Increased cholinergic activity under conditions of low estrogen leads to adverse cardiac remodeling.

Cholinesterase inhibitors are used in postmenopausal women for the treatment of neurodegenerative diseases. Despite their widespread use in the clinical practice, little is known about the impact of augmented cholinergic signaling on cardiac function under reduced estrogen conditions. To address this gap, we subjected a genetically engineered murine model of systemic vesicular acetylcholine transporter overexpression (Chat-ChR2) to ovariectomy and evaluated cardiac parameters. Left-ventricular function was similar between Chat-ChR2 and wild-type (WT) mice. Following ovariectomy, WT mice showed signs of cardiac hypertrophy. Conversely, ovariectomized (OVX) Chat-ChR2 mice evolved to cardiac dilation and failure. Transcript levels for cardiac stress markers atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) were similarly upregulated in WT/OVX and Chat-ChR2/OVX mice. 17ß-Estradiol (E2) treatment normalized cardiac parameters in Chat-ChR2/OVX to the Chat-ChR2/SHAM levels, providing a link between E2 status and the aggravated cardiac response in this model. To investigate the cellular basis underlying the cardiac alterations, ventricular myocytes were isolated and their cellular area and contractility were assessed. Myocytes from WT/OVX mice were wider than WT/SHAM, an indicative of concentric hypertrophy, but their fractional shortening was similar. Conversely, Chat-ChR2/OVX myocytes were elongated and presented contractile dysfunction. E2 treatment again prevented the structural and functional changes in Chat-ChR2/OVX myocytes. We conclude that hypercholinergic mice under reduced estrogen conditions do not develop concentric hypertrophy, a critical compensatory adaptation, evolving toward cardiac dilation and failure. This study emphasizes the importance of understanding the consequences of cholinesterase inhibition, used clinically to treat dementia, for cardiac function in postmenopausal women.

Developmental exposure to glyphosate-based herbicide and depressive-like behavior in adult offspring: Implication of glutamate excitotoxicity and oxidative stress.

We have previously demonstrated that maternal exposure to glyphosate-based herbicide (GBH) leads to glutamate excitotoxicity in 15-day-old rat hippocampus. The present study was conducted in order to investigate the effects of subchronic exposure to GBH on some neurochemical and behavioral parameters in immature and adult offspring. Rats were exposed to 1% GBH in drinking water (corresponding to 0.36% of glyphosate) from gestational day 5 until postnatal day (PND)-15 or PND60. Results showed that GBH exposure during both prenatal and postnatal periods causes oxidative stress, affects cholinergic and glutamatergic neurotransmission in offspring hippocampus from immature and adult rats. The subchronic exposure to the pesticide decreased L-[14C]-glutamate uptake and increased 45Ca2+ influx in 60-day-old rat hippocampus, suggesting a persistent glutamate excitotoxicity from developmental period (PND15) to adulthood (PND60). Moreover, GBH exposure alters the serum levels of the astrocytic protein S100B. The effects of GBH exposure were associated with oxidative stress and depressive-like behavior in offspring on PND60, as demonstrated by the prolonged immobility time and decreased time of climbing observed in forced swimming test. The mechanisms underlying the GBH-induced neurotoxicity involve the NMDA receptor activation, impairment of cholinergic transmission, astrocyte dysfunction, ERK1/2 overactivation, decreased p65 NF-κB phosphorylation, which are associated with oxidative stress and glutamate excitotoxicity. These neurochemical events may contribute, at least in part, to the depressive-like behavior observed in adult offspring.

Cholinergic abnormalities, endosomal alterations and up-regulation of nerve growth factor signaling in Niemann-Pick type C disease.

BACKGROUND: Neurotrophins and their receptors regulate several aspects of the developing and mature nervous system, including neuronal morphology and survival. Neurotrophin receptors are active in signaling endosomes, which are organelles that propagate neurotrophin signaling along neuronal processes. Defects in the Npc1 gene are associated with the accumulation of cholesterol and lipids in late endosomes and lysosomes, leading to neurodegeneration and Niemann-Pick type C (NPC) disease. The aim of this work was to assess whether the endosomal and lysosomal alterations observed in NPC disease disrupt neurotrophin signaling. As models, we used i) NPC1-deficient mice to evaluate the central cholinergic septo-hippocampal pathway and its response to nerve growth factor (NGF) after axotomy and ii) PC12 cells treated with U18666A, a pharmacological cellular model of NPC, stimulated with NGF. RESULTS: NPC1-deficient cholinergic cells respond to NGF after axotomy and exhibit increased levels of choline acetyl transferase (ChAT), whose gene is under the control of NGF signaling, compared to wild type cholinergic neurons. This finding was correlated with increased ChAT and phosphorylated Akt in basal forebrain homogenates. In addition, we found that cholinergic neurons from NPC1-deficient mice had disrupted neuronal morphology, suggesting early signs of neurodegeneration. Consistently, PC12 cells treated with U18666A presented a clear NPC cellular phenotype with a prominent endocytic dysfunction that includes an increased size of TrkA-containing endosomes and reduced recycling of the receptor. This result correlates with increased sensitivity to NGF, and, in particular, with up-regulation of the Akt and PLC-γ signaling pathways, increased neurite extension, increased phosphorylation of tau protein and cell death when PC12 cells are differentiated and treated with U18666A. CONCLUSIONS: Our results suggest that the NPC cellular phenotype causes neuronal dysfunction through the abnormal up-regulation of survival pathways, which causes the perturbation of signaling cascades and anomalous phosphorylation of the cytoskeleton.

Developmental aspects of the cholinergic system.

Beyond its importance in sustaining or modulating different aspects of the activity of the central nervous system (CNS), the cholinergic system plays important roles during development. In the current review, we focus on the developmental aspects associated with major components of the cholinergic system: Acetylcholine, choline acetyltransferase, vesicular acetylcholine transporter, high-affinity choline transporter, acetylcholinesterase, nicotinic and muscarinic receptors. We describe when and where each one of these components is first identified in the CNS and the changes in their levels that occur during the course of prenatal and postnatal development. We also describe how these components are relevant to many events that occur during the development of the CNS, including progenitor cells proliferation and differentiation, neurogenesis, gliogenesis, neuronal maturation and plasticity, axonal pathfinding, regulation of gene expression and cell survival. It will be noticed that evidence regarding the developmental aspects of the cholinergic system comes mostly from studies that used agonists, such as nicotine, and antagonists, such as hemicholinium-3. Studies using immunohistochemistry and genetically altered mice also provided valuable information.

Nicotinic receptors, amyloid-beta, and synaptic failure in Alzheimer's disease.

Dysfunctional cholinergic transmission is thought to underlie, at least in part, memory impairment and cognitive deficits in Alzheimer's disease (AD). However, it is still unclear whether this is a consequence of the loss of cholinergic neurons and elimination of nicotinic acetycholine receptors (nAChRs) in AD brain or of a direct impact of molecular interactions of the amyloid-beta (Abeta) peptide with nAChRs, leading to dysregulation of receptor function. This review examines recent progress in our understanding of the roles of nicotinic receptors in mechanisms of synaptic plasticity, molecular interactions of Abeta with nAChRs, and how Abeta-induced dysregulation of nicotinic receptor function may underlie synaptic failure in AD.

Pre-treatment with ebselen and vitamin E modulate acetylcholinesterase activity: interaction with demyelinating agents.

The ethidium bromide (EB) demyelinating model was associated with vitamin E (Vit E) and ebselen (Ebs) treatment to evaluate acetylcholinesterase (AChE) activity in the striatum (ST), hippocampus (HP), cerebral cortex (CC) and erythrocytes. Rats were divided into seven groups: I-Control (saline), II-(canola); III-(Ebs), IV-(Vit E); V-(EB); VI-(EB+Ebs) and VII-(EB+Vit E). At 3 days after the EB injection, AChE activity in the CC and HC was significantly reduced in groups III, IV, V, VI and VII (p<0.05) and in the ST it was reduced in groups III and V (p<0.05) when compared to the control group. At 21 days after the EB injection, AChE activity in the CC was significantly reduced in groups III, IV and V, while in groups VI and VII a significant increase was observed when compared to the control group. In the HC and ST, AChE activity was significantly reduced in groups V, VI and VII when compared to the control group (p<0.05). In the erythrocytes, at 3 days after the EB injection, AChE activity was significantly reduced in groups III, IV, V, VI and VII and at 21 days there was a significant reduction only in groups VI and VII (p<0.05) when compared to the control group. In conclusion, this study demonstrated that Ebs and Vit E interfere with the cholinergic neurotransmission by altering AChE activity in the different brain regions and in the erythrocytes. Furthermore, treatment with Vit E and Ebs protected against the demyelination lesion caused by EB. In this context, we can suggest that ebselen and Vit E should be considered potential therapeutics and scientific tools to be investigated in brain disorders associated with demyelinating events.

Nitric oxide modulates the cardiovascular effects elicited by acetylcholine in the NTS of awake rats.

Microinjection of acetylcholine chloride (ACh) in the nucleus of the solitary tract (NTS) of awake rats caused a transient and dose-dependent hypotension and bradycardia. Because it is known that cardiovascular reflexes are affected by nitric oxide (NO) produced in the NTS, we investigated whether these ACh-induced responses depend on NO in the NTS. Responses to ACh (500 pmol in 100 nl) were strongly reduced by ipsilateral microinjection of the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 10 nmol in 100 nl) in the NTS: mean arterial pressure (MAP) fell by 50 +/- 5 mmHg before L-NAME to 9 +/- 4 mmHg, 10 min after L-NAME, and HR fell by 100 +/- 26 bpm before L-NAME to 20 +/- 10 bpm, 10 min after L-NAME (both P < 0.05). Microinjection of the selective inhibitor of neuronal nitric oxide synthase (nNOS), 1-(2-trifluoromethylphenyl) imidazole (TRIM; 13.3 nmol in 100 nl), in the NTS also reduced responses to ACh: MAP fell from 42 +/- 3 mmHg before TRIM to 27 +/- 6 mmHg, 10 min after TRIM (P < 0.05). TRIM also tended to reduce ACh-induced bradycardia, but this effect was not statistically significant. ACh-induced hypotension and bradycardia returned to control levels 30-45 min after NOS inhibition. Control injections with D-NAME and saline did not affect resting values or the response to ACh. In conclusion, injection of ACh into the NTS of conscious rats induces hypotension and bradycardia, and these effects may be mediated at least partly by NO produced in NTS neurons.

Glial alterations in the hippocampus of rats submitted to ibotenic-induced lesion of the nucleus basalis magnocellularis.

Lesion of the nucleus basalis magnocellularis (nbm) is a suitable approach to study cognitive deficit and behavior alterations involving cholinergic dysfunction, which is associated with the major types of dementia. Cortical astrogliosis also has been described in this model, but it is not clear whether hippocampal astrocytes are activated. In this study, we investigated possible specific astrocyte alterations in the hippocampi of Wistar rats submitted to nbm damage with ibotenic acid, investigating the content and immunohistochemistry of glial fibrillary acidic protein (GFAP), as well as S100B protein content, glutamate uptake and glutamine synthetase activity on the 7th and 28th post-lesion days. Cognitive deficit was confirmed by the step-down inhibitory avoidance task. Interestingly, we found a decrease in GFAP content, S100B content and glutamate uptake activity in the hippocampus on the 28th day after nbm lesion. No alterations were observed in glutamine synthetase activity or in the cerebrospinal fluid S100B content. Although our data suggest caution in the use of nbm lesion with ibotenic acid as a dementia model, it is possible that these alterations could contribute to the cognitive deficit observed in these rats.

Cholinergic afferents to the locus coeruleus and noradrenergic afferents to the medial septum mediate LTP-reinforcement in the dentate gyrus by stimulation of the amygdala.

Transient long-term potentiation (E-LTP) can be transformed into a long-lasting LTP (L-LTP) in the dentate gyrus (DG) by behavioral stimuli with high motivational content. Previous research from our group has identified several brain structures, such as the basolateral amygdala (BLA), the locus coeruleus (LC), the medial septum (MS) and transmitters as noradrenaline (NA) and acetylcholine (ACh) that are involved in these processes. Here we have investigated the functional interplay among brain structures and systems which result in the conversion of a E-LTP into a L-LTP (reinforcement) by stimulation of the BLA (BLA-R). We used topical application of specific drugs into DG, and other targets, while following the time course of LTP induced by stimulation of the perforant pathway (PP) to study their specific contribution to BLA-R. One injection cannula, a recording electrode in the DG and stimulating electrodes in the PP and the BLA were stereotactically implanted one week before electrophysiological experiments. Topical application of atropine or propranolol into the DG blocked BLA-R in both cases, but the effect of propranolol occurred earlier, suggesting a role of NA within the DG during an intermediate stage of LTP maintenance. The injection of lidocaine into the LC abolished BLA-R indicating that the LC is part of the functional neural reinforcing system. The effect on the LC is mediated by cholinergic afferents because application of atropine into the LC produced the same effect. Injection of lidocaine inactivating the MS also abolished BLA-R. This effect was mediated by noradrenergic afferents (probably from the LC) because the application of propranolol into the MS prevented BLA-R. These findings suggest a functional loop for BLA-R involving cholinergic afferents to the LC, a noradrenergic projection from the LC to the DG and the MS, and finally, the cholinergic projection from the MS to the DG.

Cholinergic activity in the insular cortex is necessary for acquisition and consolidation of contextual memory.

Experiences with a high emotional content (aversive) tend to be stored as long-term memories; however, there are also contextual recollections, which form a significant part of our memories. Different research has shown that the insular cortex (IC) plays an important role during aversive memory formation, yet its role during incidental/non-aversive learning like pre-exposure contextual memory formation has received little attention. The objective of this research was to establish the role of cholinergic activity in the IC through its muscarinic receptors during the formation of inhibitory avoidance (IA) memory, as well as during pre-exposure contextual memory, using a paradigm such as latent inhibition (LI). Rats with bilateral cannulae directed into the IC were trained in the LI paradigm of IA or IA task alone. The muscarinic antagonist receptor scopolamine was infused bilaterally into the IC 5 min before the pre-exposure into the dark chamber of the IA cage, one day before the conventional IA training or during the IA training day. During the IA test, the entrance latency into the dark chamber of the IA cage was measured as an index of contextual memory. The results showed that scopolamine infused before and after IA training disrupts inhibitory avoidance memory. Also, it showed that the pre-exposed saline-infused animals (LI) had a lower entrance latency compared to the group not pre-exposed (IA). However, the group that received scopolamine into the IC before, but not after, the pre-exposure to the dark chamber, presented a similar latency to the IA group, showing a blockade of the latent inhibition of the IA. These results suggest that cholinergic activity in the insular cortex is necessary during the acquisition and consolidation of avoidance memory, but appears necessary only during the acquisition of pre-exposure non-aversive contextual memory.

Estrogens and neuroendocrine hypothalamic-pituitary-adrenal axis function.

The function of the HPA axis is subject to regulation by many factors, which achieve relevance under normal and pathological conditions. In the case of aging, this period of life is associated with disturbances of the HPA axis and signs of hippocampal vulnerability. We examined 20-month-old male rats, in which abnormalities of the HPA axis included altered response to stress, reduced effectiveness of the steroid negative feedback and low expression of hippocampal glucocorticoid receptors (GR). Estrogen treatment of aging rats normalized the response to stress, restored the dexamethasone inhibition of the stress response and increased GR density in defined hippocampal areas. Although estrogens could influence the hippocampus of aging animals directly, their effects could be also mediated by estrogen-sensitive forebrain cholinergic neurons projecting to the hippocampus. Additionally, estrogens normalized the deficient granule cell proliferation that aging mice present in the dentate gyrus, and attenuated several markers of hippocampal aging, such as astrocytosis, high lipofucsin content and neuronal loss in the hilus of the dentate gyrus. These effects may be important for the regulation of the HPA axis, in the context that hippocampal function as a whole was normalized by estrogen action. Therefore, estrogens are powerful neuroprotectants in cases of hippocampal dysfunction, and as part of this effect, they contribute to stabilize the function of the HPA axis.

The effect of sevoflurane on intracellular calcium concentration from cholinergic cells.

The mechanism of action of volatile anesthetics is not completely understood. Calcium release from internal stores may alter signaling pathways that influence neurotransmission. Abnormalities of the regulation of intracellular calcium concentration ([Ca2+]i) from patients with malignant hyperthermia is a hallmark of this syndrome indicating the potential of these agents to interact with proteins involved in Ca2+ signaling. In the present study, a cholinergic cell line (SN56) was used to examine whether the release of calcium from intracellular stores occurs in the presence of sevoflurane. Changes in [Ca2+]i were measured using fluo-4, a fluorescent calcium sensitive dye and laser scanning confocal microscopy. Sevoflurane induced an increase on [Ca2+]i from SN56 cells. The sevoflurane-induced increase on [Ca2+]i remained even when the cells were perfused with medium lacking extracellular calcium. However, this effect was abolished by BAPTA-AM, a chelator of intracellular calcium, suggesting the involvement of intracellular Ca2+ stores. Using cyclopiazonic acid, an inhibitor of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase, we investigated whether the depletion of intracellular Ca2+ stores interfered with the effect of sevoflurane. In the presence of this agent, sevoflurane caused a small but not significant rise on [Ca2+]i of the SN56 cells. Dantrolene, an inhibitor of ryanodine-sensitive calcium stores did not modify the sevoflurane increase on [Ca2+]i. Carbachol, a drug that releases Ca2+ from the IP3 pool, abolished the effect of sevoflurane. In addition, xestospongin D, a cell-permeant IP3 receptor antagonist, decreased significantly the sevoflurane increase on [Ca2+]i. Our data suggest that the sevoflurane-induced increase on [Ca2+]i from SN56 cells occurs through the release of calcium from IP3-sensitive calcium stores.

Acetylcholinesterase induces the expression of the beta-amyloid precursor protein in glia and activates glial cells in culture.

Acetylcholinesterase (AChE) activities in CNS physiopathology are increasingly diverse and range from neuritogenesis, through synaptogenesis, to enhancement of amyloid fiber assembly. In Alzheimer's disease, senile plaques and neurodegeneration specially affect regions enriched for cholinergic synapses. In this study we show an effect of AChE that could contribute to the increased deposition of Abeta in certain regions. Affinity-purified AChE induced the expression of amyloid-beta-precursor protein (beta-APP) in glial cells in a concentration-dependent manner up to 5 nM. In glia, AChE also increased inducible nitric oxide synthase (iNOS) assessed by immunocytochemistry and decreased reductive metabolism as evidence of cell activation. AChE could increase the expression of beta-APP in astrocytes and microglia as result of the activation of glial cells. As a whole, we found that AChE has additional effects that could result in an increased synthesis of Abeta, both by increasing beta-APP expression of astrocytes and by further activating glial cells.

Striatal dopaminergic stimulation produces c-Fos expression in the PPT and an increase in wakefulness.

Striatal activation can modify activity in cortical areas related to specific striatal functions possibly through a process of disinhibition within the basal ganglia. Anatomical studies have shown substantial GABAergic innervation from these nuclei to the pedunculopontine tegmental nucleus (PPT). Thus, dopaminergic stimulation of the striatum could produce PPT disinhibition and result in non-specific cortical activation. To test this hypothesis, d-amphetamine was infused both into the striatum of freely moving rats for motor and electrocorticographic recordings, and into the striatum of animals under deep anesthesia for c-Fos immunohistochemistry. The results show that intrastriatal amphetamine increases wakefulness independent of motor activity, and it increases c-Fos expression in the PPT and adjacent areas. They also suggest that the striatum participates in non-specific cortical activation probably as a result of its relationship with the PPT.

Effects of infantile/prepubertal chronic estrogen treatment and chemical sympathectomy with guanethidine on developing cholinergic nerves of the rat uterus.

The innervation of the uterus is remarkable in that it exhibits physiological changes in response to altered levels in the circulating levels of sex hormones. Previous studies by our group showed that chronic administration of estrogen to rats during the infantile/prepubertal period provoked, at 28 days of age, an almost complete loss of norepinephrine-labeled sympathetic nerves, similar to that observed in late pregnancy. It is not known, however, whether early exposure to estrogen affects uterine cholinergic nerves. Similarly, it is not known to what extent development and estrogen-induced responses in the uterine cholinergic innervation are affected by the absence of sympathetic nerves. To address this question, in this study we analyzed the effects of infantile/prepubertal chronic estrogen treatment, chronic chemical sympathectomy with guanethidine, and combined sympathectomy and chronic estrogen treatment on developing cholinergic nerves of the rat uterus. Cholinergic nerves were visualized using a combination of acetylcholinesterase histochemistry and the immunohistochemical demonstration of the vesicular acetylcholine transporter (VAChT). After chronic estrogen treatment, a well-developed plexus of cholinergic nerves was observed in the uterus. Quantitative studies showed that chronic exposure to estrogen induced contrasting responses in uterine cholinergic nerves, increasing the density of large and medium-sized nerve bundles and reducing the intercept density of fine fibers providing myometrial and perivascular innervation. Estrogen-induced changes in the uterine cholinergic innervation did not appear to result from the absence/impairment of sympathetic nerves, because sympathectomy did not mimic the effects produced by estrogen. Estrogen-induced responses in parasympathetic nerves are discussed, considering the direct effects of estrogen on neurons and on changes in neuron-target interactions.

Treatment with 7-nitroindazole enhances kainic acid induced cholinergic neurotoxicity in the rat striatum: a neuroprotective role for neuronal nitric oxide.

1. In this study we investigated the effect of 7-nitroindazole (7-NI), a preferential inhibitor of neuronal nitric oxide synthase (nNOS), on kainic acid (KA) induced neurotoxicity in rats. Choline acetyltransferase activity (CAT), a cholinergic marker, and histological changes were employed to assess neurotoxicity. 2. In control rats, the local intrastriatal injection of 0.5 microg of KA reduced CAT from 22.9 +/- 2.2 to 14.7 +/- 2.0 nmol/h/mg tissue ((38 +/- 6)% reduction) (P < 0.001). Greater reductions in CAT were observed with 1 and 2 microg of KA ((70 +/- 6)% and (80 +/- 3)%, respectively). 7-NI aggravated KA-induced cholinergic and histological damage. KA reduced CAT by (68.2 +/- 4)% in 7-NI-treated rats, by (38 +/- 6)% in saline-treated controls, and by (41 +/- 4)% in peanut-oil- (7-NI-vehicle-) treated rats (P = 0.0047). 3. After KA, CAT activity averaged 14.3 +/- 2.0 in peanut-oil-treated rats and 7.9 +/- 1.0 nmol/h/mg tissue in 7-NI- (peanut-oil-) treated rats (P = 0.015). Similarly to changes in CAT, 7-NI treatment aggravated KA-induced histological changes indicative of neuronal damage (acute ischemic neuronal changes, disorganization of myelinated fibers bundle, and vacuolation changes of the neuropil). Treatment with 7-NI was not associated with increased mortality. 4. Our findings suggest that neuronal NO plays a neuroprotective action on excitotoxicity.

Effects of cholinergic deafferentation upon the expression of the alpha2 subunit of the nicotinic acetylcholine receptors in the chick lateral spiriform nucleus.

Lesion, immunohistochemical, and immunoblotting methods were used to evaluate the effects of cholinergic deafferentation upon the expression of the alpha2 subunit of the nicotinic acetylcholine receptors in the lateral spiriform nucleus (SpL) of the chick brain. The expression of the alpha2 subunit in the SpL showed biphasic changes after lesion of its cholinergic source (nucleus semilunaris), with an increase after 2 days postlesion and a decrease after 3-7 days. Our results could represent a correlate of the phenomena of nicotinic receptor up- and down-regulation, induced by removal of the cholinergic input.

[Genetic expression of nerve growth factor in the central nervous system. Evaluation of an experimental model for Alzheimer's dementia]. / Expresión genética del factor de crecimiento neural en el sistema nervioso central. Evaluación en un modelo experimental de demencia de Alzheimer.

INTRODUCTION AND OBJECTIVE: Several authors have suggested that loss of neuronal trophic support may be an important element in the physiopathology of degenerative conditions of the central nervous system such as Alzheimer's dementia, Parkinson's disease or amyotrophic lateral sclerosis amongst others. In the light of present knowledge, the survival of cholinergic populations of the anterior basal cerebrum, closely involved with cognitive processes of memory and learning, is associated with adequate function of the neural growth factor (NGF). These populations are markedly damaged in Alzheimer's disease, and this has been correlated with the progressive loss of memory and intellectual involvement seen in this disorder. The model used in this study was based on section of the septohippocampal connecting pathways, so that transport of regulatory impulses from the hippocampus to the medial septum was interrupted. This has lethal results for the cholinergic neurons of the latter. We have developed a study designed to characterize the expression of the gene of NGF in different regions of the brain, involved in cholinergic neurotransmission in healthy and in damaged tissue. MATERIAL AND METHODS: We used a molecular hybridization technique with a cDNA catheter complementary to the radio-isotope marked NGF human gene. RESULTS AND CONCLUSIONS: The highest levels of expression were found in the healthy cortex and hippocampus. The reduction in the levels of mRNA of NGF in the damaged hippocampus supports the current thesis which considers synaptic activity to be a major regulator of the synthesis of this molecule in the brain.