Endogenous GABAA receptor activity suppresses glioma growth.

Although genome alterations driving glioma by fueling cell malignancy have largely been resolved, less is known of the impact of tumor environment on disease progression. Here, we demonstrate functional GABAA receptor-activated currents in human glioblastoma cells and show the existence of a continuous GABA signaling within the tumor cell mass that significantly affects tumor growth and survival expectancy in mouse models. Endogenous GABA released by tumor cells, attenuates proliferation of the glioma cells with enriched expression of stem/progenitor markers and with competence to seed growth of new tumors. Our results suggest that GABA levels rapidly increase in tumors impeding further growth. Thus, shunting chloride ions by a maintained local GABAA receptor activity within glioma cells has a significant impact on tumor development by attenuating proliferation, reducing tumor growth and prolonging survival, a mechanism that may have important impact on therapy resistance and recurrence following tumor resection.

Three-dimensional Imaging Reveals New Compartments and Structural Adaptations in Odontoblasts.

In organized tissues, the precise geometry and the overall shape are critical for the specialized functions that the cells carry out. Odontoblasts are major matrix-producing cells of the tooth and have also been suggested to participate in sensory transmission. However, refined morphologic data on these important cells are limited, which hampers the analysis and understanding of their cellular functions. We took advantage of fluorescent color-coding genetic tracing to visualize and reconstruct in 3 dimensions single odontoblasts, pulp cells, and their assemblages. Our results show distinct structural features and compartments of odontoblasts at different stages of maturation, with regard to overall cellular shape, formation of the main process, orientation, and matrix deposition. We demonstrate previously unanticipated contacts between the processes of pulp cells and odontoblasts. All reported data are related to mouse incisor tooth. We also show that odontoblasts express TRPM5 and Piezo2 ion channels. Piezo2 is expressed ubiquitously, while TRPM5 is asymmetrically distributed with distinct localization to regions proximal to and within odontoblast processes.

Presynaptic adenosine A2A receptors dampen cannabinoid CB1 receptor-mediated inhibition of corticostriatal glutamatergic transmission.

BACKGROUND AND PURPOSE: Both cannabinoid CB1 and adenosine A2A receptors (CB1 receptors and A2A receptors) control synaptic transmission at corticostriatal synapses, with great therapeutic importance for neurological and psychiatric disorders. A postsynaptic CB1 -A2A receptor interaction has already been elucidated, but the presynaptic A2A receptor-mediated control of presynaptic neuromodulation by CB1 receptors remains to be defined. Because the corticostriatal terminals provide the major input to the basal ganglia, understanding the interactive nature of converging neuromodulation on them will provide us with novel powerful tools to understand the physiology of corticostriatal synaptic transmission and interpret changes associated with pathological conditions. EXPERIMENTAL APPROACH: Pharmacological manipulation of CB1 and A2A receptors was carried out in brain nerve terminals isolated from rats and mice, using flow synaptometry, immunoprecipitation, radioligand binding, ATP and glutamate release measurement. Whole-cell patch-clamp recordings were made in horizontal corticostriatal slices. KEY RESULTS: Flow synaptometry showed that A2A receptors were extensively co-localized with CB1 receptor-immunopositive corticostriatal terminals and A2A receptors co-immunoprecipitated CB1 receptors in these purified terminals. A2A receptor activation decreased CB1 receptor radioligand binding and decreased the CB1 receptor-mediated inhibition of high-K(+) -evoked glutamate release in corticostriatal terminals. Accordingly, A2A receptor activation prevented CB1 receptor-mediated paired-pulse facilitation and attenuated the CB1 receptor-mediated inhibition of synaptic transmission in glutamatergic synapses of corticostriatal slices. CONCLUSIONS AND IMPLICATIONS: Activation of presynaptic A2A receptors dampened CB1 receptor-mediated inhibition of corticostriatal terminals. This constitutes a thus far unrecognized mechanism to modulate the potent CB1 receptor-mediated presynaptic inhibition, allowing frequency-dependent enhancement of synaptic efficacy at corticostriatal synapses.

Thioflavins released from nanoparticles target fibrillar amyloid beta in the hippocampus of APP/PS1 transgenic mice.

For the delivery of drugs into the brain, the use of nanoparticles as carriers has been described as a promising approach. Here, we prepared nanoparticles as carriers for the model drugs thioflavin T and thioflavin S that bind fibrillar amyloid beta peptides (Abeta). These polymer colloids are composed of a polystyrene core and a degradable PBCA [poly(butyl-2-cyanoacrylate)] shell with a diameter of 90-100nm as shown by dynamic light scattering. Fluorescence spectrophotometric analysis revealed that encapsulated thioflavin T exhibited significantly stronger fluorescence than the free fluorophore. The enzymatic degradation of core-shell nanoparticles, as required in vivo, was shown after their treatment with porcine liver esterase, a non-specific esterase, in vitro. Shells of nanoparticles were dose-dependently degraded while their polystyrene cores remained intact. In the cortices of 7-14 months old APP/PS1 mice with age-dependent beta-amyloidosis, thioflavins selectively targeted fibrillar Abeta after biodegradation-induced release from their nanoparticulate carriers upon intracerebral injection. Collectively, our data suggest that core-shell nanoparticles with controlled degradation in vivo can become versatile tools to trace and clear Abeta in the brain.

17beta-estradiol enhances cortical cholinergic innervation and preserves synaptic density following excitotoxic lesions to the rat nucleus basalis magnocellularis.

Estradiol exerts beneficial effects on neurodegenerative disorders associated with the decline of cognitive performance. The present study was designed to further investigate the effect of 17beta-estradiol on learning and memory, and to evaluate its neuroprotective action on cholinergic cells of the nucleus basalis magnocellularis, a neural substrate of cognitive performance. Female rats were ovariectomized at an age of 6 months. Three weeks later they received injections of either a mid-physiological dose of 17beta-estradiol or vehicle (oil), every other day for 2 weeks. The effect of estradiol on cognitive performance was tested in two associative learning paradigms. In the two-way active shock avoidance task estradiol-replaced animals learned significantly faster, while in the passive shock avoidance test no differences were observed between the experimental groups. Subsequent unilateral infusion of N-methyl-D-aspartate in the nucleus basalis magnocellularis resulted in a significant loss of cholinergic neurons concomitant with the loss of their fibers invading the somatosensory cortex. Estradiol treatment did not affect the total number of choline-acetyltransferase-immunoreactive neurons and their coexpression of the p75 low-affinity neurotrophin receptor either contralateral or ipsilateral to the lesion. In contrast, cholinergic fiber densities in estradiol-treated animals were greater both in the contralateral and ipsilateral somatosensory cortices as was detected by quantitative choline-acetyltransferase and vesicular acetylcholine transporter immunocytochemistry. However, estradiol treatment did not affect the lesion-induced relative percentage loss of cholinergic fibers. A significant decline of synaptophysin immunoreactivity paralleled the cholinergic damage in the somatosensory cortex of oil-treated animals, whereas an almost complete preservation of synaptic density was determined in estradiol-treated rats. Our results indicate that estradiol treatment enhances the cortical cholinergic innervation but has no rescuing effect on cholinergic nerve cells in the basal forebrain against excitotoxic damage. Nevertheless, estradiol may restore or maintain synaptic density in the cerebral cortex following cholinergic fiber loss. This estradiol effect may outweigh the lack of cellular protection on cholinergic cells at the functional level.

Short-term consequences of N-methyl-D-aspartate excitotoxicity in rat magnocellular nucleus basalis: effects on in vivo labelling of cholinergic neurons.

Cholinergic neurons of the basal forebrain form one of the neuron populations that are susceptible to excitotoxic injury. Whereas neuropharmacological studies have aimed at rescuing cholinergic neurons from acute excitotoxic attacks, the short-term temporal profile of excitotoxic damage to cholinergic nerve cells remains largely elusive. The effects of N-methyl-D-aspartate (NMDA) infusion on cytochemical markers of cholinergic neurons in rat magnocellular nucleus basalis were therefore determined 4, 24 and 48 h post-lesion. Additionally, the influence of excitotoxic damage on the efficacy of in vivo labelling of cholinergic neurons with carbocyanine 3-192IgG was investigated. Carbocyanine 3-192IgG was unilaterally injected in the lateral ventricle. Twenty-four hours later, NMDA (60 nM/microl) was infused in the right magnocellular nucleus basalis, while control lesions were performed contralaterally. Triple immunofluorescence labelling for carbocyanine 3-192IgG, NMDA receptor 2A and B subunits and choline-acetyltransferase (ChAT) was employed to determine temporal changes in NMDA receptor immunoreactivity on cholinergic neurons. The extent of neuronal degeneration was studied by staining with Fluoro-Jade. Moreover, changes in the numbers of ChAT or p75 low-affinity neurotrophin receptor immunoreactive neurons, and the degree of their co-labelling with carbocyanine 3-192IgG were determined in basal forebrain nuclei. The effects of NMDA-induced lesions on cortical projections of cholinergic nucleus basalis neurons were studied by acetylcholinesterase (AChE) histochemistry. Characteristic signs of cellular damage, as indicated by decreased immunoreactivity for NMDA receptors, ChAT and p75 low-affinity neurotrophin receptors, were already detected at the shortest post-lesion interval investigated. Fluoro-Jade at 4 h post-lesion only labelled the core of the excitotoxic lesion. Longer survival led to enhanced Fluoro-Jade staining, and to the decline of ChAT immunoreactivity reaching a maximum 24 h post-surgery. Significant loss of p75 low-affinity neurotrophin receptor immunoreactivity and of cortical AChE-positive projections only became apparent 48 h post-lesion. Carbocyanine 3-192IgG labelling in the ipsilateral basal forebrain exceeded that of the contralateral hemisphere at all time points investigated and progressively declined in the damaged magnocellular nucleus basalis up to 48 h after NMDA infusion. The present study indicates that excitotoxic lesion-induced alteration of cholinergic neuronal markers is a rapid and gradual process reaching its maximum 24 h post-surgery. Furthermore, in vivo labelling of cholinergic neurons may be applied to indicate neuronal survival under pathological conditions, and enable to follow their degeneration process under a variety of experimental conditions.

Oral post-lesion administration of 5-HT(1A) receptor agonist repinotan hydrochloride (BAY x 3702) attenuates NMDA-induced delayed neuronal death in rat magnocellular nucleus basalis.

Recent evidence indicates that stimulation of postsynaptic 5-HT(1A) receptors abates excitotoxic neuronal death. Here we investigated whether oral post-lesion administration of the 5-HT(1A) receptor agonist (-)-(R)-2-[4-[[(3,4-dihydro-2H-1-benzopyran-2-yl)methyl]amino]butyl]-1,2-benzisothiazol-3(2H)-one 1,1-dioxide monohydrochloride (Repinotan HCl) attenuates N-methyl-D-aspartate (NMDA) excitotoxicity (60 nmol/microl) in the rat magnocellular nucleus basalis. Repinotan HCl (1 mg/kg) was administered from day 1, 2, 3, or 6 post-surgery twice daily for five consecutive days. This delayed drug administration protocol was employed to investigate the initiation period during which 5-HT(1A) receptor agonists may significantly influence ongoing neurodegeneration processes. 8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 1 mg/kg) served as reference compound. Twenty-four hours after drug delivery a small open-field test, while on day 14 post-surgery a passive avoidance test was performed. Effects of Repinotan HCl treatment on the survival of cholinergic magnocellular nucleus basalis neurons and their cortical projections were determined by quantitative acetylcholinesterase (AChE) and choline-acetyltransferase (ChAT) histochemistry. Moreover, AChE and ChAT activities were biochemically measured both in the cerebral cortex and in the magnocellular nucleus basalis. Repinotan HCl treatment markedly increased spontaneous activities in the small open-field at any time-point investigated. Improved memory performance was only demonstrated when Repinotan HCl was administered from day 1 post-lesion on wards. Repinotan HCl treatment from day 2 and 3 post-lesion on markedly attenuated both histochemical and neurochemical characteristics of NMDA excitotoxicity on cholinergic magnocellular nucleus basalis neurons and on their cortical projections. Whereas the neuroprotective profile of Repinotan HCl was superior to that of 8-OH-DPAT, oral administration of both 5-HT(1A) receptor agonists yielded largely equivalent behavioral recovery after NMDA infusion in the magnocellular nucleus basalis. In conclusion, the present data indicate the potent neuroprotective action of the 5-HT(1A) receptor agonist Repinotan HCl with a peak efficacy of delayed (2-3 day) post-lesion drug treatment in vivo. Post-lesion treatment with 5-HT(1A) receptor agonists may therefore be of significance in the intervention of neuronal damage associated with acute excitotoxic conditions.

Increased amyloid precursor protein expression and serotonergic sprouting following excitotoxic lesion of the rat magnocellular nucleus basalis: neuroprotection by Ca(2+) antagonist nimodipine.

In the present study plastic neural responses to N-methyl-D-aspartate-induced excitotoxic lesions and the neuroprotective effects of the L-type voltage-dependent Ca(2+) channel antagonist nimodipine were investigated in the rat magnocellular nucleus basalis. Assessment of spontaneous behaviour in the elevated plus maze and small open-field paradigms on day 5 and day 14 post-surgery indicated anxiety and persistent hypoactivity of N-methyl-D-aspartate-lesioned rats, as compared with sham-operated controls. Nimodipine administration significantly alleviated the behavioural deficits. Quantitative histochemical analysis of acetylcholinesterase-positive fibre innervation of the somatosensory cortex and determination of the numbers of choline-acetyltransferase-positive proximal fibre branches of cholinergic projection neurons in the magnocellular nucleus basalis demonstrated a severe cholinergic deficit as a consequence of the excitotoxic lesion 14 days post-surgery. Nimodipine pre-treatment significantly attenuated the loss of cortical cholinergic innervation and preserved the functional integrity of cholinergic projection neurons in the magnocellular nucleus basalis. Double-labelling immunocytochemistry demonstrated increased amyloid precursor protein expression in shrinking and presumably apoptotic choline-acetyltransferase-positive neurons, whereas surviving cholinergic nerve cells were devoid of excessive amyloid precursor protein immunoreactivity. Moreover, as a consequence of N-methyl-D-aspartate infusion, rim-like accumulation of amyloid precursor protein-positive astrocytes was visualized in a penumbra-like zone of the excitotoxic injury. Furthermore, abundant sprouting of serotonergic projection fibres invading the damaged magnocellular nucleus basalis subdivision was demonstrated. Pharmacological blockade by the Ca(2+) antagonist nimodipine significantly attenuated both neuronal and glial amyloid precursor protein immunoreactivity and serotonergic fibre sprouting following N-methyl-D-aspartate infusion. The present data characterize plastic endogenous glial and neuronal responses in the magnocellular nucleus basalis model of acute excitotoxic brain damage. The increased amyloid precursor protein expression may indicate effective means of intrinsic neuroprotection, as secreted amyloid precursor protein isoforms are suggested to play a role in neuronal rescue following excitotoxic injury. From a pharmacological point of view, extensive sprouting of serotonergic projections in the damaged magnocellular nucleus basalis may also counteract N-methyl-D-aspartate excitotoxicity via serotonin-induced inhibition of Ca(2+) currents and membrane hyperpolarization. Hence, lesion-induced changes in spontaneous animal behaviour, such as anxiety and novelty-induced hypoactivity, may well be attributed to the considerable re-distribution of serotonergic projections in the basal forebrain. In conclusion, our present data emphasize a role of neuron-glia and neurotransmitter-system interactions in functional recovery after acute excitotoxic brain injury, and the efficacy of L-type Ca(2+) channel blockade by the selective 1,4-dihydropyridine antagonist nimodipine.

Postnatal treatment with ACTH-(4-9) analog ORG 2766 attenuates N-methyl-D-aspartate-induced excitotoxicity in rat nucleus basalis in adulthood.

It has been reported that the ACTH-(4-9) analog H-Met(O(2))-Glu-His-Phe-D-Lys-Phe-OH (ORG 2766) administered in adulthood has trophic effects on neuronal tissue and when given postnatally, it can induce long-lasting changes in brain development. In the present study, we investigated whether early postnatal treatment with ORG 2766 affects adult neuronal vulnerability, i.e. the sensitivity of cholinergic neurons against excitotoxic damage. Wistar rat pups received injections of ORG 2766 or saline on postnatal days 1, 3 and 5 and were then left undisturbed until adulthood. At the age of 6 months, the animals were subjected to unilateral lesion of magnocellular basal nucleus by infusion of high dose of N-methyl-D-aspartate (NMDA). The effects of the excitotoxic insult were studied 28 hours and 12 days after the lesion by measuring both the acute cholinergic and glial responses, and the final outcome of the degeneration process. Twenty eight hours after NMDA infusion, postnatally ACTH-(4-9)-treated animals showed stronger suppression of choline-acetyltransferase immunoreactivity and increased reaction of glial fibrillary acidic protein -immunopositive astrocytes in the lesioned nucleus compared to control animals. However, 12 days post-surgery, the NMDA-induced loss of cholinergic neurons, as well as the decrease of their acetylcholinesterase -positive fibre projections in the cortex, were less in ACTH-(4-9) animals. Our data indicate that the early developmental effects of ACTH-(4-9) influence intrinsic neuroprotective mechanisms and reactivity of neuronal and glial cells, thereby resulting in a facilitated rescuing mechanism following excitotoxic injury.

Neuroprotective approaches in experimental models of beta-amyloid neurotoxicity: relevance to Alzheimer's disease.

1. beta-Amyloid peptides (A beta s) accumulate abundantly in the Alzheimer's disease (AD) brain in areas subserving information acquisition and processing, and memory formation. A beta fragments are produced in a process of abnormal proteolytic cleavage of their precursor, the amyloid precursor protein (APP). While conflicting data exist in the literature on the roles of A beta s in the brain, and particularly in AD, recent studies have provided firm experimental evidence for the direct neurotoxic properties of A beta. 2. Sequence analysis of A beta s revealed a high degree of evolutionary conservation and inter-species homology of the A beta amino acid sequence. In contrast, synthetic A beta fragments, even if modified fluorescent or isotope-labeled derivatives, are pharmacological candidates for in vitro and in vivo modeling of their cellular actions. During the past decade, acute injection, prolonged mini-osmotic brain perfusion approaches or A beta infusions into the blood circulation were developed in order to investigate the effects of synthetic A beta s, whereas transgenic models provided insight into the distinct molecular steps of pathological APP cleavage. 3. The hippocampus, caudate putamen, amygdala and neocortex all formed primary targets of acute neurotoxicity screening, but functional consequences of A beta infusions were primarily demonstrated following either intracerebroventricular or basal forebrain (medial septum or magnocellular basal nucleus (MBN)) infusions of A beta fragments. 4. In vivo investigations confirmed that, while the active core of A beta is located within the beta(25-35) sequence, the flanking peptide regions influence not only the folding properties of the A beta fragments, but also their in vivo neurotoxic potentials. 5. It has recently been established that A beta administration deranges neuron-glia signaling, affects the glial glutamate uptake and thereby induces noxious glutamatergic stimulation of nerve cells. In fact, a critical role for N-methyl-D-aspartate (NMDA) receptors was postulated in the neurotoxic processes. Additionally, A beta s might become internalized, either after their selective binding to cell-surface receptors or after membrane association in consequence of their highly lipophilic nature, and induce free radical generation and subsequent oxidative injury. Ca(2+)-mediated neurotoxic events and generation of oxygen free radicals may indeed potentiate each other, or even converge to the same neurotoxic events, leading to cell death. 6. Neuroprotection against A beta toxicity was achieved by both pre- and post-treatment with NMDA receptor channel antagonists. Moreover, direct radical-scavengers, such as vitamin E or vitamin C, attenuated A beta toxicity with high efficacy. Interestingly, combined drug treatments did not necessarily result in additive enhanced neuroprotection. 7. Similarly to the blockade of NMDA receptors, the neurotoxic action of A beta s could be markedly decreased by pharmacological manipulation of voltage-dependent Ca(2+)-channels, serotonergic IA or adenosine A1 receptors, and by drugs eliciting membrane hyperpolarization or indirect blockade of Ca(2+)-mediated intracellular consequences of intracerebral A beta infusions. 8. A beta neurotoxicity might be dose-dependently modulated by trace metals. In spite of the fact that zinc (Zn) may act as a potent inhibitor of the NMDA receptor channel, high Zn doses accelerate A beta fibril formation, stabilize the beta-sheet conformation and thereby potentiate A beta neurotoxicity. Combined trace element supplementation with Se, Mn, or Mg, which prevails over the expression of detoxifying enzymes or counteracts intracellular elevations of Ca2+, may reduce the neurotoxic impact of A beta s. 9. Alterations in the regulatory functions of the hypothalamo-pituitary-adrenal axis may contribute significantly to neurodegenerative changes in the brain. Furthermore, AD patients exhibit substantially increased circadia

Beta-amyloid(Phe(SO3H)24)25-35 in rat nucleus basalis induces behavioral dysfunctions, impairs learning and memory and disrupts cortical cholinergic innervation.

Long-term behavioral effects, changes in learning and memory functions and aberrations of cholinergic fibers projecting to the parietal cortex were investigated after bilateral injections of beta-amyloid(Phe(SO3H)24)25-35 peptide in rat nucleus basalis magnocellularis (nbm). The beta-amyloid peptide used in these experiments contained the original beta-amyloid 25-35 sequence which was coupled to a phenylalanine-sulphonate group at position 24. This additional residue serves as a protective cap on the molecule without influencing its neurotoxic properties and results in water-solubility, stability and low rates of peptide metabolism. In this paper, home cage, locomotor and open-field activities, passive shock-avoidance and 'Morris' water maze learning abilities were assessed throughout a 35-day survival period. Subsequently, acetylcholinesterase (AChE) histochemistry was used to visualize alterations of parietal cortical cholinergic innervation. In response to the neurotoxic action of beta-amyloid(Phe(SO3H)24)25-35, a progressive hyperactivity developed in the rats in their home cages which were maintained throughout the 5-week post-injection period. This was accompanied by a significant hypoactivity in the novel environment of a locomotor arena. Beta-amyloid(Phe(SO3H)24)25-35-treated animals showed greatly impaired cortical memory functions in the step-through passive shock-avoidance paradigm, while spatial learning processes remained unaffected. Moreover, beta-amyloid(Phe(SO3H)24)25-35 injections in the nucleus basalis suppressed explorative behavior in rats and inhibited conditioned stress responses 28 days after surgery. Reductions of cortical cholinergic (AChE-positive) projections provided anatomical substrate for the behavioral changes. This indicated extensive, long-lasting neurodegenerative processes as a result of beta-amyloid(Phe(SO3H)24)25-35 infusion.

Chronic ethanol ingestion-induced changes in open-field behavior and oxidative stress in the rat.

The effects of chronic ethanol intoxication on the open-field behavior, on antioxidant enzyme activities, and the degree of lipid peroxidation were investigated. Rats consuming a liquid diet containing 7% ethanol for 4, 7, 14, or 21 days exhibited a significantly decreased ambulation activity, accompanied by a reduced frequency and duration of explorative rearing in an open-field task 4, 7, and 14 days after chronic ethanol ingestion, whereas presumed adaptation to the neurologic effects of ethanol was observed on day 21. Changes in the activities of glutathione peroxidase (GSH-Px): glutathione reductase (GSH-R), and catalase, and in the content of reduced glutathione (GSH) in blood samples were determined by means of biochemical methods. The degree of lipid peroxidation was measured via thiobarbituric acid assays. Chronic ethanol ingestion elicited a significant increase in GSH-Px activity (by a maximum of approximately 32% on day 14), whereas opposite alterations in GSH-R and catalase activities were recorded (49% of the control value on day 4 and 17% on day 21, respectively). Highly elevated contents of thiobarbituric acid reactive substances reflected extensive lipid peroxidation processes throughout the experiment. These changes indicate that ethanol toxicity induces profound changes in explorative behavior, mediated, at least partly, by changes in the free radical metabolism.

Chronic aluminum treatment results in aluminum deposits and affects Ml muscarinic receptors in rat brain.

The effects of chronic aluminum (Al) administration on the deposition of the metal and on the receptor binding characteristics of the Ml muscarinic acetylcholine receptors (MlAChR) were studied in selected rat brain areas. Animals were injected intraperitoneally with an AlCl3 solution of 1.0 mg/ml/100 g of body weight for 5 weeks, 5 days a week. Al accumulation was detected by solochrome azurine histochemistry in the brain, where the metal could be visualized in capillaries, endothelial cells and surrounding brain tissues. Changes in the binding properties of the MlAChR after chronic Al treatment were determined with the use of selective and nonselective muscarinic antagonists. Significantly decreased number of maximal MlAChR binding sites (Bmax) as measured by the equilibrium binding of [3H]pirenzepine, were detected in all of the brain areas examined. While the nonselective antagonist [3H] (-)QNB displayed a generally decreased Bmax, value, it reached the level of significance only in the striatum. These results provide a further indication that chronic Al treatment results in the accumulation of Al in the brain and consequently affects the cholinergic neurotransmission.