Biology subjects

Hamor, P. U.

Publications and source records attributed to Hamor, P. U..

6 recordsLinked to original sources

bioRxiv2026

Expanding Hippocampal Ensembles through LINE-1 RNA Downregulation Enhances Cognition

Episodic memories are encoded through the activation of small overlapping neuronal ensembles, a coding principle that ensures efficient encoding and high memory capacity. While cellular excitability is known to drive the allocation of select hippocampal neurons into these ensembles, the underlying molecular mechanisms remain elusive. Here, an epigenetic-functional analysis of hippocampal dentate granule cells revealed robust nuclear expression of RNA from autonomous LINE-1 retrotransposons, with significantly lower LINE-1 RNA levels in environmentally activated neurons compared to non-activated counterparts. Knockdown of LINE-1 RNA in the dentate gyrus increased action potential firing capacity and expanded the number of environmentally activated cells, indicating that LINE-1 expression is inversely correlated with ensemble eligibility. LINE-1 RNA knockdown enhanced spatial working memory at the expense of pattern separation, a trade-off consistent with expanded dentate gyrus ensembles and diminished sparse coding. Together, these findings demonstrate that nuclear LINE-1 RNA was co-opted during evolution to control ensemble eligibility in dentate granule cells, a novel postmitotic neuronal function for LINE-1 RNA that restricts ensemble size to preserve sparse coding and support pattern separation.

neuroscience↗

bioRxiv2025

Prenatal adversity configures a subpopulation of ventral dentate granule cells for recruitment to drive innate anxiety

Adverse prenatal environment is a risk factor for the development of psychiatric disorders. Although studies have implicated epigenetic mechanisms, little is known about how epigenomic changes come about and lead to abnormal behaviors in affected individuals. We sought to identify epigenomic and transcriptomic signatures induced by a proinflammatory gestational environment in the ventral dentate gyrus (vDG), a hippocampal region linked to avoidance of threatening contexts, that persist and promote anxiety-like behavior in mice. Here we show that adversity shifted the methylation of enhancers and promoters with intermediate methylation and altered synapse-related gene expression, resulting in epigenetic and transcriptional heterogeneity in the vDG. Exposure to an anxiogenic environment recruited vDG neurons with the most transcriptional alterations. Differentially expressed synapse-relevant genes in ensemble neurons tended to be differentially methylated. Finally, this ensemble exhibited higher activity in threatening than safe environment suggesting a prenatal adversity-induced epigenetic and neurobiological sequence that leads to anxiety.

neuroscience↗

bioRxiv2023

Rapid nongenomic estrogen signaling controls alcohol drinking behavior

Ovarian-derived estrogen is a key modulator of numerous physiological processes via genomic and nongenomic mechanisms, including signaling non-canonically at membrane-associated estrogen receptors in the brain to rapidly regulate neuronal function. However, the mechanisms mediating estrogen regulation of behaviors such as alcohol consumption remain unclear. Early alcohol drinking confers greater risk for alcohol use disorder in women than men, and binge alcohol drinking is correlated with high circulating estrogen levels, but a causal role for estrogen signaling in driving alcohol drinking in gonadally-intact animals has not been established. We found that female mice displayed greater binge alcohol drinking and reduced avoidance behavior when circulating estrogen was high during the proestrus phase of the estrous cycle than when it was low, contributing to sex differences in these behaviors. The pro-drinking, but not anxiolytic, effect of high endogenous estrogen state occurred via rapid estrogen signaling at membrane-associated estrogen receptor alpha in the bed nucleus of the stria terminalis, which promoted synaptic excitation of corticotropin-releasing factor neurons and facilitated their activity during alcohol drinking behavior. This study is the first to demonstrate a rapid, nongenomic signaling mechanism for ovarian-derived estrogen signaling in the brain controlling behavior in gonadally intact females, and it establishes a causal role for estrogen in an intact hormonal context for driving alcohol consumption that contributes to known sex differences in this behavior.

neuroscience↗

bioRxiv2023

Morphine-context associative memory and locomotor sensitization in mice are modulated by sex and context in a dose-dependent manner

Sex differences in opioid use, development of opioid used disorder, and relapse behaviors indicate potential variations in opioid effects between men and women. The locomotor and interoceptive effects of opioids play essential roles in opioid addiction, and uncovering the neural mechanisms underlying these effects remain crucial for developing effective treatments. In this study, we examined the dose-dependent effects of morphine on locomotor sensitization and the strength and stability of morphine-context associations in the conditioned place preference (CPP) paradigm in male and female mice, as well as the relationships between these measures. We observed that while CPP is similar between sexes, the locomotor effects of repeated morphine administration and withdrawal differentially contributed to the strength and stability of morphine-context associations. Specifically, females exhibited higher morphine-induced hyperlocomotion than males regardless of the context in which morphine was experienced. Greater locomotor sensitization to morphine in females than males emerged in a dose-dependent manner only when there was sufficient context information for CPP to be established. Additionally, the relationships between the locomotor effects of morphine and the strength and stability of CPP were different in males and females. In females, positive acute and sensitizing locomotor effects of morphine were correlated with a higher CPP score, while the opposite direction of this relationship was found in males. These results suggest that different aspects of the subjective experience of morphine intoxication and withdrawal are important for morphine abuse-related behaviors and highlight the importance of sex-specific responses in the context of opioid addiction.

neuroscience↗

bioRxiv2023

Valence and salience encoding by parallel circuits from the paraventricular thalamus to the nucleus accumbens

The anterior and posterior subregions of the paraventricular thalamus (aPVT and pPVT, respectively) play unique roles in learned behaviors, from fear conditioning to alcohol/drug intake, potentially through differentially organized projections to limbic brain regions including the nucleus accumbens medial shell (mNAcSh). Here, we found that the aPVT projects broadly to the mNAcSh and that the aPVT-mNAcSh circuit encodes positive valence, such that in vivo manipulations of the circuit modulated both innately programmed and learned behavioral responses to positively and negatively valenced stimuli, particularly in females. Further, the endogenous activity of aPVT presynaptic terminals in the mNAcSh was greater in response to positively than negatively valenced stimuli, and the probability of synaptic glutamate release from aPVT neurons in the mNAcSh was higher in females than males. In contrast, we found that the pPVT-mNAcSh circuit encodes stimulus salience regardless of valence. While pPVT-mNAcSh circuit inhibition suppressed behavioral responses in both sexes, circuit activation increased behavioral responses to stimuli only in males. Our results point to circuit-specific stimulus feature encoding by parallel PVT-mNAcSh circuits that have sex-dependent biases in organization and function.

neuroscience↗

bioRxiv2020

Ceftriaxone and mGlu2/3 interactions in the nucleus accumbens core affect the reinstatement of cocaine-seeking in male and female rats

RationaleThe beta-lactam antibiotic ceftriaxone reliably attenuates the reinstatement of cocaine-seeking. While the restoration of nucleus accumbens core (NA core) GLT-1 expression is necessary for ceftriaxone to attenuate reinstatement, AAV-mediated GLT-1 overexpression is not sufficient to attenuate reinstatement and does not prevent glutamate efflux during reinstatement. AimsHere, we test the hypothesis that ceftriaxone attenuates reinstatement through interactions with glutamate autoreceptors mGlu2 and mGlu3 in the NA core. MethodsMale and female rats self-administered cocaine for 12 days followed by 2-3 weeks of extinction training. During the last 6-10 days of extinction, rats received ceftriaxone (200 mg/kg IP) or vehicle. In experiment 1, rats were killed, and NA core tissue was biotinylated for assessment of total and surface expression of mGlu2 and mGlu3 via western blotting. In experiment 2, we tested the hypothesis that mGlu2/3 signaling is necessary for ceftriaxone to attenuate cue- and cocaine-primed reinstatement by administering bilateral intra-NA core infusion of mGlu2/3 antagonist LY341495 or vehicle immediately prior to reinstatement testing. ResultsmGlu2 expression was reduced by cocaine and restored by ceftriaxone. There were no effects of cocaine or ceftriaxone on mGlu3 expression. We observed no effects of estrus on expression of either protein. The antagonism of mGlu2/3 in the NA core during both cue- and cocaine-primed reinstatement tests prevented ceftriaxone from attenuating reinstatement. ConclusionsThese results indicate that ceftriaxones effects depend on mGlu2/3 function and possibly mGlu2 receptor expression. Future work will test this hypothesis by manipulating mGlu2 expression in pathways that project to the NA core.

neuroscience↗