Neurotransmitter uptake in various brain regions of chronically morphinized rats

Rats were long-term morphine-intoxicated by a fluid-diet model ensuring an equal nutrient intake in morphinized and control rats. Uptake of neurotransmitters and D-ala²-met⁵-enkephalinamide (Enk) was studied in the particulate fractions (obtained at 10,000g) from well defined brain regions of long-term intoxicated and morphine withdrawn rats. In control animals the accumulation of [³H]glutamate and [³H]-aminobutyric acid (GABA) reached the highest tissue/medium (T/M) ratio values, 30–120, in the regions studied while monoamine T/M values were 2–10. No active uptake of [³H]Enk could be demonstrated. Striatum showed the most evident modifications in neurotransmitter uptake. In this region the equilibrium T/M ratio for [³H]glutamate and [³H]GABA was significantly lower in intoxicated rats versus controls. Moreover, the T/M ratio for [³H]5-hydroxytryptamine (5-HT) was lower, while that for [³H]dopamine (DA) was higher in abstinent rats in comparison with the controls. [³H]glutamate and [³H]GABA uptakes were also significantly lower, respectively, in frontal cortex, hippocampus and brain stem in intoxicated rats, while [³H]5-HT uptake was significantly lower in hypothalamus after morphine withdrawal. The possible involvement of the endogenous opioid system in the etiology of the alterations is discussed.     

Development of liver glycogen reserves in rats subjected to chronic alcoholic intoxication]

Literature offers many but very different informations about the effects of alcohol on the hepatic carbohydrates metabolism. Therefore we have tried to observe, in process of time, the evolution of the hepatic glycogen reserves on rats intoxicated by ethanol 40% during variable durations. Stuffing is made by oesophageal way at the rate of 6,4 g/kg/day. During this period of poisoning, we note a significant increasing of the hepatic glycogen reserves.     

Neurotransmitter mediation of morphine hypothermia in rats.

Subcutaneous (sc) injections of morphine (10 mg/kg) caused transient falls in body temperature of rats. The hypothermic responses to morphine were inhibited by the prior intracerebroventricular (icv) administration of methysergide or phentolamine. Methysergide treatment also prevented hypothermic responses to icv 5-hydroxytryptamine (5-HT), but not responses to icv norepinephrine or dopamine. Phentolamine inhibited responses to icv norepinephrine and dopamine, but not to 5-HT. Haloperidol, which inhibited responses to icv dopamine, did not alter the hypothermia induced by sc or icv morphine. The results indicate that both 5-HT and norepinephrine participate as central mediators of morphine-induced hypothermia.     

Changes in the aminopeptidase activity in the brain neurons of rats subjected long-term to alcoholic intoxication

A histochemical investigation was made of aminopeptidase activities using L-leucine-beta-naphthylamide and D, L-alanine-beta-naphthylamine as respective substrates in the rat's sensomotor cortex neurons during the period of ethanol withdrawal after a prolonged alcohol intoxication. Alcohol intoxication of the rat continued for 8 months. Different dynamics of aminopeptidase activities was shown depending on the substrate used during ethanol withdrawal. The results are discussed from the point of view of the existence of multiple forms of aminopeptidase in the brain and of their involvement in protein metabolism in pathological states.     

Lipid peroxidation and antioxidant systems in the blood of young rats subjected to chronic fluoride toxicity

Wistar albino rats were exposed to 30 or 100 ppm fluoride in drinking water during their fetal, weanling and post-weaning stages of life up to puberty. Extent of lipid peroxidation and response of the antioxidant systems in red blood cells and plasma to prolonged fluoride exposure were assessed in these rats in comparison to the control rats fed with permissible level (0.5 ppm) of fluoride. Rats treated with 100 ppm fluoride showed enhanced lipid peroxidation as evidenced by elevated malondialdehyde (MDA) levels in red blood cells but, 30 ppm fluoride did not cause any appreciable change in RBC MDA level. 30 ppm fluoride-intake resulted in increased levels of total and reduced glutathione in red blood cells and ascorbic acid in plasma while 100 ppm fluoride resulted in decreases in these levels. The activity of RBC glutathione peroxidase was elevated in both the fluoride-treated groups, more pronounced increase was seen with 100 ppm. Reduced to total glutathione ratio in RBC and uric acid levels in plasma decreased in both the groups. RBC superoxide dismutase activity decreased significantly on high-fluoride treatment. These results suggest that long-term high-fluoride intake at the early developing stages of life enhances oxidative stress in the blood, thereby disturbing the antioxidant defense of rats. Increased oxidative stress could be one of the mediating factors in the pathogenesis of toxic manifestations of fluoride.     

Liver collagen of rats submitted to chronic intoxication with acetaldehyde

It was found that chronic intoxication of rats with acetaldehyde results in a distinct, progressive increase of 5-³H-proline incorporation into collagen synthesized by liver. At the same time biosynthesis of other proline-containing (noncollagenous) proteins does not change significantly. On the other hand the collagen content in the rat liver did not increase in the early stage of acetaldehyde administration, but increased when acetaldehyde feeding was continued for 6 months. About 40% increase of total collagen content was found in livers of the intoxicated animals. All the investigated collagen types (I, III, IV and V) grew in the same degree. No changes in proportional relationships between collagens of different types were found.     

Neurotransmitter accumulation and calcium-dependent release from different regions of rat brain.

High affinity accumulation and calcium-dependent release of ³H-NE, ³H-dopamine, ¹⁴C-GABA and ¹⁴C-choline/ACh were investigated in 12 regions of the rat brain. Regional differences in accumulation and fractional calcium-dependent release were observed for all four substances. The corpus striatum exhibited particularly high accumulation values and high release rates for all four substances. Caudal structures exhibited low accumulation and release values. The differences are discussed in terms of possible differences in neurotransmitter dynamics in the different regions.     

Acetylcholinesterase activity in brain slices of rats subjected to cooling

The acetylcholinesterase (AChE) activity is studied in rat slices of the cerebral cortex, corpus striatum, hypothalamus and medulla oblongata of rats during hypothermia (20 degrees C) and also 1 and 7 days after the posthypothermal period. Cooling of animals down to 20 degrees C is accompanied by an increase in the AChE activity in the brain both under incubation temperature of 20 degrees and 37 degrees C. Under prolonged hypothermia the AChE activity in the investigated brain regions, except for corpus striatum, returns to the control level. By the 7th day of posthypothermal period the AChE activity in corpus striatum, hypothalamus and medulla oblongata does not restore completely. The most substantial changes in the AChE activity both under hypothermia and posthypothermal period occur in corpus striatum, which obviously reflects its complicated functional role.     

Cocaine abusers show a blunted response to alcohol intoxication in limbic brain regions

Cocaine and alcohol are frequently used simultaneously and this combination is associated with enhanced toxicity. We recently showed that active cocaine abusers have a markedly enhanced sensitivity to benzodiazepines. Because both benzodiazepines and alcohol facilitate GABAergic neurotransmission we questioned whether cocaine abusers would also have an enhanced sensitivity to alcohol that could contribute to the toxicity. In this study we compared the effects of alcohol (0.75 g/kg) on regional brain glucose metabolism between cocaine abusers (n = 9) and controls (n = 10) using PET and FDG. Alcohol significantly decreased whole brain metabolism and this effect was greater in controls (26+/-6%) than in abusers (17+/-10%) even though they had equivalent levels of alcohol in plasma. Analysis of the regional measures showed that cocaine abusers had a blunted response to alcohol in limbic regions, cingulate gyrus, medial frontal and orbitofrontal cortices. CONCLUSIONS: The blunted response to alcohol in cocaine abusers contrasts with their enhanced sensitivity to benzodiazepines suggesting that targets other than GABA-benzodiazepine receptors are involved in the blunted sensitivity to alcohol and that the toxicity from combined cocaine-alcohol use is not due to an enhanced sensitivity to alcohol in cocaine abusers. The blunted response to alcohol in limbic regions and in cortical regions connected to limbic areas could result from a decreased sensitivity of reward circuits in cocaine abusers.     

Effect of chronic exposure to aspartame on oxidative stress in brain discrete regions of albino rats

This study was aimed at investigating the chronic effect of the artificial sweetener aspartame on oxidative stress in brain regions of Wistar strain albino rats. Many controversial reports are available on the use of aspartame as it releases methanol as one of its metabolite during metabolism. The present study proposed to investigate whether chronic aspartame (75 mg/kg) administration could release methanol and induce oxidative stress in the rat brain. To mimic the human methanol metabolism, methotrexate (MTX)-treated rats were included to study the aspartame effects. Wistar strain male albino rats were administered with aspartame orally and studied along with controls and MTX-treated controls. The blood methanol level was estimated, the animal was sacrificed and the free radical changes were observed in brain discrete regions by assessing the scavenging enzymes, reduced glutathione, lipid peroxidation (LPO) and protein thiol levels. It was observed that there was a significant increase in LPO levels, superoxide dismutase (SOD) activity, GPx levels and CAT activity with a significant decrease in GSH and protein thiol. Moreover, the increases in some of these enzymes were region specific. Chronic exposure of aspartame resulted in detectable methanol in blood. Methanol per se and its metabolites may be responsible for the generation of oxidative stress in brain regions.     

Increased brain P-glycoprotein in morphine tolerant rats

The objective of this study was to determine whether chronic morphine exposure increased P-glycoprotein in rat brain. Male Sprague-Dawley rats were treated with morphine, saline, or dexamethasone for 5 days. On day 6, antinociceptive effect was measured to evaluate the extent of functional tolerance to morphine. Brain P-glycoprotein was detected by Western blot analysis of whole brain homogenate. Morphine- and dexamethasone-treated rats exhibited decreased antinociceptive response when compared to saline-treated controls. Brain P-glycoprotein was approximately 2-fold higher in morphine-treated rats compared to saline controls based on Western blot analysis. Chronic morphine exposure appears to increase P-glycoprotein in rat brain. P-glycoprotein induction may enhance morphine efflux from the brain, thus reducing morphine's pharmacologic activity. Induction of P-glycoprotein may be one mechanism involved in the development of morphine tolerance.     

慢性吗啡耐受大鼠脑内孤啡肽生成与释放增加

本文彩放射免疫分析法测定了慢性吗啡耐受过程中大鼠脑室灌流液、中脑导水管周围灰质（ＰＡＧ）及杏仁核中孤啡肽（ＯＦＱ）免疫活性的动态变化。结果观察到：（１）大鼠连续５ｄ皮下注射递增剂量的盐酸吗中民慢性吗啡耐受,其脑室灌流中ＯＦＱ－ｉｒ随吗啡注射剂量和注射次数的增加逐渐上升,第５ｄ注射后较对照组升高了５２％;（２）皮下注射吗啡１ｄ、３ｄ、５ｄ的大鼠ＰＡＧ中ＯＦＱ－ｉｒ比对照组分别升高了１７％、４８％和８     

Gene expression profile of the hippocampus of rats subjected to traumatic brain injury

Traumatic brain injury (TBI) is a serious public health problem as well as a leading cause of severe posttraumatic disability. Numerous studies indicate that the differentially expressed genes (DEGs) of neural signaling pathways are strongly correlated with brain injury. To further analyze the roles of the DGEs in the central nervous system, here we systematically investigated TBI on the hippocampus and its injury mechanism at the whole genome level. On the basis of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes Analyses, we revealed that the DEGs were involved in many signaling pathways related to the nervous system, especially neuronal survival-related pathways. Finally, we verified the microarray results and detected the gene expression of neuronal survival-related genes in the hippocampus by using real-time quantitative polymerase chain reaction. With Western blot and axon growth assay, the expression of P2rx3 was upregulated in rats subjected to TBI, and overexpression of P2rx3 promoted neurite growth of NG108 cells. Our results suggested that the DEGs (especially P2rx3) and several signaling pathways might play a pivotal role in TBI. We also provided several targeted genes related to TBI for future investigation.     

Erythrocyte ion transport in rats subjected to acute and chronic hypobaric hypoxia

Our study addresses selected parameters of rat erythrocyte ion transport (Na(+)-K(+) pump, Na(+)-K(+)-2Cl- cotransport, and passive cation fluxes) after acute or chronic hypoxia exposure. We did not find any significant change of ion transport after acute hypoxia. However, chronic hypoxia could modify ion transport because the affinity of Na(+)-K(+) pump for intracellular Na(+) seems to be decreased.     

慢性吗啡给予、戒断及再给药过程中大鼠海马感觉门控的动态变化

药物成瘾被认为是药物长期作用于脑而产生的一种慢性复吸性脑疾病,长期反复的药物（如吗啡）滥用会导致一系列严重后果,如药物依赖、药物耐受、强迫性药物寻求等。本实验利用条件化位置偏好（conditioned place preference,CPP）模型来检测大鼠对吗啡依赖和心理渴求等过程;采用双声刺激听觉诱发电位来研究大鼠在慢性吗啡给予、戒断以及再给药过程中海马感觉门控（N40）的动态变化。吗啡组大鼠注射吗啡（10mg／kg,i．p．）12d,经历第一次戒断12d,再次注射吗啡（2．5mg／kg,i．P．）1d,之后经历第二次戒断2d;对照组大鼠注射同体积生理盐水,其余实验条件与吗啡组相同。CPP实验表明,这种药物给予方法促使大鼠对吗啡产生药物依赖和心理渴求。双声刺激诱发电位实验表明,吗啡组大鼠在吗啡给予期间海马感觉门控受到损伤;第一次戒断期的第1～2天海马感觉门控能力减弱,第3天增强,第4～12天逐渐恢复到正常水平;再次给予吗啡后海马感觉门控能力与对照组相比显著降低,并且随后2d的戒断期内海马感觉门控能力也一直保持较低水平,表明再次给药使大鼠海马感觉门控对吗啡更加敏感化。结果提示,长期反复的吗啡给予及再给药干扰了海马的感觉门控能力,吗啡成瘾对大脑可能产生长期影响。     

An analysis of GABA receptor changes in the discrete regions of mouse brain after acute and chronic treatments with morphine

Abstract: The effects of morphine on the affinity and distribution of GABA receptors in the mouse regions (striatum, medulla, diencephalon, cortex, and cerebellum) were investigated in relation to: (a) acute administration, (b) chronic administration (tolerance), (c) precipitated withdrawal by naloxone, an opiate antagonist, and (d) abrupt withdrawal for 8 and 24 h. The alterations in the affinity as reflected by the dissociation constant (K_D) and the number of receptors (B_max) in the synaptic membranes obtained from controls and various treatments were determined by radioligand binding assay using [³H]muscimol as a ligand. Significant changes were observed in striatum, medulla, and diencephalon, whereas other regions including whole brain exhibited marginal changes. In general the number of GABA receptors increased after tolerance development, which upon abrupt withdrawal returned to control levels except in the case of naloxone-induced precipitated withdrawal. The affinity changes in different regions were diverse in nature and were not evident in the whole brain membranes. These results indicate that: (a) the regional alterations in the affinity and distribution of GABA receptors may play a role in the induction, maintenance, and regression of morphine tolerance; (b) abrupt withdrawal and antagonist precipitated withdrawal affect the GABA system differently, (c) chronic morphine treatment appears to influence the GABA receptors in the cerebellum, a region generally known for its lack of opiate receptors.     

GABA-ergic system in brain regions of glutamate-lesioned rats

Subcutaneous administration of high doses of glutamate to rats during their first 10 days after birth produced a great reduction of GABA content and GAD activity in the adult mediobasal hypothalamus, both in male and female. In addition GABA content and GAD activity showed a slight significant decrease in female cerebellum and male striatum. Glutamate treatment was also followed by a significant increase in GABA content and GAD activity of male substantia nigra, cerebellum, hippocampus and of female olfactory bulb. No reduction in GABA-T activity was observed in different brain areas studied except in mediobasal hypothalamus. The results support the view that glutamate treatment had a direct toxic effect on GABA-ergic neurons in mediobasal hypothalamus. The changes in GAD activity observed in all areas studied may reflect the neuroendocrine changes determined by nucleus arcuate lesions.     

Electroacupuncture alters catecholamines in brain regions of rats

Electroacupuncture (EA) stimulation mediated the release of [³H]norepinephrine (NE) from synaptosomes prelabeled with [³H]NE. The pulse release of [³H]NE by EA stimulation was dependent on the presence of Ca²⁺. Treatment of rats with EA for 30 min at 4 Hz did not significantly alter the dopamine (DA) content in hypothalamus, cerebellum, pons, midbrain, and cerebral cortex regions, but the DA level was decreased by 20% in caudate nucleus. The NE level was found to increase by 43% in caudate nucleus and 38% in hypothalamus. The results indicate that only certain neuronal pathways are affected by the EA treatment, and that NE and DA may respond differently to such stimulation.