Neurodegeneration Of Cholinergic Neurons Research Articles

Acetyl-L-Carnitine Aids in Preservation of Cholinergic Neurons and Memory in the Drosophila melanogaster Model of Alzheimer's Disease.

The lack of effective therapy for the treatment of Alzheimer's disease demands both the search for new drugs and the reconsideration of already known substances currently used in other areas of medicine. Drosophila melanogaster offers the potential to model features of Alzheimer's disease, study disease mechanisms, and conduct drug screening. The purpose of this work was to analyze the neuroprotective properties of the drug "carnicetine", which is an acetylated form of the natural low molecular weight compound L-carnitine. The drug is able to cross the blood-brain barrier and is currently used as a means of improving cellular metabolism. Using tissue-specific drivers, direct expression of amyloid beta peptide (42 amino acids) was exhibited in certain groups of neurons in the Drosophila melanogaster brain, namely in dopaminergic and cholinergic neurons. The effect of acetyl-L-carnitine (carnicetine) on the death of these neurons and the memory of flies was analyzed. The expression of amyloid beta peptide in dopaminergic or cholinergic neurons resulted in neurodegeneration of cholinergic neurons in the Drosophila brain and memory impairment. The use of carnicetine added to animal food made it possible to treat these disorders. At the same time, no effect on dopaminergic neurons was noted. The data obtained confirmed the neuroprotective properties of the drug under study, demonstrating its participation in the restoration of the cholinergic system and the feasibility of using carnicetine for the treatment of Alzheimer's disease.

Intrahippocampal Amyloid-β (1-40) Injections Injure Medial Septal Neurons in Rats

Alzheimer's disease (AD) is a devastating disorder that leads to memory loss and dementia. Neurodegeneration of cholinergic neurons in the septum and other basal forebrain areas is evident in early stages of AD. Glutamatergic neurons are also affected early in AD. In these stages, amyloid-β-peptide (Aβ) plaques are present in the hippocampus and other cortices but not in the basal forebrain, which includes the septum. We postulate that early deposition of hippocampal Aβ damages the axon terminals of cholinergic and glutamatergic septo-hippocampal neurons, leading to their degeneration. To determine the mechanisms underlying septal degeneration, fibrillar Aβ1-40 was injected into the Cornu Ammonis (CA1) hippocampal region of rats. Controls were injected with reverse peptide Aβ40-1. A 16% reduction in NeuN+ cells was observed around the injection sites when compared to controls (p < 0.05) one week after injections. Stereology was used to estimate the number of choline acetyl transferase (ChAT), glutamate and glutamic acid decarboxylase 67 (GAD67) immunoreactive septal neurons. Medial septal ChAT and glutamate immunoreactive neurons were reduced 38% and 26%, respectively by hippocampal injections of Aβ1-40 peptide in relation to controls. In contrast, the number of GAD67 inmunoreactive neurons was not significantly reduced. Apoptotic cells were detected in the medial septal region of Aβ1-40 treated animals but not in controls. These results indicate that limited Aβ-induced hippocampal lesions lead to an overall damage of vulnerable septal neuronal populations, most likely by Aβ interaction with septo-hippocampal axon terminals. Thus, axon terminals constitute an important target for novel therapeutics dedicated to control Aβ-induced toxicity.

S100b Counteracts Neurodegeneration of Rat Cholinergic Neurons in Brain Slices after Oxygen-Glucose Deprivation

Alzheimer's disease is a severe chronic neurodegenerative disorder characterized by beta-amyloid plaques, tau pathology, cerebrovascular damage, inflammation, reactive gliosis, and cell death of cholinergic neurons. The aim of the present study is to test whether the glia-derived molecule S100b can counteract neurodegeneration of cholinergic neurons after oxygen-glucose deprivation (OGD) in organotypic brain slices of basal nucleus of Meynert. Our data showed that 3 days of OGD induced a marked decrease of cholinergic neurons (60% of control), which could be counteracted by 50 μg/mL recombinant S100b. The effect was dose and time dependent. Application of nerve growth factor or fibroblast growth factor-2 was less protective. C-fos-like immunoreactivity was enhanced 3 hours after OGD indicating metabolic stress. We conclude that S100b is a potent neuroprotective factor for cholinergic neurons during ischemic events.

Rotenone induces cell death of cholinergic neurons in an organotypic co-culture brain slice model.

In Alzheimer and Parkinson's disease cell death of cholinergic and dopaminergic neurons are characteristic hallmarks, respectively. It is well established that rotenone, an inhibitor of complex I of the electron transport chain, induces cell death of dopaminergic neurons, however, not much is known on the effects of rotenone on cholinergic neurons. The aim of the present study was to evaluate the effects of rotenone on cholinergic neurons in an organotypic in vitro brain co-slice model. When co-cultures were treated with 10 μM rotenone for 24 h a significantly decreased number of cholinergic neurons was found in the basal nucleus of Meynert but not in the dorsal striatum. This cell death exhibited apoptotic DAPI-positive malformed nuclei and enhanced TUNEL-positive cells. In summary, inhibition of complex I of the electron transport chain may play a role in neurodegeneration of cholinergic neurons.

Motor dysfunction in a mouse model for Down syndrome

Motor deficits are among the most frequently occurring features of Down syndrome (DS). Individuals with DS exhibit disturbances in the dynamics of movement production and postural control that are thought to have a significant impact in delaying their acquisition of motor skills. The origin of these deficits has been hypothesized to be cerebellar. The Ts65Dn mouse is the most robust and genetically sound animal model for DS currently available. Ts65Dn mice show many DS-like features, including significant learning deficits in different behavioral tasks and neurodegeneration of cholinergic neurons. In the present study, we investigate the motor function of these animals. We have analyzed hind paw print patterns during walking, running speeds, rotarod performance, grip force production, swim paths, and swimming speeds. Our results indicate that Ts65Dn mice present mild to severe dysfunction according to all of the above assessments. The most evident impairments presented by these mice were related to equilibrium and motor coordination, which agrees with reported clinical observations made on individuals with DS. Because none of these findings were readily apparent by simple inspection of these animals, these findings reiterate the need for a careful evaluation of any mutant mouse strain for which there is reason to suspect motor deficits. The identification of motor dysfunction in Ts65Dn mice may have important consequences for the interpretation of some previous assessments of learning and memory of these animals that assumed intact motor function, and further strengthens the use of this aneuploid mouse strain as a model for DS.