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.

Sexual coordination in a whole-brain map of prairie vole pair bonding.

Sexual bonds are central to the social lives of many species, including humans, and monogamous prairie voles have become the predominant model for investigating such attachments. We developed an automated whole-brain mapping pipeline to identify brain circuits underlying pair-bonding behavior. We identified bonding-related c-Fos induction in 68 brain regions clustered in seven major brain-wide neuronal circuits. These circuits include known regulators of bonding, such as the bed nucleus of the stria terminalis, paraventricular hypothalamus, ventral pallidum, and prefrontal cortex. They also include brain regions previously unknown to shape bonding, such as ventromedial hypothalamus, medial preoptic area, and the medial amygdala, but that play essential roles in bonding-relevant processes, such as sexual behavior, social reward, and territorial aggression. Contrary to some hypotheses, we found that circuits active during mating and bonding were largely sexually monomorphic. Moreover, c-Fos induction across regions was strikingly consistent between members of a pair, with activity best predicted by rates of ejaculation. A novel cluster of regions centered in the amygdala remained coordinated after bonds had formed, suggesting novel substrates for bond maintenance. Our tools and results provide an unprecedented resource for elucidating the networks that translate sexual experience into an enduring bond.

Cell-type-specific optogenetic fMRI on basal forebrain reveals functional network basis of behavioral preference.

The basal forebrain (BF) is a complex structure that plays key roles in regulating various brain functions. However, it remains unclear how cholinergic and non-cholinergic BF neurons modulate large-scale functional networks and their relevance in intrinsic and extrinsic behaviors. With an optimized awake mouse optogenetic fMRI approach, we revealed that optogenetic stimulation of four BF neuron types evoked distinct cell-type-specific whole-brain BOLD activations, which could be attributed to BF-originated low-dimensional structural networks. Additionally, optogenetic activation of VGLUT2, ChAT, and PV neurons in the BF modulated the preference for locomotion, exploration, and grooming, respectively. Furthermore, we uncovered the functional network basis of the above BF-modulated behavioral preference through a decoding model linking the BF-modulated BOLD activation, low-dimensional structural networks, and behavioral preference. To summarize, we decoded the functional network basis of differential behavioral preferences with cell-type-specific optogenetic fMRI on the BF and provided an avenue for investigating mouse behaviors from a whole-brain view.

Basal forebrain cholinergic systems as circuits through which traumatic stress disrupts emotional memory regulation.

Contextual and spatial systems facilitate changes in emotional memory regulation brought on by traumatic stress. Cholinergic basal forebrain (chBF) neurons provide input to contextual/spatial systems and although chBF neurons are important for emotional memory, it is unknown how they contribute to the traumatic stress effects on emotional memory. Clusters of chBF neurons that project to the prefrontal cortex (PFC) modulate fear conditioned suppression and passive avoidance, while clusters of chBF neurons that project to the hippocampus (Hipp) and PFC (i.e. cholinergic medial septum and diagonal bands of Broca (chMS/DBB neurons) are critical for fear extinction. Interestingly, neither Hipp nor PFC projecting chMS/DBB neurons are critical for fear extinction. The retrosplenial cortex (RSC) is a contextual/spatial memory system that receives input from chMS/DBB neurons, but whether this chMS/DBB-RSC circuit facilitates traumatic stress effects on emotional memory remain unexplored. Traumatic stress leads to neuroinflammation and the buildup of reactive oxygen species. These two molecular processes may converge to disrupt chBF circuits enhancing the impact of traumatic stress on emotional memory.

Functionally refined encoding of threat memory by distinct populations of basal forebrain cholinergic projection neurons.

Neurons of the basal forebrain nucleus basalis and posterior substantia innominata (NBM/SIp) comprise the major source of cholinergic input to the basolateral amygdala (BLA). Using a genetically encoded acetylcholine (ACh) sensor in mice, we demonstrate that BLA-projecting cholinergic neurons can 'learn' the association between a naive tone and a foot shock (training) and release ACh in the BLA in response to the conditioned tone 24 hr later (recall). In the NBM/SIp cholinergic neurons express the immediate early gene, Fos following both training and memory recall. Cholinergic neurons that express Fos following memory recall display increased intrinsic excitability. Chemogenetic silencing of these learning-activated cholinergic neurons prevents expression of the defensive behavior to the tone. In contrast, we show that NBM/SIp cholinergic neurons are not activated by an innately threatening stimulus (predator odor). Instead, VP/SIa cholinergic neurons are activated and contribute to defensive behaviors in response to predator odor, an innately threatening stimulus. Taken together, we find that distinct populations of cholinergic neurons are recruited to signal distinct aversive stimuli, demonstrating functionally refined organization of specific types of memory within the cholinergic basal forebrain of mice.

Cholinergic Basal Forebrain Connectivity to the Basolateral Amygdala Modulates Food Intake.

Obesity results from excessive caloric input associated with overeating and presents a major public health challenge. The hypothalamus has received significant attention for its role in governing feeding behavior and body weight homeostasis. However, extrahypothalamic brain circuits also regulate appetite and consumption by altering sensory perception, motivation, and reward. We recently discovered a population of basal forebrain cholinergic (BFc) neurons that regulate appetite suppression. Through viral tracing methods in the mouse model, we found that BFc neurons densely innervate the basolateral amygdala (BLA), a limbic structure involved in motivated behaviors. Using channelrhodopsin-assisted circuit mapping, we identified cholinergic responses in BLA neurons following BFc circuit manipulations. Furthermore, in vivo acetylcholine sensor and genetically encoded calcium indicator imaging within the BLA (using GACh3 and GCaMP, respectively) revealed selective response patterns of activity during feeding. Finally, through optogenetic manipulations in vivo, we found that increased cholinergic signaling from the BFc to the BLA suppresses appetite and food intake. Together, these data support a model in which cholinergic signaling from the BFc to the BLA directly influences appetite and feeding behavior.

Ventral pallidum neurons projecting to the ventral tegmental area reinforce but do not invigorate reward-seeking behavior.

Reward-predictive cues acquire motivating and reinforcing properties that contribute to the escalation and relapse of drug use in addiction. The ventral pallidum (VP) and ventral tegmental area (VTA) are two key nodes in brain reward circuitry implicated in addiction and cue-driven behavior. In the current study, we use in vivo fiber photometry and optogenetics to record from and manipulate VP→VTA in rats performing a discriminative stimulus task to determine the role these neurons play in invigoration and reinforcement by reward cues. We find that VP→VTA neurons are active during reward consumption and that optogenetic stimulation of these neurons biases choice behavior and is reinforcing. Critically, we find no encoding of reward-seeking vigor, and optogenetic stimulation does not enhance the probability or vigor of reward seeking in response to cues. Our results suggest that VP→VTA activity is more important for reinforcement than for invigoration of reward seeking by cues.

Accelerated neurodegeneration of basal forebrain cholinergic neurons in HIV-1 gp120 transgenic mice: Critical role of the p75 neurotrophin receptor.

Human Immunodeficiency Virus-1 (HIV) infection of the brain induces HIV-associated neurocognitive disorders (HAND). The set of molecular events employed by HIV to drive cognitive impairments in people living with HIV are diverse and remain not completely understood. We have shown that the HIV envelope protein gp120 promotes loss of synapses and decreases performance on cognitive tasks through the p75 neurotrophin receptor (p75NTR). This receptor is abundant on cholinergic neurons of the basal forebrain and contributes to cognitive impairment in various neurological disorders. In this study, we examined cholinergic neurons of gp120 transgenic (gp120tg) mice for signs of degeneration. We observed that the number of choline acetyltransferase-expressing cells is decreased in old (12-14-month-old) gp120tg mice when compared to age matched wild type. In the same animals, we observed an increase in the levels of pro-nerve growth factor, a ligand of p75NTR, as well as a disruption of consolidation of extinction of conditioned fear, a behavior regulated by cholinergic neurons of the basal forebrain. Both biochemical and behavioral outcomes of gp120tg mice were rescued by the deletion of the p75NTR gene, strongly supporting the role that this receptor plays in the neurotoxic effects of gp120. These data indicate that future p75NTR-directed pharmacotherapies could provide an adjunct therapy against synaptic simplification caused by HIV.

Degeneration of the cholinergic system in individuals with subjective cognitive decline: A systematic review.

BACKGROUND: Subjective cognitive decline (SCD) is a risk factor for future cognitive impairment and dementia. It is uncertain whether the neurodegeneration of the cholinergic system is already present in SCD individuals. We aimed to review the current evidence about the association between SCD and biomarkers of degeneration in the cholinergic system. METHOD: Original articles were extracted from three databases: Pubmed, Web of Sciences, and Scopus, in January 2023. Two researchers screened the studies independently. RESULTS: A total of 11 research articles were selected. SCD was mostly based on amnestic cognitive complaints. Cholinergic system biomarkers included neuroimaging markers of basal forebrain volume, functional connectivity, transcranial magnetic stimulation, or biofluid. The evidence showed associations between basal forebrain atrophy, poorer connectivity of the cholinergic system, and SCD CONCLUSIONS: Degenerative changes in the cholinergic system can be present in SCD. Subjective complaints may help when identifying individuals with brain changes that are associated with cognitive impairment. These findings may have important implications in targeting individuals that may benefit from cholinergic-target treatments at very early stages of neurodegenerative diseases.

Role of Basal Forebrain Neurons in Adrenomyeloneuropathy in Mice and Humans.

OBJECTIVE: X-linked adrenoleukodystrophy is caused by mutations in the peroxisomal half-transporter ABCD1. The most common manifestation is adrenomyeloneuropathy, a hereditary spastic paraplegia of adulthood. The present study set out to understand the role of neuronal ABCD1 in mice and humans with adrenomyeloneuropathy. METHODS: Neuronal expression of ABCD1 during development was assessed in mice and humans. ABCD1-deficient mice and human brain tissues were examined for corresponding pathology. Next, we silenced ABCD1 in cholinergic Sh-sy5y neurons to investigate its impact on neuronal function. Finally, we tested adeno-associated virus vector-mediated ABCD1 delivery to the brain in mice with adrenomyeloneuropathy. RESULTS: ABCD1 is highly expressed in neurons located in the periaqueductal gray matter, basal forebrain and hypothalamus. In ABCD1-deficient mice (Abcd1-/y), these structures showed mild accumulations of α-synuclein. Similarly, healthy human controls had high expression of ABCD1 in deep gray nuclei, whereas X-ALD patients showed increased levels of phosphorylated tau, gliosis, and complement activation in those same regions, albeit not to the degree seen in neurodegenerative tauopathies. Silencing ABCD1 in Sh-sy5y neurons impaired expression of functional proteins and decreased acetylcholine levels, similar to observations in plasma of Abcd1-/y mice. Notably, hind limb clasping in Abcd1-/y mice was corrected through transduction of ABCD1 in basal forebrain neurons following intracerebroventricular gene delivery. INTERPRETATION: Our study suggests that the basal forebrain-cortical cholinergic pathway may contribute to dysfunction in adrenomyeloneuropathy. Rescuing peroxisomal transport activity in basal forebrain neurons and supporting glial cells might represent a viable therapeutic strategy. ANN NEUROL 2024;95:442-458.

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.

Microstructural and functional alterations of the ventral pallidum are associated with levodopa-induced dyskinesia in Parkinson's disease.

BACKGROUND AND PURPOSE: The ventral pallidum (VP) regulates involuntary movements, but it is unclear whether the VP regulates the abnormal involuntary movements in Parkinson's disease (PD) patients who have levodopa-induced dyskinesia (LID). To further understand the role of the VP in PD patients with LID (PD-LID), we explored the structural and functional characteristics of the VP in such patients using multimodal magnetic resonance imaging (MRI). METHODS: Thirty-one PD-LID patients, 39 PD patients without LID (PD-nLID), and 28 healthy controls (HCs) underwent T1-weighted MRI, quantitative susceptibility mapping, multi-shell diffusion MRI, and resting-state functional MRI (rs-fMRI). Different measures characterizing the VP were obtained using a region-of-interest-based approach. RESULTS: The left VP in the PD-LID group showed significantly higher intracellular volume fraction (ICVF) and isotropic volume fraction (IsoVF) compared with the PD-nLID and HC groups. Rs-MRI revealed that, compared with the PD-nLID group, the PD-LID group in the medication 'off' state had higher functional connectivity (FC) between the left VP and the left anterior caudate, left middle frontal gyrus and left precentral gyrus, as well as between the right VP and the right posterior ventral putamen and right mediodorsal thalamus. In addition, the ICVF values of the left VP, the FC between the left VP and the left anterior caudate and left middle frontal gyrus were positively correlated with Unified Dyskinesia Rating Scale scores. CONCLUSION: Our multimodal imaging findings show that the microstructural changes of the VP (i.e., the higher ICVF and IsoVF) and the functional change in the ventral striatum-VP-mediodorsal thalamus-cortex network may be associated with pathophysiological mechanisms of PD-LID.

Pontine parabrachial nucleus-basal forebrain circuitry regulating cortical and hippocampal arousal.

INTRODUCTION: The basal forebrain (BF) and the medial septum (MS) respectively drive neuronal activity of cerebral cortex and hippocampus (HPC) in sleep-wake cycle. Our previous studies of lesions and neuronal circuit tracing have shown that the pontine parabrachial nucleus (PB) projections to the BF and MS may be a key circuit for cortical and HPC arousal. AIMS: This study aims to demonstrate that PB projections to the BF and MS activate the cerebral cortex and HPC. RESULTS: By using chemogenetic stimulation of the BF, the PB-BF and the PB-MS pathway combined with electroencephalogram (EEG) Fast Fourier Transformation (FFT) analysis in rats, we demonstrated that chemogenetic stimulation of the BF or PB neurons projecting to the BF activated the cerebral cortex while chemogenetic stimulation of the MS or PB neurons projecting to the MS activated HPC activity, in sleep and wake state. These stimulations did not significantly alter sleep-wake amounts. CONCLUSIONS: Our results support that PB projections to the BF and MS specifically regulating cortical and HPC activity.

Cholinergic basal forebrain system degeneration underlies postural instability/gait difficulty and attention impairment in Parkinson's disease.

BACKGROUND AND PURPOSE: The specific pathophysiological mechanisms underlying postural instability/gait difficulty (PIGD) and cognitive function in Parkinson's disease (PD) remain unclear. Both postural and gait control, as well as cognitive function, are associated with the cholinergic basal forebrain (cBF) system. METHODS: A total of 84 PD patients and 82 normal controls were enrolled. Each participant underwent motor and cognitive assessments. Diffusion tensor imaging was used to detect structural abnormalities in the cBF system. The cBF was segmented using FreeSurfer, and its fiber tract was traced using probabilistic tractography. To provide information on extracellular water accumulation, free-water fraction (FWf) was quantified. FWf in the cBF and its fiber tract, as well as cortical projection density, were extracted for statistical analyses. RESULTS: Patients had significantly higher FWf in the cBF (p < 0.001) and fiber tract (p = 0.021) than normal controls, as well as significantly lower cBF projection in the occipital (p < 0.001), parietal (p < 0.001) and prefrontal cortex (p = 0.005). In patients, a higher FWf in the cBF correlated with worse PIGD score (r = 0.306, p = 0.006) and longer Trail Making Test A time (r = 0.303, p = 0.007). Attentional function (Trail Making Test A) partially mediated the association between FWf in the cBF and PIGD score (indirect effect, a*b = 0.071; total effect, c = 0.256; p = 0.006). CONCLUSIONS: Our findings suggest that degeneration of the cBF system in PD, from the cBF to its fiber tract and cortical projection, plays an important role in cognitive-motor interaction.

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.

The role of amygdala-ventral pallidum pathway in depression-like behaviors in male mice.

The basolateral amygdala (BLA) appears to serve an important function in the pathophysiology of depression. Depressive symptoms, such as anhedonia are largely caused by dysfunction in the brain's reward system, in which the ventral pallidum (VP) participates in by controlling dopamine release. However, the role of the BLA-VP pathway in the development of depression remains poorly understood. To investigate this pathway, we employed the Chronic Unpredictable Mild Stress (CUMS) mouse model, in which we injected retroAAV expressing GFP-Cre into the VP and AAV expressing hM4Di-mCherry into the BLA. We then used CNO to activate the Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) for all behavioral tests. The CUMS procedure resulted in significant depression symptoms such as decreased sucrose preference, limited weight gain, decreased immobile latency, and increased immobile time in the forced swim and tail suspension tests. Inhibition of the BLA-VP glutamatergic projections reversed these depression-like behaviors. We found that suppressing the BLA-VP circuitry had beneficial effects on CUMS-induced depression-like behaviors such as anorexia, anhedonia, and despair. Specifically, upon suppression of glutamatergic projections in the BLA-VP circuitry, these depression-like behaviors were significantly alleviated, which highlights the vital role of this circuitry in the development of depression. Furthermore, the beneficial effects of suppressing this circuitry seem to be associated with the brain's reward system, warranting further investigation.

Basal forebrain cholinergic activity is necessary for upward firing rate homeostasis in the rodent visual cortex.

Bidirectional homeostatic plasticity allows neurons and circuits to maintain stable firing in the face of developmental or learning-induced perturbations. In the primary visual cortex (V1), upward firing rate homeostasis (FRH) only occurs during active wake (AW) and downward during sleep, but how this behavioral state-dependent gating is accomplished is unknown. Here, we focus on how AW enables upward FRH in V1 of juvenile Long Evans rats. A major difference between quiet wake (QW), when upward FRH is absent, and AW, when it is present, is increased cholinergic (ACh) tone, and the main cholinergic projections to V1 arise from the horizontal diagonal band of the basal forebrain (HDB ACh). We therefore chemogenetically inhibited HDB ACh neurons while inducing upward homeostatic compensation using direct activity-suppression in V1. We found that synaptic scaling up and intrinsic homeostatic plasticity, two important cellular mediators of upward FRH, were both impaired when HDB ACh neurons were inhibited. Most strikingly, HDB ACh inhibition flipped the sign of intrinsic plasticity so that it became anti-homeostatic, and this effect was phenocopied by knockdown of the M1 ACh receptor in V1, indicating that this modulation of intrinsic plasticity is the result of direct actions of ACh within V1. Finally, we found that upward FRH induced by visual deprivation was completely prevented by HDB ACh inhibition. Together, our results show that HDB ACh modulation is a key enabler of upward homeostatic plasticity and FRH, and more broadly suggest that neuromodulatory inputs can segregate upward and downward homeostatic plasticity into distinct behavioral states.

Sleep Deficits Inter-Link Lower Basal Forebrain-Posterior Cingulate Connectivity and Perceived Stress and Anxiety Bidirectionally in Young Men.

BACKGROUND: The basal nucleus of Meynert (BNM), a primary source of cholinergic projections to the cortex, plays key roles in regulating the sleep-wake cycle and attention. Sleep deficit is associated with impairment in cognitive and emotional functions. However, whether or how cholinergic circuit, sleep, and cognitive/emotional dysfunction are inter-related remains unclear. METHODS: We curated the Human Connectome Project data and explored BNM resting state functional connectivities (rsFC) in relation to sleep deficit, based on the Pittsburgh Sleep Quality Index (PSQI), cognitive performance, and subjective reports of emotional states in 687 young adults (342 women). Imaging data were processed with published routines and evaluated at a corrected threshold. We assessed the correlation between BNM rsFC, PSQI, and clinical measurements with Pearson regressions and their inter-relationships with mediation analyses. RESULTS: In whole-brain regressions with age and alcohol use severity as covariates, men showed lower BNM rsFC with the posterior cingulate cortex (PCC) in correlation with PSQI score. No clusters were identified in women at the same threshold. Both BNM-PCC rsFC and PSQI score were significantly correlated with anxiety, perceived stress, and neuroticism scores in men. Moreover, mediation analyses showed that PSQI score mediated the relationship between BNM-PCC rsFC and these measures of negative emotions bidirectionally in men. CONCLUSIONS: Sleep deficit is associated with negative emotions and lower BNM rsFC with the PCC. Negative emotional states and BNM-PCC rsFC are bidirectionally related through poor sleep quality. These findings are specific to men, suggesting potential sex differences in the neural circuits regulating sleep and emotional states.

Selective optogenetic modulation of the PBN terminals in the lateral hypothalamic area and basal forebrain regulates emergence from isoflurane anesthesia in mice.

While the mechanism of general anesthesia has been extensively studied, the underlying neural circuitry has yet to be fully understood. The parabrachial nucleus (PBN) plays a crucial role in modulating wakefulness and promoting arousal from general anesthesia. However, the specific role of PBN projections in the process of general anesthesia remains unclear. In this study, we bilaterally injected AAV-associated viruses encoding excitatory or inhibitory optogenetic probes into the PBN and implanted optical fibers in the LH or BF area. After four weeks, we optogenetically activated or inhibited the PBN-LH and PBN-BF pathways under 1.5 vol% isoflurane. We calculated the time it took for anesthesia induction and emergence, simultaneously monitoring changes in the burst-suppression ratio using electroencephalogram recording. Our findings indicate that optogenetic activation of the PBN-LH and PBN-BF projections plays a significant role in promoting both cortical and behavioral emergence from isoflurane inhalation, without significantly affecting the induction time. Conversely, photoinhibition of these pathways prolonged the recovery time, with no notable difference observed during the induction phase.In summary, our results demonstrate that the PBN-LH and PBN-BF pathways are crucial for promoting arousal from isoflurane general anesthesia, but do not have a pronounced impact on the induction phase.

Maternal choline supplementation protects against age-associated cholinergic and GABAergic basal forebrain neuron degeneration in the Ts65Dn mouse model of Down syndrome and Alzheimer's disease.

Down syndrome (DS) is a genetic disorder caused by triplication of human chromosome 21. In addition to intellectual disability, DS is defined by a premature aging phenotype and Alzheimer's disease (AD) neuropathology, including septohippocampal circuit vulnerability and degeneration of basal forebrain cholinergic neurons (BFCNs). The Ts65Dn mouse model recapitulates key aspects of DS/AD pathology, namely age-associated atrophy of BFCNs and cognitive decline in septohippocampal-dependent behavioral tasks. We investigated whether maternal choline supplementation (MCS), a well-tolerated treatment modality, protects vulnerable BFCNs from age- and genotype-associated degeneration in trisomic offspring. We also examined the effect of trisomy, and MCS, on GABAergic basal forebrain parvalbumin neurons (BFPNs), an unexplored neuronal population in this DS model. Unbiased stereological analyses of choline acetyltransferase (ChAT)-immunoreactive BFCNs and parvalbumin-immunoreactive BFPNs were conducted using confocal z-stacks of the medial septal nucleus and the vertical limb of the diagonal band (MSN/VDB) in Ts65Dn mice and disomic (2N) littermates at 3-4 and 10-12 months of age. MCS trisomic offspring displayed significant increases in ChAT-immunoreactive neuron number and density compared to unsupplemented counterparts, as well as increases in the area of the MSN/VDB occupied by ChAT-immunoreactive neuropil. MCS also rescued BFPN number and density in Ts65Dn offspring, a novel rescue of a non-cholinergic cell population. Furthermore, MCS prevented age-associated loss of BFCNs and MSN/VDB regional area in 2N offspring, indicating genotype-independent neuroprotective benefits. These findings demonstrate MCS provides neuroprotection of vulnerable BFCNs and non-cholinergic septohippocampal BFPNs, indicating this modality has translational value as an early life therapy for DS, as well as extending benefits to the aging population at large.