Superoxide dismutase activity in rat brain during acute and chronic alcohol intoxication

The effect of acute and chronic ethanol administration on rat brain superoxide dismutase (SOD) activity was studied. Intraperitoneal injections of ethanol led to an inhibition of SOD activity. When ethanol was fed as the sole fluid, the SOD activity decreased progressively, reaching a plateau after 6 weeks of treatment. Withdrawal of ethanol produced a recovery of control values within 48 hr. SOD activity was also decreased in rats born from ethanol-drinking mothers. Inhibition of SOD activity by ethanol may allow an accumulation of cytotoxic O₂ ^– radicals; this may account for some nervous system disorders during alcohol intoxication.     

Lipid composition of rat brain myelin in triethyl tin-induced edema

Chronic triethyl tin intoxication was induced in young adult rats by oral feeding of triethyl tin sulfate. Progressively severe brain edema developed during the 3-month experimental period. The yield of myelin from the brains of the experimental animals decreased to almost half normal per brain, but the isolated myelin appeared morphologically normal. The analysis of whole brain showed corresponding decreases in proteolipid protein and total lipid, particularly galactolipids. The proportions of the major constituents of isolated myelin (chloroform-methanol-insoluble residue, proteolipid protein, and total lipid) were unchanged despite the low yield. However, the proportion of cholesterol increased from 16 to 21% dry weight, and that of total galactolipid decreased from 21 to 15%, as the yield of myelin decreased. This decrease of total galactolipid was mainly due to the decrease in cerebroside. Total phospholipid remained constant initially but showed a slight decrease toward the end of the experiment, due mostly to decreased ethanolamine phospholipid. There was no preferential loss or preservation of phosphatidalethanolamine. The fatty acid composition of sulfatide showed statistically significant shifts to less long-chain fatty acids and less monoenoic acids, but cerebroside and sphingomyelin did not show significant changes in the fatty acid composition. There was no increase in esterified cholesterol. These findings generally support our hypothesis of nonspecific chemical abnormalities of the myelin sheath undergoing secondary degeneration. In an acute experiment, a single intraperitoneal injection of triethyl tin sulfate produced acute and transient brain edema. There were slight decreases in the yield of myelin, but no detectable changes in the chemical composition.     

The effects of acute and chronic morphine treatment and of morphine withdrawal on rat brain in vivo

1. The effects of morphine, nalorphine, acetazolamide, and 10% CO₂ on brain metabolite concentrations of 24h-starved rats were studied. 2. A single dose of morphine (20mg/kg body wt.) caused an increase in brain glucose concentration (42%) and decreased concentrations of lactate (24%), pyruvate (29%), citrate (20%), α-oxoglutarate (16%), malate (14%) and creatine phosphate (10%) after 30min. No changes were found in adenine nucleotide concentrations. 3. The same dose of morphine increased arterial CO₂ from 5.07 to 7.60 kN/m² (38 to 57 Torr), decreased the pH from 7.41 to 7.31 and decreased O₂ from 14.1 to 10.8kN/m² (106 to 81 Torr) at 30min. 4. Rats injected with morphine three times daily (20mg/kg body wt.) for 2 weeks had no changes in brain metabolite concentrations or in blood gases 30min after their last injection. 5. Nalorphine (an antagonist of morphine) caused essentially no changes in brain metabolite concentrations in normal rats. When nalorphine (20mg/kg) was administered to rats previously treated with morphine three times daily for 2 weeks, there was an increase in brain glucose (100%), lactate (23%), pyruvate (18%) and citrate (10%) concentrations. 6. Acetazolamide (an inhibitor of carbonic anhydrase) and 10% CO₂ increased the arterial CO₂ from 4.79 to 6.78kN/m² (36 to 51 Torr) and from 5.32 to 10.8kN/m² (40 to 81 Torr) respectively. 7. Both acetazolamide and 10% CO₂ caused changes in brain metabolite concentrations similar to those for acutely administered morphine. Thus 10% CO₂ caused increased brain glucose concentration (123%) and decreased brain lactate (46%), pyruvate (34%), citrate (26%), α-oxoglutarate (33%), malate (45%) and creatine phosphate (7%) concentrations. No changes in adenine nucleotide concentrations were found. 8. The results indicate that the effect of morphine on brain metabolite concentrations may be accounted for by the increased [CO₂]. 9. These findings constitute a consistent pattern of metabolic changes after acute morphine administration, morphine addiction, and withdrawal from morphine addiction.     

Adult rat brain synaptic vesicles II. Lipid composition

The lipid composition of synaptic vesicles isolated from adult rat brain was determined. Vesicles contained cholesterol and phospholipid but very little ganglioside, galactolipid, free fatty acid and triglyceride was detected. Ethanolamine and choline phosphoglycerides were the dominant phospholipids. Lysophosphatidyl choline was present in very low amounts. The fatty acid composition of the phosphoglycerides was characterized by high levels of docosahexaenoic acid in the ethanolamine and serine phosphoglycerides, and the absence of long chain fatty acids from the sphingomyelins. All the characteristic features of the lipid composition of the synaptosomal plasma membrane (with the exception of the ganglioside content) were seen in the synaptic vesicle lipids. The results are discussed in terms of the exocytosis mechanism of transmitter release.     

Adaptive changes in rat liver plasma membranes after chronic alcohol administration and its subsequent withdrawal

Rat hepatic plasma membranes isolated after chronic alcohol feeding displayed a different buoyant density range with a significantly increased peak density value when spun isopycnically in a 30-50% sucrose (w/w) gradient. This change persisted up to 48 h of withdrawal from alcohol. Analysis of membrane lipids revealed certain significant alterations in the phospholipids as well as the fatty acyl composition in individual phospholipids of the experimental plasma membranes. During withdrawal of alcohol for 48 h, all the alcohol-induced changes in the phospholipids returned to normal. Most initial changes in fatty acids reverted to the control composition during this time, but new changes in fatty acyl distribution were also observed. These were interpreted to represent readaptation to the withdrawal of the alcohol. It is not established how long this readaptation period lasts.     

Acetylcholine turnover rates in rat brain regions during cocaine self-administration

The involvement of cholinergic neurons in the brain processes underlying reinforcement has been recently demonstrated. This experiment assessed the potential role of cholinergic neurons in cocaine reinforcement by measuring the turnover rates of acetylcholine in brain regions of rats self-administering cocaine and in yoked cocaine and yoked vehicle-infused controls. The activity of cholinergic innervations of and/or interneurons in the olfactory tubercle, caudate putamen, diagonal band-pre-optic region, ventral pallidum, lateral and medial hypothalamus, hippocampus, ventral tegmental area and visual cortices reflected by the turnover rates of acetylcholine were significantly altered in rats self-administering cocaine compared to yoked cocaine infused controls. These changes implicate the involvement of cholinergic neurons with cell bodies in the diagonal band-pre-optic region, the medial septum and several brainstem nuclei and interneurons in the caudate-putamen and ventral pallidum in the processes underlying cocaine self-administration. The identified cholinergic neuronal systems may have a broader role in the brain processes for natural reinforcers (i.e. food, water, etc.) since drugs of abuse are believed to produce reinforcing effects through these systems.     

Determination of monoamines in rat brain regions after chronic administration of lithium

The effect of chronic administration of lithium on the concentration of biogenic amines and some of their metabolites in striatum, hippocampus, hypothalamus, pons-medulla and parietal cortex of rat were studied. Longterm lithium treatment modifies significantly the content of indoleamines in striatum and hypothalamus with minor changes in other structures. Catecholamine levels change after the treatment in striatum, hypothalamus, pons-medulla and parietal cortex. These results indicate that lithium treatment at therapeutic doses selectively modifies the catecholamine and indoleamine contents in discrete areas of the brain.     

Myelination in rat brain: changes in myelin composition during brain maturation

Abstract— Myelin was isolated from rat brains during development by a procedure giving fractions of constant purity at all ages. The lipid composition of these fractions and of whole brains of littermates was determined. The amount of myelin recovered per brain was a nearly linear function of the logarithm of age from the youngest (15 days) to the oldest (425 days) animals studied. With the exception of the earliest age point, the isolated myelin accounted for approximately 40 per cent of total brain galactolipid, evidence that a constant fraction (calculated to be 60 per cent) of myelin was recovered at all ages. Although the lipid-protein ratio of the myelin was constant with age, marked changes were seen in the amounts of cerebroside, sulphatide, phosphatidylcholine and desmosterol. The total galactolipid increased from 21 per cent of the total lipid at age 15 days to about 31 per cent at maturity. Phosphatidylcholine decreased from 17 to 11 per cent during the same period. Desmosterol decreased from 2.5 per cent of the total sterol to 0.2-0.3 per cent. All of these changes were complete between 2 and 5 months of age; no other ‘lower phase’ lipids showed significant changes with age. Although qualitatively similar to those reported by others, the changes differed in magnitude, with more stability in the levels of cholesterol and phosphatidalethanolamine with development. A sensitive indicator of the maturation of myelin was the mole ratio galactolipid/phosphatidylcholine, which varied from 1.2 at age 15 days to 2.8 at maturity. The maximum rate of myelination occurred at 20 days of postnatal age when myelin was deposited at the rate of 3.5 mg day^?1 brain^?1. However, at this age the rat brain had only 15 per cent of its eventual complement of myelin. The rate of accumulation of cerebroside in the whole brain paralleled that of myelin, and was the only lipid to show this relationship. Myelin deposition appeared to be almost solely responsible for the continued increase in brain weight after about 100 days of age.     

Effects of maternal thiamine deficiency on the development of thiamine-dependent enzymes in regions of the rat brain

Previous studies suggest that developing rat brain is susceptible to reduced thiamine intake. In order to assess the metabolic basis for this susceptibility, activities of three thiamine-dependent enzymes (pyruvate dehydrogenase complex, -ketoglutarate dehydrogenase and transketolase) were measured in homogenates of brain tissue from the offspring of thiamine-deficient mothers. Control groups of animals were pair-fed to equal food consumption with the thiamine-deficient animals. The study revealed region-selective delays in the establishment of adult activities of thiamine-dependent enzymes as a result of maternal thiamine deficiency. Pyruvate dehydrogenase complex activities in cerebral cortex were significantly reduced (by 20% P < 0.05); -ketoglutarate dehydrogenase activities were also reduced in cerebral cortex (by 30% P < 0.05). In the case of transketolase, enzyme activities were significantly reduced in cerebral cortex, cerebellum and brainstem. Following thiamine replenishment, defective enzyme activities were restored to normal in all cases. However, since thiamine-dependent enzymes are important for the establishment of adult patterns of cerebral energy metabolism and also in myelin synthesis, maternal thiamine deficiency resulting in reductions of thiamine-dependent enzymes at a vulnerable period in brain development could have serious metabolic consequences leading to permanent neurological sequellae in the offspring.     

Protein synthesis rates in rat brain regions and subcellular fractions during aging

In vivo protein synthesis rates in various brain regions (cerebral cortex, cerebellum, hippocampus, hypothalamus, and striatum) of 4-, 12-, and 24-month-old rats were examined after injection of a flooding dose of labeled valine. The incorporation of labeled valine into proteins of mitochondrial, microsomal, and cytosolic fractions from cerebral cortex and cerebellum was also measured. At all ages examined, the incorporation rate was 0.5% per hour in cerebral cortex, cerebellum, hippocampus, and hypothalamus and 0.4% per hour in striatum. Of the subcellular fractions examined, the microsomal proteins were synthesized at the highest rate, followed by cytosolic and mitochondrial proteins. The results obtained indicate that the average synthesis rate of proteins in the various brain regions and subcellular fractions examined is fairly constant and is not significantly altered in the 4 to 24-month period of life of rats.A preliminary report of these results was previously presented at: WFN-ESN Joint Meeting on: Cerebral Metabolism in Aging and Neurological Disorders, Baden, August 28–31, 1986.     

Changes in hexokinase isoenzymes in regions of rat brain during thyroid deficiency

In this work, activities of hexokinase isoenzymes Type I and Type II were measured in the soluble and particulate fractions from the brain regions (cerebral hemispheres (cerebrum), cerebellum and brain stem) of the thyroidectomized adult rats as well as of the thyroidectomized rats administered with triiodothyronine. Thyroidectomy generally decreased the hexokinase activity associated with particulate and soluble fractions. Hexokinase Type II isoenzyme was more affected than the Type I isoenzyme. Administration of triiodothyronine to the hypothyroid rats abolished the effect of thyroidectomy. Adult brain enzymes have been generally considered not be affected by thyroid hormones. The data obtained in this work are suggestive of an effect of thyroid hormones on hexokinase in the adult brain. Since the effects of thyroidectomy on the energy metabolism of the heart tissue are well known, the heart tissue was also studied for comparison.     

Lipid biosynthesis in anoxic-ischaemic rat brain

The uptake of [U-¹⁴C]glucose and [2-¹⁴C]acetate into lipids was measured in brain slices from anoxic, unilaterally ischaemic, unilaterally anoxic-ischaemic, and control rats. The rate of incorporation was significantly decreased in the brain slices from the treated animals except for the contralateral hemisphere of the unilaterally ischaemic animals. Also, there was no significant difference between the anoxic and the anoxic-ischaemic cerebral hemispheres of the anoxic-ischaemic animals. Fractionation of the total lipid extract demonstrated that the decrease in incorporation was general and not due to any particular class of lipid.     

Effect of chronic ethanol consumption on basic carboxypeptidase activity in regions of the rat brain

It is discovered that chronic consumption of ethanol induced decrease of carboxypeptidase H activity in striatum by 27%; increase of carboxypeptidase M activity in hippocampus by 67% and decrease in cerebral hemispheres by 34%; phenylmethylsulfonyl fluoride-inhibited carboxypeptidase activity increase in hypothalamus by 141%, in striatum by 60% and in optic and lamina quadrigemina by 34%. The role of basic carboxypeptidases in mechanisms of ethanol influence on the peptidergic systems are discussed.     

Changes in phosphofructokinase and pyruvate kinase in rat brain regions during alloxan-induced diabetes

Changes in the profile of two glycolytic enzymes, phosphofructokinase and pyruvate kinase, in different regions of rat brain were studied under alloxan-induced diabetes. A regional variation of the effect of diabetes on brain was noted - the cerebral hemispheres and cerebellum showed decreased activity of the enzymes, while the brain stem remained relatively unaffected. The changes in enzyme activities in the brain regions were more pronounced at the early days of diabetes, particularly at 8 days. Insulin administration to the diabetic animals restored the activity of the enzymes. The results indicate a regionally variable effect of diabetes on the two key glycolytic enzymes, and bring out a role of insulin in the regulation of brain glycolysis.     

Nitric oxide synthase activity and the level of nitrates/nitrites in brain regions during spontaneous morphine withdrawal in rats

Activity of nitric oxide synthase (NOS) and concentrations of nitrate/nitrites (NO _x ^? ) were measured in brain regions of rats during spontaneous morphine withdrawal, which was modeled in male Wistar rats. The animals were injected with the increasing intraperitoneal doses (10–100 mg/kg, twice a day) of morphine hydrochloride for 6 days. Thirty six hours after the last injection the severity of the spontaneous morphine withdrawal syndrome was determined by specific autonomic and locomotor indices The withdrawal was accompanied by the increase of both NOS activity and NO _x ^? levels in the midbrain and hippocampus, the decrease of these parameters in striatum and hypothalamus, and lack of changes in cerebral cortex and brain stem. In cerebellum NOS activity decreased whereas NO _x ^? concentrations remained unchanged. In the cerebral cortex, striatum, midbrain, and cerebellum activity of NOS and NO _x ^? concentrations correlated with the withdrawal syndrome severity and also with the specific signs of abstinence.     

Lipid peroxidation changes in the brain in fetal alcohol syndrome]

The study was performed upon three groups of 12-week-old male rats. The first group of rats received ethanol/9 g/kg/day as 6% aqueous solution/during pregnancy and lactation, the second group received ethanol only during lactation and the third group, controls, received equicaloric sucrose solution. The concentrations of LPO products were determined in the homogenates of tissue from frontal cortex, striatum, hypothalamus, hippocamp and cerebellum. The concentration of fluorescent products in the brain structures of rats treated perinatally with ethanol was several-fold increased as compared with controls. The levels of diene conjugates were increased in most brain structures of rats with FAS. It should be pointed out that there was the same degree of increase of the levels of both fluorescent products and diene conjugates in two groups of rats with FAS. Having in mind that in the rat the increased growth of the brain occurs during the first 10 postnatal days, it might be assumed that this period is favorable for LPO.     

Effect of chronic alcohol consumption on rat brain microsome lipid composition, membrane fluidity and Na+-K+-ATPase activity

The present study reports differences in phospholipid classes, fatty acids of individual phospholipids, and changes in membrane fluidity and Na+-K+-ATPase activity in brain microsomes of rats maintained on an alcohol diet for 35 days compared to sex, age and weight-matched control rats maintained on a calorically-equivalent, non-alcohol diet. Although no difference in Na+-K+-ATPase activity was found in microsomes from alcohol vs control rats when measured in the absence of added alcohol, the presence of low concentrations of ethanol (less than 100 mM) stimulated, while high concentrations (greater than 100 mM) inhibited enzyme activity. The stimulation was differentially expressed in that the microsomal enzyme from alcohol rats was stimulated to a lesser extent than the enzyme from control rats. However, the inhibiting effect of high concentrations of alcohol was similar in microsomes from both alcohol and control rats. Also in membranes from alcohol rats, there was a lower quantity of phosphatidylethanolamine (PE) and higher quantities of phosphatidylserine (PS) and phosphatidylinositol (PI) compared to membranes from control rats. The major change in fatty acid composition was a reduction in the level of polyunsaturated fatty acids, which was particularly evident in PI and PS. The linoleic acid: arachidonic acid ratio (18:2/20:4) and the saturation:unsaturation ratio were also increased in PI and PS in membranes from alcohol animals. However, the ratio of n-6/n-3 fatty acids remained the same or was reduced in membranes from alcoholic animals. Although no difference in the inherent "fluidity" of membranes from alcohol vs control rats could be demonstrated by electron paramagnetic resonance, molecular tolerance to ethanol was demonstrated in the membranes from alcohol rats by the resistance to the disordering effects of added ethanol.