Differential accumulation of gangliosides by the brains of MPTP-lesioned mice

Although gangliosides have been reported to enhance recovery from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced lesions of the substantia nigra, evidence as to whether the administered gangliosides actually reach this or any other site of lesion in the central nervous system (CNS) at which they putatively enhance recovery is lacking. Therefore, studies were carried out to determine the amount of ³H-labeled ganglioside that was accumulated by the brains of MPTP-treated mice as well as by brains of control mice. No significant difference in the accumulation of ³/-bovine brain gangliosides or ³H-GD1a was seen between lesioned and control brains up to 240 min after injection of the labeled lipids. However, significantly more label was associated with the brains of MPTP-treated mice compared to controls 120 and 240 min after the injection of ³H-GM1. Analysis of the lipids extracted from the brain of a ³H-GM1-treated mouse revealed that the majority of label was still associated with ³-GM1, 240 min after its administration. Autoradiography of tissue sections from the brains of MPTP-treated mice injected with ³H-GM1 showed that label was present in the ventricular spaces of the brain. This observation suggests that the administered gangliosides are present in the cerebrospinal fluid, which indicates that they have the potential to reach the lesioned CNS site at which they putatively enhance recovery. © 1994 Wiley-Liss, Inc.     

Thioperamide, an H3 Receptor Antagonist Prevents [3H]Glucose Uptake in Brain of Adult Rats Lesioned as Neonates with 5,7-Dihydroxytryptamine

As a first attempt at exploring an association between histaminergic and serotoninergic neuronal phenotypes in glucose regulation, the influence of the histamine H₃ receptor antagonist thioperamide on glucose uptake by brain was determined in rats in which the serotoninergic innervations of brain was largely destroyed perinatally. Male Wistar rats were initially treated on the 3rd day after birth with the serotoninergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) (75 μg icv) or saline vehicle (10 μl icv). At 8 weeks lesioned and control rats were terminated in order to validate the effectiveness of 5,7-DHT: reduction in 5-HT and 5-HIAA by 83–91% and 69–83% in striatum, frontal cortex, and hippocampus (HPLC/ED method). Other groups of rats were pretreated with thioperamide (5.0 mg/kg ip) or saline vehicle 60 min prior to 6-[³H]-D-glucose (500 μCi/kg ip). Fifteen-min later rats were decapitated and brains were excised and dissected to remove frontal cortex, striatum, hippocampus, thalamus/hypothalamus, pons, and cerebellum. Liquid scintillation spectroscopy was used to determine that [³H]glucose uptake, which was enhanced in 5,7-DHT lesioned rats in cortex (by 88%), hippocampus, thalamus/hypothalamus, pons and cerebellum (each by 47–56%), and in striatum (by 35%). In contrast, thioperamide prevented the enhancement in [³H]glucose uptake in all brain regions of 5,7-DHT neonatally lesioned rats; and [³H]glucose levels were significantly different in all brain regions (except thalamus/hypothalamus) in thioperamide-versus saline-treated rats. These findings indicate a functional association between histaminergic and serotoninergic systems in brain in relation to glucose regulation.     

Immunohistochemical evidence for degeneration of cholinergic neurons in the forebrain of the rat following injection of AF64A-picrylsulfonate into the dorsal hippocampus

The cholinergic neurotoxin, AF64A-picrylsulfonate, was unilaterally infused into the dorsal hippocampus of Wistar rats (2 nmol/2 μl/4 min; A 6.2, L^s 1.5, H 6.5, Paxinos and Watson). After 19 days the animals' brains were processed for immunohistochemical staining of choline acetyltransferase (ChAT). Morphometry and counting of ChAT-immunoreactive profiles revealed shrinkage and disappearance of cholinergic neurons in the medial septum and diagonal band of Broca at the lesioned brain side. These data indicate a retrograde degeneration of cholinergic neurons following injection of AF64-A-picrylsulfonate into the dorsal hippocampus of the rat.     

Effects of short- and long-term ganglioside treatment on the recovery of neurochemical markers in the ibotenic acid-lesioned rat striatum

The striatum of adult rats was bilaterally lesioned with stereotaxic injections of ibotenic acid in a dose (16 nmoles) that resulted in subtotal lesions. Some rats received systemic ganglioside treatment starting the day before operation and lasting for 6 or 24 days after operation; they were compared with lesioned rat receiving systemic saline injections as well as with corresponding groups of sham-operated animals. Specific neurochemical markers for cholinergic neurons (choline acetyltransferase, ChAT), GABAergic neurons (glutamate decarboxylase; GAD), and astrocytes (glutamine synthetase; GS) were assayed to asses the neurochemical recovery promoted by ganglioside treatment. Twenty-four, but not six, days after operation a significant increase of ChAT and GAD was measured in the striatum of lesioned rats treated with gangliosides in comparison with the saline group. Furthermore, a significant increase of both enzymes occurred in the striatum of lesioned rats receiving ganglioside treatment for 24 days in comparison with rats receiving ganglioside treatment for 6 days only. A small but significant increase of ChAT was measured in the striatum of sham-operated rats after 24 days of ganglioside treatment in comparison with the corresponding saline group. Finally, the increase of GS caused by the glial reaction to the ibotenic acid lesion was not affected by ganglioside treatment. The results indicate that a relatively long-lasting ganglioside treatment stimulates the recovery of specific neuronal transmitter markers and that some effect is, in addition, exerted on unlesioned cholinergic striatal neurons.     

Activities of enzymes metabolizing phospholipids in rat cerebral ischemia

Ischemic rat brains were prepared by decapitation followed by incubation in an artificial cerebrospinal fluid at various times at 37°C, and the levels of phospholipids, free fatty acids, and enzymes involved in their metabolism were studied. Activities of phospholipase A, phospholipase C, and di- and monoglyceride lipase, assayed with optimal concentrations of Ca²⁺ and lysophospholipase, did not significantly change by 60 min of ischemia, whereas acylation enzymes of lysophospholipid decreased in activity to an extent of 70% of control at 15 min after the ischemic treatment. The maximal activities were found at 8×10^?3 M, 1×10^?3 M, and 2×10^?2 M Ca²⁺ for phospholipase A, phospholipase C, and di- and monoglyceride lipases, respectively in microsomal fractions of both control and ischemic brain. Furthermore, the sensitivity of microsomal enzymes to endogenous Ca²⁺ was estimated in control and ischemic brain. The sensitivity of phospholipase C was found to be increased after 1 min of ischemic treatment, but those of phospholipase A and di- and monoglyceride lipase were not increased.     

Influence of growth environment on the ganglioside composition of an experimental mouse brain tumor

Ganglioside composition was examined in an experimental mouse brain tumor growing as a solid tumor in vivo and as a cultured cell line in vitro. Gangliosides were also studied in the solid tmor rederived from the cultured tumor cell line. Although GM3-NeuAc was the major ganglioside in both the solid tumor and cultured tumor cells, several gangliosides expressed in the solid tumors (e.g., GM2-NeuGc, GM1, and GM1b) were not expressed in the cultured tumor cells. These gangliosides, however, are major components of mouse macrophages. Furthermore, significant amounts of gangliosides containingN-glycolylneuraminic acid (NeuGc) were found in the solid tumor growing in vivo, but only trace amounts were present in the cultured tumor cells. NeuGc is a common ganglioside sialic acid in mouse nonneural cells, whereasN-acetylneuraminic (NeuAc) is the predominant sialic acid in mouse brain. The trace amounts of NeuGc in the cultured cells are attributed to contamination from the fetal bovine serum. Radiolabeling of the cultured tumor cell gangliosides with [¹⁴C]galactose revealed that GM3-NeuAc was the only ganglioside synthesized by the tumor cells. The results suggest that nontumorinfiltrating cells, e.g., macrophages, lymphocytes, and endothelial cells, may contribute significantly to the total ganglioside composition of solid tumors growing in vivo.     

Selective cortical decrease of high-affinity choline uptake carrier in Alzheimer's disease: An autoradiographic study using3H-hemicholinium-3

Summary ³H-hemicholinium-3 (³H-HC-3) binding, a marker of the presynaptic high-affinity choline uptake carrier (HACU), was measured by autoradiography in several brain regions of 17 Alzheimer's disease (AD) patients and of 11 matched controls. A significant decrease in the density of³H-HC-3 binding sites was found in entorhinal cortex, hippocampus and layers I–III of the frontal cortex. By contrast, in the caudate-putamen the number of³H-HC-3 binding sites in AD cases was comparable to that of control striata. These data concur with previous results using classical presynaptic markers and reflect the loss in the activity of HACU, and, hence, in the synthesis of acetylcholine, that selectively occurs in cortical areas of AD brains due to the degeneration of presynaptic cholinergic terminals arising from the basal forebrain. However, the relatively low mean reduction in HACU in cortical areas (–40%), together with the apparent indemnity of this marker in certain severely demented AD cases, suggest that AD dementia cannot be explained simply by the loss of presynaptic terminals originating in the basal forebrain. These data seem to be a good explanation for the poor response to cholinergic replacement in AD.     

Agression intraspécifique induite par chocsélectriques et réactivitéaprès lésion du raphéchez le rat. Effets de la physostigmineShock-induced aggression and reactivity following raphe lesions in rats. Effects of physostigmine

Shock-induced fighting behavior, flinch-jump thresholds and locomotor open-field activity were studied following dorsal and medial raphe lesions in rats. Attack scores were raised for low-intensity shocks (1 mA) only, whereas they remained unchanged for shocks of higher intensity (2 mA), as compared to controls. The jump threshold is decreased in raphe lesioned animals, but the flinch threshold is unchanged. Physostigmine (0,2-0,5 mg/kg) reduces the lesion-induced hyperreactivity: locomotor open-field activity is reduced to a greater extent than in the controls, and habituation to the open-field situation is restored. Doses of physostigmine (e.g. 0,2 mg/kg), that do not modify shock-induced aggression in controls, reduce aggression in lesioned animals to the level shown by controls for low-intensity shocks. In conclusion, shock-induced aggression is not directly dependent on a serotonergic brain mechanism. The behavioral changes observed are related to the hyperreactivity induced by raphe lesions. This hyperreactivity presumably results from a reduced activity of cholinergic brain mechanisms.     

Quantitative autoradiography of serotonin uptake sites in rat brain using [H]cyanoimipramine

The binding of [³H]cyanoimipramine to serotonin uptake sites in rat brain slices was studied using quantitative autoradiography. Binding was of high affinity and was to a single class of binding site. This is in contrast to results previously obtained by others with [³H]imipramine where two binding sites were observed. The sites labeled by [³H]cyanoimipramine had properties consistent with this ligand labeling serotonin uptake sites, as: (1) binding is displaced by drugs which are potent inhibitors of serotonin uptake but not by drugs which are weak inhibitors of uptake; (2) binding is dependent on the presence of sodium ions as is the uptake of serotonin; (3) binding is almost completely eliminated in the brains of rats lesioned by the serotonin neurotoxin 5,7-dihydroxytryptamine; (4) the distribution of binding sites throughout the rat brain is highly correlated with that found previously for [³H]indalpine, a potent serotonin uptake inhibitor, and for [³H]imipramine. The properties of binding of [³H]cyanoimipramine make it an ideal ligand for the quantitative autoradiography of serotonin uptake sites.     

Sequential changes of cholinergic and dopaminergic receptors in brains after 6-hydroxydopamine lesions of the medial forebrain bundle in rats

Summary. We studied sequential changes in muscarinic cholinergic receptors, high-affinity choline uptake sites and dopamine D₂ receptors in the brain after 6-hydroxydopamine lesions of the medial forebrain bundle in rats. The animals were unilaterally lesioned in the medial forebrain bundle and the brains were analyzed at 1, 2, 4 and 8 weeks postlesion. [³H]Quinuclidinylbenzilate (QNB), [³H]hemicholinum-3 (HC-3) and [³H]raclopride were used to label muscarinic cholinergic receptors, high-affinity choline uptake sites and dopamine D₂ receptors, respectively. The degeneration of nigrostriatal pathway produced a transient decrease in [³H]QNB binding in the parietal cortex of both ipislateral and contralateral sides at 2 and 8 weeks postlesion. [³H] QNB binding also showed a mild but insignificant decrease in the ipsilateral striatum throughout the postlesion periods. No significant change was observed in the substantia nigra (SN) of both ipsilateral and contralateral sides throughout the postlesion periods. In contrast, [³H]HC-3 binding showed no significant change in the parietal cortex of both ipsilateral and contralateral sides during the postlesion. However, [³H]HC-3 binding was upregulated in the ipsilateral dorsolateral striatum throughout the postlesion periods. The ventromedial striatum also showed a significant increase in [³H]HC-3 binding at 1 week and 2 weeks postlesion. On the other hand, no significant change in [³H]raclopride binding was found in the parietal cortex of both ipsilateral and contralateral sides during the postlesion. [³H]Raclopride binding showed a conspicuous increase in the ipsilateral striatum (35–52% of the sham-operated values in the lateral part and 39–54% in the medial part) throughout the postlesion periods. In the contralateral side, a mild increase in [³H]raclopride binding was also found in the striatum (10–15% of the sham-operated values in the lateral part and 22% in the medial part) after lesioning. However, a significant decline in [³H]raclopride binding was observed in the ipsilateral SN and ventral tegmental area during the postlesion. The present study indicates that 6-hydroxydopamine injection of medial forebrain bundle in rats can cause functional changes in high-affinity choline uptake site in the striatum, as compared with muscarinic cholinergic receptors. Furthermore, our studies demonstrate an upregulation in dopamine D₂ receptors in the striatum and a decrease in the receptors in the SN and ventral tegmental area after the 6-hydroxydopamine injection. Thus, these findings provide further support for neurodegeneration of the nigrostriatal pathway that occurs in Parkinson's disease. Received April 26, 1999; accepted November 12, 1999     

Effects of acetyl-L-carnitine on regional cerebral glucose metabolism in awake rats

The time-course and relation to dose of regional metabolic rates for glucose (rCMRglc) were measured in awake adult Fischer-344 rats after administration of acetyl-l-carnitine (ALCAR), an agent that modulates neuronal energy processes and neurotransmitter synthesis. rCMRglc were determined with the quantitative [¹⁴C]2-deoxy-d-glucose technique in 50 brain regions at 10, 30 and 60 min after i.v. administration of ALCAR 500 mg/kg and at 30 min after ALCAR 250 and 700 mg/kg or coadministration of acetate (500 mg/kg) and carnitine (500 mg/kg). ALCAR resulted in significant rCMRglc increases that were maximal by 30 min; by that time, ALCAR 250 produced small, non-significant increase in rCMRglc (no region affected, mean increase 13%) and ALCAR 500 and 750 similar, larger increases in rCMRglc (eight and 11 brain regions affected, mean increases 21 and 22%, respectively). In contrast with ALCAR, carnitine plus acetate did not alter significantly rCMRglc in any brain regions, suggesting that acetate metabolism and carrier are not involved in ALCAR pharmacological activities. ALCAR increased rCMRglc more markedly in subcortical cholinergic (i.e. diagonal band, preoptic magnocellular area) and non-cholinergic (i.e. locus coeruleus, median raphe) nuclei and, to a lesser degree, in limbic and sensorimotor cortical areas. The topographic distribution of rCMRglc increases induced by ALCAR differs from those produced by cholinergic muscarinic agonists and suggest a preferential activation of nicotinic receptors.     

[18F]fluoroethoxy-benzovesamicol,a PET radiotracer for the vesicular acetylcholine transporter and cholinergic synapses

Loss of cholinergic transmission in the cortex and hippocampus is a characteristic feature of Alzheimer's disease, and visualization of functional cholinergic synapses in the brain with PET could be a useful method for studying this degenerative condition in living humans. We investigated [¹⁸F]fluoroethoxybenzovesamicol, (−)-[¹⁸F]FEOBV, (−)-(2R,3R)-trans-2-hydroxy-3-(4-phenylpiperidino)-5-(2-[¹⁸F]fluoroethoxy)-1,2,3,4-tetralin, a high affinity positron emitting ligand for the vesicular acetylcholine transporter, as a potential in vivo cholinergic synapse mapping agent. Rodent biodistribution, dosimetry, stereospecificity of biological effects, pharmacologic blocking studies, in vivo rodent brain autoradiography and metabolites were examined. (−)-[¹⁸F]FEOBV brain uptake following intravenous injection was robust, with 2.65% dose/brain in mice at 5 min, and the regional localization matched the known distributions of presynaptic cholinergic markers at later times. Both the cholinergic localization and curare-like effects of FEOBV were associated with the “(−)”-enantiomer exclusively. (−)-[¹⁸F]FEOBV regional brain distribution in rodents was changed little by pretreatment with haloperidol, (+)-3-PPP, or E-2020, indicating FEOBV, unlike other vesamicol analogs, did not interact in vivo with dopamine or σ receptor systems. Autoradiography of rat brain 3 h following i.v. injection of (−)-[¹⁸F]FEOBV showed high localization in brain areas rich in presynaptic cholinergic elements. Metabolic defluorination in rodents was modest, and analysis of brain tissue following tracer administration found FEOBV as the only extractable radioactive species. (−)-[¹⁸F]FEOBV dosimetry calculated from rat data estimate 10 mCi doses can be given to humans. These studies show FEOBV maps cholinergic areas with high specificity in vivo, and may provide a noninvasive means to safely and accurately gauge the functional integrity of cholinergic synapses in man using PET. Synapse 30:263–274, 1998. © 1998 Wiley-Liss, Inc.     

Hydrogels Containing Peptide or Aminosugar Sequences Implanted into the Rat Brain: Influence on Cellular Migration and Axonal Growth

Biocompatible polymer matrices for implantation into lesion sites in the brain were synthesized by incorporating peptide or aminosugar sequences intoN-(2-hydroxypropyl)methacrylamide (HPMA) hydrogels. RGD peptide sequences were chemically linked to the hydrogel backbone via a glycylglycine spacer; aminosugars were glucosamine (NHGlc) orN-acetylglucosamine residues. Unmodified or sequence containing HPMA hydrogels were implanted into the lesioned optic tract or cerebral cortex of juvenile (17- to 19-day-old) or adult rat brains, respectively. After 10–12 months host animals were perfused and the brains were processed for immunohistochemistry using antibodies to neurofilaments (RT97), laminin, glial fibrillary acidic protein (GFAP), carbonic anhydrase II (CAII), S100 protein, macrophages (ED1), and myelin basic protein (MBP). Unmodified (control) HPMA hydrogels contained no cellular infiltration or axonal growth. Peptide (RGD)- and aminosugar-modified hydrogels showed increased adhesion properties with host neural tissue, were vascularized, and were infiltrated by host nonneuronal cells. Astrocytes (GFAP⁺) and macrophages (ED1⁺) were the major cell types seen within modified HPMA hydrogels, the largest numbers being found in RGD-containing polymers. CAII⁺oligodendroglia were not seen within any of the hydrogel matrices. RT97⁺/MBP⁻axons grew into both the RGD and NHGlc hydrogel matrices for small distances. The number of axons was greatest in hydrogels implanted into cerebral cortex but in both cortex and optic tract implants the highest density of axons was seen in polymers containing RGD. The findings of this study are discussed in the context of CNS tissue replacement and the construction of bioactive scaffolds to promote regenerative axonal growth across areas of injury in the brain and spinal cord.     

Heterogeneity of the glial fibrillary acidic protein in gliosed human brains

The glial fibrillary acidic (GFA) protein from gliosed human brains was separated into 3 immunologically active components on 12.5% SDS-acrylamide gel electrophoresis and on urea-acrylamide gel electrophoresis. The ratio between 2 of these components (component $\text{b}\text{component}\text{c}$) remained constant during several purification procedures and in different preparations from the same brain, but varied considerably from brain to brain (0.4–1.3). The slower migrating component a was a minor component in 2 brains constituting less than 1% of the total protein on the gel in several preparations from one brain. In 2 other brains component a was present in larger amounts. It was found to be enriched by 25% ammonium sulfate precipitation and its content varied throughout the elution of GFA protein from DEAE-Sephadex. Alanine was the only N-terminal amino acid in all preparations. Three major amino acids of GFA protein, viz. glutamic acid, alanine and leucine, were present in the same amounts in components b and c.     

Effects of intraventricular transplantation of NGF-secreting cells on cholinergic basal forebrain neurons after partial immunolesion

The aim of the present study was to examine the effects of nerve growth factor on brain cholinergic function after a partial immunolesion to the rat cholinergic basal forebrain neurons (CBFNs) by 192 IgG-saporin. Two weeks after intraventricular injections of 1.3 μg of 192 IgG-saporin, about 50% of CBFNs were lost which was associated with 40–60% reductions of choline acetyltransferase (ChAT) and high-affinity choline uptake (HACU) activities throughout the basal forebrain cholinergic system. Two groups of lesioned animals received intraventricular transplantations of mouse 3T3 fibroblasts retrovirally transfected with either the rat NGF gene (3T3^NGF+) or the retrovirus alone (3T3^NGF−) and were sacrificed eight weeks later. In vivo production of NGF by 3T3^NGF+ cells was confirmed by NGF immunohistochemistry on the grafts and NGF immunoassay on cerebrospinal fluid (CSF) samples. Both ChAT and HACU activities returned to normal control levels in the basal forebrain and cortex after 3T3^NGF+ transplants, whereas no recovery was observed in 3T3^NGF− transplanted animals. There was a 25% increase in the size of remaining CBFNs and an increased staining intensity for NGF immunoreactivity in these cells after NGF treatments. Acetylcholinesterase (AChE) histochemistry revealed that the optical density of AChE-positive fibers in the cerebral cortex and hippocampus were reduced by about 60% in immunolesioned rats which were completely restored by 3T3^NGF+ grafts. In addition, decreases in growth-associated protein (GAP)-43 immunoreactivity after immunolesion and increases in synaptophysin immunoreactivity after 3T3^NGF+ grafts were observed in the hippocampus. Our results further confirm the notion that transfected NGF-secreting cells are useful in long-term in vivo NGF treatment and NGF can upregulate CBFN function. They also highly suggest that NGF induces terminal sprouting from remaining CBFNs. © 1996 Wiley-Liss, Inc.     

Selective Immunolesion of the Basal Forebrain Cholinergic Neurons: Effects on Hippocampal Activity During Sleep and Wakefulness in the Rat

Intracerebroventricular injection of the toxin 192 IgG-saporin (4μg) kills the cholinergic neurons of the basal forebrain bearing the low affinity NGF receptor (NGFr). The effect of this cholinergic denervation on the hippocampal and cortical electrical activity (EEG) was studied during sleep and wakefulness. EEG was recorded under freely-moving conditions in lesioned (n=10) and control (n=6) rats (8–16 days post-injection). In lesioned rats, active (AW) and quiet (QW) wakefulness episode durations were similar to those of controls whereas the REM sleep duration was reduced, 8 days post-lesion (P<0.01). Bouts of REM sleep were more numerous but shorter. The hippocampal theta activity was still present in lesioned-rats during AW (type 1 theta), QW (type 2 theta) and REM sleep. The frequency was unchanged but the amplitude of the three types of theta was significantly reduced (P<0.01). Type 2 theta occurred with shorter and less regular bouts (P<0.05). Abnormal slow waves (2–4 Hz) were observed during wakefulness. Histology showed a dramatic loss of NGFr-positive neurons in the basal forebrain and a decline in hippocampal and cortical acetylcholinesterase activity. These results suggest that the cholinergic septohippocampal input is not the primary pacemaker for the hippocampal theta rhythm.     

Glycoproteins in Tay-sachs disease: isolation and carbohydrate composition of glycopeptides

The concentration of N-acetylneuraminic acid (NANA) in the non-dialyzable and dialyzable glycopeptides derived from Tay-Sachs brain tissue was the same as that found in normal controls. This suggests that the heteropolysaccharide chains of the brain glycoproteins do not contain the structural feature which is responsible for the accumulation of Tay-Sachs ganglioside. It is known that Tay-Sachs ganglioside becomes elevated in this disease due to the terminal location of N-acetylgalactosamine which cannot be cleaved due to the deficiency of hexosaminase A. Gangliosidic NANA becomes elevated since the cleavage of this sugar is dependent upon the prior removal of the terminal N-acetylgalactosamine.     

Ganglioside GM1 protects cAMP 3′ 5′: Phosphodiesterase from inactivation caused by lipid peroxidation in brain synaptosomes of rats

The preincubation of synaptosomes with nanomolar concentrations of ganglioside GM1 was shown to protect Ca²⁺-dependent and Ca²⁺-independent cyclic nucleotide phosphodiesterase from inactivation caused by lipid peroxidation (LPO) induction. Thus, Ca²⁺-dependent phosphodiesterase activity decreased to approximately 34% of the initial value following 30 min of LPO induction, but it constituted more than 60% of the control activity if synaptosomes were preincubated with 10^?8 M GM1, the difference being statistically significant. 10^?6 M α-tocopherol had a similar effect. As far as the lipid matrix is concerned, gangliosides were found to prevent to a great extent malonic dialdehyde (MDA) accumulation and to protect polyenoic fatty acids from oxidative destruction. The ability of gangliosides to protect phosphodiesterase from inactivation caused by LPO induction appears to be owing not only to the inhibition of the accumulation of LPO products, but to the direct activation of the enzyme as well, 10^?7 M of ganglioside GM1 having the maximal activating effect. In contrast to α-tocopherol and other antioxidants reacting directly with free radicals, the inhibitory effect of gangliosides appears to be mediated by signal transduction systems.     

Effect of maternal nicotine on the development of sites for [3H]nicotine binding in the fetal brain

The sites for [³H]nicotine binding in fetal brains were examined after administration of nicotine into pregnant rats. Administration of unlabelled nicotine into the pregnant rats increased Bmax values for the sites for [³H]nicotine binding without affecting K_d values in the fetal brains. Treatment with this regimen, however, did not show any significant change in the sites for [³H]quinuclidinyl benzylate (QNB) binding. In addition, treatment with this regimen increased Bmax values of the sites for [³H]nicotine binding in the brains of pregnant rats. α-Bungarotoxin had no effect on the sites for [³H]nicotine binding.It is inferred, therefore, that a similar response is elicited by nicotine binding sites to administered nicotine in both the fetal and maternal brains. Furthermore, a possible effect of nicotine in pregnant rats may be the facilitation of the development of nicotine acetylcholine receptors in the fetal brain.     

Cerebrospinal dopamine metabolites in rats after intrastriatal administration of 6-hydroxydopamine or 1-methyl-4-phenylpyridinium ion

Dopamine (DA) and its main cerebral metabolites, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured in striatum and cerebrospinal fluid (CSF) from cisterna magna in rats bilaterally lesioned by intrastriatal administration of 6-hydroxydopamine (6-OHDA) or 1-methyl-4-phenylpyridinium ion (MPP⁺). 6-OHDA caused a progressive lesion in striatum that is only moderately reflected in the decrease in dopamine metabolite concentration in CSF. MPP⁺ caused an acute but less selective lesion in the dopamine striatal system, as indicated by a significant reduction in striatal GABA content, followed by a slow recovery in dopamine striatal metabolism and content. The locomotor activity was dramatically reduced in both groups 48 hours after the treatment but remained significantly decreased after two months only in 6-OHDA lesioned animals. A positive correlation was found between HVA CSF concentration and striatal DA content in MPP⁺ lesioned rats, but not in 6-OHDA lesioned rats. It is concluded that the concentration of dopamine metabolites in CSF can be altered only after a severe striatal lesion: reduction of striatal dopamine content below 50% of normal values and involvement of neuronal or non-neuronal elements other than the dopaminergic system, similarly to the lesions caused by MPP⁺. These results may partly explain why CSF dopamine metabolites concentrations were significantly decreased both in advanced stages of parkinsonism and in other neurodegenerative disorders.