Postnastal changes in the concentration of carnitine and acylcarnitines in the rat brain

Rational analysis of data from LC-MS/MS: new insights in acylcarnitines as biomarkers for brain disorders or neurotoxicity

Objective

LC-MS/MS-based metabolomics is an important tool for studying disease-related biomarkers. Conventionally, different strategies have been used to screen biomarkers. However, many studies for biomarker screening by different strategies have ignored the dose-response relationship between the biomarker level and exposure level, and no relevant studies have described and compared different strategies in detail. Phenobarbital (PHB) which belongs to the barbiturates, was selected as the typical representative of neurotoxins. Acylcarnitines have been promising candidates for diagnostic biomarkers for several neurological disorders and neurotoxicity. In this work, we aimed to use an acute PHB poisoning animal model to clarify PHB poisoning effects on plasma and brain acylcarnitine changes and how to rationally analyze data from LC-MS/MS.

Methods

The acylcarnitine profiles in plasma and brain regions in an actuate PHB poisoning animal model were utilized. The dose-response relationship between plasma PHB and carnitine and acylcarnitines (CARs) in plasma and brain were assessed by the variance analysis trend test and Spearman's rank correlation test. In different strategies, principal component analysis (PCA) and partial least squares discriminant analysis (OPLS-DA) screened the differential CARs, variable importance plots (VIPs) were utilized to select putative biomarkers for PHB-induced toxicity, and receiver operating characteristic (ROC) curve analysis then illustrated the reliability of biomarkers.

Results

Under the first strategy, 14 potential toxicity biomarkers were obtained including eight downregulated CARs with AUC >0.8. Under the second strategy, 11 potential toxicity biomarkers were obtained containing five downregulated CARs with AUC >0.8. Only when the dose-response relationship was fully considered, different strategies screen for the same biomarkers (plasma acetyl-carnitine (C2) and plasma decanoyl-carnitine (C10)), which indicated plasma acylcarnitines might serve as toxicity biomarkers. In addition, the plasma CAR level changes showed differences from brain CAR level changes, and correlations between plasma CARs and their brain counterparts were weak.

Conclusion

We found that plasma C2 and C10 might serve as toxicity biomarkers for PHB poisoning disorders, and PHB poisoning effects on changes in plasma CARs may not be fully representative of changes in brain CARs.

L-Carnitine in the Treatment of Psychiatric and Neurological Manifestations: A Systematic Review

OBJECTIVE

L-carnitine (LC), a vital nutritional supplement, plays a crucial role in myocardial health and exhibits significant cardioprotective effects. LC, being the principal constituent of clinical-grade supplements, finds extensive application in the recovery and treatment of diverse cardiovascular and cerebrovascular disorders. However, controversies persist regarding the utilization of LC in nervous system diseases, with varying effects observed across numerous mental and neurological disorders. This article primarily aims to gather and analyze database information to comprehensively summarize the therapeutic potential of LC in patients suffering from nervous system diseases while providing valuable references for further research.

METHODS

A comprehensive search was conducted in PubMed, Web Of Science, Embase, Ovid Medline, Cochrane Library and Clinicaltrials.gov databases. The literature pertaining to the impact of LC supplementation on neurological or psychiatric disorders in patients was reviewed up until November 2023. No language or temporal restrictions were imposed on the search.

RESULTS

A total of 1479 articles were retrieved, and after the removal of duplicates through both automated and manual exclusion processes, 962 articles remained. Subsequently, a meticulous re-screening led to the identification of 60 relevant articles. Among these, there were 12 publications focusing on hepatic encephalopathy (HE), while neurodegenerative diseases (NDs) and peripheral nervous system diseases (PNSDs) were represented by 9 and 6 articles, respectively. Additionally, stroke was addressed in five publications, whereas Raynaud's syndrome (RS) and cognitive disorder (CD) each had three dedicated studies. Furthermore, migraine, depression, and amyotrophic lateral sclerosis (ALS) each accounted for two publications. Lastly, one article was found for other symptoms under investigation.

CONCLUSION

In summary, LC has demonstrated favorable therapeutic effects in the management of HE, Alzheimer's disease (AD), carpal tunnel syndrome (CTS), CD, migraine, neurofibromatosis (NF), PNSDs, RS, and stroke. However, its efficacy appears to be relatively limited in conditions such as ALS, ataxia, attention deficit hyperactivity disorder (ADHD), depression, chronic fatigue syndrome (CFS), Down syndrome (DS), and sciatica.

Acetyl-L-carnitine reduces depression and improves quality of life in patients with minimal hepatic encephalopathy

BACKGROUND

Minimal hepatic encephalopathy (MHE) represents a common complication present in well-compensated cirrhotic patients that impairs patients' daily functioning and health-related quality of life (HRQL). Acetyl-L-carnitine (ALC) has been shown to be useful in improving blood ammonia and cognitive functions in cirrhotic patients with MHE.

OBJECTIVE

This study evaluated the effects of ALC treatment on HRQL and depression in patients with MHE.

STUDY DESIGN

This was a randomized, double-blind, placebo-controlled study. Sixty-seven patients with MHE were recruited to the study. They were randomly assigned to two groups and received either 2 g acetyl-L-carnitine twice a day (n = 33) or placebo (n = 34) for 90 days. The primary efficacy measures were changes in aspartate aminotransferase, alanine aminotransferase, γ-glutamyl-transpeptidase, albumin, alkaline phosphatase, prothrombin time, and ammonia. Clinical and laboratory assessments, psychometric tests and automated electroencephalogram (EEG) analysis were performed for all patients.

RESULTS

At the end of the study period, between the two groups, we observed a significant difference in physical function (p < 0.001), role physical (p < 0.001), general health (p < 0.001), social function (p < 0.05), role emotional (p < 0.05), mental health (p < 0.05), Beck Depression Inventory (p < 0.001), TMT-B s (p < 0.001), State Trait Inventory (p < 0.001), urea (p < 0.05), NH(4)(+) (p < 0.001), and bilirubin (p < 0.001).

CONCLUSIONS

This study shows that ALC treatment is associated with significant improvement in patient energy levels, general functioning and well-being. The improvement of quality of life is associated with reduction of anxiety and depression.

Oral acetyl-L-carnitine therapy reduces fatigue in overt hepatic encephalopathy: a randomized, double-blind, placebo-controlled study

BACKGROUND

Fatigue is frequently reported in hepatic encephalopathy (HE) and may be related to hyperammonemia. Acetyl-L-carnitine (ALC) offers neuroprotective benefits and improves mitochondrial energetics and function.

OBJECTIVE

This study evaluated the effect of exogenous ALC on physical and mental fatigue, fatigue severity, and physical activity in patients with mild and moderate hepatoencephalopathy (HE1 and HE2, respectively).

DESIGN

A total of 121 patients with overt HE were recruited to the study and were subdivided into 2 groups according to their initial HE grade [HE1 (n = 61) or HE2 (n = 60)]. Thirty-one patients with HE1 and 30 with HE2 received 2 g ALC, and 30 patients with HE1 and 30 patients with HE2 received placebo twice a day for 90 d. All patients underwent clinical and laboratory assessments and automated electroencephalogram analysis.

RESULTS

At the end of the study period, the ALC-treated patients in the HE1 group showed significantly better improvement than did the placebo group in mental fatigue score (-1.7 compared with -0.3; P < 0.05), the fatigue severity scale (-6.4 compared with 2.3; P < 0.001), 7-d Physical Activity Recall questionnaire score (17.1 compared with -2.5; P < 0.001), and Short Physical Performance Battery (2.1 compared with 0.2; P < 0.001); the HE2 group showed significantly better improvement in the fatigue severity scale (-8.1 compared with -5.1; P < 0.001) and 6-min walk test (19.9 compared with 2.3; P < 0.05). Significant decreases in NH(4)(+) were observed in both groups (P < 0.001).

CONCLUSION

Patients with HE treated with ALC showed a decrease in the severity of both mental and physical fatigue and an increase in physical activity. This trial was registered at clinicaltrials.gov as NCT01223742.

The effect of starvation on brain carnitine concentration in neonatal rats

BACKGROUND

We examined carnitine concentrations in fasted neonatal rat brain to evaluate the effect of starvation on fatty acid metabolism.

METHODS

The free- and acylcarnitine concentrations in neonatal rat brain and heart were determined after a 72-hour starvation period from the 3rd to 6th postnatal day. They were also determined in rats at 3 and 6 days of age fed normally by the mother rats as controls.

RESULTS

In the brain, the mean free carnitine concentration in the fasted group showed an increase similar to that in normal rats and there was no difference between the fasted and 6-day-old control rats. However, the mean acylcarnitine concentration was significantly higher in the fasted group than in the control group at both 3 and 6 days of age. Almost all of the increased acylcarnitine in the fasted group was short-chain acylcarnitine. In the heart, there was no difference in the mean free carnitine concentration between the fasted group and control group at 6 days of age. The 6-day-old rats in both the fasted and control groups showed higher levels compared to 3-day-old rats in the control group. The mean acylcarnitine concentration in the fasted group was not different from that in control group at 6 days of age, while the amount of short-chain acylcarnitine was less than that in the control group at 6 days of age.

CONCLUSIONS

These findings suggest that in the brain, carnitine is accumulated as a result of redistribution during starvation, and is utilized for energy supply by fatty acid oxidation.

Effect of acetyl-L-carnitine on hyperactivity and spatial memory deficits of rats exposed to neonatal anoxia

The effect of acetyl-L-carnitine (ALC) on behavioral deficits following neonatal anoxia (N2 100% for 25 min at 30 h after birth) was studied in the rat. Transient hyperactivity at P20-P45 postnatal days and permanent spatial memory deficits were shown by anoxic rats. A chronic ALC treatment (50 mg/kg per die injected intraperitoneally from P2, after anoxia, to P60) significantly reduced the transient increase in sniffing, rearing and locomotory activity of anoxic rats, but, mostly, ameliorated the spatial memory performances in a maze at P30-P40 and in a water maze at P50-P60. No behavioral changes were seen in ALC-treated animals that received sham-exposure at birth. On the basis of these results, the use of ALC for the treatment of perinatal asphyctic insults in children is suggested.

Stimulation of choline acetyl transferase activity by l- and d-carnitine in brain areas of neonate rats

Acetyl-CoA supply to the cytosol and its regulatory influence on acetylcholine biosynthesis is still an unsolved question. Acetylcarnitine through the carnitine acetyl transferase (CarAT) system has been proposed to be the acetyl donor in this process. Carnitine isomers were injected into rat developing brains every day for 14 days after birth. Results showed that carnitine and its associated forms produced a choline acetyl transferase (ChAT) activity increase in the striatum and the hippocampus. Carnitine acetyl transferase activity was stimulated by the treatment of l-carnitine in the hippocampus but it remained unchanged in the striatum and the cerebral cortex. These results suggest that ChAT and CarAT activities might be modulated by Acetyl-CoA derived preferentially from acetylcarnitine. It is suggested that ChAT activity enhancement depends on intrinsic and extrinsic cholinergic afferents to these brain areas.

Carnitine, carnitine acetyltransferase, and glutathione in Alzheimer brain

Glutathione and "total" carnitine (i.e., free carnitine plus acid-soluble carnitine esters) were measured in an affected (superior frontal gyrus; SFG) and unaffected (cerebellum: CBL) region of Alzheimer disease (AD) and control brains. Average glutathione content in AD SFG (n = 13) and AD CBL (n = 7) (7.9 +/- 2.1 and 11.9 +/- 4.0 nmol/mg protein, respectively (mean +/- S.D.)) was similar to that in control SFG (n = 13) and CBL (n = 6) (7.7 +/- 2.0 and 11.6 +/- 2.6 nmol/mg protein, respectively). However, glutathione increased significantly with age in AD brain (p = 0.003) but not in control brain. Average total carnitine in AD SFG (84 +/- 47 pmol/mg protein; n = 10) and AD CBL (108 +/- 86 pmol/mg protein; n = 7) was not significantly different from that in the corresponding regions of control brain (148 +/- 97 (n = 10) and 144 +/- 107 (n = 6) pmol/mg protein, respectively). However, a significant decline of total carnitine with age in both regions was noted for AD brain, but not for control brain. Carnitine acetyltransferase activity in the AD SFG (n = 13) was not significantly different from that of control SFG (n = 13) (1.83 +/- 1.05 and 2.04 +/- 0.82 nmol/min/mg protein, respectively). However, carnitine acetyltransferase activity of AD CBL (n = 7) was significantly lower than that of control CBL (n = 6) (1.33 +/- 0.88 versus 2.26 +/- 0.66 nmol/min/mg protein; p = 0.05).

Acetyl-L-carnitine arginyl amide (ST857) increases calcium channel density in rat pheochromocytoma (PC12) cells

We used the patch clamp technique to study the effect of acetyl-L-carnitine arginyl amide (ALCAA) and of nerve growth factor (NGF) on availability of L-type Ca2+ channels in rat pheochromocytoma (PC12) cells maintained in defined medium. Channel availability was measured as number of channels in the patch x the probability of opening (n.Po). In patches from control cells, cells exposed to NGF (10 ng/ml) for six days, and cells exposed to ALCAA (1 mM) for six days, n.Po, measured during 200-240 ms pulses to -10 mV (holding potential, -60 mV), was 0.102 +/- 0.089 (5 cells), 0.173 +/- 0.083 (5 cells), and 0.443 +/- 0.261 (7 cells), respectively. The 4.3-fold increase for the ALCAA-treated cells was significantly different from control (P < 0.05), whereas that for the NGF-treated cells was not. For the same conditions, the maximum number of superimposed openings at -10 mV was 1.3 +/- 0.5 (6 cells), 1.6 +/- 0.5 (8 cells), and 3.3 +/- 1.8 (8 cells), with the value for the ALCAA-treated cells being significantly different from control (P < 0.001). Additional analysis showed that the distribution of channel open times, the time constants, and the voltage dependence of activation were not changed by prolonged exposure to ALCAA. Short-term exposure to both ALCAA as well as to the parent compound, acetyl-L-carnitine (ALCAR), did not cause an increase but rather a decrease in n.Po, and this short-term effect of both compounds was blocked by neomycin, an inhibitor of phospholipase C.(ABSTRACT TRUNCATED AT 250 WORDS)

L-carnitine uptake into primary rat cortical cultures: interaction with GABA

The ability of the primary rat cortical cells to take up L-carnitine increased with the age of the cultures and plateaued at around day 11 up to 25 days in vitro (DIV) when a slight decline was evident and by 32 DIV there was a major decrease in L-carnitine uptake. The uptake of L-carnitine displayed complex components. Elimination of mitochondrial energy supply by NaCN (1 mM), rotenone (1.25 microM) and DNP (50 microM), caused a small but significant decrease in the uptake (21, 11 and 16%, respectively). The uptake was highly dependent on the Na gradient, since ouabain (0.5 mM) and Na free buffer (replaced by 250 mM sucrose), reduced uptake by 54 and 63%, respectively. There was competition of L-carnitine uptake by molecules resembling its structure, e.g. gamma-aminobutyric acid (GABA), acetyl-L-carnitine (ALC), D-carnitine, L-aminocarnitine and L-choline, with GABA being the most potent inhibitor (57% at 50 microM) and L-choline not being significantly active. The Na-dependent uptake of L-carnitine was saturable with a high Km (692 microM) and Vmax (839 pmol/min/mg). This Na-dependent component was not further additive with the GABA (500 microM) or the DNP (50 microM) inhibitable component, suggesting that it represented the same phenomenon, probably the Na gradient dependent transport of L-carnitine. The results indicate that the uptake of L-carnitine occurs by Na-dependent saturable process as well as non-saturable, Na-independent processes. At least the former uptake mechanism is potently inhibited by GABA.

GABA-activated chloride currents of postnatal mouse retinal ganglion cells are blocked by acetylcholine and acetylcarnitine: how specific are ion channels in immature neurons?

The goal of this study was to clarify pharmacological properties of GABAA receptors in cells of the mouse retinal ganglion cell layer in situ. Spontaneous synaptic currents and responses to exogenous GABA were recorded from individual neurons in retinal whole mounts (postnatal days 1-3) or retinal stripe preparations (postnatal days 4-6). Drugs were applied by a fast local superfusion system. Current responses were measured with the patch-clamp technique in the whole-cell configuration. All cells responded to exogenous GABA (average EC50 and Hill coefficient: 16.7 microM and 0.95 respectively) and generated GABAergic synaptic currents in response to elevated KCl. GABA-induced currents of retinal ganglion cells were blocked by bicuculline, picrotoxin and Zn2+, as well as strychnine, and increased by pentobarbital, clonazepam and 3 alpha-hydroxy-5 alpha-pregnan-20-one. In some retinal ganglion cells GABA caused an increase in the frequency of spontaneous synaptic currents, which points to a partially depolarizing action of this traditionally inhibitory neurotransmitter in the neural retina. Our major observation is that acetylcholine and acetylcarnitine blocked or reduced GABAergic inhibitory postsynaptic currents and responses to exogenous GABA. This effect was seen in only a fraction of retinal ganglion cells and occurred in both the undesensitized and the desensitized state of the GABAA receptor. The block was voltage-independent and persisted during coapplication with the nicotinic and muscarinic acetylcholine receptor antagonists D-tubocurarine and atropine. In contrast to GABA-activated Cl- currents, glycine-activated Cl- currents remained unaffected by acetylcholine and acetylcarnitine.(ABSTRACT TRUNCATED AT 250 WORDS)

Carnitine and derivatives in the central nervous system of chick embryo

1. Carnitine contents and the activity of carnitine acetyltransferase in the egg, in the embryo, and in different brain areas of central nervous system in chick embryo were determined in the course of development. 2. The egg showed low levels of free carnitine and acetylcarnitine. 3. In the whole embryo, at first stages of development, long chain acylcarnitine and acetylcarnitine were the best represented classes of carnitines. 4. In the brain regions acetylcarnitine levels, high at the first days, showed a continual decrease during development. 5. The activity of carnitine acetyltransferase increased and was totally related to development.

Effects of acetyl-L-carnitine on the survival of adult rat sensory neurons in primary cultures

Acetyl-L-carnitine produces a significant increase in the survival time-course of adult rat sensory neurons maintained in primary cultures up to 40 days. The analysis of our data suggests that 200 microM acetyl-L-carnitine added to the medium, slows down neuronal decay especially in the first 10 days in vitro, sparing a fraction of cells which would otherwise be lost. Patch-clamp recordings from these neurons show that superfusion with acetyl-L-carnitine (100-1000 microM) does not induce any membrane current. In addition an agonist muscarinic effect particularly concerning high-voltage activated calcium channel modulation appears to be ruled out. In conclusion our data favour the role of acetyl-L-carnitine in the trophism of sensory neurons in adult rats. In agreement with other in vivo experiments our data reinforce the hypothesis that this substance might be involved in reducing neuronal loss observed in nervous system aging.

Effect of acetyl-L-carnitine on the dopaminergic system in aging brain

We studied the effect of acetyl-L-carnitine (ALCAR) on dopamine release and the effect of long-term acetyl-L-carnitine treatment on age-related changes in striatal dopamine receptors and brain amino acid levels. In striatal tissue that had been incubated with [3H]dopamine, acetyl-L-carnitine increased the release of [3H]dopamine evoked by electrical stimulation. In striatal tissue from aged mice administered acetyl-L-carnitine for 3 months, the release of [3H]dopamine evoked by electrical stimulation was higher than that of its aged control; the release after a second stimulation was similar in the two groups. There was a significant decline in the number of D1 striatal dopamine receptors with age. The Bmax was 51% lower in 1.5-year-old mice than in 4-month-old animals. Administration of acetyl-L-carnitine for 3 months diminished the reduction in the binding of [3H]SCH-23390. [3H]Spiperone binding to D2 receptors was not decreased with age and was not affected by acetyl-L-carnitine treatment. Age-related decreases in levels of several amino acids were observed in several brain regions. Acetyl-L-carnitine lessened the reduction in the level of taurine only in the striatum. The findings confirm the multiple effects of acetyl-L-carnitine in brain, and suggest that its administration can have a positive effect on age-related changes in the dopaminergic system.

Effect of aging and acetyl-L-carnitine on the lipid composition of rat plasma and erythrocytes

The effect of aging and treatment with acetyl-L-carnitine on the lipid composition of rat plasma and erythrocytes was studied. It was found that aging increases the levels of free and esterified cholesterol. Fatty acid patterns in the plasma of aged rats show remarkable alterations when compared with control rats. These changes reverted to normal after three hours of acetyl-L-carnitine treatment. No significant differences in the erythrocyte lipid pattern of young and aged rats were observed. This study provides the first proof that acetyl-L-carnitine probably acts by lowering free and esterified cholesterol and arachidonic acid (20:4) levels in the plasma.

Reduced transcription of mitochondrial DNA in the senescent rat. Tissue dependence and effect of L-carnitine

A quantitative study on the effect of senescence on mitochondrial DNA expression has been carried out by measuring the levels of the 12S rRNA and of the mRNA for the subunit I of cytochrome oxidase in several tissues of adult and senescent rats. The concentration of both RNA species/mitochondrial DNA molecule is significantly reduced in senescent brain and heart, as opposed to the respective adult tissues. No appreciable variation occurs in the liver. A 1-h pretreatment with acetyl-L-carnitine brings back the level of senescent brain and heart transcripts to that of adult tissues. The same treatment of adult rats does not cause significant changes in mitochondrial RNA content. These results suggest that the age-dependent impairment of both heavy-strand mitochondrial DNA transcription units is related to altered environmental conditions which acetyl-L-carnitine, a substance which acts by stimulating, directly or indirectly, the energy metabolism, is able to remove.

Long-term acetyl-L-carnitine preserves spatial learning in the senescent rat

1. Untreated rats of different ages and old rats chronically treated with Acetyl-1-carnitine were subjected to the spatial learning task. 2. For this test, a circular pool filled with milk-opacified water was used. The animals were to reach an escape platform with the aid of visible environmental cues. 3. The experimental results indicated a clear-cut deterioration of the old animal's acquisition ability of a spatial learning task. 4. The long-term treatment (8 months) with Acetyl-1-carnitine was found to antagonize such a deterioration.

Nerve growth factor binding in aged rat central nervous system: effect of acetyl-L-carnitine

The nerve growth factor protein (NGF) has been demonstrated to affect neuronal development and maintenance of the differentiated state in certain neurons of the peripheral and central nervous system (CNS) of mammals. In the CNS, NGF has sparing effects on cholinergic neurons of the rodent basal forebrain (BF) following lesions where it selectively induces choline acetyltransferase (ChAT). NGF also induces ChAT in the areas to which BF provides afferents. In aged rats, there is a reduction in the NGF-binding capacity of sympathetic ganglia. Here, we wish to report that there is a decrease in the NGF-binding capacity of the hippocampus and basal forebrain of aged (26-month-old) rats as compared to 4-month-old controls but no change in NGF binding in cerebellum. In all instances, equilibrium binding dissociation constants did not differ significantly. Treatment of rats with acetyl-L-carnitine, reported to improve cognitive performance of aged rats, ameliorates these age-related deficits.

Effect of acetyl-l-carnitine chronic treatment on discrimination models in aged rats

Acetyl-l-carnitine (ALC), a natural component of several biological systems, has been found to modify spontaneous and evoked electrocortical activity in young rats and to improve learning ability in old ones. In clinical application it also improves mood and attention in elderly patients. The present study was aimed at ascertaining the effect of a chronic treatment with ALC added to drinking water on two discrimination models in aged rats. In the first model, simple discrimination learning was tested and was found to be significantly improved by treatment. The second model consisted of a differential reinforcement of low rate of responding. The animals receiving treatment performed significantly better as shown by a lower number of nonrewarded responses. Because impaired learning and memory are related to alterations in hippocampal function, these data indicate that ALC is capable of antagonizing the natural age-dependent deterioration process in the hippocampal structure.

Biochemical changes in Cuprizone-induced spongiform encephalopathy. I. Changes in the activities of 2',3'-cyclic nucleotide 3'-phosphohydrolase, oligodendroglial ceramide galactosyl transferase, and the hydrolysis of the alkenyl group of alkenyl, acyl-glycerophospholipids by plasmalogenase in different regions of the brain

Cuprizone (biscyclohexanone oxaldihydrazone) which is known to produce a status spongiosus and demyelination in the CNS was administered in the diet of weanling male mice at a concentration of 0.4% by weight for a period of six weeks before returning animals to a normal diet. Changes in body weight but not brain weight were reversible. Based on the decline in CNP'ase activity and the concentration of galactocerebroside, the loss of myelin was around 70% in those sections of the cerebrum with a high content of white matter while the cerebellum was less affected. The activity of oligodendroglial HFA-ceramide galactosyl transferase was also reduced. These biochemical parameters of myelination were increased after withdrawal of Cuprizone. Remyelination in the cerebrum but not the cerebellum was incomplete. The activity of plasmalogenase hydrolysing the alkenyl group of alkenyl, acyl-phospholipids increased 2-fold in those sections in which myelin loss was most severe. The increase preceded the greatest loss of myelin components (3 to 6 weeks on Cuprizone). The origin of the increased phospholipase activity in demyelinating tissue is discussed. Following myelination, there was a deficit in plasmalogenase activity particularly in the frontal cortex of the cerebrum, where the plasmalogen concentration was higher than in controls.