis of acute mesenteric ischemia

INTRODUCTION: Acute obstruction of mesenteric artery generally has an unfavorable prognosis because of late diagnosis. In this study we evaluated the diagnostic value of plasma D-dimer level as an early indicator in acute mesenteric ischemia in rats caused by ligation of superior mesenteric artery. MATERIALS AND METHODS: Twenty-eight mature male Wistar rats were used in the study. These were divided into four groups, each consisting of seven rats. In group I, after performing a simple laparotomy, blood was sampled at minute 30. In group II, first the superior mesenteric artery was ligated, and blood samples were taken at the 30th minute. Group III consisted of rats undergoing a simple laparotomy and blood samples were taken 7 h later. From the subjects in group IV blood samples were obtained 7 h after the ligation of their superior mesenteric artery. RESULTS: Plasma D-dimer levels of the ligated groups were significantly higher both at the 30th minute and the 7th hour compared to the levels of those having undergone simple laparotomies (p<0.002). Likewise, this level was higher in the 7th hour blood samples of the ligated group than in the 30th minute (p<0.008). CONCLUSIONS: In rats undergoing acute mesenteric ischemia by ligation of superior mesenteric artery, plasma D-dimer levels increase with the duration of the intestinal ischemia period. This finding suggests that the measurement of the plasma D-dimer levels might be a useful tool for the early diagnosis of acute mesenteric obstruction.     

白果内酯对高血糖大鼠脑缺血再灌注损伤的保护作用

目的 观察白果内酯对高血糖大鼠脑缺血再灌注损伤的保护作用及其可能机制.方法 采用50%的葡萄糖溶液腹腔注射(6 ml/kg)建立急性高血糖模型.采用线栓法建立大鼠脑缺血再灌注模型,按随机数字表方法将40只大鼠分为高血糖假手术组(假手术组),高血糖+缺血再灌注损伤组(模型组),高血糖+缺血再灌注损伤+白果内酯组(白果内酯组),白果内酯分三个剂量组(2.5,5,10 mg/kg),每组各8只.白果内酯组于术前3 d连续给予白果内酯腹腔注射,术前1 h再给予腹腔注射1次.脑缺血2 h,再灌注24 h后行神经功能缺损评分、脑梗死体积及脑含水量测定,同时测定脑组织中水通道蛋白-4(AQP4)mRNA的表达,超氧化物歧化酶(SOD)的活力,计算脑组织中丙二醛(MDA)的含量及去甲肾上腺素(NE)、多巴胺(DA)和5-羟色胺(5-HT)的表达.结果 白果内酯(5,10 mg/kg)组大鼠与模型组相比,神经功能缺损评分下降,脑梗死体积缩小,脑含水量降低,缺血侧脑组织中AQP4 mRNA的表达下调,SOD活力提高,MDA含量减低,NE、DA及5-HT的含量增加,差异均有统计学意义(P<0.05).结论 白果内酯对高血糖条件下的局灶性脑缺血再灌注损伤具有一定的保护作用.     

Reflex effects on renal nerve activity and renal vascular tone during occlusion of superior mesenteric artery in anesthetized dogs

This study was designed to evaluate the contribution of the systemic baroreceptor reflex on renal nerve activity (RNA) and renal vascular resistance (RVR) during occlusion of the superior mesenteric artery (SMAO) in anesthetized dogs. Animals were divided into two groups; RVR evaluated group and RNA measured group. For evaluation of changes in RVR, the left kidney was perfused at a constant flow with heparinized blood by using a pulsatile roller pump. Renal perfusion pressure, arterial blood pressure and heart rate were measured simultaneously. During SMAO, MAP and RVR increased significantly in animals with intact systemic baroreceptors. After combined denervation of the carotid sinus and vagal nerves, a significant enhancement of this RVR response during SMAO occurred and the level of changes in RVR were significantly greater than those in animals with an intact neuraxis. In the RNA measured group, renal sympathetic nerve activity, arterial blood pressure and heart rate were measured simultaneously before and during SMAO. During SMAO, MAP and RNA increased significantly in animals with intact systemic baroreceptors. These MAP and RNA responses to SMAO were significantly enhanced in animals with combined denervation of the carotid sinus and vagal nerves. These results indicate that SMAO evokes an increase in arterial blood pressure, renal sympathetic nerve activity and renal vascular resistance. The reflex increase in renal nerve activity and renal vascular tone during SMAO is modified and minimized by an activation of systemic baroreceptors.     

Variations of monoamines and their metabolites in the human brain putamen

The levels of the monoamines dopamine (DA), serotonin (5-HT) and norepinephrine (NE) and the monoaminergic metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were measured with HPLC-ECD in 42 samples from human brain putamen. The influence of gender and of age was investigated and correlations between the monoamines were established. The DAergic system shows a significant difference between males and females, with females having lower DA and higher DOPAC levels and a higher DOPAC/DA ratio than males. No gender-related differences of 5-HT and its metabolites were observed, nor of NE. Three different age groups (group 1: 0–9.9 years; group 2: 10–59.9 years; group 3: 60 years and older) were defined according to previous studies on ontogenesis and senescence in human brain. An increase in 5-HT levels, decrease in 5-HIAA levels a d a decrease in the 5-HIAA/5-HT ratio were observed after the first decade of life. Changes in the DAergic system were seen in senescence, with decreasing DA levels and an increase in the HVA/DA ratio. DOPAC, HVA and the DOPAC/DA ratio are unaffected. NE is similar in all age groups. The analysis of the relation of the levels of the three monoamines proved a strong correlation between the DAergic and 5-HTergic systems. The nature of this relationship might have an impact on neuro-psychiatric disorders and brain function.     

脑缺血再灌注肾脏损伤老龄大鼠的单胺类神经递质和神经肽的变化意义

目的：从多巴胺(DA)、去甲肾上腺素(NE)、肾上腺素(E)、内皮素(ET)和降钙素基因相关肽(CGRP)的变化方面揭示老龄大鼠脑缺血再灌注肾脏损伤机制。方法：青年(5月龄)和老龄(20月龄以上)大鼠均分为模型组和正常对照组，观察大鼠全脑缺血30min再灌注60min后肾脏组织形态和肌酐(Cr)、尿素氮(Bun)、DA、NE、E、ET、CGRP含量的变化。结果青年和老龄模型组大鼠肾脏组织形态和功能均出现明显的病理改变，交感-肾上腺系统兴奋性增强，老龄模型组较青年模型组严重。青年对照组血浆中CGRP高于青年模型组和老龄对照组。老龄模型组血中ET高于老龄对照组和青年模型组。结论：大鼠脑缺血再灌注肾脏损伤与交感-肾上腺系统兴奋性增强以及CGRP与ET的平衡失调有关，由于增龄的变化使老龄大鼠脑缺血再灌注肾脏损伤程度和这些病理变化尤为明显并具有一定特点。     

帕罗西汀与阿米替林联用对卒中后抑郁大鼠额前皮质区与海马区的单胺类递质、脑源性神经营养因子水平的改变

目的 探究帕罗西汀与阿米替林联用对脑卒中后抑郁(post-stroke depression,PSD)大鼠额前皮质区与海马区的单胺类递质、脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)水平的影响.方法 SD大鼠被分为4组,即对照组、PSD组、帕罗西汀(Par)组和帕罗...     

Brain norepinephrine reductions in soman-intoxicated rats: association with convulsions and AChE inhibition, time course, and relation to other monoamines.

The organophosphate chemical nerve agent, soman, causes convulsions, neuropathology, and, ultimately, death. A major problem in treating soman intoxication is that peripherally acting pharmacological agents which prevent death do not prevent seizures. Although a primary cause of these symptoms is the excess of acetylcholine which follows acetylcholinesterase (AChE) inhibition, centrally acting muscarinic blockers, such as atropine, alleviate, but do not block, the convulsive actions of soman. Moreover, there is a relatively weak relationship between CNS reductions of AChE and the incidence of convulsions. There is evidence suggesting that soman intoxication stimulates the release of norepinephrine (NE) in the brain. Recent evidence has implicated NE in the induction and/or maintenance of seizures. Thus, in the present study the relations among soman-induced convulsions, AChE inhibition, and brain NE and other monoamine changes were examined. The time course of brain NE recovery was also determined. Rats were injected (im) with a single dose (78 micrograms/kg) of soman. At this dose 68% of the injected rats developed convulsions. Both convulsive and nonconvulsive rats were sacrificed between 1 and 96 h following soman injection and NE levels in the rostral forebrain and olfactory bulb were determined by HPLC with electrochemical detection. In all convulsive rats NE levels declined substantially. Forebrain NE levels were decreased by 50% at 1 h and 70% at 2 h following soman injection. Recovery of NE began at 8 h and was complete by 96 h following soman administration. Although nonconvulsive rats showed other signs of intoxication, NE levels in these rats were unchanged. Dopamine (DA) and serotonin (5-HT) levels were not significantly affected in either convulsive or nonconvulsive rats. However, 5-hydroxyindoleacetic acid, the major metabolite of 5-HT, and homovanillic acid and 3,4-dihydroxyphenylacetic acid, the two major metabolites of DA, were increased significantly in the forebrain of convulsive, but not nonconvulsive rats, indicating an increase in 5-HT and DA turnover. However, in contrast to the abrupt decline in NE, these increases in DA and 5-HT metabolites were slow and progressive. Taken together, the present results and other recent findings suggest that rapid, sustained NE release could play a role in the induction and/or maintenance of soman-induced convulsions, whereas increased release of 5-HT and DA may be a consequence of seizures. Further investigation of the role of NE in soman-induced convulsions may lead to improved treatment of soman intoxication and a better understanding of the role of NE in other forms of seizures, including human epilepsy.     

Effects of low molecular weight heparin-superoxide dismutase conjugate on serum levels of nitric oxide, glutathione peroxidase, and myeloperoxidase in a gerbil model of cerebral ischemia/reperfusion injury

BACKGROUND： Several studies have demonstrated that low molecular weight heparin-superoxide dismutase （LMWH-SOD） conjugate may exhibit good neuroprotective effects on cerebral ischemia/reperfusion injury though anticoagulation, decreasing blood viscosity, having anti-inflammatory activity, and scavenging oxygen free radicals. OBJECTIVE： To investigate the intervention effects of LMWH-SOD conjugate on serum levels of nitric oxide （NO）, glutathione peroxidase （GSH-Px）, and myeloperoxidase （MPO） following cerebral ischemia/reperfusion injury. DESIGN, TIME AND SETTING： A randomized, controlled, and neurobiochemical experiment was performed at the Institute of Biochemical Pharmacy, School of Pharmaceutical Sciences, Shandong University between April and July 2004. MATERIALS： A total of 60 Mongolian gerbils of either gender were included in this study. Total cerebral ischemia/reperfusion injury was induced in 50 gerbils by occluding bilateral common carotid arteries. The remaining 10 gerbils received a sham-operation （sham-operated group）. Kits of SOD, NO, and MPO were sourced from Nanjing Jiancheng Bioengineering Institute, China. LMWH, SOD, and LMWH-SOD conjugates were provided by Institute of Biochemistry and Biotechnique, Shandong University, China. METHODS： Fifty successful gerbil models of total cerebral ischemia/reperfusion injury were evenly randomized to five groups： physiological saline, LMWH-SOD, SOD, LMWH ＋ SOD, and LMWH. At 2 minutes prior to ischemia, 0.5 mL/65 g physiological saline, 20 000 U/kg LMWH-SOD conjugate, 20 000 U/kg SOD, a mixture of SOD （20 000 U/kg） and LMWH （LMWH dose calculated according to weight ratio, LMWH： SOD = 23.6：51）, and LMWH （dose as in the LMWH ＋ SOD group） were administered through the femoral artery in each above-mentioned group, respectively. MAIN OUTCOME MEASURES： Serum levels of NO, MPO, and GSH-Px. RESULTS： Compared with 10 sham-operated gerbils, the cerebral ischemia/reperfusion injury gerbils exhibited decreased s     

Age Related Effects of Levodopa on Rat Brain Striatal Acetylcholinesterase

Long-term treatment of Parkinson’s disease (PD) with levodopa is accompanied by dyskinesia. Alteration in striatal acetylcholine signaling is partly responsible, but the involved mechanisms have yet to be determined. This study aimed to compare repeated levodopa treatment on dopamine (DA) content and acetylcholinesterase (AChE) activity in the young and old rat brain striatum. Male Wistar rats (3 and 30 months old) were injected with a mixture of levodopa + carbidopa (10 + 1 mg/kg). Control animals received normal saline only. Rats were killed and brain striatum was homogenized and centrifuged at 4°C. AChE activity was assayed in the supernatant and DA was extracted from the homogenate and measured by high performance liquid chromatography with electrochemical detection. The levels of DA in young and aged rats were 53.1 ± 4.5 and 28.4 ± 3.1 nmol/ g wet weight tissue respectively. AChE activity in corresponding supernatant was 32.4 ± 2.7 and 58.1 ± 3.3 μmol/min/mg protein. A single dose of the drug mixture increased DA content and decreased AChE activity in both ages. When the drug mixture was injected daily for a period of 30 days, a lower DA content and a higher AChE activity were observed, though the changes were more pronounced in the aged animals. The result indicates that long-term treatment with levodopa + carbidopa in aged rat renders a dramatic rise in the striatal AChE, leading to imbalance ACh/DA levels in the striatum. It is concluded that AChE might be considered as a therapeutic target for combating levodopa-induced dyskinesia affecting PD patients.     

MONOAMINES (SEROTONIN AND CATECHOLAMINES) AND THEIR DERIVATIVES IN INFANTILE AUTISM: AGE-RELATED CHANGES AND DRUG EFFECTS

Levels of dopamine (DA) and its derivatives homovanillic acid (HVA), 3-4 dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3MT) and norepinephrine+epinephrine (NE + E), and serotonin (5HT) and its derivative 5-hydroxyindolacetic acid (5HIAA) were determined from the urine of 156 autistic children aged two to 12 years 6 months, and compared with those of age-matched mentally retarded non-autistic and normal controls. Very significant group and age effects were found for DA, HVA, 3MT, NE + E and 5HT. High HVA, 3MT, NE + E and 5HT levels were found in autistic and non-autistic children. The DA, HVA, 3MT, NE + E, 5HT and 5HIAA levels decreased significantly with age in the three groups. Significantly decreased levels of DA and HVA were observed in autistic children on haloperidol, compared with non-medicated autistic children. The results are discussed in relation to the hypothesis of a maturation defect of monoaminergic systems in autism.     

立体定向毁损大鼠杏仁核及隔核对脑内单胺类递质含量的影响

目的 :探讨杏仁核及隔核毁损后AMP模型大鼠脑内单胺类递质含量的变化。方法 :经腹腔注射苯丙胺 (amphetamine ,AMP)制作精神分裂症动物模型 ,用立体定向技术电极毁损大鼠杏仁核及隔核 ,采用荧光分光光度法和放射免疫法测定大鼠前额叶、间脑和脑干多巴胺 (DA)、5 羟色胺 ( 5 HT)和去甲肾上腺素 (NE)的含量。结果 :杏仁核及隔核毁损组前额叶DA低于模型组 (P <0 0 1) ,5 HT、NE均高于模型组 (P <0 0 1) ;杏仁核及隔核毁损组间脑DA、NE均低于模型组 (P <0 0 1) ,5 HT高于模型组 (P <0 0 1) ;脑干DA、NE均低于模型组 (P <0 0 1) ,5 HT高于模型组 (P <0 0 1)。结论 :AMP模型大鼠前额叶和脑干DA含量增高、5 HT和NE含量下降 ,间脑DA、NE含量增高、5 HT含量下降 ,立体定向毁损杏仁核及隔核能够改变脑内单胺类递质的水平。     

Therapeutic effect of post-ischemic hypothermia duration on cerebral ischemic injury

OBJECTIVE: To study the efficacy of post-ischemic mild brain hypothermia lasting for different time intervals on cerebral ischemic reperfusion injury. METHOD: Male Sprague-Dawley rats were divided into a sham-operated group, normothermia (37-38 degrees C) ischemia group and mild hypothermia (31-32 degrees C) group. The last group was subdivided into four groups: 30 minute hypothermia plus 210 minute normothermia, 60 minute hypothermia plus 180 minute nomothermia,120 minute hypothermia plus 120 minute normothermia, and 240 minute hypothermia (n=8). Global cerebral ischemia was established using the Pulsinelli four-vessel occlusion model. Brain tissue was collected following a 20 minute cerebral ischemia and 240 minute reperfusion, and was used to measure the levels of glutamate (Glu), aspartate (Asp), glycine (Gly), gamma-aminobutyric acid (GABA), dopamine (DA), norepinephrine (NE), serotonin(5-HT) and hydroxyindoleacetic acid (5-HIAA), nitrite (NO(2)), endothelin-1 (ET(1)), tumor necrosis factor alpha(TNFalpha) and interleukin-1beta (IL-1beta). Serum was collected to measure the levels of lactate dehydrogenase (LDH), aspartate aminotransferase (AST), creatine kinase (CK) and its brain band isoenzyme (CK-BB). RESULTS: Hypothermia lasting for 60-240 minutes delayed the decrease in these amino acids, postponed the decrease in DA, NE and 5-HT and increase in hydroxyindoleacetic acid (5-HIAA), and decreased the levels of IL-1beta, TNFalpha, ET(1) and NO(2) in brain tissue. Hypothermia also decreased the levels of LDH, AST, CK and CK-BB in serum as compared to normothermia group (p<0.05 or p<0.01). Hypothermia lasting for 30 minutes delayed the decreases in these amino acids and 5-HT and increase in 5-HIAA in brain tissue (p<0.05), but failed to influence the levels of IL-1beta, TNFalpha, ET(1) and NO(2) in brain tissue and the amounts of LDH, AST, CK and CK-BB in serum as compared to normothermia ischemia group (p>0.05). CONCLUSIONS: Post-ischemic mild brain hypothermia can significantly suppress the excessive release of amino acids, monoamine neurotransmitters and inflammation response in ischemic tissue. It can also stabilize the function of the cell membrane, which is associated with the mechanism of cerebral protection by mild hypothermia. These results suggest that mild hypothermia should be applied immediately after ischemia and last for more than 60 minutes in order to obtain neuroprotective effects.     

Parameters of cholinergic neurotransmission in the thalamus in Parkinson's disease and Alzheimer's disease

Loss of cholinergic cells in the basal forebrain is associated with commensurate reductions in cortical acetylcholine-related enzyme activities in both Alzheimer's disease (AD) and Parkinson's disease (PD). Nerve cell loss from the cholinergic pontine tegmental nuclei also occurs. As the latter nuclei project to the diencephalon, we used frozen tissue from 5 controls, 5 PD and 5 AD cases to study the distribution of ChAT, AChE and [3H]nicotine binding in the thalamus and subthalamic nucleus. The anterior nuclear group and the mediodorsal nucleus showed high activities of ChAT and AChE together with relatively high levels of [3H]nicotine binding. The centromedian nucleus and subthalamic nucleus contained equally high levels of ChAT but negligible levels of [3H]nicotine binding. There were no significant changes in the levels of ChAT, AChE and nicotine binding in the PD and AD groups indicating that involvement of the pedunculopontine tegmental nucleus is likely to be a secondary retrograde phenomenon rather than part of a systematic cholinergic fibre degeneration.     

Decreased Dopamine and Increased Norepinephrine Levels in the Spontaneously Epileptic Rat, a Double Mutant Rat

Summary: Dopamine (DA) and norepinephrine (NE) brain levels and turnover rate were examined in the spontaneously epileptic rat (SER: zi/zi, tm/tm), a double mutant rat obtained by mating tremor heterozygotes (tml +) with zitter homozygotes associated with epileptic seizures composed of spontaneously occurring tonic convulsion and absence-like seizure. DA and NE levels were also determined in age-matched male zitter, tremor and Kyo:Wistar rats. DA levels in caudate nucleus were significantly lower in adult age (10–12 weeks) SER, which showed epileptic seizures, and zitter rats than in adultKyo:Wistar and tremor rats. DA levels in other areas such as thalamus-hypothalamus, midbrain, and ponsmedulla were not different among SER, zitter, tremor, and Kyo:Wistar rats at age 10–12 weeks. Except in cerebral cortex and hippocampus, there were no differences in brain DA levels between young seizure-free SER (age 5 weeks) and young Kyo:Wistar rats. Furthermore, the turnover rate of DA was significantly lower in caudate nucleus of adult SER than of Kyo:Wistar rat, whereas in pons-medulla there was no difference between the two strains. In contrast, NE levels in the thalamushypothalamus, midbrain, cerebellum and pons-medulla were higher in SER and zitter rats at age 10–12 weeks than in age-matched tremor and Kyo:Wistar rats. Higher NE levels were also observed in midbrain, cerebellum, and pons-medulla of young SER as compared with young Kyo:Wistar rats. Turnover rates of NE were significantly lower in pons-medulla and cerebellum of the adult SER than in those of Kyo:Wistar rat. In genetic studies using backcross mating of zitter and BN rats, decreased DA was also observed in caudate nucleus of backcrossed zitter rats as compared with BN, F₁, and zitter wild-type rats. Increased NE contents were observed in the thalamus-hypothalamus, midbrain, and pons-medulla of zitter rats as compared with other rats, although the increase was also observed in the thalamus-hypothalamus and midbrain of zitter wild-type rats. Results suggest that a decrease in DA in caudate nucleus and an increase in NE in midbrain and pons-medulla are due to the homozygous zi gene, and together with previous findings, suggest that the decrease in DA, although probably not the only cause, facilitates appearance of tonic and absence-like seizures by lowering the threshold triggering such seizures.     

Effects of transient forebrain ischemia and reperfusion on function of dopaminergic neurons and dopamine reuptake in vivo in rat striatum.

To clarify functional changes of dopaminergic neurons and dopamine (DA) reuptake during and after ischemia, extracellular DA levels in striatum were determined using in vivo brain microdialysis in a 4-vessel occlusion model of male Wistar rats with and without pharmacological interventions. Without interventions, the extracellular DA levels markedly increased during ischemia, but upon reperfusion, rapidly returned to control level. Infusion of tetrodotoxin, a blocker of voltage-dependent Na+ channels, was without effect on the DA surge during ischemia, but decreased the DA levels after reperfusion to the same extent as in control rats. Pretreatment with nomifensine, an inhibitor of DA reuptake, was also without effect on the surge, but reduced the rate of DA decline after reperfusion to one-fifth of the rate without the pretreatment. When nomifensine was administered 40 min after reperfusion, extracellular DA levels increased to the same extent as in control rats. Infusion of high K+ 1 h after reperfusion induced a smaller increase in extracellular DA levels than that in control rats. It took 96 h for this reduced response to high K+ stimulation to recover after reperfusion. These results suggest that the DA surge during ischemia is mainly derived from action potential-independent DA release (means dysfunction of dopaminergic neurons), although activity of DA reuptake is completely inhibited. After reperfusion, the basal function of dopaminergic neurons and activity of DA reuptake rapidly recover, but the neurons are functionally disturbed to release less DA in response to a given stimulus for several days.     

Age-related alteration in catecholamine activity within microdissected brain regions of ovariectomized fischer 344 rats

The effects of increasing age on catecholamine (CA) metabolism in microdissected brain regions and on serum and pituitary hormone levels were examined in ovariectomized Fischer 344 rats. Young (4 to 5 months old) and middle-aged (9 to 10 months old) normally cycling and old repeated pseudopregnant rats (21–22 months old, PP) were ovariectomized to eliminate the complicating effects of cyclic gonadal steroid fluctuations. CA metabolism was examined 2 weeks later. To determine CA turnover rates, each agegroup was subdivided into three groups, which were killed by decapitation 0, 45, or 90 min after administration of α-methyl-para-tyrosine (α-mpt). Dopamine (DA) and norepinephrine (NE) concentrations were determined in microdissected brain regions by radioenzymatic assay, and turnover rates were estimated. Steady-state concentrations of NE were not altered in middle-aged rats, but NE turnover rates increased in middle-aged rats in five of the six areas examined. While NE concentrations did not change with age in the median eminence (ME), NE turnover rates increased significantly in the two older age groups. These data indicate that the age-related decline in NE concentrations in several ventral diencephalic nuclei is preceded by a period of hyperactivity in noradrenergic neurons. DA concentrations were generally decreased in most areas examined in old versus young rats, with dramatic DA depletions (42–78%) observed in five regions. However, no consistent relationship between DA concentrations and turnover rates was seen either in regions with stable DA levels or in those which showed an age-associated decrease in DA concentrations. In the ME, a 42% decline in DA concentration was associated with an increase in the DA turnover rate in the oldest group of rats. Serum luteinizing hormone (LH) levels were similar in all three age groups of ovariectomized rats, while serum prolactin was elevated four-fold in old compared to younger animals. These data indicate that a complex pattern of regional alterations in CA metabolism accompanies the aging process and these may be related to the pseudopregnant state and hormone secretory capacity of aging Fischer 344 rats.     

Infusion of a monoamine oxidase inhibitor into the locus coeruleus can prevent stress-induced behavioral depression

Behavioral depression produced by exposing animals to a stressor that they cannot control (uncontrollable shock) was reversed by infusion of the monoamine oxidase (MAO) inhibitor pargyline into the locus coeruleus (LC) region of the brain stem. Following exposure to uncontrollable shock, rats were infused through bilateral cannulas implanted in the LC region with either pargyline or vehicle. At 110 min after infusion, animals were tested for behavioral activity in a swim tank. Immediately following the behavioral test, animals were sacrificed for determination of the monoamines [norepinephrine (NE), dopamine (DA), serotonin (5-HT)], as well as 5-hydroxy-indoleacetic acid (5-HIAA) in various brain regions. The results showed that animals exposed to uncontrollable shock and then infused with vehicle exhibited significantly less activity in the swim test than animals not exposed to shock and similarly infused with vehicle; thus, the usual behavioral depression following exposure to uncontrollable shock was observed. On the other hand, shocked animals infused with pargyline did not show reduced activity in the swim test. Unshocked animals infused with pargyline showed no more activity than did shocked animals infused with pargyline or unshocked animals infused with vehicle, which demonstrated that the infusion of pargyline into shocked animals did not eliminate the shock-induced depression of activity simply by generally stimulating motor activity. Measurement of the concentration of NE, DA, 5-HT, and 5-HIAA present in seven brain regions at the conclusion of the swim test showed that pargyline infusion into the LC eliminated the large depletion of NE in the LC that is normally observed after exposure to uncontrollable shock while having no effect on NE levels in the other brain regions examined. The level of 5-HT in the LC was also raised by infusion of pargyline into the LC, but again, there was no effect of pargyline infusion on 5-HT levels in any of the other brain regions. In conclusion, infusion of pargyline into the LC region of the brain eliminated both the large depletion of NE in the LC region and the behavioral depression that otherwise results from exposure of animals to uncontrollable shock.     

Feline islands of Calleja complex: II. Cholinergic and cholinesterasic features

Histochemical analyses demonstrated that the islands of Calleja complex (ICC) in the cat is exceptionally rich in choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). Both enzymes are found in neuropil throughout the complex, as well as in a subset of the satellite neurons accompanying Callejal islands. Lateromedial changes in these cholinergic and cholinesterasic tissue elements were consistent with our previous finding that the feline ICC is cytoarchitecturally divided into five successively more medial types of island-satellite cell ensembles or units. In particular, satellite neurons reactive for ChAT and AChE diminished progressively in size and increased steadily in number from the most lateral to the most medial units. A concomitant increase in neuropil levels of both enzymes suggested that the strong cholinergic innervation of the feline ICC is at least partially derived from satellite cells. This possibility gained further credibility from the additional observation that very fine processes from some ChAT and AChE satellite neurons projected into the terminal-like cholinergic field permeating the granular Callejal islands. The granule cells themselves lacked ChAT and (apart from potentially artifactual cases) AChE, as did adjoining groups of dwarf cells and small pyramidal like neurons. The cholinergic and cholinesterasic satellite neurons were preferentially located above tubercular Callejal islands and in otherwise cell-poor spaces within the isla magna. Such neurons appeared to be isodendritic: they commonly had ovoidal somata with one or two processes lacking enzyme-reactive spines. Depending on the type of ICC unit involved, their mean soma length ranged from 15 to 24 micron, all but the largest of which was distinctly smaller than that of ChAT and AChE cells in striatal or basal nuclear structures. Not all the cholinesterase neurons in the feline ICC are cholinergic, judging from the finding that there are a significantly greater number of satellite neurons containing AChE than ChAT. Three cholinergic features of the feline ICC are especially noteworthy. First, each of the island-satellite cell ensembles in the complex is unified by AChE neuropil often denser than that of adjacent striatal areas. Second, cholinergic neuropil is exceptionally dense in the isla magna and in a subpial band under medial Callejal islands. Third, ChAT neurons in the isla magna are among the smallest cholinergic cells found in the brain.