Basal Forebrain Cholinergic System and Memory

Functional neuroanatomy of basal forebrain projections to the basolateral amygdala: Transmitters, receptors, and neuronal subpopulations

The projections of the basal forebrain (BF) to the hippocampus and neocortex have been extensively studied and shown to be important for higher cognitive functions, including attention, learning, and memory. Much less is known about the BF projections to the basolateral nuclear complex of the amygdala (BNC), although the cholinergic innervation of this region by the BF is actually far more robust than that of cortical areas. This review will focus on light and electron microscopic tract-tracing and immunohistochemical (IHC) studies, many of which were published in the last decade, that have analyzed the relationship of BF inputs and their receptors to specific neuronal subtypes in the BNC in order to better understand the anatomical substrates of BF-BNC circuitry. The results indicate that BF inputs to the BNC mainly target the basolateral nucleus of the BNC (BL) and arise from cholinergic, GABAergic, and perhaps glutamatergic BF neurons. Cholinergic inputs mainly target dendrites and spines of pyramidal neurons (PNs) that express muscarinic receptors (MRs). MRs are also expressed by cholinergic axons, as well as cortical and thalamic axons that synapse with PN dendrites and spines. BF GABAergic axons to the BL also express MRs and mainly target BL interneurons that contain parvalbumin. It is suggested that BF-BL circuitry could be very important for generating rhythmic oscillations known to be critical for emotional learning. BF cholinergic inputs to the BNC might also contribute to memory formation by activating M1 receptors located on PN dendritic shafts and spines that also express NMDA receptors.

An excitatory projection from the basal forebrain to the ventral tegmental area that underlies anorexia-like phenotypes

Maladaptation in balancing internal energy needs and external threat cues may result in eating disorders. However, brain mechanisms underlying such maladaptations remain elusive. Here, we identified that the basal forebrain (BF) sends glutamatergic projections to glutamatergic neurons in the ventral tegmental area (VTA) in mice. Glutamatergic neurons in both regions displayed correlated responses to various stressors. Notably, in vivo manipulation of BF terminals in the VTA revealed that the glutamatergic BF → VTA circuit reduces appetite, increases locomotion, and elicits avoidance. Consistently, activation of VTA glutamatergic neurons reduced body weight, blunted food motivation, and caused hyperactivity with behavioral signs of anxiety, all hallmarks of typical anorexia symptoms. Importantly, activation of BF glutamatergic terminals in the VTA reduced dopamine release in the nucleus accumbens. Collectively, our results point to overactivation of the glutamatergic BF → VTA circuit as a potential cause of anorexia-like phenotypes involving reduced dopamine release.

Enriched environment ameliorates fear memory impairments induced by sleep deprivation via inhibiting PIEZO1/calpain/autophagy signaling pathway in the basal forebrain

AIMS

To verify the hypothesis that an enriched environment (EE) alleviates sleep deprivation-induced fear memory impairment by modulating the basal forebrain (BF) PIEZO1/calpain/autophagy pathway.

METHODS

Eight-week-old male mice were housed in a closed, isolated environment (CE) or an EE, before 6-h total sleep deprivation. Changes in fear memory after sleep deprivation were observed using an inhibitory avoidance test. Alterations in BF PIEZO1/calpain/autophagy signaling were detected. The PIEZO1 agonist Yoda1 or inhibitor GsMTx4, the calpain inhibitor PD151746, and the autophagy inducer rapamycin or inhibitor 3-MA were injected into the bilateral BF to investigate the pathways involved in the memory-maintaining role of EE in sleep-deprived mice.

RESULTS

Mice housed in EE performed better than CE mice in short- and long-term fear memory tests after sleep deprivation. Sleep deprivation resulted in increased PIEZO1 expression, full-length tropomyosin receptor kinase B (TrkB-FL) degradation, and autophagy, as reflected by increased LC3 II/I ratio, enhanced p62 degradation, increased TFEB expression and nuclear translocation, and decreased TFEB phosphorylation. These molecular changes were partially reversed by EE treatment. Microinjection of Yoda1 or rapamycin into the bilateral basal forebrain induced excessive autophagy and eliminated the cognition-protective effects of EE. Bilateral basal forebrain microinjection of GsMTx4, PD151746, or 3-MA mimicked the cognitive protective and autophagy inhibitory effects of EE in sleep-deprived mice.

CONCLUSIONS

EE combats sleep deprivation-induced fear memory impairments by inhibiting the BF PIEZO1/calpain/autophagy pathway.

HMGB1 neuroimmune signaling and REST-G9a gene repression contribute to ethanol-induced reversible suppression of the cholinergic neuron phenotype

Adolescent binge drinking increases Toll-like receptor 4 (TLR4), receptor for advanced glycation end products (RAGE), the endogenous TLR4/RAGE agonist high-mobility group box 1 (HMGB1), and proinflammatory neuroimmune signaling in the adult basal forebrain in association with persistent reductions of basal forebrain cholinergic neurons (BFCNs). In vivo preclinical adolescent intermittent ethanol (AIE) studies find anti-inflammatory interventions post-AIE reverse HMGB1-TLR4/RAGE neuroimmune signaling and loss of BFCNs in adulthood, suggesting proinflammatory signaling causes epigenetic repression of the cholinergic neuron phenotype. Reversible loss of BFCN phenotype in vivo is linked to increased repressive histone 3 lysine 9 dimethylation (H3K9me2) occupancy at cholinergic gene promoters, and HMGB1-TLR4/RAGE proinflammatory signaling is linked to epigenetic repression of the cholinergic phenotype. Using an ex vivo basal forebrain slice culture (FSC) model, we report EtOH recapitulates the in vivo AIE-induced loss of ChAT+IR BFCNs, somal shrinkage of the remaining ChAT+ neurons, and reduction of BFCN phenotype genes. Targeted inhibition of EtOH-induced proinflammatory HMGB1 blocked ChAT+IR loss while disulfide HMBG1-TLR4 and fully reduced HMGB1-RAGE signaling decreased ChAT+IR BFCNs. EtOH increased expression of the transcriptional repressor RE1-silencing transcription factor (REST) and the H3K9 methyltransferase G9a that was accompanied by increased repressive H3K9me2 and REST occupancy at promoter regions of the BFCN phenotype genes Chat and Trka as well as the lineage transcription factor Lhx8. REST expression was similarly increased in the post-mortem human basal forebrain of individuals with alcohol use disorder, which is negatively correlated with ChAT expression. Administration of REST siRNA and the G9a inhibitor UNC0642 blocked and reversed the EtOH-induced loss of ChAT+IR BFCNs, directly linking REST-G9a transcriptional repression to suppression of the cholinergic neuron phenotype. These data suggest that EtOH induces a novel neuroplastic process involving neuroimmune signaling and transcriptional epigenetic gene repression resulting in the reversible suppression of the cholinergic neuron phenotype.

Distinct Sleep Alterations in Alcohol Use Disorder Patients with and without Korsakoff's Syndrome: Relationship with Episodic Memory

Alcohol Use Disorder (AUD) results in sleep disturbances that may have deleterious impacts on cognition, especially on memory. However, little is known about the sleep architecture in patients with Korsakoff's syndrome (KS). This study aims at characterizing sleep disturbances in KS compared to AUD without KS and at specifying the relationships with cognitive impairments. Twenty-nine AUD patients (22 without KS and 7 with KS) and 15 healthy controls underwent a neuropsychological assessment and a polysomnography. The severity of sleep-disordered breathing and sleep fragmentation was similar in AUD and KS patients compared to controls. Sleep architecture differed between both patient groups: the proportion of slow-wave sleep was reduced in AUD patients only, while a lower proportion of rapid-eye movement (REM) sleep was specifically observed in KS patients. The proportion of REM sleep correlated with the severity of episodic memory deficits when AUD and KS were examined together. These data provide evidence for both similarities and specificities regarding sleep alterations in AUD patients with and without KS. They also indicate that altered sleep architecture may contribute to the pathophysiology of alcohol-related memory disorders.

Morus alba fruit diet ameliorates cognitive deficit in mouse model of streptozotocin-induced memory impairment

Mounting evidence shows that dietary intake of fruits with polyphenols is beneficial to improve impaired memory functions. This study explored the preventive as well as therapeutic effects of diet enriched with Morus alba fruits extract (DEMA) in streptozotocin (STZ) induced mouse model of memory impairment. The study consisted of two facets: one aspect consisted of pretreatment of animals with DEMA for two weeks followed by STZ (i.c.v) intervention and the second phase involved induction of dementia with STZ (i.c.v) followed by treatment with DEMA for 14 days. Cognitive functions of animals were measured by Morris Water Maze test and to delineate the associated mechanism of action, brain biochemical estimations (acetyl-cholinesterase activity, myeloperoxidase activity, thiobarbituric acid reactive species, superoxide dismutase activity, reduced glutathione and nitrite/nitrate) and histopathological studies (haematoxylin and eosin staining) were performed. Pre- and post- treatment with DEMA significantly prevented and attenuated, respectively, the detrimental effects of STZ on mice brain. The results demonstrated that dietary modification, by incorporation of M. alba fruits, reduces the incidence and aids in treatment of memory disorder in mice by reducing central cholinergic activity, decreasing oxidative stress and preventing neurodegeneration.

Cholinergic neurons in the basal forebrain are involved in behavioral abnormalities associated with Cul3 deficiency: Role of prefrontal cortex projections in cognitive deficits

Loss-of-function mutations of the gene Cul3 have been identified as a risk factor for autism-spectrum disorder (ASD), but the pathogenic mechanisms are not well understood. Conditional Cul3 ablation in cholinergic neurons of mice (ChatCRECul3F/+) recapitulated ASD-like social and sensory gating phenotypes and caused significant cognitive impairments, with diminished activity of cholinergic neurons in the basal forebrain (BF). Chemogenetic inhibition of BF cholinergic neurons in healthy mice induced similar social and cognitive deficits. Conversely, chemogenetic stimulation of BF cholinergic neurons in ChatCRECul3F/+ mice reversed abnormalities in sensory gating and cognition. Cortical hypofunction was also found after ChAT-specific Cul3 ablation and stimulation of cholinergic projections from the BF to the prefrontal cortex (PFC) mitigated cognitive deficits. Overall, we demonstrate that cholinergic dysfunction due to Cul3 deficiency is involved in ASD-like behavioral abnormalities, and that BF cholinergic neurons are particularly critical for cognitive component through their projections to the PFC.

Altered microstructural pattern of the cortex and basal forebrain cholinergic system in wilson's disease: an automated fiber quantification tractography study

Basal forebrain (BF) cholinergic projection neurons form a highly extensive input to the cortex. Failure of BF cholinergic circuits is responsible for the cognitive impairment associated with Wilson's disease (WD), but whether and how the microstructural changes in fiber projections between the BF and cerebral cortex influence prospective memory (PM) remain poorly understood. We collected diffusion tensor imaging (DTI) data from 21 neurological WD individuals and 26 healthy controls (HCs). The experiment reconstructed the probabilistic streamlined tractography of 18 white matter tracts using an automated fiber quantification (AFQ) toolkit. Tract properties (FA, MD, RD, and AD) were computed for 100 points along each tract for each participant, and the differences between the groups were examined. Subsequently, correlation analysis was performed to evaluate whether abnormal microstructural white matter integrity measures correlate with PM performance. Additional investigations used a tract-based spatial statistics (TBSS) approach to identify regions with altered white matter structure between groups and verify the reliability of the AFQ results. The highest nonoverlapping DTI-related differences were detected in the anterior thalamic radiation (ATR), corticospinal tract (CST), corpus callosum, association fibers, and limbic system fibers. Additionally, PM parameters of the patient group were highly correlated with white matter microstructure changes in the inferior longitudinal fasciculus. Our study highlights that the performance of projections between cholinergic input and output areas-the cerebral cortex and BF-may serve as neural biomarkers of PM and disease prognosis.

Muscarinic antagonists impair multiple aspects of operant discrimination learning and performance

Acetylcholine signaling can strengthen associations between environmental cues and reward availability. Diverse subtypes (M1-M5) of the muscarinic acetylcholine receptor (mAChR) family may have distinct roles in different learning and memory processes, such as encoding cue-reward associations and consolidating these associations in long-term memory. Using an operant discrimination learning task in which mice are trained to nose poke during a tone to receive a food reward, we found that acquisition of the task requires mAChR signaling in the central nervous system. In addition, post-session injections of a broad mAChR antagonist, scopolamine impaired consolidation of the cue-reward memory. Further, after successful learning of a cue-reward contingency across multiple training sessions, mice that received a single pre-session injection of scopolamine were unable to use the learned cue association to receive rewards. Taken together, these data demonstrate distinct roles for muscarinic signaling in acquisition, consolidation and recall of the operant discrimination learning task. Understanding mechanisms underlying natural reward-related responding may provide insight into other maladaptive forms of reward learning such as addiction.

Activation of basal forebrain cholinergic neurons improves colonic hyperpermeability through the vagus nerve and adenosine A2B receptors in rats

Intestinal barrier dysfunction, a leaky gut, contributes to the pathophysiology of various diseases such as dementia and irritable bowel syndrome (IBS). We recently clarified that orexin, ghrelin, or adenosine A2B signaling in the brain improved leaky gut through the vagus nerve. The present study was performed to clarify whether basal forebrain cholinergic neurons (BFCNs) are implicated in the central regulation of intestinal barrier function. We activated BFCNs using benzyl quinolone carboxylic acid (BQCA), a positive muscarinic M1 allosteric modulator, and evaluated colonic permeability by quantifying the absorbed Evans blue in rat colonic tissue. Intracisternal (not intraperitoneal) injection of BQCA blocked the increased colonic permeability in response to lipopolysaccharide. Vagotomy blocked BQCA-induced improvement of colonic hyperpermeability. Intracisternally administered pirenzepine, a muscarinic M1 selective antagonist, prevented intestinal barrier function improvement by intravenously administered 2-deoxy-d-glucose, central vagal stimulant. Adenosine A2B receptor antagonist but not dopamine or opioid receptor antagonist prevented BQCA-induced blockade of colonic hyperpermeability. Additionally, intracisternal injection of pirenzepine blocked orexin- or butyrate-induced intestinal barrier function improvement. These results suggest that BFCNs improve leaky gut through adenosine A2B signaling and the vagal pathway. Furthermore, BFCNs mediate orexin- or butyrate-induced intestinal barrier function improvement. Since BFCNs play a role in cognitive function and a leaky gut is associated with dementia, the present finding may lead us to speculate that BFCNs are involved in the development of dementia by regulating intestinal barrier function.

Increased functional connectivity between nucleus basalis of Meynert and amygdala in cognitively intact elderly along the Alzheimer's continuum

BACKGROUND

A growing body of research reported the degeneration of the basal forebrain (BF) cholinergic system in the early course of Alzheimer's disease (AD). However, functional changes of the BF in asymptomatic individuals along the Alzheimer's continuum remain unclear.

METHODS

A total of 229 cognitively intact participants were included from the Alzheimer's Disease Neuroimaging Initiative dataset and further divided into four groups based on the "A/T" profile using amyloid and tau positron emission tomography (PET). All A-T+ subjects were excluded. One hundred and seventy-three subjects along the Alzheimer's continuum (A-T-, A+ T-, A+ T+) were used for further study. The seed-based functional connectivity (FC) maps of the BF subregions (Ch1-3 and Ch4 [nucleus basalis of Meynert, NBM]) with whole-brain voxels were constructed. Analyses of covariance to detect the between-group differences and to further investigated the relations between FC values and AD biomarkers or cognition.

RESULTS

We found increased FC between right Ch4 and bilateral amygdala among three groups, and the FC value could well distinguish between the A-T- group and the Alzheimer's continuum groups. Furthermore, increased FC between the Ch4 and amygdala was associated with higher pathological burden reflected by amyloid and tau PET in the entire population as well as better logistic memory function in A + T+ group.

CONCLUSION

Our study demonstrated the NBM functional connectivity increased in cognitively normal elderly along the Alzheimer's continuum, which indicated a potential compensatory mechanism to counteract pathological changes in AD and maintain intact cognitive function.

Cholinergic REST-G9a gene repression through HMGB1-TLR4 neuroimmune signaling regulates basal forebrain cholinergic neuron phenotype

Lipopolysaccharide (LPS) and high-mobility group box 1 (HMGB1) are Toll-like receptor (TLR4) agonists that activate proinflammatory neuroimmune signaling linked to loss of basal forebrain cholinergic neurons (BFCNs) and cognitive deficits. Loss of choline acetyltransferase immunoreactive (ChAT + IR) BFCNs is generally interpreted as cell death, but recent in vivo studies find anti-inflammatory interventions restore adolescent ethanol exposure-induced persistent loss of adult ChAT + IR neurons and cognitive deficits, suggesting proinflammatory signaling-induced reversible gene repression of ChAT in BFCNs. Using an ex vivo Wistar rat basal forebrain slice culture (FSC) model to investigate TLR4 involvement in repression of the BFCN phenotype, we report that direct TLR4 activation with LPS decreases expression of multiple BFCN markers in the absence of observable neuronal loss or cell death. Inhibition of HMGB1 blunts while inhibition of TLR4 blocks the LPS-induced loss of ChAT + IR neurons. TLR4 activation induces the transcriptional repressor RE1-silencing transcription factor (REST) and the methyltransferase G9a while increasing repressive histone 3 lysine 9 dimethylation and REST occupancy at cholinergic gene promoters. G9a inhibitors both prevent and reverse the LPS-induced loss of ChAT + IR whereas siRNA inhibition of REST blocks the LPS-induced loss of ChAT + IR BFCNs. These data suggest in vivo HMGB1-TLR4 signaling in BFCNs leads to a reversible loss of the cholinergic neuron phenotype through epigenetic gene repressive mechanisms.

Oxytocin: An Old Hormone, A Novel Psychotropic Drug And Possible Use In Treating Psychiatric Disorders

BACKGROUND

Oxytocin is a nonapeptide synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Historically, this molecule has been involved as a key factor in the formation of infant attachment, maternal behavior and pair bonding and, more generally, in linking social signals with cognition, behaviors and reward. In the last decades, the whole oxytocin system has gained a growing interest as it was proposed to be implicated in etiopathogenesis of several neurodevelopmental and neuropsychiatric disorders.

METHODS

With the main goal of an in-depth understanding of the oxytocin role in the regulation of different functions and complex behaviors as well as its intriguing implications in different neuropsychiatric disorders, we performed a critical review of the current state of art. We carried out this work through PubMed database up to June 2021 with the search terms: 1) "oxytocin and neuropsychiatric disorders"; 2) "oxytocin and neurodevelopmental disorders"; 3) "oxytocin and anorexia"; 4) "oxytocin and eating disorders"; 5) "oxytocin and obsessive-compulsive disorder"; 6) "oxytocin and schizophrenia"; 7) "oxytocin and depression"; 8) "oxytocin and bipolar disorder"; 9) "oxytocin and psychosis"; 10) "oxytocin and anxiety"; 11) "oxytocin and personality disorder"; 12) "oxytocin and PTSD".

RESULTS

Biological, genetic, and epigenetic studies highlighted quality and quantity modifications in the expression of oxytocin peptide or in oxytocin receptor isoforms. These alterations would seem to be correlated with a higher risk of presenting several neuropsychiatric disorders belonging to different psychopathological spectra. Collaterally, the exogenous oxytocin administration has shown to ameliorate many neuropsychiatric clinical conditions.

CONCLUSION

Finally, we briefly analyzed the potential pharmacological use of oxytocin in patient with severe symptomatic SARS-CoV-2 infection due to its anti-inflammatory, anti-oxidative and immunoregulatory properties.

Oxytocin-Cholinergic Central Interaction: Implications for Non-Social Memory Formation

Oxytocin (OT) and vasopressin (AVP) are two closely related neuropeptides implicated in learning and memory processes, anxiety, nociception, addiction, feeding behavior and social information processing. Regarding learning and memory, OT has induced long-lasting impairment in different behaviors, while the opposite was observed with AVP. We have previously evaluated the effect of peripheral administration of OT or its antagonist (AOT) on the inhibitory avoidance response of mice and on the modulation of cholinergic mechanisms. Here, we replicate and validate those results, but this time through central administration of neuropeptides, considering their poor passage through the blood-brain barrier (BBB). When we delivered OT (0.10 ng/mouse) and its antagonist (0.10 ng/mouse) through intracerebroventricular (ICV) injections, the neuropeptide impaired and AOT enhanced the behavioral performance on an inhibitory avoidance response evaluated 48 h after training in a dose-dependent manner. On top of that, we investigated a possible central interaction between OT and the cholinergic system. Administration of anticholinesterases inhibitors with access to the central nervous system (CNS), the activation of muscarinic acetylcholine (Ach) receptors and the increase of evoked ACh release using linopirdine (Lino) (3-10 µg/kg, IP), reversed the impairment of retention performance induced by OT. Besides, either muscarinic or nicotinic antagonists with unrestricted access to the CNS reduced the magnitude of the performance-facilitating effect of AOT's central infusion. We suggest that OT might induce a cholinergic hypofunction state, resulting in an impairment of IA memory formation, a process for which the cholinergic system is crucially necessary.

Targeted Tshz3 deletion in corticostriatal circuit components segregates core autistic behaviors

We previously linked TSHZ3 haploinsufficiency to autism spectrum disorder (ASD) and showed that embryonic or postnatal Tshz3 deletion in mice results in behavioral traits relevant to the two core domains of ASD, namely social interaction deficits and repetitive behaviors. Here, we provide evidence that cortical projection neurons (CPNs) and striatal cholinergic interneurons (SCINs) are two main and complementary players in the TSHZ3-linked ASD syndrome. In the cerebral cortex, TSHZ3 is expressed in CPNs and in a proportion of GABAergic interneurons, but not in cholinergic interneurons or glial cells. In the striatum, TSHZ3 is expressed in all SCINs, while its expression is absent or partial in the other main brain cholinergic systems. We then characterized two new conditional knockout (cKO) models generated by crossing Tshz3^flox/flox with Emx1-Cre (Emx1-cKO) or Chat-Cre (Chat-cKO) mice to decipher the respective role of CPNs and SCINs. Emx1-cKO mice show altered excitatory synaptic transmission onto CPNs and impaired plasticity at corticostriatal synapses, with neither cortical neuron loss nor abnormal layer distribution. These animals present social interaction deficits but no repetitive patterns of behavior. Chat-cKO mice exhibit no loss of SCINs but changes in the electrophysiological properties of these interneurons, associated with repetitive patterns of behavior without social interaction deficits. Therefore, dysfunction in either CPNs or SCINs segregates with a distinct ASD behavioral trait. These findings provide novel insights onto the implication of the corticostriatal circuitry in ASD by revealing an unexpected neuronal dichotomy in the biological background of the two core behavioral domains of this disorder.

Inhibitory Effects of Selenium on Arsenic-Induced Anxiety-/Depression-Like Behavior and Memory Impairment

Elevated arsenic (As) contamination in drinking water was detected in many areas of Pakistan. The intoxication of As causes various neurological diseases in humans, which can be inhibited by the administration of potent antioxidants. Trace elements are also found in drinking water such as selenium (Se), which possess antioxidant potential. The main purpose of the current study is to find out the protective effect of Se against As toxicity which can cause anxiety- and depression-like behaviors as well as memory impairment. Thirty-six male rats were divided into six groups: (1) distilled water (dw)+dw, (2) dw+Se (0.175 mg/ml/kg), (3) dw+Se (0.35mg/ml/kg), (4) dw+As (2.5mg/ml/kg), (5) As (2.5mg/ml/kg) + Se (0.175 mg/ml/kg), and (6) As (2.5mg/ml/kg) + Se (0.35 mg/ml/kg). Rats were treated with respective treatment for 4 weeks. Sub-chronic treatment of As reduced time spent in open arm (elevated plus maze), and lightbox (light-dark activity test) and increased immobility time in forced swim test indicate anxiety- and/or depression-like behavior, respectively. Conversely, rats treated with As+Se (at both doses) increased time spent in open arm (elevated plus maze), and lightbox (light-dark activity test) and decreased immobility time in forced swim test indicate the anxiolytic and anti-depressive effect of Se, respectively. Co-administration of Se (0.175 and 0.35) inhibited As instigated reduction of spatial memory performed in Morris water maze. The reversal in the reduced level of malondialdehyde and activity of acetylcholinesterase in the hippocampus by Se was observed in As-treated animals, while the activity of antioxidant enzymes in the hippocampus was increased in As+Se than dw+As-treated animals. Histopathological studies have shown the reversal of hippocampus deterioration by Se in As-treated rats. The results may imply to prevent the intoxication of As instigated impairment in behavioral and biochemical indices by Se supplementation and/or increased safer intake.

GABAergic basal forebrain projections to the periaqueductal gray promote food consumption, reward and predation

Behaviors central to the procurement and consumption of food are among those most fundamental to survival, but their inappropriate expression can lead to overeating and obesity. Nevertheless, we have a poor understanding of circuits that promote feeding independent of physiological demand. Here we demonstrate that activation of basal forebrain (BF) GABAergic neurons results in consumption of food as well as non-food items in well-fed mice, and performance of fictive eating in the absence of ingestible materials. In addition, stimulation of these cells disrupts defensive threat responses and elicits reward-like motivational effects. Finally, BF GABAergic activity triggers skilled predatory attacks of live prey and prey-like objects, but not social targets. These effects were entirely recapitulated by selective stimulation of BF GABAergic projections to the periaqueductal gray (PAG). Our results outline a potent circuit mechanism for increased feeding through recruitment of distinct but synergistic behaviors, and add to growing evidence that PAG is an important integrator of feeding-related activity.

A tacrine-tetrahydroquinoline heterodimer potently inhibits acetylcholinesterase activity and enhances neurotransmission in mice

Cholinergic neurons are ubiquitous and involved in various higher brain functions including learning and memory. Patients with Alzheimer's disease exhibit significant dysfunction and loss of cholinergic neurons. Meanwhile, such cholinergic deficits can be potentially relieved pharmacologically by increasing acetylcholine. Acetylcholinesterase (AChE) inhibitors have been used to improve cholinergic transmission in the brain for two decades and have proven effective for alleviating symptoms in the early stages of Alzheimer's disease. Therefore, the search for AChE inhibitors for drug development is ongoing. The enzymatic pocket of AChE has long been the target of several drug designs over the last two decades. The peripheral and catalytic sites of AChE are simultaneously bound by several dimeric molecules, enabling more-efficient inhibition. Here, we used 6-chlorotacrine and the tetrahydroquinolone moiety of huperzine A to design and synthesize a series of heterodimers that inhibit AChE at nanomolar potency. Specifically, compound 7b inhibits AChE with an IC₅₀ < 1 nM and spares butyrylcholinesterase. Administration of 7b to mouse brain slices restores synaptic activity impaired by pirenzepine, a muscarinic M1-selective antagonist. Moreover, oral administration of 7b to C57BL/6 mice enhances hippocampal long-term potentiation in a dose-dependent manner and is detectable in the brain tissue. All these data supported that 7b is a potential cognitive enhancer and is worth for further exploration.

Diffusion MRI detects basal forebrain cholinergic abnormalities in the 3xTg-AD mouse model of Alzheimer's disease

Degeneration of the basal forebrain (BF) is detected early in the course of Alzheimer's disease (AD). Reduction in the number of BF cholinergic (ChAT) neurons associated with age-related hippocampal cholinergic neuritic dystrophy is described in the 3xTg-AD mouse model; however, no prior diffusion MRI (dMRI) study has explored the presence of BF alterations in this model. Here we investigated the ability of diffusion MRI (dMRI) to detect abnormalities in BF microstructure for the 3xTg-AD mouse model, along with related pathology in the hippocampus (HP) and white matter (WM) tracks comprising the septo-hippocampal pathway. 3xTg-AD and normal control (NC) mice were imaged in vivo using the specific dMRI technique known as diffusional kurtosis imaging (DKI) at 2, 8, and 15 months of age, and 8 dMRI parameters were measured at each time point. Our results revealed significant lower dMRI values in the BF of 2 months-old 3xTg-AD mice compared with NC mice, most likely related to the increased number of ChAT neurons seen in this AD mouse model at this age. They also showed significant age-related dMRI changes in the BF of both groups between 2 and 8 months of age, mainly a decrease in fractional anisotropy and axial diffusivity, and an increase in radial kurtosis. These dMRI changes in the BF may be reflecting the complex aging and pathological microstructural changes described in this region. Group differences and age-related changes were also observed in the HP, fimbria (Fi) and fornix (Fx). In the HP, diffusivity values were significantly higher in the 2 months-old 3xTg-AD mice, and the HP of NC mice showed a significant increase in axial kurtosis after 8 months, reflecting a normal pattern of increased fiber density complexity, which was not seen in the 3xTg-AD mice. In the Fi, mean and radial diffusivity values were significantly higher, and fractional anisotropy, radial kurtosis and kurtosis fractional anisotropy were significantly lower in the 2 months-old 3xTg-AD mice. The age trajectories for both NC and TG mice in the Fi and Fx were similar between 2 and 8 months, but after 8 months there was a significant decrease in diffusivity metrics associated with an increase in kurtosis metrics in the 3xTg-AD mice. These later HP, Fi and Fx dMRI changes probably reflect the growing number of dystrophic neurites and AD pathology progression in the HP, accompanied by WM disruption in the septo-hippocampal pathway. Our results demonstrate that dMRI can detect early cytoarchitectural abnormalities in the BF, as well as related aging and neurodegenerative changes in the HP, Fi and Fx of the 3xTg-AD mice. Since DKI is widely available on clinical scanners, these results also support the potential of the considered dMRI parameters as in vivo biomarkers for AD disease progression.

The Free-movement pattern Y-maze: A cross-species measure of working memory and executive function

Numerous neurodegenerative and psychiatric disorders are associated with deficits in executive functions such as working memory and cognitive flexibility. Progress in developing effective treatments for disorders may benefit from targeting these cognitive impairments, the success of which is predicated on the development of animal models with validated behavioural assays. Zebrafish offer a promising model for studying complex brain disorders, but tasks assessing executive function are lacking. The Free-movement pattern (FMP) Y-maze combines aspects of the common Y-maze assay, which exploits the inherent motivation of an organism to explore an unknown environment, with analysis based on a series of sequential two-choice discriminations. We validate the task as a measure of working memory and executive function by comparing task performance parameters in adult zebrafish treated with a range of glutamatergic, cholinergic and dopaminergic drugs known to impair working memory and cognitive flexibility. We demonstrate the cross-species validity of the task by assessing performance parameters in adapted versions of the task for mice and Drosophila, and finally a virtual version in humans, and identify remarkable commonalities between vertebrate species' navigation of the maze. Together, our results demonstrate that the FMP Y-maze is a sensitive assay for assessing working memory and cognitive flexibility across species from invertebrates to humans, providing a simple and widely applicable behavioural assay with exceptional translational relevance.

Forgetting Unwanted Memories: Active Forgetting and Implications for the Development of Psychological Disorders

Intrusive memories are a common feature of many psychopathologies, and suppression-induced forgetting of unwanted memories appears as a critical ability to preserve mental health. In recent years, biological and cognitive studies converged in revealing that forgetting is due to active processes. Recent neurobiological studies provide evidence on the active role of main neurotransmitter systems in forgetting, suggesting that the brain actively works to suppress retrieval of unwanted memories. On the cognitive side, there is evidence that voluntary and involuntary processes (here termed "intentional" and "incidental" forgetting, respectively) contribute to active forgetting. In intentional forgetting, an inhibitory control mechanism suppresses awareness of unwanted memories at encoding or retrieval. In incidental forgetting, retrieval practice of some memories involuntarily suppresses the retrieval of other related memories. In this review we describe recent findings on deficits in active forgetting observed in psychopathologies, like post-traumatic stress disorder, depression, schizophrenia, and obsessive-compulsive disorder. Moreover, we report studies in which the role of neurotransmitter systems, known to be involved in the pathogenesis of mental disorders, has been investigated in active forgetting paradigms. The possibility that biological and cognitive mechanisms of active forgetting could be considered as hallmarks of the early onset of psychopathologies is also discussed.

Multidimensional Intersection of Nicotine, Gene Expression, and Behavior

The cholinergic system plays a crucial role in nervous system function with important effects on developmental processes, cognition, attention, motivation, reward, learning, and memory. Nicotine, the reinforcing component of tobacco and e-cigarettes, directly acts on the cholinergic system by targeting nicotinic acetylcholine receptors (nAChRs) in the brain. Activation of nAChRs leads to a multitude of immediate and long-lasting effects in specific cellular populations, thereby affecting the addictive properties of the drug. In addition to the direct actions of nicotine in binding to and opening nAChRs, the subsequent activation of circuits and downstream signaling cascades leads to a wide range of changes in gene expression, which can subsequently alter further behavioral expression. In this review, we provide an overview of the actions of nicotine that lead to changes in gene expression and further highlight evidence supporting how these changes can often be bidirectional, thereby inducing subsequent changes in behaviors associated with further drug intake.

Loss of Basal Forebrain Cholinergic Neurons Following Adolescent Binge Ethanol Exposure: Recovery With the Cholinesterase Inhibitor Galantamine

Binge drinking and alcohol abuse are common during adolescence and cause both cognitive deficits and lasting cholinergic pathology in the adult basal forebrain. Acetylcholine is anti-inflammatory and studies using the preclinical adolescent intermittent ethanol (AIE; 5.0 g/kg, i.g., 2 day on/2 day off from postnatal day [P]25 to P54) model of human adolescent binge drinking report decreased basal forebrain cholinergic neurons (BFCNs) and induction of proinflammatory genes that persist long into adulthood. Recent studies link AIE-induced neuroimmune activation to cholinergic pathology, but the underlying mechanisms contributing to the persistent loss of BFCNs are unknown. We report that treatment with the cholinesterase inhibitor galantamine (4.0 mg/kg, i.p.) administered during AIE (i.e., P25-P54) or following the conclusion of AIE (i.e., P57-P72) recovered the persistent loss of cholinergic neuron phenotype markers (i.e., ChAT, TrkA, and p75NTR) and somal shrinkage of residual ChAT + neurons known to persist in AIE-exposed adults. Galantamine treatment also recovered the AIE-increased expression of the proinflammatory receptors TLR4 and RAGE, the endogenous TLR4/RAGE agonist HMGB1, and the transcription activation marker pNF-κB p65. Interestingly, we find BFCNs express TLR4 and RAGE, and that AIE treatment increased pNF-κB p65 expression in adult ChAT + IR neurons, consistent with intracellular HMGB1-TLR4/RAGE signaling within BFCNs. AIE increased epigenetic transcription silencing markers (i.e., H3K9me2 and H3K9me3) in the adult basal forebrain and H3K9me2 occupancy at cholinergic phenotype gene promoters (i.e., ChAT and TrkA). The finding of no AIE-induced changes in total basal forebrain NeuN + neurons with galantamine reversal of AIE-induced ChAT + neuron loss, TLR4/RAGE-pNF-κB p65 signals, and epigenetic transcription silencing markers suggests that AIE does not cause cell death, but rather the loss of the cholinergic phenotype. Together, these data suggest that AIE induces HMGB1-TLR4/RAGE-pNF-κB p65 signals, causing the loss of cholinergic phenotype (i.e., ChAT, TrkA, and p75NTR) through epigenetic histone transcription silencing that result in the loss of the BFCN phenotype that can be prevented and restored by galantamine.

Natural Cannabinoids as Templates for Sleep Disturbances Treatments

The sleep-wake cycle is a complex composition of specific physiological and behavioral characteristics. In addition, neuroanatomical, neurochemical and molecular systems exerts influences in the modulation of the sleep-wake cycle. Moreover, homeostatic and circadian mechanisms interact to control the waking or sleeping states. As many other behaviors, sleep also develops pathological features that include several signs and symptoms corresponding to medical conditions known as sleep disorders.In addition to the neurobiological mechanisms modulating sleep, external elements also influence the sleep-wake cycle, including the use of Cannabis sativa (C. sativa). In this regard, and over the last decades, the interest of studying the pharmacology of Δ⁹-tetrahydrocannabinol (Δ⁹-THC), the principal psychoactive constituent of C. sativa, has been addressed. Moreover, in recent years, the focus of scientific interest has moved on to studying the second plant constituent with non-psychotropic pharmacological properties: Cannabidiol (CBD).The pharmacological and pharmaceutical interest of CBD has been focus of attention due to the accumulating body of evidence regarding the positive outcomes of using CBD for the treatment of several health issues, such as psychiatric and neurodegenerative disorders, epilepsy, etc. Since the most prominent sleep disruptions include excessive daytime sleepiness (EDS), current treatments include the use of drugs such as stimulants of antidepressants. Notwithstanding, side effects are commonly reported among the patients under prescription of these compounds. Thus, the search of novelty therapeutical approaches aimed to treat ESD may consider the use of cannabinoid-derived compounds, such as CBD. In this chapter, we will show experimental evidence regarding the potential role of CBD as a wake-inducing compound aimed to manage EDS.

Ramelteon modulates gamma oscillations in the rat primary motor cortex during non-REM sleep

Sleep disorders adversely affect daily activities and cause physiological and psychiatric problems. The shortcomings of benzodiazepine hypnotics have led to the development of ramelteon, a melatonin MT1 and MT2 agonist. Although the sleep-promoting effects of ramelteon have been documented, few studies have precisely investigated the structure of sleep and neural oscillatory activities. In this study, we recorded electrocorticograms in the primary motor cortex, the primary somatosensory cortex and the olfactory bulb as well as electromyograms in unrestrained rats treated with either ramelteon or vehicle. A neural-oscillation-based algorithm was used to classify the behavior of the rats into three vigilance states (e.g., awake, rapid eye movement (REM) sleep, and non-REM (NREM) sleep). Moreover, we investigated the region-, frequency- and state-specific modulation of extracellular oscillations in the ramelteon-treated rats. We demonstrated that in contrast to benzodiazepine treatment, ramelteon treatment promoted NREM sleep and enhanced fast gamma power in the primary motor cortex during NREM sleep, while REM sleep was unaffected. Gamma oscillations locally coordinate neuronal firing, and thus, ramelteon modulates neural oscillations in sleep states in a unique manner and may contribute to off-line information processing during sleep.

Strength training or green tea prevent memory deficits in a β-amyloid peptide-mediated Alzheimer's disease model

Antioxidant supplementation and physical exercise have been discussed as strategies to minimize neurodegeneration in Alzheimer's disease (AD). We investigated the neuroprotective effects of strength exercise (StrEx) and green tea (GT) supplementation, combined or not, on memory impairments induced by β-amyloid characterizing an AD-like condition in rats. Wistar rats were submitted to 8 weeks of StrEx, GT supplementation, or StrEx and GT combined. AD-like condition was induced by injection of Aβ (25-35) in the hippocampus. We evaluate object recognition (OR) and social recognition (SR) memory, and removed the rats' hippocampus for biochemical analysis. StrEx improved OR and SR. StrEx combined with GT improved OR and did not improve SR. GT reduced antioxidant capacity and improved acetylcholinesterase activity. Both strength exercise and green tea are neuroprotective against impairments resultant of β-amyloid, but benefits do not add up when the two interventions are associated.

Royal Jelly as an Intelligent Anti-Aging Agent-A Focus on Cognitive Aging and Alzheimer's Disease: A Review

The astronomical increase of the world's aged population is associated with the increased prevalence of neurodegenerative diseases, heightened disability, and extremely high costs of care. Alzheimer's Disease (AD) is a widespread, age-related, multifactorial neurodegenerative disease that has enormous social and financial drawbacks worldwide. The unsatisfactory outcomes of available AD pharmacotherapy necessitate the search for alternative natural resources that can target various the underlying mechanisms of AD pathology and reduce disease occurrence and/or progression. Royal jelly (RJ) is the main food of bee queens; it contributes to their fertility, long lifespan, and memory performance. It represents a potent nutraceutical with various pharmacological properties, and has been used in a number of preclinical studies to target AD and age-related cognitive deterioration. To understand the mechanisms through which RJ affects cognitive performance both in natural aging and AD, we reviewed the literature, elaborating on the metabolic, molecular, and cellular mechanisms that mediate its anti-AD effects. Preclinical findings revealed that RJ acts as a multidomain cognitive enhancer that can restore cognitive performance in aged and AD models. It promotes brain cell survival and function by targeting multiple adversities in the neuronal microenvironment such as inflammation, oxidative stress, mitochondrial alterations, impaired proteostasis, amyloid-β toxicity, Ca excitotoxicity, and bioenergetic challenges. Human trials using RJ in AD are limited in quantity and quality. Here, the limitations of RJ-based treatment strategies are discussed, and directions for future studies examining the effect of RJ in cognitively impaired subjects are noted.

Orexin and Alzheimer's Disease: A New Perspective

Orexin's role in human cognition has recently been emphasized and emerging evidences indicate its close relationship with Alzheimer's disease (AD). This review aimed to demonstrate recent research on the relationship between orexin and AD. Orexin's role in stress regulation and memory is discussed, with significant findings related to sexual disparities in stress response, with potential clinical implications pertaining to AD pathology. There are controversies regarding the orexin levels in AD patients, but the role of orexin in the trajectory of AD is still emphasized in recent literatures. Orexin is also accentuated in the context of tau pathology, and orexin as a potential therapeutic target for AD is frequently discussed. Future directions with regard to the relationship between orexin and AD are suggested: 1) consideration for AD trajectory in the measurement of orexin levels, 2) the need for objective measure such as polysomnography and actigraphy, 3) the need for close observation of cognitive profiles of orexin-deficient narcolepsy patients, 4) the need for validation studies by neuroimaging 5) the need for taking account sexual disparities in orexinergic activiation, and 6) consideration for orexin's role as a stress regulator. The aforementioned new perspectives could help unravel the relationship between orexin and AD.

Activation of brain-derived neurotrophic factor signaling in the basal forebrain reverses acute sleep deprivation-induced fear memory impairments

INTRODUCTION

The mechanisms underlying sleep deprivation-induced memory impairments and relevant compensatory signaling pathways remain elusive. We tested the hypothesis that increased brain-derived neurotrophic factor (BDNF) expression in the basal forebrain following acute sleep deprivation was a compensatory mechanism to maintain fear memory performance.

METHODS

Adult male Wistar rats were deprived of 6-hr total sleep from the beginning of the light cycle. The effects of sleep deprivation on BDNF protein expression and activation of downstream tropomyosin receptor kinase B (TrkB)/phospholipase C-γ1 (PLCγ1) signaling in the basal forebrain and fear memory consolidation were examined. BDNF or selective downstream TrkB receptor antagonist ANA-12 was further injected into the basal forebrain bilaterally to observe the changes in fear memory consolidation in response to modulation of the BDNF/TrkB signaling.

RESULTS

Six hours of sleep deprivation-induced both short- and long-term fear memory impairments. Increased BDNF protein expression and TrkB and PLCγ1 phosphorylation in the basal forebrain were observed after sleep deprivation. Microinjection of BDNF into the basal forebrain partly reversed fear memory deficits caused by sleep deprivation, which were accompanied by increased BDNF protein levels and TrkB/PLCγ1 activation. After ANA-12 microinjection, sleep deprivation-induced activation of the BDNF/TrkB pathway was inhibited and impairments of fear memory consolidation were further aggravated.

CONCLUSIONS

Acute sleep deprivation induces compensatory increase of BDNF expression in the basal forebrain. Microinjection of BDNF into the basal forebrain mitigates the fear memory impairments caused by sleep deprivation by activating TrkB/PLCγ1 signaling.

Neuroimmune and epigenetic involvement in adolescent binge ethanol-induced loss of basal forebrain cholinergic neurons: Restoration with voluntary exercise

Binge drinking and alcohol abuse are common during adolescence and cause lasting pathology. Preclinical rodent studies using the adolescent intermittent ethanol (AIE; 5.0 g/kg, i.g., 2‐day on/2‐day off from postnatal day [P]25 to P55) model of human adolescent binge drinking report decreased basal forebrain cholinergic (ie, ChAT+) neurons that persist into adulthood (ie, P56‐P220). Recent studies link AIE‐induced neuroimmune activation to cholinergic pathology, but the underlying molecular mechanisms contributing to the persistent loss of basal forebrain ChAT+ neurons are unknown. We report here that the AIE‐induced loss of cholinergic neuron markers (ie, ChAT, TrkA, and p75^NTR), cholinergic neuron shrinkage, and increased expression of the neuroimmune marker pNF‐κB p65 are restored by exercise exposure from P56 to P95 after AIE. Our data reveal that persistently reduced expression of cholinergic neuron markers following AIE is because of the loss of the cholinergic neuron phenotype most likely through an epigenetic mechanism involving DNA methylation and histone 3 lysine 9 dimethylation (H3K9me2). Adolescent intermittent ethanol caused a persistent increase in adult H3K9me2 and DNA methylation at promoter regions of Chat and H3K9me2 of Trka, which was restored by wheel running. Exercise also restored the AIE‐induced reversal learning deficits on the Morris water maze. Together, these data suggest that AIE‐induced adult neuroimmune signaling and cognitive deficits are linked to suppression of Chat and Trka gene expression through epigenetic mechanisms that can be restored by exercise. Exercise restoration of the persistent AIE‐induced phenotypic loss of cholinergic neurons via epigenetic modifications is novel mechanism of neuroplasticity.

Inorganic fluoride and functions of brain

Although actively disputed and questioned, it has been proposed that chronic exposure to inorganic fluoride (F^-) is toxic for brain. The major question for this review was whether an excessive F^- intake is causally related to adverse neurological and cognitive health conditions in human beings and animals. The paper systematically and critically summarizes the findings of the studies showing positive associations between F^- intoxication and various intellectual defects, as well as of those which attempted to clarify the nature of F^- neurotoxicity. Many works provide support for a link between pre- and postnatal F^- exposure and structural and functional changes in the central nervous system responsible for neurological and cognitive disorders. The mechanisms suggested to underlie F^- neurotoxicity include the disturbances in synaptic transmission and synaptic plasticity, premature death of neurons, altered activities of components of intracellular signaling cascades, impaired protein synthesis, deficit of neurotrophic and transcriptional factors, oxidative stress, metabolic changes, inflammatory processes. However, the majority of works have been performed on laboratory rodents using such F^- doses which are never exist in the nature even in the regions of endemic fluorosis. Thus, this kind of treatment is hardly comparable with human exposure even taking into account the higher rate of F^- clearance in animals. Of special importance are the data collected on humans chronically consuming excessive F^- doses in the regions of endemic fluorosis or contacting with toxic F^- compounds at industrial sites, but those works are scarce and often criticized due to low quality. New, expertly performed studies with repeated exposure assessment in independent populations are needed to prove an ability of F^- to impair neurological and intellectual development of human beings and to understand the molecular mechanisms implicated in F^--induced neurotoxicity.

Mumefural Ameliorates Cognitive Impairment in Chronic Cerebral Hypoperfusion via Regulating the Septohippocampal Cholinergic System and Neuroinflammation

Chronic cerebral hypoperfusion (CCH) causes cognitive impairment and neurogenic inflammation by reducing blood flow. We previously showed that Fructus mume (F. mume) improves cognitive impairment and inhibits neuroinflammation in a CCH rat model. One of the components of F. mume, Mumefural (MF), is known to improve blood flow and inhibit platelet aggregation. Whether MF affects cerebral and cognitive function remains unclear. We investigated the effects of MF on cognitive impairment and neurological function-related protein expression in the rat CCH model, established by bilateral common carotid arterial occlusion (BCCAo). Three weeks after BCCAo, MF (20, 40, or 80 mg/kg) was orally administrated once a day for 42 days. Using Morris water maze assessment, MF treatment significantly improved cognitive impairment. MF treatment also inhibited cholinergic system dysfunction, attenuated choline acetyltransferase-positive cholinergic neuron loss, and regulated cholinergic system-related protein expressions in the basal forebrain and hippocampus. MF also inhibited myelin basic protein degradation and increased the hippocampal expression of synaptic markers and cognition-related proteins. Moreover, MF reduced neuroinflammation, inhibited gliosis, and attenuated the activation of P2X7 receptor, TLR4/MyD88, NLRP3, and NF-κB. This study indicates that MF ameliorates cognitive impairment in BCCAo rats by enhancing neurological function and inhibiting neuroinflammation.

Aging with alcohol-related brain damage: Critical brain circuits associated with cognitive dysfunction

Alcoholism is associated with brain damage and impaired cognitive functioning. The relative contributions of different etiological factors, such as alcohol, thiamine deficiency and age vulnerability, to the development of alcohol-related neuropathology and cognitive impairment are still poorly understood. One reason for this quandary is that both alcohol toxicity and thiamine deficiency produce brain damage and cognitive problems that can be modulated by age at exposure, aging following alcohol toxicity or thiamine deficiency, and aging during chronic alcohol exposure. Pre-clinical models of alcohol-related brain damage (ARBD) have elucidated some of the contributions of ethanol toxicity and thiamine deficiency to neuroinflammation, neuronal loss and functional deficits. However, the critical variable of age at the time of exposure or long-term aging with ARBD has been relatively ignored. Acute thiamine deficiency created a massive increase in neuroimmune genes and proteins within the thalamus and significant increases within the hippocampus and frontal cortex. Chronic ethanol treatment throughout adulthood produced very minor fluctuations in neuroimmune genes, regardless of brain region. Intermittent "binge-type" ethanol during the adolescent period established an intermediate neuroinflammatory response in the hippocampus and frontal cortex, that can persist into adulthood. Chronic excessive drinking throughout adulthood, adolescent intermittent ethanol exposure, and thiamine deficiency all led to a loss of the cholinergic neuronal phenotype within the basal forebrain, reduced hippocampal neurogenesis, and alterations in the frontal cortex. Only thiamine deficiency results in gross pathological lesions of the thalamus. The behavioral impairment following these types of treatments is hierarchical: Thiamine deficiency produces the greatest impairment of hippocampal- and prefrontal-dependent behaviors, chronic ethanol drinking ensues mild impairments on both types of tasks and adolescent intermittent ethanol exposure leads to impairments on frontocortical tasks, with sparing on most hippocampal-dependent tasks. However, our preliminary data suggest that as rodents age following adolescent intermittent ethanol exposure, hippocampal functional deficits began to emerge. A necessary requirement for the advancement of understanding the neural consequences of alcoholism is a more comprehensive assessment and understanding of how excessive alcohol drinking at different development periods (adolescence, early adulthood, middle-aged and aged) influences the trajectory of the aging process, including pathological aging and disease.

Nigella sativa and thymoquinone attenuate oxidative stress and cognitive impairment following cerebral hypoperfusion in rats

Nigella sativa, a plant widely used in traditional medicine, possesses anti-inflammatory, antioxidant and neuroprotective properties. In the present study, we investigated the effect of hydroalcoholic extract of N. sativa seeds (NSE) and its active constituent, thymoquinone (TQ), on learning and memory deficits, hippocampal acetylcholine esterase (AChE) activity, and markers of redox status, mainly lipid peroxidation and superoxide dismutase (SOD) activity following cerebral hypoperfusion in rats. Cerebral hypoperfusion was induced by permanent occlusion of bilateral common carotid arteries (2VO). Male Wistar rats were administered either a vehicle (sham group: 10 ml/kg/day, ip), NSE (100, 200, and 400 mg/kg/day, ip), TQ (10, 20, and 40 mg/kg/day, ip), or donepezil (5 mg/kg/day, ip) for 10 days (three days before and seven days after ligation). Spatial learning and memory deficits were investigated using the Morris water maze (MWM) task. 2VO produced significant learning and memory deficits as evidenced by increased latency time to reach the hidden platform, increased swimming time, and decreased time spent in the target quadrant in the probe trial in the MWM task. There was also a significant increase in the lipid peroxidation level and AChE activity, and a significant decrease in SOD activity in the hippocampal portion of hypoperfused rats, as compared with the sham group. Treatment with NSE (400 mg/kg/day; p < 0.001) and TQ (40 mg/kg/day; p < 0.001), as well as donepezil significantly prevented learning and memory impairments and alleviated changes in the hippocampal lipid peroxide level and SOD and AChE activities in this model. In conclusion, our data suggest that N. sativa and thymoquinone have a beneficial role in cerebrovascular insufficiency states and dementia.

Adolescent binge ethanol-induced loss of basal forebrain cholinergic neurons and neuroimmune activation are prevented by exercise and indomethacin

Basal forebrain cholinergic neurons mature in adolescence coinciding with development of adult cognitive function. Preclinical studies using the rodent model of adolescent intermittent ethanol (AIE; 5.0 g/kg, i.g., 2-days on/2-days off from postnatal day [P]25 to P55) reveal persistent increases of brain neuroimmune genes that are associated with cognitive dysfunction. Adolescent intermittent ethanol exposure also reduces basal forebrain expression of choline acetyltransferase (ChAT), an enzyme critical for acetylcholine synthesis in cholinergic neurons similar to findings in the post-mortem human alcoholic basal forebrain. We report here that AIE decreases basal forebrain ChAT+IR neurons in both adult female and male Wistar rats following early or late adolescent ethanol exposure. In addition, we find reductions in ChAT+IR somal size as well as the expression of the high-affinity nerve growth factor (NGF) receptor tropomyosin receptor kinase A (TrkA) and the low-affinity NGF receptor p75NTR, both of which are expressed on cholinergic neurons. The decrease in cholinergic neuron marker expression was accompanied by increased phosphorylation of NF-κB p65 (pNF-κB p65) consistent with increased neuroimmune signaling. Voluntary wheel running from P24 to P80 prevented AIE-induced cholinergic neuron shrinkage and loss of cholinergic neuron markers (i.e., ChAT, TrkA, and p75NTR) as well as the increase of pNF-κB p65 in the adult basal forebrain. Administration of the anti-inflammatory drug indomethacin (4.0 mg/kg, i.p prior to each ethanol exposure) during AIE also prevented the loss of basal forebrain cholinergic markers and the concomitant increase of pNF-κB p65. In contrast, treatment with the proinflammatory immune activator lipopolysaccharide (1.0 mg/kg, i.p. on P70) caused a loss of cholinergic neuron markers that was paralleled by increased pNF-κB p65 in the basal forebrain. These novel findings are consistent with AIE causing lasting activation of the neuroimmune system that contributes to the persistent loss of basal forebrain cholinergic neurons in adulthood.

The Color of Noise and Weak Stationarity at the NREM to REM Sleep Transition in Mild Cognitive Impaired Subjects

In Older Adults (OAs), Electroencephalogram (EEG) slowing in frontal lobes and a diminished muscle atonia during Rapid Eye Movement sleep (REM) have each been effective tracers of Mild Cognitive Impairment (MCI), but this relationship remains to be explored by non-linear analysis. Likewise, data provided by EEG, EMG (Electromyogram) and EOG (Electrooculogram)—the three required sleep indicators—during the transition from REM to Non-REM (NREM) sleep have not been related jointly to MCI. Therefore, the main aim of the study was to explore, with results for Detrended Fluctuation Analysis (DFA) and multichannel DFA (mDFA), the Color of Noise (CN) at the NREM to REM transition in OAs with MCI vs. subjects with good performances. The comparisons for the transition from NREM to REM were made for each group at each cerebral area, taking bilateral derivations to evaluate interhemispheric coupling and anteroposterior and posterior networks. In addition, stationarity analysis was carried out to explore if the three markers distinguished between the groups. Neuropsi and the Mini-Mental State Examination (MMSE) were administered, as well as other geriatric tests. One night polysomnography was applied to 6 OAs with MCI (68.1 ± 3) and to 7 subjects without it (CTRL) (64.5 ± 9), and pre-REM and REM epochs were analyzed for each subject. Lower scores for attention, memory and executive funcions and a greater index of arousals during sleep were found for the MCI group. Results confirmed that EOGs constituted significant markers of MCI, increasing the CN for the MCI group in REM sleep. The CN of the EEG from the pre-REM to REM was higher for the MCI group vs. the opposite for the CTRL group at frontotemporal areas. Frontopolar interhemispheric scaling values also followed this trend as well as right anteroposterior networks. EMG Hurst values for both groups were lower than those for EEG and EOG. Stationarity analyses showed differences between stages in frontal areas and right and left EOGs for both groups. These results may demonstrate the breakdown of fractality of areas especially involved in executive functioning and the way weak stationarity analyses may help to distinguish between sleep stages in OAs.

Systemic Injections of Cannabidiol Enhance Acetylcholine Levels from Basal Forebrain in Rats

Cannabis sativa is a plant that contains more than 500 components, of which the most studied are Δ⁹-tetrahydrocannabinol (Δ⁹-THC) and cannabidiol (CBD). Several studies have indicated that CBD displays neurobiological effects, including wake promotion. Moreover, experimental evidence has shown that injections of CBD enhance wake-related compounds, such as monoamines (dopamine, serotonin, epinephrine, and norepinephrine). However, no clear evidence is available regarding the effects of CBD on additional wake-related neurochemicals such as acetylcholine (ACh). Here, we demonstrate that systemic injections of CBD (0, 5, 10 or 30 mg/kg, i.p.) at the beginning of the lights-on period, increase the extracellular levels of ACh collected from the basal forebrain and measured by microdialysis and HPLC means. Moreover, the time course effects on the contents of ACh were present 5 h post-injection of CBD. Altogether, these data demonstrate that CBD increases ACh levels in a brain region related to wake control. This study is the first to show the effects of ACh levels in CBD-treated rats and suggests that the basal forebrain might be a site of action of CBD for wakefulness modulation.

The Requirement of L-Type Voltage-Dependent Calcium Channel (L-VDCC) in the Rapid-Acting Antidepressant-Like Effects of Scopolamine in Mice

BACKGROUND

Previous studies have shown that a low dose of scopolamine produces rapid-acting antidepressant-like actions in rodents. Understanding the mechanisms underlying this effect and the dose-dependent variations of drug responses remains an important task. L-type voltage-dependent calcium channels were found to mediate rapid-acting antidepressant effects of certain medications (e.g., ketamine). Therefore, it is of great interest to determine the involvement of L-type voltage-dependent calcium channels in the action of scopolamine.

METHODS

Herein, we investigated the mechanisms underlying behavioral responses to various doses of scopolamine in mice to clarify the involvement of L-type voltage-dependent calcium channels in its modes of action. Open field test, novel object recognition test, and forced swimming test were performed on mice administered varied doses of scopolamine (0.025, 0.05, 0.1, 1, and 3 mg/kg, i.p.) alone or combined with L-type voltage-dependent calcium channel blocker verapamil (5 mg/kg, i.p.). Then, the changes in brain-derived neurotrophic factor and neuropeptide VGF (nonacronymic) levels in the hippocampus and prefrontal cortex of these mice were analyzed.

RESULTS

Low doses of scopolamine (0.025 and 0.05 mg/kg) produced significant antidepressant-like effects in the forced swimming test, while higher doses (1 and 3 mg/kg) resulted in significant memory deficits and depressive-like behaviors. Moreover, the behavioral changes in responses to various doses may be related to the upregulation (0.025 and 0.05 mg/kg) and downregulation (1 and 3 mg/kg) of brain-derived neurotrophic factor and VGF in the hippocampus and prefrontal cortex in mice. We further found that the rapid-acting antidepressant-like effects and the upregulation on brain-derived neurotrophic factor and VGF produced by a low dose of scopolamine (0.025 mg/kg) were completely blocked by verapamil.

CONCLUSIONS

These results indicate that L-type voltage-dependent calcium channels are likely involved in the behavioral changes in response to various doses of scopolamine through the regulation of brain-derived neurotrophic factor and VGF levels.