Project description:Cholinergic projection neurons of the nucleus basalis and substantia innominata (NBM/SI) densely innervate the basolateral amygdala (BLA) and have been shown to contribute to the encoding of fundamental and life-threatening experiences. Given the vital importance of these circuits in the acquisition and retention of memories that are essential for survival in a changing environment, it is not surprising that the basic anatomical organization of the NBM/SI is well conserved across animal classes as diverse as teleost and mammal. What is not known is the extent to which the physiology and morphology of NBM/SI neurons have also been conserved. To address this issue, we made patch-clamp recordings from NBM/SI neurons in ex vivo slices of two widely divergent mammalian species, mouse and rhesus macaque, focusing our efforts on cholinergic neurons that project to the BLA. We then reconstructed most of these recorded neurons post hoc to characterize neuronal morphology. We found that rhesus macaque BLA-projecting cholinergic neurons were both more intrinsically excitable and less morphologically compact than their mouse homologs. Combining measurements of 18 physiological features and 13 morphological features, we illustrate the extent of the separation. Although macaque and mouse neurons both exhibited considerable within-group diversity and overlapped with each other on multiple individual metrics, a combined morphoelectric analysis demonstrates that they form two distinct neuronal classes. Given the shared purpose of the circuits in which these neurons participate, this finding raises questions about (and offers constraints on) how these distinct classes result in similar behavior.
Project description:As the frequency of cannabis use by 14-16-year-olds increases, it becomes increasingly important to understand the effect of cannabis on the developing central nervous system. Using mice as a model system, we treated adolescent (28 day old) C57BL6/J mice of both sexes for 3 weeks with 3 mg/kg tetrahydrocannabinol (THC). Starting a week after the last treatment, several cognitive behaviors were analyzed. Mice treated with THC as adolescents acquired proficiency in a working memory task more slowly than vehicle-treated mice. Working memory recall in both sexes of THC-treated mice was also deficient during increasing cognitive load compared to vehicle-treated mice. Our adolescent THC treatment did not strongly affect social preference, anxiety behaviors, or decision-making behaviors on the elevated T maze task. In summary, under the conditions of this study, adolescent THC treatment of mice markedly affected the establishment, and persistence of working memory, while having little effect on decision-making, social preference or anxiety behaviors. This study provides further support that adolescent THC affects specific behavioral domains.
Project description:Differentiation of pluripotent stem cells (PSCs) is a promising approach to obtaining large quantities of skeletal myogenic progenitors for disease modeling and cell-based therapy. However, generating skeletal myogenic cells with high regenerative potential is still challenging. We recently reported that skeletal myogenic progenitors generated from mouse PSC-derived teratomas possess robust regenerative potency. We have also found that teratomas derived from human PSCs contain a skeletal myogenic population. Here, we showed that these human PSC-derived skeletal myogenic progenitors had exceptional engraftability. A combination of cell surface markers, CD82, ERBB3, and NGFR enabled efficient purification of skeletal myogenic progenitors. These cells expressed PAX7 and were able to differentiate into MHC+ multinucleated myotubes. We further discovered that these cells are expandable in vitro. Upon transplantation, the expanded cells formed new dystrophin+ fibers that reconstituted almost ¾ of the total muscle volume, and repopulated the muscle stem cell pool. Our study, therefore, demonstrates the possibility of producing large quantities of engraftable skeletal myogenic cells from human PSCs.
Project description:Alzheimer's disease (AD) represents the most prevalent type of dementia in elderly people, primarily characterized by brain accumulation of beta-amyloid (Aβ) peptides, derived from Amyloid Precursor Protein (APP), in the extracellular space (amyloid plaques) and intracellular deposits of the hyperphosphorylated form of the protein tau (p-tau; tangles or neurofibrillary aggregates). The Nerve growth factor receptor (NGFR/p75NTR) represents a low-affinity receptor for all known mammalians neurotrophins (i.e., proNGF, NGF, BDNF, NT-3 e NT-4/5) and it is involved in pathways that determine both survival and death of neurons. Interestingly, also Aβ peptides can blind to NGFR/p75NTR making it the "ideal" candidate in mediating Aβ-induced neuropathology. In addition to pathogenesis and neuropathology, several data indicated that NGFR/p75NTR could play a key role in AD also from a genetic perspective. Other studies suggested that NGFR/p75NTR could represent a good diagnostic tool, as well as a promising therapeutic target for AD. Here, we comprehensively summarize and review the current experimental evidence on this topic.
Project description:The basal forebrain cholinergic system projects broadly throughout the cortex and constitutes a critical source of neuromodulation for arousal and attention. Traditionally, this system was thought to function diffusely. However, recent studies have revealed a high degree of spatiotemporal specificity in cholinergic signaling. How the organization of cholinergic afferents confers this level of precision remains unknown. Here, using intersectional genetic fate mapping, we demonstrate that cholinergic fibers within the mouse cortex exhibit remarkable laminar and regional specificity and that this is organized in accordance with cellular birthdate. Strikingly, birthdated cholinergic projections within the cortex follow an inside-out pattern of innervation. While early born cholinergic populations target deep layers, late born ones innervate superficial laminae. We also find that birthdate predicts cholinergic innervation patterns within the amygdala, hippocampus, and prefrontal cortex. Our work reveals previously unappreciated specificity within the cholinergic system and the developmental logic by which these circuits are assembled.
Project description:The ventral pallidum (VP) mediates motivated behaviors largely via the action of VP GABA and glutamatergic neurons. In addition to these neuronal subtypes, there is a population of cholinergic projection neurons in the VP, whose functional significance remains unclear. To understand the functional role of VP cholinergic neurons, we first examined behavioral responses to an appetitive (APP) odor that elicited approach, and an aversive (AV) odor that led to avoidance. To examine how VP cholinergic neurons were engaged in APP vs. AV responses, we used an immediate early gene marker and in-vivo fiber photometry, examining the activation profile of VP cholinergic neurons in response to each odor. Exposure to each odor led to an increase in the number of cFos counts and increased calcium signaling of VP cholinergic neurons. Activity and cre-dependent viral vectors were designed to label engaged VP cholinergic neurons in two distinct contexts: (1) exposure to the APP odor, (2) followed by subsequent exposure to the AV odor, and vice versa. These studies revealed two distinct, non-overlapping subpopulations of VP cholinergic neurons: one activated in response to the APP odor, and a second distinct population activated in response to the AV odor. These two subpopulations of VP cholinergic neurons are spatially intermingled within the VP, but show differences in electrophysiological properties, neuronal morphology, and projections to the basolateral amygdala. Although VP cholinergic neurons are engaged in behavioral responses to each odor, VP cholinergic signaling is only required for approach behavior. Indeed, inhibition of VP cholinergic neurons not only blocks approach to the APP odor, but reverses the behavior, leading to active avoidance. Our results highlight the functional heterogeneity of cholinergic projection neurons within the VP. These two subpopulations of VP cholinergic neurons differentially encode valence of olfactory stimuli and play unique roles in approach and avoidance behaviors.
Project description:A fundamental hindrance to building data-driven reduced-order models (ROMs) is the poor topological quality of a low-dimensional data projection. This includes behavior such as overlapping, twisting, or large curvatures or uneven data density that can generate nonuniqueness and steep gradients in quantities of interest (QoIs). Here, we employ an encoder-decoder neural network architecture for dimensionality reduction. We find that nonlinear decoding of projection-dependent QoIs, when embedded in a dimensionality reduction technique, promotes improved low-dimensional representations of complex multiscale and multiphysics datasets. When data projection (encoding) is affected by forcing accurate nonlinear reconstruction of the QoIs (decoding), we minimize nonuniqueness and gradients in representing QoIs on a projection. This in turn leads to enhanced predictive accuracy of a ROM. Our findings are relevant to a variety of disciplines that develop data-driven ROMs of dynamical systems such as reacting flows, plasma physics, atmospheric physics, or computational neuroscience.
Project description:Understanding neural representations of behavioral routines is critical for understanding complex behavior in health and disease. We demonstrate here that accentuated activity of striatal projection neurons (SPNs) at the beginning and end of such behavioral repertoires is a supraordinate representation specifically marking previously rewarded behavioral sequences independent of the individual movements making up the behavior. We recorded spike activity in the striatum and primary motor cortex as individual rats learned specific rewarded lever-press sequences, each one unique to a given rat. Motor cortical neurons mainly responded in relation to specific movements regardless of their sequence of occurrence. By contrast, striatal SPN populations in each rat fired preferentially at the initiation and termination of its acquired sequence. Critically, the SPNs did not exhibit this bracketing signal when the same rats performed unreinforced sequences containing the same sub-movements that were present in their acquired sequence. Thus, the SPN activity was specifically related to a given repetitively reinforced movement sequence. This striatal beginning-and-end activity did not appear to be dependent on motor cortical inputs. However, strikingly, simultaneously recorded fast-spiking striatal interneurons (FSIs) showed equally selective but inverse firing patterns: they fired in between the initiation and termination of the acquired sequences. These findings suggest that the striatum contains networks of neurons representing acquired sequences of behavior at a level of abstraction higher than that of the individual movements making up the sequence. We propose that such SPN-FSI networks of the striatum could underlie the acquisition of chunked behavioral units.
Project description:In this paper, we report the synthesis of a unique silicon(I)-based metalla-disilirane and report on its reactivity toward TMS-azide and benzophenone. Metal complexes containing disilylenes ((bis)silylenes with a Si-Si bond) are known, but direct ligation of the Si(I) centers to transition metals always generated dinuclear species. To overcome this problem, we targeted the formation of a mononuclear iron(0)-silicon(I)-based disilylene complex via templated synthesis, starting with ligation of two Si(II) centers to iron(II), followed by a two-step reduction. The DFT structure of the resulting η2-disilylene-iron complex reveals metal-to-silicon π-back donation and a delocalized three-center-two-electron (3c-2e) aromatic system. The Si(I)-Si(I) bond displays unusual but well-defined reactivity. With TMS-azide, both the initial azide adduct and the follow-up four-membered nitrene complex could be isolated. Reaction with benzophenone led to selective 1,4-addition into the Si-Si bond. This work reveals that selective reactions of Si(I)-Si(I) bonds are made possible by metal ligation.
Project description:The acute effects of ethanol on the neurons of the striatum, a basal ganglia nucleus crucially involved in motor control and action selection, were investigated using whole-cell recordings. An intoxicating concentration of ethanol (50 mM) produced inhibitory effects on striatal large aspiny cholinergic interneurons (LAIs) and low-threshold spike interneurons (LTSIs). These effects persisted in the presence of tetrodotoxin and were because of an increase in potassium currents, including those responsible for medium and slow afterhyperpolarizations. In contrast, fast-spiking interneurons (FSIs) were directly excited by ethanol, which depolarized these neurons through the suppression of potassium currents. Medium spiny neurons (MSNs) became hyperpolarized in the presence of ethanol, but this effect did not persist in the presence of tetrodotoxin and was mimicked and occluded by application of the M1 muscarinic receptor antagonist telenzepine. Ethanol effects on MSNs were also abolished by 100 μM barium. This showed that the hyperpolarizations observed in MSNs were because of decreased tonic activation of M1 muscarinic receptors, resulting in an increase in Kir2 conductances. Evoked GABAergic responses of MSNs were reversibly decreased by ethanol with no change in paired-pulse ratio. Furthermore, ethanol impaired the ability of thalamostriatal inputs to inhibit a subsequent corticostriatal glutamatergic response in MSNs. These results offer the first comprehensive description of the highly cell type-specific effects of ethanol on striatal neurons and provide a cellular basis for the interpretation of ethanol influence on a brain area crucially involved in the motor and decisional impairment caused by this drug.