Although 17β-estradiol (E 2 ) is a critical neuromodulator of hippocampus-dependent memory and synaptic plasticity, the molecular mechanisms underlying these effects remain incompletely understood. Previous studies showed that E 2 enhances dorsal hippocampus-dependent memory consolidation by activating signaling pathways that promote protein synthesis and dendritic spine formation. However, these studies largely overlooked the contribution of protein degradation mediated by the ubiquitin proteasome system (UPS), despite extensive evidence implicating UPS activity in long-term memory and synaptic plasticity. Here, we combined temporally specific dorsal hippocampal infusions of the proteasome inhibitor β-lactone with three-dimensional spine morphometry to examine the role of UPS-mediated protein degradation in E 2 -induced memory consolidation and CA1 spinogenesis. Immediate post-training bilateral infusion of β-lactone into the dorsal hippocampus of ovariectomized female mice blocked E 2 -induced enhancement of object recognition memory and attenuated E 2 -associated improvements in spatial memory. Arbor-wide Golgi-based analyses revealed robust E 2 -induced increases in spine number across the apical dendritic tree and smaller parallel effects within the basal arbor. Segment-level analyses showed that E 2 produced the greatest structural changes on tertiary apical dendritic segments, increasing total, mushroom, and thin spine density and enhancing multiple morphometric features, including mushroom spine surface area and head-to-neck ratio. Secondary basal dendritic segments exhibited smaller, more variable changes. Many E 2 -associated structural effects were attenuated or abolished by β-lactone. Together, these findings provide the first evidence that proteasomal protein degradation contributes to estrogenic enhancement of hippocampus-dependent memory and CA1 dendritic spine remodeling, identifying UPS-mediated protein degradation as a previously unrecognized mechanism regulating estrogenic memory consolidation and structural plasticity. Significance Statement 17β-estradiol (E 2 ) rapidly enhances hippocampal memory consolidation and promotes CA1 dendritic spinogenesis, yet the molecular mechanisms that support these effects remain unclear. Here, we combine temporally specific dorsal hippocampal proteasome inhibition with three-dimensional Golgi-based spine analyses to show that proteasomal protein degradation is required for E 2 -induced enhancement of object recognition memory and contributes to E 2 -associated improvements in spatial memory in ovariectomized female mice. We further demonstrate that proteasome activity contributes to E 2 -induced increases in apical CA1 spine density and morphology. These findings reveal new insights into estrogenic modulation of cognition that may provide novel protein targets whose levels could be regulated to reduce memory dysfunction related to menopause, depression, and other conditions for which women are at greater risk.
The aperiodic, 1/f-like component of electrophysiological activity is increasingly recognized as a meaningful feature of neural function rather than background noise. Meanwhile, many EEG studies interpret transient post-stimulus changes in oscillatory power as signatures of attention, salience, or cognitive control. Such interpretations typically depend on baseline normalization, which assumes aperiodic activity remains stable from pre- to post-stimulus periods. Using high-density EEG from typically developing children, we tested this assumption across two paradigms: an audiovisual simple reaction-time task (n = 36, 19 males and 17 females) and a visual oddball task (n = 38, 20 males and 18 females). In each, conventional spectral analyses were compared with analyses that explicitly modeled and removed aperiodic activity in both windows. Across tasks, stimulus onset produced robust increases in aperiodic exponent and offset, indicating systematic 1/f changes. In the audiovisual task these were modality-specific, with central, parieto-occipital, or combined topographies by stimulus type. They diminished but persisted after ERP removal, suggesting they were not fully explained by phase-locked activity. Critically, once aperiodic activity was accounted for, the apparent theta increase was largely abolished in both tasks, including the canonical fronto-central enhancement to infrequent targets. The conventional method also overestimated beta desynchronization, especially in the induced signal, indicating a spurious consequence of spectral slope steepening. By contrast, alpha desynchronization remained robust and was enhanced, reflecting genuine suppression. Together, these findings suggest many conventional time-frequency effects, particularly apparent theta synchronization, may reflect stimulus-driven aperiodic changes rather than robust narrowband changes, challenging core assumptions of these analyses. Significance statement Frequency-domain neural activity comprises both narrowband oscillations and broadband aperiodic activity. Conventional time–frequency analyses use baseline normalization to isolate oscillatory responses, implicitly assuming that aperiodic activity remains stable following stimulus onset. Across two EEG paradigms, we show that stimulus presentation systematically alters aperiodic activity in a sensory- and attention-dependent manner. These changes can produce apparent increases in theta-band power that do not reflect genuine narrowband oscillations and can exaggerate beta desynchronization. In contrast, alpha desynchronization remained robust after accounting for aperiodic activity. These findings demonstrate that stimulus-related aperiodic changes can substantially influence conventional time–frequency measures and should be explicitly considered when interpreting post-stimulus oscillatory responses.
The central melanocortin system is crucial for controlling food intake and metabolism. It includes neurons that produce pro-opiomelanocortin (POMC), a prohormone that generates the melanocortin receptor (MCR) agonist alpha-melanocyte-stimulating hormone (α-MSH), and neurons that produce agouti-related protein (AgRP), an endogenous MCR antagonist. This system also influences neuroendocrine neurons, thereby impacting pituitary hormone secretion. However, it remains unclear whether the central melanocortin system also modulates growth hormone (GH) secretion. Here we showed that arcuate nucleus (ARH) GH-releasing hormone (GHRH) neurons receive inputs from α-MSH and AgRP axons. α-MSH activates a subset (∼25%) of ARH GHRH neurons. Serial blood GH measurements were taken before and after systemic saline or clozapine N-oxide injections in mice expressing the excitatory hM3Dq-Gq receptor in POMC-expressing cells. Activation of POMC-expressing cells elevated blood GH levels compared with baseline or saline-injected mice, in both males and females. To determine whether AgRP neurons inhibit GH secretion, mice expressing the hM3Dq-Gq receptor simultaneously in AgRP- and GHRH-expressing cells were created. While chemogenetic activation of GHRH neurons caused a strong GH secretion, co-activation of AgRP neurons inhibited this response in both sexes. Additionally, Fos expression in GHRH-activated neurons was blunted when AgRP neurons were co-stimulated. Mice expressing the hM3Dq-Gq receptor only in MC4R-expressing cells were also investigated; however, activation of MC4R neurons did not alter GH levels. In conclusion, the central melanocortin system modulates the activity of GHRH neurons and GH secretion possibly through MC4R-independent pathways. These findings highlight a critical hypothalamic neurocircuit that integrates metabolic cues to regulate the somatotropic axis. Significance Statement The central melanocortin system processes both short- and long-term nutritional signals to regulate metabolism and various neuroendocrine axes. Here, we show that growth hormone (GH) secretion is controlled by hypothalamic neurons of the central melanocortin system, including populations that express POMC and AgRP. This regulation occurs, at least in part, through modulation of GH-releasing hormone neuron activity, a key group of cells that control pituitary GH secretion. Overall, these findings reveal a hypothalamic circuit that links nutritional status to the regulation of the GH axis, providing new insights into how growth is adaptively controlled by energy availability.
Nestin-Cre is the most widely used Cre driver for conditional genetic manipulation in the central nervous system (CNS), underpinning hundreds of studies in neurodevelopment, lineage tracing, brain tumor modeling, and circuit analysis. Despite its dominant role, divergent recombination outcomes-spanning developmental onset, penetrance, mosaicism, and ectopic activity-are frequently reported, creating substantial interpretive challenges across the field. Here we provide a practical guide to selecting and using Nestin-Cre and Nestin-CreER(T2) mouse lines for CNS research. We systematically examine 22 independently generated lines (1996-2025), synthesizing data from >400 published studies. Rather than cataloguing line histories, we organize this knowledge around the decisions experimentalists actually face: whether to use a constitutive or inducible system, which lines best target specific CNS compartments and developmental windows, and how to achieve uniform versus sparse recombination. We show that reported variability is not an intrinsic limitation of Nestin-based drivers but arises from definable, controllable factors-construct architecture, transgene integration context, reporter sensitivity, breeding configuration, and, for inducible systems, tamoxifen formulation and dosing. Each factor is addressed with specific guidance. For inducible lines, we provide a comparative ranking of recombination efficiency against background leakiness to inform line selection. We highlight breeding strategy as a critical and frequently mismanaged variable, discuss Cre-dosage effects on neural progenitor survival, and address reporter-dependent differences in apparent recombination efficiency. Together, this TechSight article offers a consolidated, decision-oriented framework for reproducible CNS-targeted genetic experiments, converts the thesis into bench practice, and reduces wasted cohorts.
