Biology subjects

Lupica, C. R.

Publications and source records attributed to Lupica, C. R..

6 recordsLinked to original sources

bioRxiv2026

Title: Unilateral loss of tyrosine hydroxylase in adult midbrain dopaminergic neurons reveals reduction to neuregulin1 in rat model of acute dopaminergic dysfunction

Dopamine, produced primarily in the midbrain, is required for movement and reward-based signaling all throughout life. Loss of dopaminergic function can result in changes to motor systems, mood, motivation, and cognition. Dopaminergic cell death or dopaminergic hypofunction are implicated in a variety of diseases including synucleinopathies, neuropsychiatric disorders, and substance use disorders. Loss of dopaminergic neurons (DANs) in the substantia nigra pars compacta (SNpc) and subsequent dysregulation of dopamine signaling in striatum are implicated to varying degrees in all synucleinopathies. By the time patients present with motor symptoms in Parkinson's disease, the most common synucleinopathy, >30% of DANs are lost in the SNpc because of ongoing degeneration for years prior to diagnosis. Studying the early consequences of dopamine loss is critical to understanding mechanisms of dopamine depletion disease progression and identifying biomarkers for earlier diagnosis so that effective treatment can ensue. Here, we created a model of dopamine loss in adult rats to study early transcriptional changes following loss of dopamine synthesis. We used CRISPR to knock out tyrosine hydroxylase (TH), the rate-limiting enzyme for dopamine synthesis, in the adult rat midbrain through injection of Th guide RNAs into transgenic rats expressing Cas9 nuclease specifically in dopamine transporter positive neurons and performed single nucleus RNA sequencing on midbrain and dorsal striatal tissue. Two weeks after injection, we measured a 90% loss of TH and dopamine in the midbrain, but striatal TH and dopamine were unaffected. Despite preceding striatal dopamine loss, our data identified alterations to genes involved in synaptic signaling, organization, and function in both midbrain and striatal neurons. We found the neurotrophic factor, neuregulin1, to be significantly reduced in dopaminergic neurons, which may account for transcriptional changes in surrounding cells that precede detectable reductions to striatal dopamine. These data establish a new rat model of adult TH loss and identify early transcriptional consequences of dopamine loss in the adult midbrain after normal development, providing potential biomarkers for early-stage dopamine loss in PD, synucleinopathies and related disorders of dopamine depletion.

neuroscience↗

bioRxiv2025

Impaired synaptic inhibition and enhanced aversion encoding by lateral habenula neurons during Δ9-tetrahydrocannabinol withdrawal.

The lateral habenula (LHb) integrates cortical and basal forebrain (BF) input to control monoaminergic outflow and is implicated in depression, anxiety, impulsivity, and aversion. Although cannabis withdrawal is associated with negative affect and heightened anxiety, LHb involvement is not established. Here, effects of withdrawal from the psychoactive cannabis constituent {Delta}9-tetrahydrocannabinol ({Delta}9-THC) on LHb neurons were assessed with photometric calcium measurement during fear conditioning and in vitro electrophysiology. LHb calcium signals were larger during footshock, and presentation of a tone paired with footshock in {Delta}9-THC withdrawn rats. Fear-induced freezing to the tone was also larger during {Delta}9-THC withdrawal. Electrophysiology revealed larger LHb excitatory-inhibitory (E-I) ratios during {Delta}9-THC withdrawal, resulting from impaired synaptic GABA release. Moreover, GABA release via optogenetic activation of BF-LHb inputs was impaired during {Delta}9-THC withdrawal, whereas no changes occurred at ventral tegmental area-LHb inputs. Recovery of BF-LHb GABA release and cannabinoid CB1 receptor desensitization were incomplete at 30 days of {Delta}9-THC withdrawal. The data show that LHb responsivity to primary aversive and conditioned stimuli are increased during {Delta}9-THC withdrawal, and that this is likely mediated by altered E-I balance. We propose negative affect experienced during cannabis withdrawal is related to LHb hypersensitivity to aversive stimuli and this facilitates encoding of associated environmental cues.

neuroscience↗

bioRxiv2023

A subtle structural modification of a synthetic cannabinoid receptor agonist drastically increases its efficacy at the CB1 receptor

The emergence of synthetic cannabinoid receptor agonists (SCRAs) as illicit psychoactive substances has posed considerable public health risks that include fatalities. Many SCRAs exhibit much higher efficacy and potency, compared with the phytocannabinoid {Delta}9-tetrahydrocannabinol (THC), at the cannabinoid receptor 1 (CB1R), a G protein-coupled receptor involved in modulating neurotransmitter release. In this study, we investigated structure activity relationships (SAR) of aminoalkylindole SCRAs at CB1Rs, focusing on 5F-pentylindoles containing an amide linker attached to different head moieties. Using in vitro bioluminescence resonance energy transfer (BRET) assays, we identified a few of SCRAs exhibiting significantly higher efficacy in engaging the Gi protein and recruiting {beta}-arrestin than the reference CB1R full agonist CP55940. Importantly, adding a methyl group at the head moiety of 5F-MMB-PICA yielded 5F-MDMB-PICA, an agonist exhibiting a large increase in efficacy and potency at the CB1R. This pharmacological observation was supported by a functional assay of the effects of these SCRAs on glutamate field potentials recorded in hippocampal slices. Molecular modeling and simulations of the CB1R bound with either of the SCRAs revealed critical structural determinants contributing to the higher efficacy of 5F-MDMB-PICA, and how these subtle differences propagated to the receptor-G protein interface. Thus, we find that apparently minor structural changes in the head moiety of SCRAs can cause major changes in efficacy. Our results highlight the need for close monitoring of structural modifications of newly emerging SCRAs and their potential for toxic drug responses in humans.

pharmacology and toxicology↗

bioRxiv2021

Stress deceleration theory: chronic adolescent stress exposure results in decelerated neurobehavioral maturation

Normative development in adolescence indicates that the prefrontal cortex is still under development thereby unable to exert efficient top-down inhibitory control on subcortical regions such as the basolateral amygdala and the nucleus accumbens. This imbalance in the developmental trajectory between cortical and subcortical regions is implicated in expression of the prototypical impulsive, compulsive, reward seeking and risk-taking adolescent behavior. Here we demonstrate that a chronic mild unpredictable stress procedure during adolescence in male Wistar rats arrests the normal behavioral maturation such that they continue to express adolescent-like impulsive, hyperactive, and compulsive behaviors into late adulthood. This arrest in behavioral maturation is associated with the hypoexcitability of prelimbic cortex (PLC) pyramidal neurons and reduced PLC-mediated synaptic glutamatergic control of BLA and nucleus accumbens core (NAcC) neurons that lasts late into adulthood. At the same time stress exposure in adolescence results in the hyperexcitability of the BLA pyramidal neurons sending stronger glutamatergic projections to the NAcC. Chemogenetic reversal of the PLC hypoexcitability decreased compulsivity and improved the expression of goal-directed behavior in rats exposed to stress during adolescence, suggesting a causal role for PLC hypoexcitability in this stress-induced arrested behavioral development.

neuroscience↗

bioRxiv2021

Reversing anterior insular cortex neuronal hypoexcitability attenuates compulsive behavior in juvenile rats

Development of self-regulatory competencies during adolescence is partially dependent on normative brain maturation. Here we report that juvenile rats as compared to adults exhibit impulsive and compulsive-like behavioral traits, the latter being associated with lower expression of mRNA levels of the immediate early gene zif268 in the anterior insula (AI). This observation suggests that deficits in AI function in juvenile rats could explain their immature pattern of interoceptive cue integration in rational decision-making and compulsive phenotype. In support of this, here we report hypoexcitability of juvenile layer-V pyramidal neurons in the AI, concomitant with reduced glutamatergic synaptic input to these cells. Chemogenetic activation of the AI attenuated the compulsive trait suggesting that delayed maturation of the AI results in suboptimal integration of sensory and cognitive information in adolescents and this contributes to inflexible behaviors in specific conditions of reward availability.

neuroscience↗

bioRxiv2021

Lateral habenula M2 muscarinic receptor control of neuronal activity and cocaine seeking behavior

The lateral habenula (LHb) plays a central role in balancing reward and aversion by opposing the contributions of brain reward nuclei. Using a rat cocaine self-administration model, we previously found that LHb inhibition or non-selective blockade of LHb muscarinic acetylcholine receptors (mAChRs) led to persistent cocaine seeking despite its signaled unavailability. As understanding roles for the LHb and cholinergic signaling in behavioral control is important to psychiatric illness and addiction, we examine how mAChRs act on LHb neurons using in vitro electrophysiology. We find that different groups of LHb neurons are depolarized or hyperpolarized by the cholinergic agonist carbachol (CCh), and that CCh could inhibit GABAergic and glutamatergic synaptic inputs to these cells. Presynaptic CCh effects were reversed by the M2 mAChR (M2R) antagonist AFDX-116, but not by pirenzepine, an M1R antagonist. Contemporaneous measurement of CCh effects on synaptic inhibition and excitation in LHb neurons showed a smaller effect on inhibition, suggesting a net shift in synaptic integration toward greater inhibition by mAChRs. Synaptic currents elicited by light-activation of ventral tegmental area (VTA) axons in the LHb, following channelrhodopsin-2 transfection of VTA, were also inhibited by M2Rs, suggesting the VTA as at least one M2R-sensitive LHb afferent. Finally, Go-NoGo cocaine seeking studies showed that blockade of LHb M2Rs, and not M1Rs, triggered continued cocaine seeking. These data identify LHb M2Rs as a potential control point of LHb function that enables withholding responses for cocaine and define cellular mechanisms through which mAChRs modulate LHb activity.

neuroscience↗