Choline Acetyltransferase Activity In Hippocampus Research Articles

Cornuside ameliorates cognitive impairments in scopolamine induced AD mice: Involvement of neurotransmitter and oxidative stress

Ethnopharmacological relevanceCornus officinalis Sieb. et Zucc., traditional Chinese medicine, has been widely used in the treatment of dementia. Cornel iridoid glycosides of Cornus officinalis is therapeutic to Alzheimer's disease (AD), while its pharmacodynamic material basis is not clear. Cornuside, an iridoid glycoside extracted from of Cornus officinalis Sieb. et Zucc, might be a potential anti-AD candidate. Aim of the studyCornuside was evaluated for its effect on scopolamine induced AD mice, and its action mechanisms were explored. Materials and methodsICR mice were administered with 1 mg/kg scopolamine intraperitoneally to induce amnesia. The therapeutic effect of cornuside of cognitive function was evaluated via series of behavioral tests, including Morris water maze test, step-through test and step-down test. In addition, specific enzyme reaction tests were used to detect the content of acetylcholine (ACh) and malondialdehyde (MDA), as well as the activities of acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), choline acetyltransferase (ChAT), superoxide dismutase (SOD), catalase (CAT), monoamine oxidase (MAO) in the brain. The levels of monoamine neurotransmitters were detected by high performance liquid chromatography-electrochemical detection (HPLC-ECD). ResultsCornuside ameliorated the spatial memory impairment in Morris water maze test and cognitive disruption in step-through and step-down test. Furthermore, cornuside improved the level of ACh by reducing the activities of AChE and BuChE, and increasing the activity of ChAT in hippocampus. Cornuside also increased the levels of monoamine neurotransmitters by inhibiting MAO activity in hippocampus and cortex. In addition, cornuside attenuated MDA by enhancing the activities of SOD and CAT in hippocampus and cortex. ConclusionCornuside improved cognitive dysfunction induced by scopolamine in behavioral tests. The mechanisms of cornuside were further investigated from the aspects of neurotransmitters and oxidative stress. Cornuside could inhibit oxidative stress and neurotransmitter hydrolases, increase ACh and monoamine neurotransmitters, which finally contributed to its therapeutic effect on scopolamine induced amnesia.

The neuroprotective effect of betanin in trimethyltin-induced neurodegeneration in mice.

Betanin, a natural food colorant with powerful antioxidative properties, has not been studied in terms of neurodegenerative disease intervention. Therefore, the present study aimed to investigate the neuroprotective effects of betanin against trimethyltin chloride (TMT) -induced neurodegeneration in mice. Forty male ICR mice were randomly divided into four groups: Sham-veh, TMT-veh, TMT-Bet50 and TMT-Bet100. In the TMT groups, neurodegeneration was induced with a one-time intraperitoneal injection of 2.6mg/kg TMT. Betanin-treated groups (Bet) were given oral doses of 50 or 100mg/kg dissolved in normal saline solution. Administrations were started 24h prior to TMT injection and continued for 2weeks. Anxious behavior and spatial cognition were evaluated, respectively. After behavioral tests, brain oxidative status, hippocampal histology and choline acetyltransferase (ChAT) activity were evaluated. Results showed that TMT significant induce anxious behavior and spatial learning and memory deficits (p < 0.05). These were found concurrently with significant decreases in CA1 ChAT activity, brain tissue catalase (CAT) and superoxide dismutase (SOD) activities with significant increase in hippocampal CA1 degeneration (p < 0.05). Betanin 100mg/kg exhibited significant anxiolytic effect, preventive effect on CA1 degeneration and CA1 ChAT activity alteration as well as improvement of spatial learning and memory deficits (p < 0.05). These were found concurrently with significant increases of reduced glutathione, CAT and SOD activities as well as the decrease in malondialdehyde (p < 0.05). We conclude that betanin 100mg/kg exhibits neuroprotective effects against TMT-induced neurodegeneration in mice via its anti-oxidative properties, protective against hippocampal CA1 degeneration and ChAT activity alteration. Therefore, betanin is interesting in further neurodegenerative therapeutic study and applications.

Myrtus communis subsp. communis improved cognitive functions in ovariectomized diabetic rats.

The purpose of this study was to investigate the possible effects of Myrtus communis subsp. communis (MC) on cognitive impairment in ovariectomized diabetic rats. Female Sprague-Dawley rats were divided into 5 groups consisting of 15 rats each; Control (C), Diabetes (D), Ovariectomy and diabetes (OVX+D), Ovariectomy, diabetes and donepezil (OVX+D+Don), Ovariectomy, diabetes and Myrtus communis subsp. communis (OVX+D+MC). Blood glucose measurements were made at the beginning and end of the experiments. The animals underwent the novel object recognition test (NORT) and their performance was evaluated. In hippocampal tissues; amyloid beta (Aβ) and neprilysin levels, acetylcholinesterase (AChE), and choline acetyltransferase (ChAT) activities, polysialylated neural cell adhesion molecule (PSA-NCAM), α7 subunit of neuronal nicotinic acetylcholine receptor (α7-nAChR) and brain derived neurotrophic factor (BDNF) gene expressions were examined. Animals with ovariectomy and diabetes showed increased levels of blood glucose, AChE activity and Aβ levels, and decreased neprilysin levels, ChAT activity, α7-nAChR, PSA-NCAM and BDNF gene expressions in parallel with a decrease in NORT performance score. On the other hand, in the MC-treated OVX+D group, there was a significant decrease observed in blood glucose levels and AChE activities while there was improvement in NORT performances and an increase in hippocampal ChAT activity, neprilysin levels, α7-nAChR, PSA-NCAM and BDNF expressions. These results suggest that MC extract could improve cognitive and neuronal functions with its anticholinesterase and antihyperglycemic properties.

Enhancing effect of Tiliacora triandra leaves extract on spatial learning, memory and learning flexibility as well as hippocampal choline acetyltransferase activity in mice.

The present study investigates the effect of Tiliacora triandra leaf extract on spatial learning, memory, and learning flexibility as well as hippocampal choline acetyltransferase (ChAT) activity in mice. Thirty male ICR mice were randomly divided into three groups including 10% Tween 80, T. triandra 300 mg/kg and T. triandra 600 mg/kg. All administrations were done orally for 18 consecutive days. Spatial learning, memory and learning flexibility were assessed using the Morris water maze. ChAT activity and hippocampal neuronal cell number were assessed by immunohistochemistry and histological methods, respectively. The results demonstrated that T. triandra leaf extract (300 and 600 mg/kg) significantly enhances spatial learning and learning flexibility. Only 300 mg/kg of T. triandra significantly improved the spatial memory. The hippocampal ChAT activity and total hippocampal cell number were significantly increased in T. triandra-treated groups. The present study indicated that T. triandra leaf extract improves the spatial learning, memory and learning flexibility, exerts neuroprotective effects on hippocampal neurons and maintains ChAT activity in this brain area.

The effects of gestational and lactational exposure to Nonylphenol on c-jun, and c-fos expression and learning and memory in hippocampus of male F1 rat.

Objective(s):To investigate the effects of Nonylphenol (NP) in pups from dams exposed during gestational and lactational periods on immediate early genes (c-jun, c-fos) in hippocampus and the learning and memory of F1 rats.Materials and Methods:Twenty eight pregnant dams, stratified by pregnancy date, were randomly assigned into 4 groups, which were gavaged with NP at the doses of 50 mg/kg/day, 100 mg/kg/day, 200 mg/kg/day and groundnut oil, respectively. Step-down avoidance test, and learning and memory effects of NP were evaluated on 8-weeks-old pups. The expressions of c-jun and c-fos and the activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AchE) were evaluated in hippocampus of pups.Results:Compared to the control, reaction time (RT) that pups spent to jump to the platform was longer (P=0.02), the number of errors were higher (P=0.01), and the step-down latency was shorter in the 200 mg/kg/day NP-treated group (P=0.04). Exposure to NP induced a significant reduction in ChAT activity in hippocampus in the 100 (P=0.005) and 200 mg/kg/day NP-treated groups (P=0.002), whereas exposure to 200 mg/kg/day caused a significant increase in AchE activity (P=0.004); a dose–response relationship was revealed between ChAT and AchE activities and NP exposure in the hippocampus of pups (r=-0.821, P=0.01; r=0.757, P=0.04). Exposure to NP in the 100 and 200 mg/kg/day NP-treated groups exhibited an increase in number of c-fos and c-jun positive cells.Conclusion:Exposure to NP might negatively affect learning and memory ability in F1 rats, possibly due to the alterations in the expression of c-jun and c-fos, and ChAT, AchE activities in hippocampus of pups.

In vivo knockdown of basal forebrain p75 neurotrophin receptor stimulates choline acetyltransferase activity in the mature hippocampus.

This study seeks to determine whether knockdown of basal forebrain p75 neurotrophin receptor (p75(NTR) ) expression elicits increased hippocampal choline acetyltransferase (ChAT) activity in mature animals. Antisense (AS) oligonucleotides (oligos) targeting p75(NTR) were infused into the medial septal area of mature rats continuously for 4 weeks. In all rats, the cannula outlet was placed equidistant between the left and the right sides of the vertical diagonal band of Broca. We tested phosphorothioate (PS), morpholino (Mo), and gapmer (mixed PS/RNA) oligos. Gapmer AS infusions of 7.5 and 22 μg/day decreased septal p75(NTR) mRNA by 34% and 48%, respectively. The same infusions increased hippocampal ChAT activity by 41% and 55%. Increased hippocampal ChAT activity correlated strongly with septal p75(NTR) downregulation in individual rats. Infusions of PS and Mo AS oligos did not downregulate p75(NTR) mRNA or stimulate ChAT activity. These results demonstrate that p75(NTR) can dynamically regulate hippocampal ChAT activity in the mature CNS. They also reveal the different efficacies of three diverse AS oligo chemistries when infused intracerebrally. Among the three types, gapmer oligos worked best.

Effects of Maternal Choline Supplementation on the Septohippocampal Cholinergic System in the Ts65Dn Mouse Model of Down Syndrome.

Down syndrome (DS), caused by trisomy of chromosome 21, is marked by intellectual disability (ID) and early onset of Alzheimer's disease (AD) neuropathology including hippocampal cholinergic projection system degeneration. Here we determined the effects of age and maternal choline supplementation (MCS) on hippocampal cholinergic deficits in Ts65Dn mice compared to 2N mice sacrificed at 6-8 and 14-18 months of age. Ts65Dn mice and disomic (2N) littermates sacrificed at ages 6-8 and 14-18 mos were used for an aging study and Ts65Dn and 2N mice derived from Ts65Dn dams were maintained on either a choline-supplemented or a choline-controlled diet (conception to weaning) and examined at 14-18 mos for MCS studies. In the latter, mice were behaviorally tested on the radial arm Morris water maze (RAWM) and hippocampal tissue was examined for intensity of choline acetyltransferase (ChAT) immunoreactivity. Hippocampal ChAT activity was evaluated in a separate cohort. ChAT-positive fiber innervation was significantly higher in the hippocampus and dentate gyrus in Ts65Dn mice compared with 2N mice, independent of age or maternal diet. Similarly, hippocampal ChAT activity was significantly elevated in Ts65Dn mice compared to 2N mice, independent of maternal diet. A significant increase with age was seen in hippocampal cholinergic innervation of 2N mice, but not Ts65Dn mice. Degree of ChAT intensity correlated negatively with spatial memory ability in unsupplemented 2N and Ts65Dn mice, but positively in MCS 2N mice. The increased innervation produced by MCS appears to improve hippocampal function, making this a therapy that may be exploited for future translational approaches in human DS.

Hippocampal P3-like auditory event-related potentials are disrupted in a rat model of cholinergic degeneration in Alzheimer's disease: reversal by donepezil treatment.

P300 (P3) event-related potentials (ERPs) have been suggested to be an endogenous marker of cognitive function and auditory oddball paradigms are frequently used to evaluate P3 ERPs in clinical settings. Deficits in P3 amplitude and latency reflect some of the neurological dysfunctions related to several psychiatric and neurological diseases, e.g., Alzheimer's disease (AD). However, only a very limited number of rodent studies have addressed the back-translational validity of the P3-like ERPs as suitable markers of cognition. Thus, the potential of rodent P3-like ERPs to predict pro-cognitive effects in humans remains to be fully validated. The current study characterizes P3-like ERPs in the 192-IgG-SAP (SAP) rat model of the cholinergic degeneration associated with AD. Following training in a combined auditory oddball and lever-press setup, rats were subjected to bilateral intracerebroventricular infusion of 1.25 μg SAP or PBS (sham lesion) and recording electrodes were implanted in hippocampal CA1. Relative to sham-lesioned rats, SAP-lesioned rats had significantly reduced amplitude of P3-like ERPs. P3 amplitude was significantly increased in SAP-treated rats following pre-treatment with 1 mg/kg donepezil. Infusion of SAP reduced the hippocampal choline acetyltransferase activity by 75%. Behaviorally defined cognitive performance was comparable between treatment groups. The present study suggests that AD-like deficits in P3-like ERPs may be mimicked by the basal forebrain cholinergic degeneration induced by SAP. SAP-lesioned rats may constitute a suitable model to test the efficacy of pro-cognitive substances in an applied experimental setup.

Rac1b Increases with Progressive Tau Pathology within Cholinergic Nucleus Basalis Neurons in Alzheimer's Disease

Cholinergic basal forebrain (CBF) nucleus basalis (NB) neurons display neurofibrillary tangles (NFTs) during Alzheimer's disease (AD) progression, yet the mechanisms underlying this selective vulnerability are currently unclear. Rac1, a member of the Rho family of GTPases, may interact with the proapoptotic pan-neurotrophin receptor p75(NTR) to induce neuronal cytoskeletal abnormalities in AD NB neurons. Herein, we examined the expression of Rac1b, a constitutively active splice variant of Rac1, in NB cholinergic neurons during AD progression. CBF tissues harvested from people who died with a clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment, or AD were immunolabeled for both p75(NTR) and Rac1b. Rac1b appeared as cytoplasmic diffuse granules, loosely aggregated filaments, or compact spheres in p75(NTR)-positive NB neurons. Although Rac1b colocalized with tau cytoskeletal markers, the percentage of p75(NTR)-immunoreactive neurons expressing Rac1b was significantly increased only in AD compared with both mild cognitive impairment and NCI. Furthermore, single-cell gene expression profiling with custom-designed microarrays showed down-regulation of caveolin 2, GNB4, and lipase A in AD Rac1b-positive/p75(NTR)-labeled NB neurons compared with Rac1b-negative/p75(NTR)-positive perikarya in NCI. These proteins are involved in Rac1 pathway/cell cycle progression and lipid metabolism. These data suggest that Rac1b expression acts as a modulator or transducer of various signaling pathways that lead to NFT formation and membrane dysfunction in a subgroup of CBF NB neurons in AD.

Involvement of hippocampal phosphatidylethanolamine‐binding protein in morphine dependence and withdrawal

Drug addiction is thought to result from an intractable and aberrant learning and memory in response to drug-related stimulation, and cholinergic neurotransmission plays an important role in this process. Phosphatidylethanolamine-binding protein (PEBP) is the precursor of the hippocampal cholinergic neurostimulating peptide (HCNP), an 11 amino acid peptide that enhances the production of choline acetyltransferase (ChAT) and assists in the development of cholinergic projections from the medial septal nuclei to the hippocampus. However, whether PEBP is involved in drug addiction remains unclear. In the present study, PEBP expression in the hippocampus, as detected by proteomics analysis, was found to be dramatically up-regulated after rats received chronic morphine treatment. Western blotting analysis revealed a specific up-regulation of PEBP expression in the hippocampus but not in any other brain regions assessed. A down-regulation of hippocampal PEBP levels induced by antisense oligodeoxynucleotides resulted in aggravated morphine dependence. Together, these findings indicate that PEBP is involved in morphine dependence. Moreover, the time course of PEBP expression changes and ChAT activity was investigated during chronic morphine treatment and withdrawal. The results showed that the hippocampal PEBP levels were up-regulated during chronic morphine treatment and returned to the baseline 3 days after withdrawal, after which PEBP levels were persistently up-regulated for 28 days after withdrawal. The changes in hippocampal ChAT activity followed a pattern that was similar to that of the PEBP levels. Taken together, these results suggest that hippocampal PEBP is involved in morphine dependence and withdrawal, perhaps through modulating cholinergic transmission in the hippocampus.

The p75 neurotrophin receptor has nonapoptotic antineurotrophic actions in the basal forebrain

Because of controversy about the role of the p75 neurotrophin receptor (p75(NTR) ) in the cholinergic basal forebrain (CBF), we investigated this region in p75(NTR) third exon knockout mice that were congenic with 129/Sv controls. They express a shortened intracellular form of p75(NTR) , permitting detection of p75(NTR) -expressing cells. We performed separate counts of choline acetyltransferase (ChAT)-expressing and p75(NTR) -expressing neurons. In agreement with past reports, the number of ChAT-immunoreactive neurons in knockout mice was greater than in wild-type mice, and this was evident in each of the main anatomical divisions of the CBF. In contrast, the number of p75(NTR) -immunoreactive neurons did not differ between genotypes. The biggest increase in ChAT neurons (27%) was in the horizontal limb of the diagonal band of Broca (HDB), in which region the number of p75(NTR) -positive neurons was unchanged. Double staining revealed that some neurons in wild-type mice expressed p75(NTR) but not ChAT. In the knockout mice, all p75(NTR) -expressing neurons expressed ChAT. The increase in cholinergic neurons, therefore, was at least partially attributable to a higher proportion of ChAT immunoreactivity within the population of p75(NTR) -expressing neurons. Cholinergic neurons were also larger in knockout mice than in controls. In the hippocampal CA1 region, knockout mice had a greater number of cholinergic fibers. There was a 77% increase in hippocampal ChAT activity in knockout mice and a 38% increase in heterozygotes. The data do not support an apoptotic role but indicate a broad antineurotrophic role of p75(NTR) in the cholinergic basal forebrain.

Galanthamine plus estradiol treatment enhances cognitive performance in aged ovariectomized rats

We hypothesize that beneficial effects of estradiol on cognitive performance diminish with age and time following menopause due to a progressive decline in basal forebrain cholinergic function. This study tested whether galanthamine, a cholinesterase inhibitor used to treat memory impairment associated with Alzheimer's disease, could enhance or restore estradiol effects on cognitive performance in aged rats that had been ovariectomized in middle-age. Rats were ovariectomized at 16–17months of age. At 21–22months of age rats began receiving daily injections of galanthamine (5mg/day) or vehicle. After one week, half of each group also received 17ß-estradiol administered subcutaneously. Rats were then trained on a delayed matching to position (DMP) T-maze task, followed by an operant stimulus discrimination/reversal learning task. Treatment with galanthamine+estradiol significantly enhanced the rate of DMP acquisition and improved short-term delay-dependent spatial memory performance. Treatment with galanthamine or estradiol alone was without significant effect. Effects were task-specific in that galanthamine+estradiol treatment did not significantly improve performance on the stimulus discrimination/reversal learning task. In fact, estradiol was associated with a significant increase in incorrect responses on this task after reversal of the stimulus contingency. In addition, treatments did not significantly affect hippocampal choline acetyltransferase activity or acetylcholine release. This may be an effect of age, or possibly is related to compensatory changes associated with long-term cholinesterase inhibitor treatment. The data suggest that treating with a cholinesterase inhibitor can enhance the effects of estradiol on acquisition of a DMP task by old rats following a long period of hormone deprivation. This could be of particular benefit to older women who have not used hormone therapy for many years and are beginning to show signs of mild cognitive impairment. Potential mechanisms for these effects are discussed.

Protective effect of stilbenes containing extract-fraction from Cajanus cajan L. on Aβ 25–35-induced cognitive deficits in mice

Cajanus cajan (L.) is a traditional Chinese herb medicine which contains a lot of potential active components. In the present study, we identified the effects of the stilbenes containing extract-fraction from C. cajan L. (sECC) on Aβ 25–35-induced cognitive deficits, oxidative stress and cholinergic dysfunction in mice. Mice were treated with sECC (100 and 200 mg/kg/d) for 1-week, and then received a single intracerebroventricular (i.c.v.) injection of Aβ 25–35 (5 μg/mice). Behavioral changes and neuron apoptosis in mice were evaluated using Morris water maze and TUNEL tests. Furthermore, superoxide dismutase (SOD), choline acetyl transferase (ChAT) and acetylcholine esterase (AchE) activity in hippocampus and cortex were analyzed by spectrophotometric method. The data showed that consumption of sECC (200 mg/kg) significantly ameliorated the cognitive deficits and neuron apoptosis caused by i.c.v. injection of Aβ 25–35. At the same time, the decreased SOD and ChAT activity in hippocampus and cortex were markedly increased by sECC (200 mg/kg). sECC has no effect on AchE activity in hippocampus and cortex. These findings suggest that sECC may be a potential candidate for the development of therapeutic agents to manage cognitive impairment associated with Alzheimer's disease (AD) through increasing the activity of ChAT and anti-oxidative mechanism.

Lipoic Acid Increases Hippocampal Choline Acetyltransferase and Acetylcholinesterase Activities and Improvement Memory in Epileptic Rats

In the present study we investigated the effect of seizures on rat performance in the Morris water maze task, as well as on choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities in rat hippocampus. Wistar rats were treated with 0.9% saline (i.p., control group), lipoic acid (20 mg/kg, i.p., LA group), pilocarpine (400 mg/kg, i.p., pilocarpine group), and the association of LA (20 mg/kg, i.p.) plus pilocarpine (400 mg/kg, i.p.), 30 min before of administration of LA (LA plus pilocarpine group). After the treatments all groups were observed for 1 h. The effect of lipoic acid administration was observed on reference and working spatial memory of seized rats. The ChAT and AChE activities were measured using spectrophotometric methods and the results compared to values obtained from saline and pilocarpine-treated animals. Its activity was also determined after behavioral task. Results showed that pretreatment with lipoic acid did not alter reference memory when compared to saline-treated animals. In the working memory task, we observed a significant day's effect with significant differences between control and pilocarpine-induced seizures and pretreated animals with lipoic acid. In LA plus pilocarpine group was observed a significantly increased in ChAT and AChE activities, when compared to pilocarpine group. Results showed that acute administration of lipoic acid alone did not alter hippocampal ChAT and AChE activities. Our findings suggest that seizures caused cognitive dysfunction and a decrease of ChAT and AChE activities that might be related, at least in part, to the neurological problems presented by epileptic patients. Lipoic acid can reverse cognitive dysfunction observed in seized rats as well as increase the ChAT and AChE activities in hippocampus of rats prior to pilocarpine-induced seizures, suggesting that this antioxidant could be used in clinic treatment of epilepsy.

Enhanced spatial memory and hippocampal long‐term potentiation in p75 neurotrophin receptor knockout mice

Previous reports have described increases in the size and number of cholinergic neurons in the basal forebrain in p75 neurotrophin receptor (p75(NTR)) knockout mice. In an earlier study, we also found improved spatial memory in these mice, raising the possibility that p75(NTR) regulates hippocampal function by its effects on the cholinergic basal forebrain. We therefore investigated hippocampal long-term potentiation in p75(NTR) knockout mice that shared the same genetic background as control 129/Sv mice. We also investigated heterozygous mice, carrying just one functional p75(NTR) allele. The p75(NTR) knockout mice had enhanced long-term potentiation in the Schafer collateral fiber synapses of the hippocampus. Heterozygous mice had an intermediate level, greater than controls but less than knockout mice. Hippocampal choline acetyltransferase activity was also markedly elevated in p75(NTR) knockout mice, with a smaller increase in heterozygous mice. In the Barnes maze, p75(NTR) knockout mice displayed markedly superior learning to controls, and this was evident over the three age brackets tested. At each age, the performance of heterozygous mice was intermediate to the other groups. In the open field test, p75(NTR) knockout mice exhibited greater stress-related behavioral responses, including freezing, than did control animals. There were no differences between the three groups in a test of olfactory function. The dose-dependent effects of p75(NTR) gene copy number on hippocampal plasticity and spatial memory indicate that p75(NTR) has profound effects on hippocampal function. Bearing in mind that p75(NTR) is very sparsely expressed in the adult hippocampus and has a potent effect on hippocampal choline acetyltransferase activity, the effects of p75(NTR) on hippocampal function are likely to be mediated indirectly, by its actions on basal forebrain cholinergic neurons.

The effect of central cholinergic and noradrenergic denervation on hippocampal sympathetic ingrowth and apoptosis-like reactivity in the rat

In this study, the effect of intraseptal injection of specific cholinotoxin 192-IgG saporin (SAP) ± intraperitoneal injection of N-[chloroethyl]- N-ethyl-2-bromobenzylamine (DSP-4) (noradrenergic fiber neurotoxin) was examined in rat hippocampus. Medial septal lesions resulted not only in selective cholinergic denervation of hippocampus (Medial septal lesion + ganglionectomy; SAP + Gx) but also in hippocampal sympathetic ingrowth (IG) of adrenergic fibers (Medial septal lesion + sham ganglionectomy; SAP + IG). Saporin-induced septal lesions produced a significant reduction in hippocampal choline acetyltransferase activity in all tested groups (SAP + IG ± DSP-4 and SAP + Gx ± DSP-4), and an increase in noradrenaline concentration in the SAP + IG group. Visualization of noradrenergic fibers by histofluorescence revealed a mixture of fine and thick varicosities in the SAP + IG but only fine fibers in control and SAP + Gx animals. SAP + IG + DSP-4 lesions produced significant reduction in noradrenaline concentration in all groups with a concomitant decrease in visualization of central noradrenergic fibers in dorsal and ventral hippocampus. Treatment of SAP + IG animals with DSP-4 left mostly thick fibers, probably derived from peripheral sympathetic ingrowth. No fluorescence was seen in either the control + DSP-4 or SAP + Gx + DSP-4 animals. Apoptotic-like changes, using in situ oligonucleotide ligation techniques, were also assessed. Proapoptotic changes were seen in the SAP + Gx ± DSP-4 group as compared to CON ± DSP-4 groups. SAP + IG regardless of DSP-4 treatment protected hippocampal cells from apoptotic cell death when compared to positive control and SAP + Gx ± DSP-4 groups. In summary, elevated noradrenaline concentration following specific cholinergic denervation probably reflects compensatory hippocampal ingrowth originating from the peripheral sympathetic system which may be responsible for neuroprotective effects, i.e., antiapoptosis-like effect. Since cholinergic and noradrenergic systems are known to be involved in Alzheimer's disease and related cognitive function, knowing how these neurotransmitters work after specific lesions may be of importance as an animal model of Alzheimer's disease and as a potential target for Alzheimer's disease drug therapies.

Influence of a combination of two tetrachlorobiphenyl congeners (PCB 47; PCB 77) on thyroid status, choline acetyltransferase (ChAT) activity, and short- and long-term memory in 30-day-old Sprague-Dawley rats.

The important role of thyroid hormones in growth and development, maintenance of body temperature, digestion, cardiac function, and normal brain development can be disrupted by environmental contaminants like polychlorinated biphenyls (PCB). Polychlorinated biphenyls are environmental contaminants that are widespread, persistent, lipophilic, and bioaccumulate through food webs, concentrating in adipose tissue. Placental and lactational PCB exposure of offspring causes metabolic and endocrine disruptions including hypothyroxinemia, spatial learning and memory deficits, neurochemical and neurobehavioral alterations, and reproductive problems. Previous studies in our lab using the individual congeners PCB 47 (2,2',4,4'-tetrachlorobiphenyl, ortho-substituted) and PCB 77 (3,3',4,4'-tetrachlorobiphenyl, non-ortho-substituted) have demonstrated alterations in thyroid hormone levels, alterations in brain choline acetyltransferase (ChAT) activity, and spatial learning deficits. In the present study, pregnant Sprague-Dawley rats were fed a diet with or without a mixture of PCB 47/77 at 1.25 ppm, 12.5 ppm or 25.0 ppm (w/w). Rat pups were swum in the Morris water maze four times a day on days 21-29 in order for the animals to learn the position of a submerged fixed platform. A probe test was run on day 24 (30 min after last swim) for short-term memory, and on day 29 (24 h after the last swim) for long-term memory after removal of the platform. Time spent in the quadrant previously containing the platform was recorded. Rats were decapitated on day 30, serum collected and frozen at -20 degrees. ChAT activity was measured radiometrically in basal forebrain and hippocampus. All PCB-treated animals experienced a depression in both triiodothyronine (T3) and thyroxine (T4). The present study found that all doses of PCB depressed ChAT activity in hippocampus with no significant alteration in the basal forebrain. In PCB-treated animals, short-term memory showed a trend toward improvement and long-term memory toward depression, but these trends were not significant. The consequences likely stem from endocrine disruption, especially with regard to the thyroid.

Cognitive and neurological deficits induced by early and prolonged basal forebrain cholinergic hypofunction in rats

In the present study we examined the long-term effects of neonatal lesion of basal forebrain cholinergic neurons induced by intracerebroventricular injections of the immunotoxin 192 IgG saporin. Animals were then characterised behaviourally, electrophysiologically and molecularly. Cognitive effects were evaluated in the social transmission of food preferences, a non-spatial associative memory task. Electrophysiological effects were assessed by recording of cortical electroencephalographic (EEG) patterns. In addition, we measured the levels of proteins whose abnormal expression has been associated with neurodegeneration such as amyloid precursor protein (APP), presenilin 1 and 2 (PS-1, PS-2), and cyclooxygenases (COX-1 and COX-2). In animals lesioned on postnatal day 7 and tested 6 months thereafter, memory impairment in the social transmission of food preferences was evident, as well as a significant reduction of choline acetyltransferase activity in hippocampus and neocortex. Furthermore, similar to what observed in Alzheimer-like dementia, EEG cortical patterns in lesioned rats presented changes in α, β and δ activities. Levels of APP protein and mRNA were not affected by the treatment. Levels of hippocampal COX-2 protein and mRNA were significantly decreased whereas COX-1 remained unaltered. PS-1 and PS-2 transcripts were reduced in hippocampus and neocortex. These findings indicate that neonatal and permanent basal forebrain cholinergic hypofunction is sufficient to induce behavioural and neuropathological abnormalities. This animal model could represent a valid tool to evaluate the role played by abnormal cholinergic maturation in later vulnerability to neuropathological processes associated with cognitive decline and, possibly, to Alzheimer-like dementia.

Cognitive function in young and adult IL (interleukin)-6 deficient mice

Interleukin-6 (IL-6) is a cytokine shown to affect brain function and to be involved in pathological neurodegenerative disorders such as Alzheimer’s disease (AD). In the present study we investigated the cognitive function in transgenic mice not expressing IL-6 (IL-6 KO) and in wild type (WT) genotype at 4 and 12 months of age, using a passive avoidance and an eight-arm radial maze tasks. Motor function was quantified using an Animex apparatus. Hippocampal choline acetyltransferase (ChAT) activity was evaluated in both genotypes. No difference was observed in both genotypes for spontaneous motor activity. The mean latency (s) to re-enter the shock box, was similar in both young mutant and WT mice. However, a decreased sensitivity (50%) to scopolamine (1 mg/kg) in mutant compared to WT mice, was obtained. IL-6 KO mice exhibited a facilitation of radial maze learning over 30 days, in terms of a lower number of working memory errors and a higher percentage of animals reaching the criterion as compared with WT genotype tested at both ages. Furthermore, mutant mice, at the age of 12 months, showed a faster acquisition (22 days versus 30 days to reach the criterion). The pattern of arm entry exhibited by IL-6 KO mice showed a robust tendency to enter an adjacent arm at both ages, while WT only at the age of 4 months. ChAT activity was inversely correlated with memory performance. These findings suggest a possible involvement of IL-6 on memory processes, even if the mechanism remains still unclear.

Cholinergic plasticity in hippocampus of individuals with mild cognitive impairment: correlation with Alzheimer's neuropathology.

Several recent studies indicate that activity of cholinergic enzymes in the cortex of people with mild cognitive impairment (MCI) and early Alzheimer's disease (AD) are preserved. We correlated levels of hippocampal choline acetyltransferase (ChAT) activity with the extent of AD lesions in subjects from the Religious Order Study, including cases with no cognitive impairment (NCI), MCI, and with mild to moderate AD. Hippocampal ChAT activity levels were also determined in a group of end-stage AD patients who were enrolled in the University of Pittsburgh Alzheimer's Disease Research Center. MCI subjects were characterized with increased hippocampal ChAT activity. This elevation was no longer present in mild AD cases, which were not different from NCI subjects. Severe AD cases showed markedly depleted hippocampal ChAT levels. In NCI, MCI, and mild-moderate AD, there was a positive correlation between hippocampal ChAT activity levels and progression of neuritic plaque pathology in entorhinal cortex and hippocampus. A significant elevation of hippocampal ChAT in the MCI group was found selectively in the limbic (i.e., entorhinal-hippocampal, III/IV) Braak stages. We hypothesize that cholinergic changes in the hippocampus of MCI subjects reflect a compensatory response to the progressive denervation of the hippocampus by lost entorhinal cortex input. Moreover, the present findings suggest that the short-term memory loss observed in MCI is not caused by cholinergic deficits; it more likely relates to disrupted entorhinal-hippocampal connectivity.