Publications by authors named "Christopher A Guevara"

Article Synopsis
  • Anxiety is a common non-motor symptom of Parkinson's disease that can begin before noticeable motor symptoms, with a higher prevalence in females despite the disease being more common in males.
  • A study used young adult mice with a specific mutation related to Parkinson's to investigate differences in stress-induced anxiety behaviors between male and female subjects, revealing no baseline differences in anxiety responses.
  • Following chronic stress, male mice showed different responses compared to their wildtype counterparts but female mice exhibited similar anxiety reactions to stress regardless of mutation, highlighting a significant sex-specific difference in how the mutation affects stress-related anxiety behaviors.
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Parkinson's disease (PD) is a multifactorial disease that affects multiple brain systems and circuits. While defined by motor symptoms caused by degeneration of brainstem dopamine neurons, debilitating non-motor abnormalities in fronto-striatal-based cognitive function are common, appear early, and are initially independent of dopamine. Young adult mice expressing the PD-associated G2019S missense mutation in also exhibit deficits in fronto-striatal-based cognitive tasks.

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Anxiety is a psychiatric non-motor symptom of Parkinson's that can appear in the prodromal period, prior to significant loss of brainstem dopamine neurons and motor symptoms. Parkinson's-related anxiety affects females more than males, despite the greater prevalence of Parkinson's in males. How stress, anxiety and Parkinson's are related and the basis for a sex-specific impact of stress in Parkinson's are not clear.

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Unlabelled: Parkinson's (PD) is a multi-factorial disease that affects multiple brain systems and circuits. While defined by motor symptoms caused by degeneration of brainstem dopamine neurons, debilitating non-motor abnormalities in fronto-striatal based cognitive function are common, appear early and are initially independent of dopamine. Young adult mice expressing the PD-associated G2019S missense mutation in also exhibit deficits in fronto-striatal-based cognitive tasks.

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Article Synopsis
  • - The study investigates how prefrontal cortex (PFC) projections develop and affect action-outcome associations in the dorsal striatum of postnatal mice, revealing that PFC axons achieve an adult-like pattern and synaptic strength early in development.
  • - By using Hotspot analysis, researchers found that PFC axons form clusters within the first week after birth, stabilizing over time, while excitatory synapse density continues to increase until adulthood.
  • - Mutant mice lacking the protein Cadherin-8 showed improper PFC axon targeting and reduced synaptic activity, leading to difficulties in action-outcome learning, emphasizing the importance of Cdh8 for the correct formation of these neural pathways.
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Article Synopsis
  • Rational decision-making relies on connections between the prefrontal cortex and the dorsomedial striatum, and disruptions in this projection are linked to various mental health disorders.
  • A study using Hotspot Analysis found that the anatomical positioning of these projections develops early and remains largely stable into adulthood, with steady synapse formation throughout late postnatal development.
  • Mice lacking the adhesion protein Cdh8 showed altered axon terminal positioning and difficulties in learning action-outcome associations, suggesting that early developmental mechanisms play a critical role in the function of corticostriatal connections.
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The estrous cycle is a potent modulator of neuron physiology. In rodents, ventral tegmental area (VTA) dopamine (DA) activity has been shown to fluctuate across the estrous cycle. Although the behavioral effect of fluctuating sex steroids on the reward circuit is well studied in response to drugs of abuse, few studies have focused on the molecular adaptations in the context of stress and motivated social behaviors.

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Clinical evidence suggests that rapid and sustained antidepressant action can be attained with a single exposure to psychedelics. However, the biological substrates and key mediators of psychedelics' enduring action remain unknown. Here, we show that a single administration of the psychedelic DOI produces fast-acting effects on frontal cortex dendritic spine structure and acceleration of fear extinction via the 5-HT receptor.

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Article Synopsis
  • The study investigates how food restriction affects dopamine-mediated learning and reinforcement, using a method called optical intracranial self-stimulation (oICSS) in mice.
  • By genetically altering mice to express channelrhodopsin in midbrain dopamine neurons, researchers were able to observe how light-induced dopamine release influenced self-stimulation behavior in a lever-pressing task.
  • Findings reveal that food restriction leads to quicker acquisition and more vigorous self-stimulation responses, highlighting the impact of dopamine signaling and suggesting that oICSS is a valuable tool for studying reinforcement learning changes related to neuroadaptations.
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Parkinson's disease (PD) is a progressive neurodegenerative disorder that has been recognized for over 200 years by its clinically dominant motor system impairment. There are prominent non-motor symptoms as well, and among these, psychiatric symptoms of depression and anxiety and cognitive impairment are common and can appear earlier than motor symptoms. Although the neurobiology underlying these particular PD-associated non-motor symptoms is not completely understood, the identification of PARK genes that contribute to hereditary and sporadic PD has enabled genetic models in animals that, in turn, have fostered ever deepening analyses of cells, synapses, circuits, and behaviors relevant to non-motor psychiatric and cognitive symptoms of human PD.

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In humans, copy number variations in appear to have sweeping physiological and structural consequences in the brain, either producing or altering the severity of intellectual disability, autism, and schizophrenia. Independently, haploinsufficiency produces intellectual disability and, frequently, autism. Cyfip1 inhibits protein translation and promotes actin polymerization, and SynGAP1 is a synaptically localized Ras/Rap GAP.

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Parkinson's disease (PD) risk is increased by stress and certain gene mutations, including the most prevalent PD-linked mutation -G2019S. Both PD and stress increase risk for psychiatric symptoms, yet it is unclear how PD-risk genes alter neural circuitry in response to stress that may promote psychopathology. Here we show significant differences between adult G2019S knockin and wild-type (wt) mice in stress-induced behaviors, with an unexpected uncoupling of depression-like and hedonia-like responses in G2019S mice.

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