Neuronal Phospholipids Research Articles

Untargeted metabolomics to evaluate polymyxin B toxicodynamics following direct intracerebroventricular administration into the rat brain

There is a dearth of studies focused on understanding pharmacokinetics, pharmacodynamics and toxicodynamics of polymyxins following direct administration to the central nervous system (CNS). In this study, for the first time, untargeted metabolomics were employed to ascertain the perturbations of brain metabolism in the rat cerebral cortex following direct brain injection of 0.75 mg/kg polymyxin B (1 and 4 h) through the right lateral ventricle. In the right cortex metabolome, ICV polymyxin B induced a greater perturbation at 1 h compared to negligible effect at 4 h. Pathway enrichment analysis showed that sphingolipid, arginine, and histidine metabolism, together with aminoacyl-tRNA biosynthesis were significantly affected in the right cortex metabolome. Furthermore, intracerebroventricular (ICV) polymyxin B dysregulated the two arms (CDP-choline and CDP-ethanolamine) of the Kennedy pathway that governs the de novo biosynthesis of neuronal phospholipids. Importantly, the key intermediates of metabolic pathways that maintain cellular redox balance (e.g., glutathione metabolism) and mitochondrial function (e.g., electron transport chain) were markedly depleted. The abundance of key metabolites (e.g., N-acetyl-l-glutamate) associated with diverse CNS disorders (e.g., neurodegenerative disease) were also significantly perturbed. The biological significance of these metabolic perturbations on the CNS includes impaired oxidant-antioxidant balance, impaired neuronal lipid homeostasis and mitochondrial dysfunction. Furthermore, ICV polymyxin B caused a significant alteration in the abundance of several metabolic biomarkers associated with cerebral ischemia, oxidative stress as well as certain neurological disorders. These findings may facilitate the development of new pharmacokinetic/pharmacodynamic strategies to attenuate polymyxins ICV related CNS toxicities and stimulate the discovery of safer next-generation polymyxin-like lipopeptide antibiotics.

Unexpected Effects of Acetylcholine Precursors on Pilocarpine Seizure- Induced Neuronal Death.

Background:Choline alfoscerate (α-GPC) and Cytidine 5’-diphosphocholine (CDP-Choline) are both acetylcholine precursors and are considered to act as pro-cholinergic nootropic agents. Acetylcholine precursors have also recently found frequent use in the neurology clinic. Stroke and many types of dementia have been shown to respond favorably after treatment with these agents, not only in terms of cognitive dysfunction but also behavioral and psychological symptoms. The primary mechanisms of Acetylcholine precursors are the following: 1) Acetylcholine precursors themselves are used in the biosynthesis of acetylcholine and 2) byproducts like glycerophosphate have protective functions for neuronal phospholipids. However, whether acetylcholine precursors have a similar effect in treating cognitive impairment in patients with epilepsy remains controversial.Methods:Our previous studies investigating acetylcholine precursors in seizure-experienced animals have produced variable results that were dependent on the timing of administration.Results:Early administration of CDP-choline immediately after seizure increased neuronal death, blood-brain barrier (BBB) disruption and microglial activation in the hippocampus. However, administration of α-GPC starting 3 weeks after seizure (late administration) improved cognitive function through reduced neuronal death and BBB disruption, and increased neurogenesis in the hippocampus.Conclusion:These seemingly contradictory results may be attributed to both epileptogenic features and neuroprotective functions of several acetylcholine precursors.

Altered plasma and CSF levels of nutrients that enhance neuronal phospholipid synthesis in Alzheimer’s disease: A retrospective cohort study

Altered plasma and CSF levels of nutrients that enhance neuronal phospholipid synthesis in Alzheimer’s disease: A retrospective cohort study

Control of P2X3 Channel Function by Metabotropic P2Y2 UTP Receptors in Primary Sensory Neurons

Purinergic signaling contributes significantly to pain mechanisms, and the nociceptor-specific P2X3 ATP receptor channel is considered a target in pain therapeutics. Recent findings suggesting the coexpression of metabotropic P2Y receptors with P2X3 implies that ATP release triggers the activation of both ionotropic and metabotropic purinoceptors, with strong potential for functional interaction. Modulation of native P2X3 function by P2Y receptor activation was investigated in rat dorsal root ganglia (DRG) neurons using whole cell patch-clamp recordings. Application of the selective P2Y receptor agonist UTP decreased peak amplitudes of α,β-meATP-evoked homomeric P2X3-mediated currents, but had no effect on heteromeric P2X2/3-mediated currents. Treatment with phospholipase C inhibitor U73122 significantly reversed P2X3 current inhibition induced by UTP-sensitive P2Y receptor activation. We previously reported the modulation of P2X receptors by phospholipids in DRG neurons and injection of exogenous phosphatidylinositol-4,5-bisphosphate (PIP(2)) fully reverses UTP-mediated regulation of P2X3 channel activity. Pharmacological as well as functional screening of P2Y receptor subtypes indicates the predominant involvement of P2Y2 receptor in P2X3 inhibition, and immunolocalization confirms a significant cellular coexpression of P2X3 and P2Y2 in rat DRG neurons. In summary, the function of P2X3 ATP receptor can be inhibited by P2Y2-mediated depletion of PIP(2). We propose that expression of P2Y2 purinoceptor in nociceptive sensory neurons provides an homeostatic mechanism to prevent excessive ATP signaling through P2X3 receptor channels.

Mitochondrial Injury after Mechanical Stretch of Cortical Neuronsin vitro: Biomarkers of Apoptosis and Selective Peroxidation of Anionic Phospholipids

Mechanical injury of neurites accompanied by rupture of mitochondrial membranes may lead to immediate nonspecific release and spreading of pro-apoptotic factors and activation of proteases, that is, execution of apoptotic program. In the current work, we studied the time course of the major biomarkers of apoptosis as they are induced by exposure of rat cortical neurons to mechanical stretch. By using transmission electron microscopy, we found that mitochondria in the neurites were damaged early (1 h) after mechanical stretch injury whereas somal mitochondria were significantly more resistant and demonstrated structural damage and degenerative mitochondrial changes at a later time point after stretch (12 h). We also report that the stretch injury caused immediate activation of reactive oxygen species production followed by selective oxidation of a mitochondria-specific phospholipid, cardiolipin, whose individual peroxidized molecular species have been identified and quantified by electrospray ionization mass spectrometry analysis. Most abundant neuronal phospholipids - phosphatidylcholine, phophatidylethanolamine - did not undergo oxidative modification. Simultaneously, a small-scale release of cytochrome c was observed. Notably, caspase activation and phosphatidylserine externalization - two irreversible apoptotic events designating a point of no return - are substantially delayed and do not occur until 6-12 h after the initial impact. The early onset of reactive oxygen species production and cytochrome c release may be relevant to direct stretch-induced damage to mitochondria. The delayed emergence of apoptotic neuronal death after the immediate mechanical damage to mitochondria suggests a possible window of opportunity for targeted therapies.

Rola kwasu dokozaheksaenowego w czynności komórek nerwowych

Docosahexaenoic acid (DHA, C22: 6n-3) is the most abundant polyunsaturated fatty acid in neuronal phospholipids, particularly in the cortex. The main source of DHA for neural cells is food, and hepatic and astroglia DHA synthesis from essential a-linolenic acid (C18: 3n-3). Accretion of DHA in the brain is most intensive during fetal life and the first two years of life. An adequate level of DHA in cell membranes is important for many functions of neural cells and this is presumably the reason for DHA saving in the adult mammalian brain during dietary a-linolenic acid deficiency. DHA-containing phospholipids in membranes are flexible and membranes possessing a high content of them are quite thin, more permeable to ions and small molecules, have looser lipid packing, and finally are more "dynamic" than membranes composed of other fatty acid containing phospholipids. Furthermore, these membranes create an appropriate environment for integral proteins highly condensed in neurons, such as receptors, ion channels, enzymes, and peripheral proteins. The quantity of phosphatidylserine in the inner membrane lipid layer depends on the availability of DHA to neurons. Phosphatidylserine promotes neuronal survival by translocation/activation of kinase Akt and Raf-1/MEK. DHA present in membrane phospholipids facilitates v-SNARE/t-SNARE complex formation, which is necessary for fusion of synaptic vesicles and plasma membranes necessary for transmitter exocytosis, and neurite outgrowth-dependent plasticity. DHA plays an important neuroprotective role. DHA has been shown to inhibit PGE2 synthesis and COX-1 expression in astrocytes, and DHA derivatives, especially neuroprotectins D, can suppress inflammatory responses, preventing neuronal damage or apoptosis. The results of high DHA content in neuronal membranes and formation of DHA derivates, as well as the function of DHA-dependent phosphatidylserine, may explain the promising results supporting beneficial DHA supplementation in neurodegenerative diseases and improvement of brain function.

Differential distribution of DHA-phospholipids in rat brain after feeding: A lipidomic approach

On a per-weight basis, the brain is the organ richest in lipids, including a remarkable proportion of polyunsaturated fatty acids (PUFAs) of the omega 3 series, namely eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. The cerebral effects of exogenous DHA likely depend on its degree of incorporation into neuronal phospholipids and on its distribution among the various brain structures, after intake. Hence, because PUFAs are not evenly distributed among the brain phospholipid classes and because the existence of class-specific phospholipases that regulate their turnover, we sought to investigate the incorporation of omega 3 PUFAs in selected brain areas regions and specific phospholipid classes. Rats ( n=7) were administered, by oral gavage, 100 mg/kg/d of a commercially available fish oil (containing ∼84% of long-chain omega 3 fatty acids, of which ∼38% of DHA and ∼46% of EPA). Control rats ( n=7) received liquid paraffin. This treatment was continued for 30 days. Thereafter, we dissected three areas, namely the hippocampus, the striatum, and the cortex. Quantization of individual phospholipid classes and their molecular species was performed by ESI-MS/MS. Principal component analysis was used to examine the variation of the molecular lipid profiles (as percentage) induced by omega 3 supplementation. Our results show that provision of omega 3 fatty acids to rats results in their incorporation into brain phospholipids, the extent of which is lower in the striatum as compared with cortex and hippocampus. These data might in part explain the mixed therapeutic results obtained in neurological disorders, many of which are likely region-specific.

I039 Role of PRG-1, a neuronal phospholipid phosphatase, in the function of vascular smooth muscle cells

Proliferation and migration of vascular smooth muscle cells (VSMCs) leading to neointima formation are a hallmark of development and progression of some cardiovascular diseases. LPA (lysophosphatidic acid) which has been shown to induces a dedifferenciation of VSCM, resulting in cell proliferation and migration in vitro, and vascular remodelling in vivo. The aim of our project is to understand the role of PRG-1 (Plasticity Related Gene-1), or LPPR4 (Lipid Phosphate Phosphatase Related protein 4), in the regulation of VSMCs proliferation and migration induced by LPA. This enzyme acts as en ecto-enzyme dephosphorylating LPA, thereby inhibiting its activity, and was found in previous studies to be down-regulated in the media of aging and hypertensive rats. We showed that PRG-1 is expressed in the rat and human aortic media and rat VSMCs by PCR, immunofluorescence and western blot. This expression was highly decreased in cultured VSMCs as compared with what was observed in the aortic media, and restored by cells starvation, suggesting that PRG-1 expression is dependent on the differentiated phenotype of these cells. We studied the response to LPA of VSMCs infected with an adenovirus containing the human sequence of PRG1 (PRG1-VSMCs) or with an adenovirus expressing LacZ (LacZ-VSMCs). In vitro, LPA-induced migration of PRG1-VSMCs (measured by scrapewound assays) and LPA-induced proliferation (measured by BrdU incorporation) were inhibited (by 60 % and 40 % respectively) as compared with LacZ-VSMCs. In vivo, experiments of left carotid injury by ballooning followed by gene transfer with adenovirus injection, showed a 70 % reduction of neointima formation when carotids were infected with PRG-1 adenovirus as compared with infection with LacZ adenovirus. Current investigations indicate that PRG-1 seems to block Erk1/2 signalling pathway activated by LPA. Our results demonstrate that PRG-1 is expressed in the VSMCs of the media ; and this expression is modulated in conditions of vascular remodelling and primary culture. PRG-1 overexpression inhibits VSMCs migration and proliferation in vitro and neotintima formation in vivo. Taken together, these findings suggest that, in the media, PRG-1 plays a protective role in pathophysiological conditions.

Mass‐spectrometric characterization of phospholipids and their primary peroxidation products in rat cortical neurons during staurosporine‐induced apoptosis

The molecular diversity of phospholipids is essential for their structural and signaling functions in cell membranes. In the current work, we present, the results of mass spectrometric characterization of individual molecular species in major classes of phospholipids -- phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn), phosphatidylserine (PtdSer), phosphatidylinositol (PtdIns), sphingomyelin (CerPCho), and cardiolipin (Ptd(2)Gro) -- and their oxidation products during apoptosis induced in neurons by staurosporine (STS). The diversity of molecular species of phospholipids in rat cortical neurons followed the order Ptd(2)Gro > PtdEtn >> PtdCho >> PtdSer > PtdIns > CerPCho. The number of polyunsaturated oxidizable species decreased in the order Ptd(2)Gro >> PtdEtn > PtdCho > PtdSer > PtdIns > CerPCho. Thus a relatively minor class of phospholipids, Ptd(2)Gro, was represented in cortical neurons by the greatest variety of both total and peroxidizable molecular species. Quantitative fluorescence HPLC analysis employed to assess the oxidation of different classes of phospholipids in neuronal cells during intrinsic apoptosis induced by STS revealed that three anionic phospholipids -- Ptd(2)Gro >> PtdSer > PtdIns -- underwent robust oxidation. No significant oxidation in the most dominant phospholipid classes -- PtdCho and PtdEtn -- was detected. MS-studies revealed the presence of hydroxy-, hydroperoxy- as well as hydroxy-/hydroperoxy-species of Ptd(2)Gro, PtdSer, and PtdIns. Experiments in model systems where total cortex Ptd(2)Gro and PtdSer fractions were incubated in the presence of cytochrome c (cyt c) and H(2)O(2), confirmed that molecular identities of the products formed were similar to the ones generated during STS-induced neuronal apoptosis. The temporal sequence of biomarkers of STS-induced apoptosis and phospholipid peroxidation combined with recently demonstrated redox catalytic properties of cyt c realized through its interactions with Ptd(2)Gro and PtdSer suggest that cyt c acts as a catalyst of selective peroxidation of anionic phospholipids yielding Ptd(2)Gro and PtdSer peroxidation products. These oxidation products participate in mitochondrial membrane permeability transition and in PtdSer externalization leading to recognition and uptake of apoptotic cells by professional phagocytes.

Essential fatty acids and mental illness

SummaryThe treatment of psychiatric illness requires novel pharmacological strategies. There is a growing body of evidence examining the role of neuronal phospholipid abnormalities in the pathogenesis of psychiatric illness, particularly in schizophrenia. However, work in other conditions like mood disorders are also showing interesting outcomes with EPA supplementation. Diseases that are considered to have a genetic basis may be significantly influenced by environmental factors including dietary supplementation. The suggestion that EFA supplementation may prevent the onset of symptoms of a psychiatric disease or aberrant behaviour needs longitudinal randomized controlled research. In recent years the focus has shifted from omega-6 to omega-3. It is true that western diets have far more omega-6 than omega-3. In the 1980s, there were positive outcomes in research studies using GLA in schizophrenia (Vaddadi et al., ). Future research needs to incorporate studies using pure GLA. Research should not be restricted to parent fatty acid (omega-3) supplementation alone but be expanded to include bioactive down-the-chain metabolites. The recent identification of novel omega-3 derived mediators such as resolvins and neuroprotectins, which are a highly bioactive (1–10 nMol range), may well have some role to play in psychiatric disorders; however this remains highly speculative at this stage.

The neuronal lipid membrane permeability was markedly increased by bupivacaine and mildly affected by lidocaine and ropivacaine

We investigated the local anesthetic action on ionic membrane conductance (membrane conductance) and selectivity in membranes formed with neuronal phospholipids in the absence and presence of cholesterol. In membranes without cholesterol, 1 mM bupivacaine and ropivacaine increased the membrane conductance ∼4.5-fold; and 5 mM lidocaine, ropivacaine and bupivacaine increased the membrane conductance by 2.7-, 2.8- and 22.2-fold, respectively. In the presence of cholesterol, 5 mM ropivacaine had no effect, lidocaine decreased the membrane conductance by 2-fold, and bupivacaine increased the membrane conductance by 17-fold. Local anesthetics did not affect the ion selectivity in membranes without cholesterol, but they all decreased the Na + selectivity in membranes with cholesterol. Cholesterol reduced the lidocaine- and ropivacaine-induced membrane conductance increase by eliminating or reversing the Na + conductance increase and by lowering the Cl − conductance increase. In the absence of cholesterol, 5 mM bupivacaine increased both Na + conductance (38-fold) and Cl − conductance (19-fold), while in the presence of cholesterol it only increased Cl − conductance (26-fold). Of the local anesthetics studied, ropivacaine was the least membrane toxic while bupivacaine was the most toxic.

EICOSAPENTAENOIC ACID IN TREATMENT‐RESISTANT DEPRESSION ASSOCIATED WITH SYMPTOM REMISSION, STRUCTURAL BRAIN CHANGES AND REDUCED NEURONAL PHOSPHOLIPID TURNOVER

SUMMARYThe n‐3 essential fatty acid eicosapentaenoic acid (EPA) was added to the conventional antidepressant treatment of a treatment‐resistant severely depressed and suicidal male patient with a seven‐year history of unremitting depressive symptoms. The niacin skin flush test and cerebral magnetic resonance scanning were carried out at baseline and nine months later. The addition of ethyl‐EPA led to a dramatic and sustained clinical improvement in all the symptoms of depression, including a cessation of previously unremitting severe suicidal ideation, within one month. Symptoms of social phobia also improved dramatically. During the nine‐month period the volumetric niacin response increased by 30%, the relative concentration of cerebral phosphomonesters increased by 53%, and the ratio of cerebral phosphomonesters to phosphodiesters increased by 79%, indicating reduced neuronal phospholipid turnover. Registered difference images showed that the EPA treatment was accompanied by structural brain changes including, in particular, a reduction in the lateral ventricular volume.

The apolipoprotein E epsilon 4 allele is not associated with early onset temporal lobe epilepsy.

A polymorphism of the apolipoprotein E gene, in particular the epsilon 4 allele (ApoE4), has been associated with impaired neuronal phospholipid metabolism and synapse reorganization and has been implicated in several neurodegenerative disorders. Since selective neuronal cell lose and aberrant axonal reorganization represent hall-marks of Ammon's horn sclerosis (AHS) in patients with chronic temporal lobe epilepsy (TLE), the ApoE polymorphism was studied in 125 patients with TLE. The genotype analysis revealed a frequency of 15.5% for epsilon 4, and 74.8% and 9.8% for epsilon 3 and epsilon 2, respectively. These figures were not significantly different from those reported in the normal European population. In addition, no correlation was found between the ApoE4 allelotype and the age of epilepsy onset, seizure type, febrile seizures, family history of epilepsy, surgical outcome and neuropathological findings in patients with TLE. These data virtually exclude ApoE as a susceptibility gene involved in the pathogenesis of early onset TLE or AHS.

Free choline and choline metabolites in rat brain and body fluids: sensitive determination and implications for choline supply to the brain

In the central nervous system, choline is an essential precursor of choline-containing phospholipids in neurons and glial cells and of acetylcholine in cholinergic neurons. In order to study choline transport and metabolism in the brain, we developed a comprehensive methodical procedure for the analysis of choline and its major metabolites which involves a separation step, selective hydrolysis and subsequent determination of free choline by HPLC and electrochemical detection. In the present paper, we report the levels of choline, acetylcholine, phosphocholine, glycerophosphocholine and choline-containing phospholipids in brain tissue, cerebrospinal fluid and blood plasma of the untreated rat. The levels of free choline in blood plasma (11.4 μM), CSF (6.7 μM) and brain intracellular space (64.0 μM) were sufficiently similar to be compatible with an exchange of choline between these compartments. In contrast, the intracellular levels of glycerophosphocholine (1.15 mM) and phosphocholine (0.59 mM) in the brain were considerably higher than their CSF concentrations of 2.83 and 1.70 μM, respectively. In blood plasma, glycerophosphocholine was present in a concentration of 4.58 μM while phosphocholine levels were very low or absent (<0.1 μM). The levels of phosphatidylcholine and lyso-phosphatidylcholine were high in blood plasma (1267 and 268 μM) but very low in cerebrospinal fluid (<10 μM). We concluded that the transport of free choline is the only likely mechanism which contributes to the supply of choline to the brain under physiological conditions.

Bradykinin Stimulates Arachidonic Acid Release Through the Sequential Actions of an sn‐1 Diacylglycerol Lipase and a Monoacylglycerol Lipase

In cultured dorsal root ganglion (DRG) neurons prelabeled with [3H]arachidonic acid [( 3H]AA), bradykinin (BK) stimulation resulted in increased levels of radioactive diacylglycerol, monoacylglycerol, and free AA. The transient increases in content of radioactive diacylglycerol and monoacylglycerol preceded the increase in level of free AA, suggesting the contribution of a diacylglycerol lipase pathway to AA release. An analysis of the molecular species of diacylglycerols in unstimulated cultures revealed the presence of two primary [3H]AA-containing species, 1-palmitoyl-2-arachidonoyl and 1-stearoyl-2-arachidonoyl diacylglycerol. BK stimulation resulted in a preferential increase in content of 1-stearoyl-2-arachidonoyl diacylglycerol. When DRG cultures were labeled with [3H]stearic acid, treatment with BK increased the amount of label in diacylglycerol and free stearic acid, but not in monoacylglycerol. This result suggested that AA release occurred through the successive actions of an sn-1 diacylglycerol lipase and monoacylglycerol lipase. Other data supporting a diacylglycerol lipase pathway was the significant inhibition of [3H]AA release and consequent accumulation of diacylglycerol by RG 80267, which preferentially inhibits diacylglycerol lipase. Analysis of the molecular species profiles of individual phospholipids in DRG neurons indicated that phosphoinositide hydrolysis may account for a significant portion of the rapid increase in content of 1-stearoyl-2-arachidonoyl diacylglycerol. We were unable to obtain evidence that the phospholipase A2 pathway makes a significant contribution to BK-stimulated AA release in DRG cultures. Under our assay conditions there were no BK-stimulated increases in levels of radioactive lysophosphatidylinositol, lysophosphatidylcholine, or lysophosphatidylethanolamine in cultures prelabeled with [3H]inositol, [3H]choline, or [3H]-ethanolamine, respectively.

Measurement of inositol phospholipid metabolism in PC12 pheochromocytoma cells

Publisher Summary PC12 cells are a clonal cell line derived from a rat pheochromocytoma. These cells are widely used as models for both adrenal chromaffin cells and sympathetic neurons. When PC 12 cells are grown in the absence of nerve growth factor (NGF), they appear as small, round, undifferentiated cells. In the presence of NGF, the cells stop dividing, enlarge, and extend long neuronal-like processes. NGF also increases the number of muscarinic cholinergic receptors on PC12 cells. Muscarinic agonists stimulate the metabolism of inositol-containing phospholipids in PC12 cells. The ability to grow large amounts of a homogeneous population of cells, to manipulate the properties of the cells by changing the extracellular environment, and to stimulate phospholipid metabolism with specific agonists provides valuable opportunities for studying neuronal phospholipid metabolism in PC12 cells. The chapter describes the growth PC12 cells.

Influence of ethanol on fatty acid composition of phospholipids in cultured neurons

Animals chronically exposed to ethanol show changes in neural membrane lipids which may underlie the development of tolerance and physical dependence. The object of this study was to investigate changes in the fatty acid composition of neuronal phospholipids cultured in the presence of ethanol (55 or 110 mM) for periods up to 7 days. Decreases were observed in the percentage of individual and total saturated fatty acids, while the double bond index: total saturated fatty acid ratio, increased. These changes do not support the hypothesis that neural membrane lipid composition changes to counteract the fluidizing action of ethanol.

Free radical theory of aging: Effect of dietary lipids on lipofuscin accumulation in the hippocampus of rats

The fatty acid composition of central nervous system lipids is largely independent of the dietary fat except for docosahexanoic acid (22:6ω3) and its precursors, mainly linolenic acid (18:3ω3). Ingestion of these lipids increases peroxidizability of neuronal phospholipids by displacing 22:5ω6 with 22:6ω3. Since lipofuscin (age pigment) is formed by oxidative polymerization of lipid and protein it seemed likely that increases in dietary 22: 6ω3 and/or peroxidizability of the dietary lipids might enhance lipofuscin accumulation. To evaluate these possibilities groups of male Charles River CD strain rats were fed a commercial diet, or semi-synthetic diets containing either 5%w (percent by weight) lard, 20%w olive oil, or 20%w safflower oil for periods up to 28 months of age; the amount of 22:6ω3 in lard is small, but considerably more than that of 22:6ω3 plus its precursors in olive oil or safflower oil. At 24 months of age the lipofuscin content of hippocampal neurons of rats fed the lard diet was significantly greater than for the control, olive oil or safflower oil groups; there was no significant difference between the latter two groups. Thus lipofuscin accumulation in hippocampal neurons was associated with increases in neuronal content of 22:6ω3 and not with the gross peroxidizability of the dietary lipid.

Phosphatidate as a molecular link between depolarization and neurotransmitter release in the brain.

Phosphatidate, a neuronal phospholipid, stimulated the uptake of calcium by nerve terminals isolated from the striatum of rat brain. This effect was not produced by other phospholipids or glycolipids. Phosphatidate, but not other phospholipids, evoked the release of [3H] dopamine from striatal synaptosomes. The magnitude of both effects was similar to that observed after chemical depolarization of the nerve terminals. These results show that phosphatidate is the only membrane lipid component that acts as a functionally competent ionophore and support the suggestion that phosphatidate may serve as a link between depolarization and neurotransmitter release in the brain.

Dexamethasone preservation of motor function in phospholipase A 2-induced caudate lesions

Unilateral lesions of the rat caudate nucleus produced by the direct application of phospholipase A 2 resulted in motor impairment manifested by rotation. Pretreatment with the glucocorticoid, dexamethasone (0.5 mg, 1.0 mg/kg), preserved motor function in the phospholipase A 2-treated rats. The number of rotations appared to correlate with alterations in caudate phospholipid content. Caudate sections from phospholipase A 2-treated animals exhibited lysolecithin and lysophosphatidylethanolamine, two phospholipids not detected in caudate sections from normal or dexamethasone-treated animals. We conclude that phospholipase A 2 produced caudate lesions associated with rotational behavior and alteration of neuronal phospholipids, both of which were prevented by dexamethasone treatment. The therapeutic action of dexamethasone may involve the maintenance of neuronal membrane phospholipids.