A cyclic peptide that binds p75(NTR) protects neurones from beta amyloid (1-40)-induced cell death.

The current study determined the ability of a p75(NTR) antagonistic cyclic peptide to rescue cells from beta amyloid (Abeta) (1-40)-induced death. p75(NTR)-, p140(trkA)-NIH-3T3 cells or E17 foetal rat cortical neurones were incubated with 125I-NGF or 125I-Abeta (1-40) and increasing concentrations of the cyclic peptide (CATDIKGAEC). Peptide ability to displace 125I-NGF or 125I-Abeta (1-40) binding was determined. Duplicate cultures were preincubated with CATDIKGAEC (250 nM) or diluent and then stimulated with Abeta (1-40). Peptide ability to displace Abeta (1-40) binding, interfere with Abeta (1-40)-induced signalling and rescue cells from Abeta-mediated toxicity was determined by immunoprecipitation and autoradiography, Northern blotting, JNK activation, MTT and trypan blue assays. The peptide inhibited NGF and Abeta (1-40) binding to p75(NTR), but not to p140(trkA). Abeta (1-40) induced c-jun transcription (57.3% +/- 0.07%) in diluent-treated p75(NTR)-cells, but not in cells preincubated with the cyclic peptide. Also, at 250 nM, the peptide reduced Abeta (1-40)-induced phosphorylation of JNK by 71.8% +/- 0.03% and protected neurones against Abeta-induced toxicity as determined by: trypan blue exclusion assay (53% +/- 11% trypan blue-positive cells in diluent pretreated cultures vs. 28% +/- 5% in cyclic peptide-pretreated cultures); MTT assay (0.09 +/-0.03 units in diluent-pretreated cells vs. 0.12 +/- 0.004 units in cyclic peptide-pretreated cells); and visualization of representative microscopic fields. Our data suggest that a cyclic peptide homologous to amino acids 28-36 of NGF known to mediate binding to p75(NTR) can interfere with Abeta (1-40) signalling and rescue neurones from Abeta (1-40)-induced toxicity.

Toxicity of glucosylsphingosine (glucopsychosine) to cultured neuronal cells: a model system for assessing neuronal damage in Gaucher disease type 2 and 3.

Patients with Gaucher disease have been classified as type 1 nonneuronopathic, type 2 acute neuronopathic, and type 3 chronic neuronopathic phenotypes. Increased quantities of glucocerebroside and glucosylsphingosine (glucopsychosine) are present in the brain of type 2 and type 3 Gaucher patients. Galactosylsphingosine has previously been shown to be neurotoxic in globoid cell leukodystrophy (Krabbe disease). To determine whether glucosylsphingosine is also neurotoxic, we examined its effect on cultured cholinergic neuron-like LA-N-2 cells. When these cells were exposed to 1, 5, or 10 microM glucosylsphingosine for a period of 18 h, they became shriveled, neurite outgrowth was suppressed, and the activities of the lysosomal enzymes glucocerebrosidase, sphingomyelinase, and beta-galactosidase were reduced in a dose-dependent manner. Acetylcholine in cells exposed to glucosylsphingosine also declined. Cells switched to glucosylsphingosine-free medium partially recovered. The data suggest that accumulation of glucosylsphingosine contributes to neuronal dysfunction and destruction in patients with neuronopathic Gaucher disease.

Synthesis of acetylcholine by lung cancer.

The role of autocrine growth factors in the stimulation of lung cancer growth is well established. Nicotine is an agonist for acetylcholine receptors and stimulates lung cancer growth. This suggests that if lung cancers synthesize acetylcholine (ACh), then ACh may be an autocrine growth factor for lung cancer. Analysis of normal lung demonstrated that the cells of origin of lung cancers express the proteins necessary for non-neuronal ACh storage and synthesis. Analysis of mRNA from squamous cell lung carcinoma, small cell lung carcinoma (SCLC) and adenocarcinoma showed synthesis of choline acetyltransferase (ChAT) and nicotinic receptors. Immunohistochemical analysis of a retrospective series of SCLC and adenocarcinomas showed that more than 50% of the lung cancers screened expressed ChAT and nicotinic receptors. To study the effect of endogenous ACh synthesis on growth, SCLC cell lines were studied. SCLC cell lines were found to express ChAT mRNA and to secrete ACh into the medium as measured by HPLC separation and enzymatically-coupled electrochemical detection. The SCLC cell line NCI-H82 synthesized highest levels of ACh. Showing that the endogenously synthesized ACh interacted with its receptors to stimulate cell growth, addition of muscarinic and nicotinic antagonists slowed H82 cell proliferation. These findings demonstrate that lung cancer cell lines synthesize and secrete ACh to act as an autocrine growth factor. The existence of a cholinergic autocrine loop in lung cancer provides a basis for understanding the effects of nicotine in cigarette smoke on lung cancer growth and provides a new pathway to investigate for potential therapeutic approaches to lung cancer.

Generation of choline for acetylcholine synthesis by phospholipase D isoforms.

BACKGROUND: In cholinergic neurons, the hydrolysis of phosphatidylcholine (PC) by a phospholipase D (PLD)-type enzyme generates some of the precursor choline used for the synthesis of the neurotransmitter acetylcholine (ACh). We sought to determine the molecular identity of the relevant PLD using murine basal forebrain cholinergic SN56 cells in which the expression and activity of the two PLD isoforms, PLD1 and PLD2, were experimentally modified. ACh levels were examined in cells incubated in a choline-free medium, to ensure that their ACh was synthesized entirely from intracellular choline. RESULTS: PLD2, but not PLD1, mRNA and protein were detected in these cells and endogenous PLD activity and ACh synthesis were stimulated by phorbol 12-myristate 13-acetate (PMA). Introduction of a PLD2 antisense oligonucleotide into the cells reduced PLD2 mRNA and protein expression by approximately 30%. The PLD2 antisense oligomer similarly reduced basal- and PMA-stimulated PLD activity and ACh levels. Overexpression of mouse PLD2 by transient transfection increased basal- (by 74%) and PMA-stimulated (by 3.2-fold) PLD activity. Moreover, PLD2 transfection increased ACh levels by 26% in the absence of PMA and by 2.1-fold in the presence of PMA. Overexpression of human PLD1 by transient transfection increased PLD activity by 4.6-fold and ACh synthesis by 2.3-fold in the presence of PMA as compared to controls. CONCLUSIONS: These data identify PLD2 as the endogenous enzyme that hydrolyzes PC to generate choline for ACh synthesis in cholinergic cells, and indicate that in a model system choline generated by PLD1 may also be used for this purpose.

Sex steroids modulate luteinizing hormone-releasing hormone secretion in a cholinergic cell line from the basal forebrain.

The function of a particular neuronal population is in part determined by its neurotransmitter phenotype. We have found that a neuronal-derived septal cell line (SN56), known for its cholinergic properties, also synthesizes and releases luteinizing hormone-releasing hormone. In addition, these cells express the messenger RNAs encoding estrogen and progesterone receptors. The activation of these receptors by their respective ligands cooperatively modulates the depolarization-induced release of luteinizing hormone-releasing hormone in these cells. We have also found that a number of septal neurons in postnatal (1-week-old) mice are immunoreactive to both choline acetyltransferase and luteinizing hormone-releasing hormone. These results indicate that both neurotransmitters, acetylcholine and luteinizing hormone-releasing hormone, may co-exist in septal neurons of the CNS and that they could be modulated by gonadal hormones, and suggest that luteinizing hormone-releasing hormone could be involved in some of the actions of sex steroids on cholinergic neurotransmission.

[Bone morphogenetic proteins and cholinergic neurons in the central nervous system]. / Proteínas morfogenéticas óseas y neuronas colinérgicas en el sistema nervioso central.

INTRODUCTION: The discovery and characterization of factors that induce and maintain specific neurotransmitter phenotypes has profound clinical implications, and continues to be one of the major objectives in the neurosciences. DEVELOPMENT: Although much progress has been realized in this area, we still understand little of how cholinergic neurons acquire and maintain their neurotransmitter characteristics, nor do we fully comprehend why these neurons in some circumstances degenerate and loose their neurotransmitter specificity. There is evidence that some members of the bone morphogenetic protein (BMP) family have profound organizing and differentiating actions in the developing nervous system, and recent studies indicate an important role in determining the cholinergic neuronal phenotype. CONCLUSIONS: BMP may act to differentiate neuronal precursor cells into cholinergic neurons and upregulate the cholinergic phenotype of already differentiated neurons in the central nervous system. This could suggest their potential use in the treatment of certain types of brain disorders.

Protective effects of prenatal choline supplementation on seizure-induced memory impairment.

Choline is an essential nutrient for rats and humans, and its availability during fetal development has long-lasting cognitive effects (Blusztajn, 1998). We investigated the effects of prenatal choline supplementation on memory deficits associated with status epilepticus. Pregnant rats received a control or choline-supplemented diet during days 11-17 of gestation. Male offspring [postnatal day 29 (P29)-32] were tested for their ability to find a platform in a water maze before and after administration of a convulsant dose of pilocarpine at P34. There were no differences between groups in water maze performance before the seizure. One week after status epilepticus (P41-P44), animals that had received the control diet prenatally had a drastically impaired performance in the water maze during the 4 d testing period, whereas prenatally choline-supplemented rats showed no impairment. Neither the seizures nor the prenatal availability of choline had any effect on hippocampal choline acetyltransferase or acetylcholinesterase activities. This study demonstrates that prenatal choline supplementation can protect rats against memory deficits induced by status epilepticus.

Prenatal choline exposure alters hippocampal responsiveness to cholinergic stimulation in adulthood.

Manipulation of dietary choline levels during gestation results in enduring neurobehavioral changes in offspring that last into adulthood. Alterations of hippocampal function and memory are among the most striking changes. Depending upon the measures assessed, prenatal choline supplementation tends to promote excitatory synaptic efficacy in hippocampal circuits while prenatal choline deficiency diminishes it. However, the mechanisms underlying these changes remain unclear. Transverse hippocampal slices were prepared from adult offspring of dams fed choline supplemented, choline deficient, or control diets. We assessed paired-pulse inhibition, and excitatory synaptic responsiveness before and after activation of cholinergic receptors with Carbachol. Prenatally choline deficient animals yielded significantly fewer electrophysiological viable hippocampal slices than did animals from either of the other two treatment groups. Among the slices tested, there were no differences in paired pulse inhibition between the treatment groups. However, transient cholinergic activation resulted in a prolonged enhancement of the amplitude of the population EPSP (pEPSP) response in slices from prenatally choline supplemented animals. These results suggest that GABA receptor-mediated inhibition remains intact after prenatal choline manipulations, and that enhancement of the excitatory responsiveness of hippocampal circuits in slices from prenatally choline supplemented rats may be related in part to an increase in cholinergic tone within the CA1 circuit.

Acceleration of phosphatidylcholine synthesis and breakdown by inhibitors of mitochondrial function in neuronal cells: a model of the membrane defect of Alzheimer's disease.

Brain cells in Alzheimer's disease (AD) exhibit a membrane defect characterized by accelerated phospholipid turnover. The mechanism responsible for this defect remains unknown. Recent studies indicate that impairment of mitochondrial function is frequently observed in AD and may be responsible for certain aspects of its pathophysiology. We show that when PC12 cells are exposed to inhibitors of mitochondrial bioenergetics, the turnover of their major membrane phospholipid, phosphatidylcholine, is accelerated, producing a pattern of metabolic changes that mimics that observed in brains of AD patients. Abnormalities of mitochondrial function may therefore underlie the membrane defect in AD.

Cholinergic differentiation triggered by blocking cell proliferation and treatment with all-trans-retinoic acid.

This study determined whether the effect of all-trans-retinoic acid (t-RA) on markers of cholinergic differentiation in a murine septal cell line, SN56.B5.G4, differed depending upon the cell's proliferative status. To develop a model of non-proliferating cells, aphidicolin, a DNA alpha-polymerase inhibitor, was used. Cessation of proliferation by aphidicolin increased intracellular choline and acetylcholine (ACh) levels in the absence of change to choline acetyltransferase (ChAT) activity and mRNA and vesicular ACh transporter (VAChT) mRNA. Importantly, the response to t-RA differed depending upon proliferative status. Consistent with previous reports, t-RA increased ChAT and VAChT mRNA, ChAT activity and intracellular ACh levels in proliferating SN56 cells with no effect on intracellular choline levels. When cells were treated with t-RA while undergoing proliferative arrest, an additive effect of combined treatment was observed on ACh levels; nevertheless, this was only accompanied by an increase in choline levels, VAChT and ChAT mRNAs, but not ChAT activity. Indeed, aphidicolin treatment completely suppressed the t-RA-induced increase in ChAT activity observed in proliferating cells. To explore the response to t-RA in post-mitotic cells, a sequential treatment of aphidicolin and t-RA was employed. t-RA treatment was ineffective in increasing ACh and choline levels, over and above that observed with the aphidicolin treatment alone. Comparable to the combined treatment, sequential treatment lead to an increase in ChAT mRNA without any increase in ChAT activity. In conclusion, both the magnitude and the mechanism(s) of action whereby t-RA enhances the cholinergic phenotype of SN56 cells is dependent upon the cell's proliferative status.

Induction and maintenance of the neuronal cholinergic phenotype in the central nervous system by BMP-9.

Bone morphogenetic proteins (BMPs) have multiple functions in the developing nervous system. A member of this family, BMP-9, was found to be highly expressed in the embryonic mouse septum and spinal cord, indicating a possible role in regulating the cholinergic phenotype. In cultured neurons, BMP-9 directly induced the expression of the cholinergic gene locus encoding choline acetyltransferase and the vesicular acetylcholine transporter and up-regulated acetylcholine synthesis. The effect was reversed upon withdrawal of BMP-9. Intracerebroventricular injection of BMP-9 increased acetylcholine levels in vivo. Although certain other BMPs also up-regulated the cholinergic phenotype in vitro, they were less effective than BMP-9. These data indicate that BMP-9 is a differentiating factor for cholinergic central nervous system neurons.

The cholinergic neuronal phenotype in Alzheimer's disease.

The synthesis, storage and release of acetylcholine (ACh) requires the expression of several specialized proteins, including choline acetyltransferase (ChAT) and the vesicular ACh transporter (VAChT). The VAChT gene is located within the first intron of the ChAT gene. This unique genomic organization permits coordinated activation of expression of the two genes by extracellular factors. Much less is known about factors that reduce the expression of the cholinergic phenotype. A cholinergic deficit is one of the primary features of Alzheimer's disease (AD), and AD brains are characterized by amyloid deposits composed primarily of A beta peptides. Although A beta peptides are neurotoxic, part of the cholinergic deficit in AD could be attributed to the suppression of cholinergic markers in the absence of cell death. Indeed, we and others demonstrated that synthetic A beta peptides, at submicromolar concentrations that cause no cytotoxicity, reduce the expression of cholinergic markers in neuronal cells. Another feature of AD is abnormal phospholipid turnover, which might be related to the progressive accumulation of apolipoprotein E (apoE) within amyloid plaques, leading perhaps to the reduction of apoE content in the CSF of AD patients. ApoE is a component of very low density lipoproteins (VLDL). As a first step in investigating a potential neuroprotective function of apoE, we determined the effects of VLDL on ACh content in neuronal cells. We found that VLDL increases ACh levels, and that it can partially offset the anticholinergic actions of A beta peptides.

Changes in phospholipase D isoform activity and expression in multidrug-resistant human cancer cells.

Multidrug resistance (MDR) is a major cause of failure of cancer chemotherapy and is often associated with elevated expression of drug transporters such as P-glycoprotein (P-gp) in the cancer cells. MDR is, however, accompanied by additional biochemical changes including modifications of membrane composition and properties. We have shown that MDR is associated with a massive up-regulation of caveolin expression and an elevated surface density of caveolae. We report that phospholipase D (PLD), a constituent enzyme of caveolae and detergent-insoluble glycolipid-rich membranes (DIGs), is up-regulated in human MDR cancer cells. Lysates of HT-29-MDR human colon adenocarcinoma cells, MCF-7 AdrR human breast adenocarcinoma cells and the corresponding parental drug-sensitive cells, were fractionated on discontinuous sucrose density gradients. PLD activity was found to be enriched in low density fractions that contain DIGs and caveolar membranes, and the activity in these fractions was 4- to 6-fold higher in the MDR cells compared with the parental drug- sensitive cells. Utilizing specific antibodies to PLD1 and PLD2, the distribution of PLD isoforms along the gradient was determined and the PLD localized in DIGs and caveolar membranes has been identified as PLD2. Northern blot analysis of PLD1 and PLD2 mRNA levels has indicated that PLD2 mRNA is elevated in both HT-29-MDR and MCF-7 AdrR cells. PLD1 mRNA levels were either unchanged or reduced in the MDR cells. Finally, in vivo experiments have confirmed previous results showing that activation of PLD by phorbol esters is markedly potentiated in the MDR cells. We conclude that MDR is accompanied by an increase in PLD2 activity in DIGs and caveolar membranes.

Palmitoylation targets CD39/endothelial ATP diphosphohydrolase to caveolae.

Ectonucleotidases influence purinergic receptor function by the hydrolysis of extracellular nucleotides. CD39 is an integral membrane protein that is a prototype member of the nucleoside 5'-triphosphate diphosphohydrolase family. The native CD39 protein has two intracytoplasmic and two transmembrane domains. There is a large extracellular domain that undergoes extensive glycosylation and can be post-translationally modified by limited proteolysis. We have identified a potential thioester linkage site for S-acylation within the N-terminal region of CD39 and demonstrate that this region undergoes palmitoylation in a constitutive manner. The covalent lipid modification of this region of the protein appears to be important both in plasma membrane association and in targeting CD39 to caveolae. These specialized plasmalemmal domains are enriched in G protein-coupled receptors and appear to integrate cellular activation events. We suggest that palmitoylation could modulate the function of CD39 in regulating cellular signal transduction pathways.

Nutrients as trophic factors in neurons and the central nervous system: role of retinoic acid.

In multicellular organisms, death, survival, proliferation, and differentiation of a given cell depend on signals produced by neighboring and/or distant cells, resulting in the coordinated development and function of the various tissues. In the nervous system, control of cell survival and differentiation is achieved through the action of a distinct group of polypeptides collectively known as neurotrophic factors. Recent findings support the view that trophic factors also are involved in the response of the nervous system to acute injury. By contrast, nutrients are not traditionally viewed as potential trophic factors; however, there is increasing evidence that at least some influence neuronal differentiation. During development the brain is responsive to variations in nutrient supply, and this increased sensitivity or vulnerability of the brain to nutrient supply may reappear during neuronal repair, a period during which a rapid membrane resynthesis and reestablishment of synthetic pathways occur. To further evaluate the potential of specific nutrients to act as pharmacologic agents in the repair of injured neurons, the effects of retinoic acid, an active metabolite of vitamin A, and its role as a trophic factor are discussed. This literature review is intended to provide background information regarding the effect of retinoic acid on the cholinergic phenotype and the differentiation of these neurons and to explain how it may promote neuronal repair and survival following injury.

Apolipoprotein serum amyloid A down-regulates smooth-muscle cell lipid biosynthesis.

The addition of acute-phase apolipoprotein serum amyloid A (SAA) to cultured aortic smooth-muscle cells caused a decrease in the incorporation of [(14)C]acetate into lipids. Optimal inhibition of lipid biosynthesis was achieved with 2 microM SAA, and the effect was maintained for up to 1 week when SAA was included in the culture medium. Lipid extracts were subjected to TLC and it was determined that the SAA-induced decrease in [(14)C]acetate incorporation into lipids was attributable to decreases in cholesterol, phospholipid and triglyceride levels. The accumulated mass of cholesterol and phospholipid in SAA-treated cultures was significantly less than that of controls, with no change in the accumulated protein. Moreover, SAA had no effect on either protein synthesis or DNA synthesis, suggesting that SAA specifically alters lipid synthesis. By using a peptide corresponding to the cholesterol-binding domain of acute-phase SAA (amino acids 1-18), it was shown that this region of the molecule was as effective as the full-length protein in decreasing lipid synthesis and the accumulation of cholesterol and phospholipid. The implications of these findings for atherosclerosis and Alzheimer's disease are discussed.

Prenatal availability of choline alters the development of acetylcholinesterase in the rat hippocampus.

Choline (Ch) supplementation during embryonic days (ED) 12-17 enhances spatial and temporal memory in adult and aged rats, whereas prenatal Ch deficiency impairs attention performance and accelerates age-related declines in temporal processing. To characterize the neurochemical and neuroanatomical mechanisms that may mediate these behavioral effects in rats, we studied the development [postnatal days (PD) 1, 3, 7, 17, 27, 35, 90, and 26 months postnatally] of acetylcholinesterase (AChE) activity in hippocampus, neocortex and striatum as a function of prenatal Ch availability. We further measured the density of AChE-positive laminae (PD27 and PD90) and interneurons (PD20) in the hippocampus as a function of prenatal Ch availability. During ED11-ED17 pregnant Sprague-Dawley rats received a Ch-deficient, control or Ch-supplemented diet (average Ch intake 0, 1.3 and 4.6 mmol/kg/day, respectively). Prenatal Ch deficiency increased hippocampal AChE activity as compared to control animals in both males and females from the 2nd to 5th week postnatally. Moreover, prenatal Ch supplementation reduced hippocampal AChE activity as compared to control animals over the same developmental period. There was no effect of prenatal Ch status on either cortical or striatal AChE activity at any age measured, and by PD90 the effect of Ch on hippocampal AChE was no longer observed. In order to localize the early changes in hippocampal AChE activity anatomically, frozen coronal brain sections (PD20, PD27, PD90) were stained histochemically for AChE. Consistent with biochemical results, the AChE staining intensity was reduced in PD27 hippocampal laminae in the Ch-supplemented group and increased in the Ch-deficient group compared to control animals. There was no effect of the diet on hippocampal AChE staining intensity on PD90. In addition, the prenatal Ch availability was found to alter the size and density of AChE-positive PD20 interneurons. These results show that prenatal Ch availability has long-term consequences on the development of the hippocampal cholinergic system.

Activation of TrkA by nerve growth factor upregulates expression of the cholinergic gene locus but attenuates the response to ciliary neurotrophic growth factor.

Nerve growth factor (NGF) stimulates the expression of the cholinergic gene locus, which encodes choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT), the proteins necessary for the synthesis and storage of the neurotransmitter acetylcholine (ACh). To determine whether this action of NGF is mediated by the p140TrkA NGF receptor (a member of the Trk tyrosine kinase family) we used a murine basal forebrain cholinergic cell line, SN56, stably transfected with rat trkA cDNA. Treatment of these transfectants with NGF activated mitogen-activated protein kinase and increased cytosolic free calcium concentrations, confirming the reconstitution of TrkA-mediated signalling pathways. The expression of ChAT and VAChT mRNA, as well as ACh content, were coordinately up-regulated by NGF in SN56-trkA transfectants. None of these responses occurred in the parental SN56 cells, which do not express endogenous TrkA, indicating that these actions of NGF required TrkA. We previously reported that ciliary neurotrophic factor (CNTF) upregulates the expression of ChAT and VAChT, as well as ACh production, in SN56 cells. The combined treatment of SN56-trkA cells with CNTF and NGF revealed a complex interaction of these factors in the regulation of cholinergic gene locus expression. At low concentrations of CNTF (<1 ng/ml), the upregulation of ACh synthesis evoked by these factors was additive. However, at higher concentrations of CNTF (>1 ng/ml), NGF attenuated the stimulatory effect of CNTF on ChAT and VAChT mRNA and ACh content. This attenuation was not due to interference with early steps of CNTF receptor signalling, as pre-treatment of SN56-trkA cells with NGF did not affect the nuclear translocation of the transcription factor, Stat3, evoked by CNTF.

Acetylcholine and acetyl-CoA metabolism in differentiating SN56 septal cell line.

The rate of acetylcholine (ACh) synthesis was found to depend on the activity of choline acetyltransferase (ChAT) and on the concentrations of the two substrates of this enzyme, choline and acetyl-CoA. In SN56 cells treated for 3 days with 1 mM dbcAMP activities of ChAT and acetylcholinesterase (AChE) were elevated. It was accompanied by an increased activity of ATP-citrate lyase (ACL)-an enzyme responsible for provision of part of acetyl-CoA for ACh synthesis in cholinergic neurons. In contrast lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH) activities were reduced by dbcAMP. Treatment with 0.001 mM all-trans retinoic acid (RA) elevated ChAT and LDH activities but reduced the activities of AChE and ACL. The combined treatment with db-cAMP and tRA increased ChAT activity in supra-additive fashion. The effects of these two compounds on the other enzymes were not additive. Neither compound altered the activities of carnitine acetyl-transferase, acetyl-CoA synthase, or acetyl-CoA hydrolase. On the other hand, they decreased acetyl-CoA content and rate of ACh release. Overall, the results indicate that tRA upregulates only ChAT expression, whereas dbcAMP upregulates several features of cholinergic neurons including ChAT, AChE, and ACL. Low levels of acetyl-CoA in differentiated cells may result in a low rate of ACh release and resynthesis during their depolarization.

Imprinting of hippocampal metabolism of choline by its availability during gestation: implications for cholinergic neurotransmission.

Choline supplementation during the second half of the gestational period in rats permanently improves visuospatial memory. Choline availability during this period also alters the turnover of choline and acetylcholine in the hippocampus in 3-4 week-old animals in a complex pattern consistent with the notion that cholinergic neurotransmission is enhanced by prenatal choline supplementation.