Functional Changes of Rat Brain Microsomal Membrane Surface After Learning Task Depending on Dietary Fatty Acids

Abstract: Biochemical characteristics of brain microsomal membranes were examined before and after the brightness-discrimination learning tasks in rats that were fed either safflower oil (α-linolenate-deficient) or perilla oil (α-linolenate-sufficient) diets. We detected small changes in the chain elongation system for polyunsaturated fatty acids in microsomes, whereas no significant difference was detected in the inositol trisphosphate-induced calcium release and ATP-induced calcium uptake profiles of microsomes between the two dietary groups. The calcium ion-induced aggregation rate of microsomes was determined in both groups. We found that the aggregation rate of microsomes in the safflower oil group was significantly greater than that in the perilla oil group. The difference in susceptibility of microsomal membrane phospholipids to phospholipase A₂ between the groups was obvious, and the amount of released fatty acids by phospholipase A₂ from the perilla oil group microsomes was nearly half of that from the safflower oil group microsomes after the learning task. Susceptibility of sialic acids on the brain microsomal membranes to exogenous sialidase was different only after the learning task in the safflower and perilla oil groups. These results suggest that the biochemical characteristics of membrane surfaces of brain microsomes are affected significantly by the learning task itself in a dietary oil-dependent manner.     

Decrease of Brain Phospholipid Synthesis in Free-Moving n-3 Fatty Acid Deficient Rats

Abstract: The autoradiographic method with [¹⁴C]-docosahexaenoic acid ([¹⁴C]22:6 n-3) was used to determine whether a diet deficient in n-3 fatty acids, inducing a decrease in 22:6 n-3 circulating level, was associated with changes in local rates of phospholipid synthesis in the rat brain. As compared with rats fed a normal diet (peanut plus rapeseed oil), a n-3 fatty acid deficiency [peanut oil group (P group)] induced a generalized decrease (?35 to ?76%) of 22:6 n-3 incorporation rates into phospholipids in all the regions examined. This effect was confirmed by using [³H]22:6 n-3 infusion by biochemical analysis and quantifications corrected for the contribution of docosahexaenoate derived from lipid store recycling to the unesterified pool, taken as the precursor pool for phospholipid synthesis in the whole brain. In normal or n-3 fatty acid-deficient rats, the values of the brain-to-plasma 22:6 n-3 specific activity ratio (Ψ) were similar (0.03), indicating that a considerable endogenous source of 22:6 n-3 (97%), likely derived from phospholipid degradation, dilutes the specific activity of the tracer coming from plasma. Using the specific activity of 22:6 n-3 in plasma instead of brain would thus lead to a gross underestimation of the rate of phospholipid synthesis. The results also demonstrate that the pattern of ¹⁴C or ³H distribution in brain lipids was not modified by the n-3 fatty acid-deficient diet. The major lipids labeled were phospholipids, particularly phosphatidylethanolamine. Nevertheless, the unesterified 22:6 n-3 concentrations in plasma and brain were significantly reduced (eight- and threefold, respectively) in the P group. In addition, the proportion of 22:6 n-3 in the brain total lipid fraction, total phospholipids, and phosphatidylcholine, -ethanolamine, and -serine was significantly decreased in n-3 fatty acid-deficient rats. This was partially compensated for by an increase in the 22:5 n-6 level. These results are discussed in relation to the limitation of 22:6 n-3 use to quantify, by the quantitative autoradiographic method, changes in local rates of phospholipid synthesis in rat brain.     

The Antiarrhythmic Effect of n-3 Polyunsaturated Fatty Acids: Modulation of Cardiac Ion Channels as a Potential Mechanism

Sudden cardiac death remains one of the most serious medical challenges in Western countries. Increasing evidence in recent years has demonstrated that the n-3 polyunsaturated fatty acids (PUFAs) can prevent fatal ventricular arrhythmias in experimental animals and probably in humans. Dietary supplement of fish oils or intravenous infusion of the n-3 PUFAs prevents ventricular fibrillation caused by ischemia/reperfusion. Similar antiarrhythmic effects of these fatty acids are also observed in cultured mammalian cardiomyocytes. Based on clinical observations and experimental studies in vitro and in vivo, several mechanisms have been postulated for the antiarrhythmic effect of the n-3 PUFAs. The data from our laboratory and others have shown that the n-3 PUFAs are able to affect the activities of cardiac ion channels. The modulation of channel activities, especially voltage-gated Na⁺ and L-type Ca²⁺ channels, by the n-3 fatty acids may explain, at least partially, the antiarrhythmic action. It is not clear, however, whether one or more than one mechanism involves the beneficial effect of the n-3 PUFAs on the heart. This article summarizes our recent studies on the specific effects of the n-3 PUFAs on cardiac ion channels. In addition, the effect of the n-3 PUFAs on the human hyperpolarization-activated cyclic-nucleotide-modulated channel is presented.     

膳食中高n-6/n-3多不饱和脂肪酸比值对小鼠肠道菌群的影响

目的:探讨小鼠膳食中高n-6/n-3多不饱和脂肪酸比值对肠道菌群的影响。方法:随机选取健康的30只C57/B6小鼠分为对照组(基础饲料)、花生四烯酸组(基础饲料+10%花生四烯酸)、鱼油组(基础饲料+10%鱼油)。喂食16周,16周后提取小鼠肠道菌群宏基因组DNA,采用Roche 454测序技术对肠道菌群16Sr RNA基因V3-V5区域进行测序,对菌群的组成结构以及含量的变化进行分析。结果:花生四烯酸组小鼠体内厚壁菌门的含量达到(55.3±5.26)%,与对照组小鼠体内厚壁菌门的含量(30.23±8.75)%相比显著性升高(P0.05)。并且花生四烯酸组小鼠体内变形菌门的含量(3±0.762)%与对照组(1.5±0.265)%相比也显著性上升(P0.05)。结论:膳食中高n-6/n-3多不饱和脂肪酸比值会造成小鼠体内肠道菌群组成结构的失衡,导致厚壁菌门以及变形菌门的含量上升。     

Neural 22-Carbon Fatty Acids in the Weanling Rat Respond Rapidly and Specifically to a Range of Dietary Linoleic to of-Linolenic Fatty Acid Ratios

Changing the dietary ratio of the essential fatty acids (EFA), 18:2n6 and 18:3n3, while keeping the amounts of other fatty acids in the diet constant can rapidly and specifically alter the proportions of n6 and n3 22-carbon fatty acids in the brain of the weanling rat. A dietary 18:2n6/18:3n3 ratio of 165 versus 1.8 caused higher n6 and lower n3 22-carbon fatty acid levels, without changing total 22-carbon fatty acid levels, in phosphatidylethanolamine and phosphatidylcholine from several neural membrane fractions. This was apparent after only 2 weeks and showed no sign of plateauing after 12 weeks. Other neural fatty acids were essentially unaffected. The three most abundant 22-carbon fatty acids responded somewhat differently to increments in the dietary 18:2n6/18:3n3 ratio (1.8, 9, 36, and 165). Levels of 22:4n6 increased by similar absolute amounts for each four-fold increase in dietary 18:2n6/18:3n3 ratio; in contrast, the largest absolute changes in 22:5n6 and 22:6n3 levels occurred as the 18:2n6/18:3n3 ratio increased from 36 to 165. This study shows that the 18:2n6/18:3n3 ratio of diets high in fat (40% of energy) and adequate in EFA, both typical of diets in developed countries, can substantially and relatively quickly affect the 22-carbon fatty acids in the brain, even after the rapid accumulation of these fatty acids during neural growth has ceased.     

n-3 Fatty Acid Deficiency Increases Brain Protein Synthesis in the Free-Moving Adult Rat

Abstract: The autoradiographic method with l -[³⁵S]methionine was used to determine the effects of an n-3 fatty acid deficiency on brain protein synthesis. Brain protein synthesis was significantly increased (from 50 to 150%) in 45 of the 52 brain structures studied in n-3 fatty acid-deficient rats as compared with control animals. Biochemical analysis confirmed the increase in overall rate of protein synthesis in brain as a whole.     

α-Linolenic Acid Dietary Deficiency Alters Age-Related Changes of Dopaminergic and Serotoninergic Neurotransmission in the Rat Frontal Cortex

Abstract: The effects of α-linolenic acid diet deficiency on rat dopaminergic and serotoninergic neurotransmission systems were investigated in the frontal cortex, striatum, and cerebellum of male rats 2, 6, 12, and 24 months of age. The diet deficiency induced a severe decrease in the 22:6n-3 fatty acid levels in all regions and a compensatory increase in n-6 fatty acid levels. A recovery in the levels of 22:6n-3 was observed in deficient rats between 2 and 12 months of age; however, this recovery was lower in frontal cortex than in striatum and cerebellum. In the striatum and the cerebellum, dopaminergic and serotoninergic receptor densities and endogenous dopamine and serotonin levels were affected by aging regardless of the diet. In contrast, a 40–75% lower level of endogenous dopamine in the frontal cortex occurred in deficient rats according to age. The deficiency also induced an 18–46% increase in serotonin 5-HT₂ receptor density in the frontal cortex during aging, without variation in endogenous serotonin level, and a 10% reduction in density of dopaminergic D₂ receptors. Monoamine oxidase-A and -B activities showed specific age-related variations but regardless of the diet. Our results suggest that a chronically α-linolenic-deficient diet specifically affects the monoaminergic systems in the frontal cortex.     

Evidence for the Association of 2',3'-Cyclic-Nucleotide 3'-Phosphodiesterase with Myelin-Related Membranes in Peripheral Nervous System

Abstract: In PNS, the specific activity of 2′,3′-cyclic nucleotide 3′-phospho–diesterase (CNP) in myelin was not enriched over the starting homogenate. Nevertheless, most of the total activity was recovered in myelin. In myelin-deficient mutants, low CNP activities were measured in sciatic nerves. CNP specific activities were similar in myelinated and non-myelinated nerves but in non-nervous tissues, they were significantly lower than in nervous tissue. There was no indication for the presence of an isoenzyme of CNP in peripheral nerves. These results indicate that CNP is present in PNS myelin and preferentially localized in Schwann cell plasma membranes.     

Alterations in the Fatty Acid Composition of Rat Brain Cells (Neurons, Astrocytes, and Oligodendrocytes) and of Subcellular Fractions (Myelin and Synaptosomes) Induced by a Diet Devoid of n-3 Fatty Acids

Abstract: Rats were fed through four generations with a semisynthetic diet containing 1.0% sunflower oil (6.7 mg/ g n-6 fatty acids, 0.04 mg/g n-3 fatty acids). Ten days before mating, half of the animals received a diet in which sunflower was replaced by soya oil (6.6 mg/g n-6 fatty acids, 0.8 mg/g n-3 fatty acids) and analyses were performed on their pups. Fatty acid analysis in isolated cellular and subcellular material from sunflower-fed animals showed that the total amount of unsaturated fatty acids was not reduced in any cellular or subcellular fraction (except in 60-day-old rat neurons). All material from animals fed with sunflower oil showed an important reduction in the docosahexaenoic acid content, compensated (except in 60-day-old rat neurons) by an increase in the n-6 fatty acids (mainly C22:5 n-6). When comparing 60-day-old animals fed with soya oil or sunflower oil, the n-3/n-6 fatty acid ratio was reduced 16-fold in oligodendrocytes, 12-fold in myelin, twofold in neurons, sixfold in synaptosomes, and threefold in astrocytes. No trienes were detected. Saturated and monounsaturated fatty acids were hardly affected. This study provides data on the fatty acid composition of isolated brain cells.     

Dietary Enrichment with Medium Chain Triglycerides (AC-1203) Elevates Polyunsaturated Fatty Acids in the Parietal Cortex of Aged Dogs: Implications for Treating Age-Related Cognitive Decline

Dogs demonstrate an age-related cognitive decline, which may be related to a decrease in the concentration of omega-3 polyunsaturated fatty acids (n-3 PUFA) in the brain. Medium chain triglycerides (MCT) increase fatty acid oxidation, and it has been suggested that this may raise brain n-3 PUFA levels by increasing mobilization of n-3 PUFA from adipose tissue to the brain. The goal of the present study was to determine whether dietary MCT would raise n-3 PUFA concentrations in the brains of aged dogs. Eight Beagle dogs were randomized to a control diet (n = 4) or an MCT (AC-1203) enriched diet (n = 4) for 2 months. The animals were then euthanized and the parietal cortex was removed for phospholipid, cholesterol and fatty acid determinations by gas-chromatography. Dietary enrichment with MCT (AC-1203) resulted in a significant increase in brain phospholipid and total lipid concentrations (P < 0.05). In particular, n-3 PUFA within the phospholipid, unesterified fatty acid, and total lipid fractions were elevated in AC-1203 treated subjects as compared to controls (P < 0.05). Brain cholesterol concentrations did not differ significantly between the groups (P > 0.05). These results indicate that dietary enrichment with MCT, raises n-3 PUFA concentrations in the parietal cortex of aged dogs.     

Recovery of Altered Fatty Acid Composition Induced by a Diet Devoid of n-3 Fatty Acids in Myelin, Synaptosomes, Mitochondria, and Microsomes of Developing Rat Brain

Rats were fed a semisynthetic diet containing either sunflower oil or soya oil. Half the litter fed with sunflower oil diet was changed to a soya oil diet when the pups were 15 days old (during active myelination). Fatty acid analysis was then performed on subcellular fractions of the animals fed (a) soya oil, (b) sunflower oil, and (c) soya oil replacing sunflower oil from the 15th day, to determine the speed of the recovery. All material from animals fed sunflower oil showed an important reduction in docosahexaenoic acid (22:6 n-3), compensated by an increase in docosapentaenoic acid (22:5 n-6), whereas arachidonic acid (20:4 n-6) was not affected. In all fractions examined, when sunflower oil was replaced by soya oil in 15-day-old pups the recovery started from the very first day but lasted more than 2 months (this recovery was determined by the increase of 22:6 n-3 up to the normal value and decrease of the 22:5 n-6). In addition a delay was found for myelin recovery, starting only from the 25th day.     

The Significance of Mast Cells as a Source of Histamine in the Mouse Brain

Abstract: Knowledge of the relative contributions of mast cells and neurons to the overall pool of histamine in the brain is a prerequisite to determining the significance and role of this amine in brain function. Consequently, we analyzed the levels of brain histamine in four genotypes (+/+, W/+, W^v/+ , and WIW^v ) of WBB6F₁ mice, whose numbers of brain-associated mast cells vary in a genotypically specific manner. Although mast cell numbers ranged from a total absence of mast cells (W/ W^v ) to an average of about 500 mast cells/brain ( W/+ ), no significant differences between genotypes were found in the quantities of histamine in whole brains, brain regions, or crude subcellular fractions. Thus, in this strain of mice, mast cells are not a significant source of histamine in the brain. This suggests that most of the histamine is of neuronal origin. Since neuronal histamine levels are maintained only by continued histidine decarboxylase activity, complete inhibition of this enzyme by α-fluoromethylhistidine, a "suicide" inhibitor of histidine decarboxylase, would totally deplete W/W^v mice of brain histamine. This was not found to occur in the W/W^v mice, suggesting that neuronal stores of histamine can be maintained in the absence of histidine decarboxylase, or that an additional nonneuronal, non-mast cell source of histamine exists in the W/W^v mouse brain.     

Alteration in Fatty Acid Composition of Adult Rat Brain Capillaries and Choroid Plexus Induced by a Diet Deficient in n-3 Fatty Acids: Slow Recovery After Substitution with a Nondeficient Diet

Wistar rats were fed for three generations with a semisynthetic diet containing either 1.5% sunflower oil (940 mg% of C18:2n-6, 6 mg% of C18:3n-3) or 1.9% soya oil (940 mg% of C18:2n-6, 130 mg% of C18:3n-3). At 60 days of age, the male offspring of the third generation were killed. The fatty acyl composition of isolated capillaries and choroid plexus was determined. The major changes noted in the fatty acid profile of isolated capillaries were a reduction (threefold) in the level of docosahexaenoic acid and, consequently, a fourfold increase in docosapentaenoic acid in sunflower oil-fed animals. The total percentage of polyunsaturated fatty acids was close to that in the soya oil-fed rats, but the ratio of n-3/n-6 fatty acids was reduced by threefold. In the choroid plexus, the C22:6n-3 content was also reduced, but by 2.6-fold, whereas the C22:5n-6 content was increased by 2.3-fold and the ratio of n-3/n-6 fatty acids was reduced by 2.4-fold. When the diet of sunflower oil-fed rats was replaced with a diet containing soya oil at 60 days of age, the recovery in content of n-6 and n-3 fatty acids started immediately after diet substitution; it progressed slowly to reach normal values after 2 months for C22:6n-5 and 2.5 months for C22:6n-3. The recovery in altered fatty acids of choroid plexus was also immediate and very fast. Recovery in content of C22:5n-6 and C22:6n-3 was complete by 46 days after diet substitution.     

Localization of Endo-Oligopeptidase (EC 3.4.22.19) in the Rat Nervous Tissue

The subcellular and regional distribution of endo-oligopeptidase (EC 3.4.22.19), an enzyme capable of generating enkephalin by single cleavage from enkephalin-containing peptides, was determined by an enzymatic assay using metorphamide and by immunochemical techniques in the CNS of the rat. The rat CNS contains a membrane-associated form of endo-oligopeptidase, an enzyme predominantly associated with the soluble fraction of brain homogenates. Subcellular fractionation showed that approximately 17% of the total activity of the enzyme is associated with membrane fractions including synaptosomes. Synaptosomal membranes were prepared from neocortex, striatum, hypothalamus, medulla, spinal cord, and cerebellum. The amount of EC 3.4.22.19 activity solubilized by 3-[( 3-cholamidopropyl]dimethylammonio)-1-propanesulfonate from synaptosomal membranes was similar in neocortex, striatum, and hypothalamus, being three- to 10-fold greater than in spinal cord, cerebellum, and medulla. A polyclonal antibody exhibiting high affinity for endo-oligopeptidase was raised in rabbits against the purified rat brain enzyme and used to localize endo-oligopeptidase by Western blotting and by immunoperoxidase techniques. A strong band corresponding to the Mr of EC 3.4.22.19 was found in solubilized proteins obtained from synaptosomal membranes prepared from hypothalamus, neocortex, and striatum when subjected to Western blotting. The immunohistochemical localization of endo-oligopeptidase indicated that the immunoreactivity was confined to gray matter in regions known to be rich in peptide-containing neurons such as the striatum. In the cerebellum, a region poor in peptides, no staining could be detected. The nonuniform distribution of endo-oligopeptidase in rat brain suggests a role in neurotransmitter processing in the CNS.     

Analysis of α-Bungarotoxin Binding in the Goldfish Central Nervous System

Abstract: We report here the equilibrium, kinetic, and pharmacological analysis of α-¹²⁵I-bungarotoxin (α-¹²⁵I-Bgt) binding to a Triton x-100-solubilized goldfish brain synaptosomal fraction. In addition, a refined analysis of equilibrium binding to a particulate synaptosomal fraction is presented. Equilibrium binding from both particulate and soluble fractions revealed an apparent heterogeneity of binding sites. Kinetic analysis of the soluble receptor revealed linear association kinetics and nonlinear dissociation kinetics. The dissociation curve suggested the presence of at least two rate constants. Potential sources of the binding heterogeneity found in both the equilibrium binding and dissociation kinetics experiments are (1) multiple receptor species, (2) multiple ligand species, and (3) different, possibly interconvertible, states of a single receptor type. No evidence for the first two alternatives was found. Support for the third alternative was obtained by observing the effect of cholinergic ligands on α-¹²⁵I-Bgt dissociation. Carbamylcholine and d -tubocurarine increased the apparent proportion of rapidly dissociating sites, suggesting that the two binding affinities can be interconverted and may arise from a single receptor type. Evidence concerning the identity of the α -Bgt binding protein as a nicotinic acetylcholine receptor is discussed.     

Use of Inhibitors of γ-Aminobutyric Acid (GABA) Transaminase for the Estimation of GABA Turnover in Various Brain Regions of Rats: A Reevaluation of Aminooxyacetic Acid

The technique of estimating gamma-aminobutyric acid (GABA) turnover by inhibiting its major degrading enzyme GABA-T (4-aminobutyrate:2-oxoglutarate aminotransferase; EC 2.6.1.19) and measuring GABA accumulation has been used repeatedly, but, at least in rats, its usefulness has been limited by several difficulties, including marked differences in the degree of GABA-T inhibition in different brain regions after systemic injection of GABA-T inhibitors. In an attempt to improve this type of approach for measuring GABA turnover, the time course of GABA-T inhibition and accumulation of GABA in 12 regions of rat brain has been studied after systemic administration of aminooxyacetic acid (AOAA), injected at various doses and with different routes of administration. A total and rapidly occurring inhibition of GABA-T in all regions was obtained with intraperitoneal injection of 100 mg/kg AOAA, whereas after lower doses, marked regional differences in the degree of GABA-T inhibition were found, thus leading to underestimation of GABA synthesis rates, e.g., in substantia nigra. The activity of the GABA-synthesizing enzyme GAD (L-glutamate-1-decarboxylase; EC 4.1.1.15) was not reduced significantly at any time after intraperitoneal injection of AOAA, except for a small decrease in olfactory bulbs. Even the highest dose of AOAA tested (100 mg/kg) was not associated with toxicity in rats, but induced motor impairment, which was obviously related to the marked GABA accumulation found with this dose. The increase in GABA concentrations induced with intraperitoneal injection of 100 mg/kg AOAA was rapid in onset, allowing one to estimate GABA turnover rates from the initial rate of GABA accumulation, i.e., during the first 30 min after AOAA injection. GABA turnover rates thus determined were correlated in a highly significant fashion with the GAD activities determined in brain regions, with highest turnover rates measured in substantia nigra, hypothalamus, olfactory bulb, and tectum. Pretreatment of rats with diazepam, 5 mg/kg i.p., 5-30 min prior to AOAA, reduced the AOAA-induced GABA accumulation in all 12 regions examined, most probably as a result of potentiation of postsynaptic GABA function. The data indicate that AOAA is a valuable tool for regional GABA turnover studies in rats, provided the GABA-T inhibitor is administered in sufficiently high doses to obtain complete inhibition of GABA degradation.     

Alterations of Na,K-ATPase Isoenzymes in the Rat Diabetic Neuropathy: Protective Effect of Dietary Supplementation with n-3 Fatty Acids

Abstract: Diabetic neuropathy is a degenerative complication of diabetes accompanied by an alteration of nerve conduction velocity (NCV) and Na,K-ATPase activity. The present study in rats was designed first to measure diabetes-induced abnormalities in Na,K-ATPase activity, isoenzyme expression, fatty acid content in sciatic nerve membranes, and NCV and second to assess the preventive ability of a fish oil-rich diet (rich in n-3 fatty acids) on these abnormalities. Diabetes was induced by intravenous streptozotocin injection. Diabetic animals (D) and nondiabetic control animals (C) were fed the standard rat chow either without supplementation or supplemented with either fish oil (DM, CM) or olive oil (DO, CO) at a daily dose of 0.5 g/kg by gavage during 8 weeks. Analysis of the fatty acid composition of purified sciatic nerve membranes from diabetic animals showed a decreased incorporation of C16:1(n-7) fatty acids and arachidonic acids. Fish oil supplementation changed the fatty acid content of sciatic nerve membranes, decreasing C18:2(n-6) fatty acids and preventing the decreases of arachidonic acids and C18:1(n-9) fatty acids. Protein expression of Na,K-ATPase α subunits, Na,K-ATPase activity, and ouabain affinity were assayed in purified sciatic nerve membranes from CO, DO, and DM. Na,K-ATPase activity was significantly lower in sciatic nerve membranes of diabetic rats and significantly restored in diabetic animals that received fish oil supplementation. Diabetes induced a specific decrease of α1- and α3-isoform activity and protein expression in sciatic nerve membranes. Fish oil supplementation restored partial activity and expression to varying degrees depending on the isoenzyme. These effects were associated with a significant beneficial effect on NCV. This study indicates that fish oil has beneficial effects on diabetes-induced alterations in sciatic nerve Na,K-ATPase activity and function.     

Effect of Early Iron Deficiency in Rat on the γ-Aminobutyric Acid Shunt in Brain

Early iron deficiency in rat does not affect the weight or the protein, DNA, and RNA content but results in a slight reduction in gamma-aminobutyric acid (GABA) (13%, p less than 0.01) and glutamic acid (20%, p less than 0.001) content of the brain. The activities of the two GABA shunt enzymes, glutamate dehydrogenase and GABA-transaminase, and of the NAD+-linked isocitrate dehydrogenase (ICDH) were inhibited whereas the glutamic acid decarboxylase, mitochondrial NADP+-linked ICDH, and succinic dehydrogenase activities remained unaltered in brain. On rehabilitation with the iron-supplemented diet for 1 week, these decreased enzyme activities in brain attained the corresponding control values. However, the hepatic nonheme iron content increased to about 80% of the control, after rehabilitation for 2 weeks. A prolonged iron deficiency resulting in decreased levels of glutamate and GABA may lead to endocrinological, neurological, and behavioral alterations.     

Selective Depletion of Dopamine, Octopamine, and 5-Hydroxytryptamine in the Nervous Tissue of the Cockroach (Periplaneta americana)

High-performance liquid chromatography with electrochemical detection was used to measure the concentrations of 3,4-dihydroxyphenylethylamine (dopamine), 5-hydroxytryptamine (5-HT), p-hydroxyphenylethanolamine (octopamine), alpha-methyl-p-tyrosine, and tryptophan in the cerebral ganglia of cockroaches (Periplaneta americana) after peripheral administration of alpha-methyl-p-tyrosine and alpha-methyltryptophan. In addition, the levels of dopamine, 5-HT, octopamine, alpha-methyl-p-tyrosine, and tryptophan were determined after injection of alpha-methyl-p-tyrosine, 6-hydroxydopamine, or 5,7-dihydroxytryptamine directly into the cerebral ganglia by means of microinjection needles. Peripheral administration of alpha-methyl-p-tyrosine (400-1,600 micrograms/insect) caused a reduction in dopamine and 5-HT concentrations in cockroach cerebral ganglia, although the reduction in dopamine concentrations was more pronounced. Peripheral injections of alpha-methyl-p-tyrosine also reduced octopamine levels in the cerebral ganglia. Peripheral injection of alpha-methyltryptophan (400-1,600 micrograms/insect) caused a marked reduction in 5-HT and tryptophan concentrations in cockroach cerebral ganglia without altering dopamine or octopamine concentrations. Central injections of alpha-methyl-p-tyrosine (80 micrograms/insect) reduced dopamine concentrations in the cerebral ganglia. However, neither 6-hydroxydopamine (20 micrograms/insect) nor 5,7-dihydroxytryptamine (20 micrograms/insect) caused reductions in amine levels when applied near or directly into the cerebral ganglia. The results suggest that specific lesions of aminergic neurons in insects by either 6-hydroxydopamine or 5,7-dihydroxytryptamine are impractical. The specific, long-lasting depletion of 5-HT by alpha-methyltryptophan suggests that this chemical may be useful in elucidating the functions of 5-HT in insects.