The basal forebrain, an anatomically heterogeneous brain area containing multiple distinct subregions and neuronal populations, innervates many brain regions including the hippocampus (HIP), a key brain region responsible for learning and memory. Although recent studies have revealed that basal forebrain cholinergic neurons (BFCNs) are involved in olfactory associative learning and memory, the potential neural circuit is not clearly dissected yet. Here, using an anterograde monosynaptic tracing strategy, we revealed that BFCNs in different subregions projected to many brain areas, but with significant differentiations. Our rabies virus retrograde tracing results found that the dorsal HIP (dHIP) received heavy projections from the cholinergic neurons in the nucleus of the horizontal limb of the diagonal band (HDB), magnocellular preoptic nucleus (MCPO), and substantia innominate (SI) brain regions, which are known as the HMS complex (HMSc). Functionally, fiber photometry showed that cholinergic neurons in the HMSc were significantly activated in odor-cued go/no-go discrimination tasks. Moreover, specific depletion of the HMSc cholinergic neurons innervating the dHIP significantly decreased the performance accuracies in odor-cued go/no-go discrimination tasks. Taken together, these studies provided detailed information about the projections of different BFCN subpopulations and revealed that the HMSc-dHIP cholinergic circuit plays a crucial role in regulating olfactory associative learning.

Alzheimer's disease (AD) is a common neurodegenerative disease, neuroinflammation is an early pathological feature of AD. However, the alteration of the immune microenvironment in asymptomatic AD was not fully explained. In this study, we aimed to utilize the transcriptome data of AD patients in public databases to reveal the change of immune microenvironment in asymptomatic AD and screen the potential drug targets. A series of bioinformatics analyses were done, including differentially expressed genes (DEGs) screening, enrichment analysis, PPI network construction, and hub gene identification. Meanwhile, the selected hub genes were validated in APP/PS-1(AD) mice. Importantly, seven enrichment pathways and eight hub genes associated with inflammation were identified in asymptomatic AD. Correspondingly, more hub genes were increased in the hippocampus in AD mice compared to the other four brain regions. Accompanied by the activation of microglia and astrocytes, the inflammatory cytokines were increased in the hippocampus of AD mice. Subsequently, the relationship between HLA-C and inflammation was evaluated in AD mice. HLA-C was correlated with the activation of microglia, and HLA-DRB1 with IL-6 in the hippocampus. Moreover, HLA-C is expressed in the microglia cells and astrocytes. Further, five FDA-approved drugs (Itrazole, Dfo, Syrosingopine, Cefoperazone, and Pradaxa) were predicted as the common drug targeting HLA-C and HLA-DRB1 by molecular docking. Taken together, the results revealed the changes in the immune microenvironment of asymptomatic AD and provided a new perspective for the development of anti-inflammatory drugs for AD early treatment.

The extraorbital lacrimal glands (ELGs) secret tears to maintain a homeostatic environment for ocular surfaces, and pheromones to mediate social interactions. Although its distinct gender-related differences in mice and rats have been identified, its comprehensive histology together with whole-brain neuronal network remain largely unknown. The primary objective of the present study was to investigate whether sex-specific differences take place in histological and physiological perspectives. Morphological and histological data were obtained via magnetic resonance imaging (MRI), hematoxylin-eosin (HE) staining in mice and rats of both genders. The innervating network was visualized by a pseudorabies virus (PRV) mediated retrograde trans-multi-synaptic tracing system for adult C57BL6/J mice of both genders. In terms of ELGs' anatomy, mice and rats across genders both have 7 main lobes, with one exception observed in female rats which have only 5 lobes. Both female rats and mice generally have relatively smaller shape size, absolute weight, and cell size than males. Our viral tracing revealed a similar trend of innervating patterns antero-posteriorly, but significant gender differences were also observed in the hypothalamus (HY), olfactory areas (OLF), and striatum (STR). Brain regions including piriform area (Pir), post-piriform transition area (TR), central amygdalar nucleus (CEA), medial amygdalar nucleus (MEA), lateral hypothalamic area (LHA), parasubthalamic nucleus (PSTN), pontin reticular nucleus (caudal part) (PRNc), and parabrachial nucleus, (PB) were commonly labeled. In addition, chemical isotope labeling-assisted liquid chromatography-mass spectrometry (CIL-LC-MS) and nuclear magnetic resonance spectroscopy (NMR spectroscopy) were performed to reveal the fatty acids and metabolism of the ELGs, reflecting the relationship between pheromone secretion and brain network. Overall, our results revealed basic properties and the input neural networks for ELGs in both genders of mice, providing a structural basis to analyze the diverse functions of ELGs.

Optogenetic manipulation is pivotal in basic neuroscience research and in studying neuropsychiatric disorders, enabling the activation or inhibition of neuronal populations with millisecond precision. However, this technique can induce artificial neuronal hypersynchronization that is rarely observed under physiological conditions. Given that epileptic seizures arise from abnormally synchronized neuronal discharges, the potential for optogenetic stimulation to trigger seizures and confound experimental outcomes warrants close examination. Here, using electrophysiological and behavioral recordings, we demonstrate that even single-trial optogenetic stimulation of CaMKII-positive neurons in the hippocampal CA1 region, anterior piriform cortex (APC), or lateral/medial entorhinal cortex (LEnt or MEnt) can induce seizure-like discharges and behaviors in adult male C57BL/6 mice. Repeated stimulation in the APC, LEnt, or MEnt elicited more severe seizure-like activity. Furthermore, stimulation protocols characterized by high power, long duration, high frequency, and medium pulse width were more prone to inducing such events. Additionally, we found that CA1 stimulation could impair subsequent contextual fear memory. These findings provide critical cautions and practical guidelines for the design and implementation of in vivo optogenetic experiments in neuroscience research.

Alcohol addiction is regarded as a series of dynamic changes to neural circuitries. A comparison of the global network during different stages of alcohol addiction could provide an efficient way to understand the neurobiological basis of addiction. Two animal models (P-rats screened from an alcohol preference family, and NP-rats screened from an alcohol non-preference family) were trained for alcohol preference with a two-bottle free choice method for 4 weeks. To examine the changes in the neural response to alcohol during the development of alcohol preference and acute stimulation, different trials were studied with resting-state fMRI methods during different periods of alcohol preference. The correlation coefficients of 28 regions in the whole brain were calculated, and the results were compared for alcohol preference related to the genetic background/training association. The variety of coherence patterns was highly related to the state and development of alcohol preference. We observed significant special brain connectivity changes during alcohol preference in P-rats. The comparison between the P- and NP-rats highlighted the role of genetic background in alcohol preference. The results of this study support the alterations of the neural network connection during the formation of alcohol preference and confirm that alcohol preference is highly related to the genetic background. This study could provide an effective approach for understanding the neurobiological basis of alcohol addiction.