Biology subjects

Marron Fernandez de Velasco, E.

Publications and source records attributed to Marron Fernandez de Velasco, E..

3 recordsLinked to original sources

bioRxiv2026

AAV-only targeting of ventral tegmental area dopamine neurons for optical self-stimulation studies in mice

Studies employing optogenetic approaches in rodent models have highlighted the important contribution of ventral tegmental area (VTA) dopamine (DA) neurons to reward, learning, and motivation. Selective manipulation of VTA DA neurons is generally achieved in these studies using transgenic mouse or rat lines that express Cre recombinase under the control of a promoter active in DA neurons, combined with intra-VTA infusion of adeno-associated virus (AAV) vectors harboring Cre recombinase-dependent expression cassettes. Reliance on transgenic Cre driver lines is expensive and decreases study efficiency, and available driver lines have unique limitations. Here, we report the development of an AAV-only approach that permits genetic access to VTA DA neurons and can support optogenetic self-stimulation in mice. We used a 2.5 kb fragment of the mouse tyrosine hydroxylase promoter (mTH) to drive Cre expression in VTA DA neurons. Intra-VTA co-infusion of AAV8-mTH-Cre with an AAV vector harboring a Cre-dependent yellow fluorescent protein expression cassette yielded high efficiency (82%) and high fidelity (73%) targeting of tyrosine hydroxylase-positive VTA neurons in C57BL/6J mice. Co-infusion of AAV8-mTH-Cre with a vector harboring a Cre-dependent channelrhodopsin (ChR2) expression cassette permitted optical regulation of VTA neurons with electrophysiological features consistent with VTA DA neurons. Moreover, C57BL/6J mice expressing ChR2 in VTA DA neurons rapidly acquired optical self-stimulation behavior. Thus, this AAV-only approach should facilitate investigation of VTA DA neuron contributions to reward-related behaviors and permit comparative assessments in reward circuit function in inbred and mutant mouse strains.

neuroscience↗

bioRxiv2025

Synaptic Dysfunction and Compensation After NMDA Receptor Ablation in the Mouse Medial Prefrontal Cortex

N-methyl-D-aspartate receptors (NMDARs) in the prefrontal cortex (PFC) are critical regulators of neuronal excitability, synaptic plasticity, and cognitive function. NMDAR disruptions, including pharmacological blockade and anti-NMDAR encephalitis, can mimic symptoms of schizophrenia. These observations support the glutamate hypothesis of schizophrenia, which posits that symptoms arise from abnormal corticolimbic glutamatergic signaling. Further evidence for this theory includes abnormal expression of NMDARs and decreased dendritic spine density in the PFC of individuals with schizophrenia, as well as altered spine density and synaptic transmission caused by genetic manipulation of NMDARs. However, it is unknown how progressive loss of NMDAR function in the PFC during adolescence - a developmental time period associated with significant synaptic pruning and symptom onset in schizophrenia - affects excitatory synaptic structure and function. In this study, we used in vivo genome editing to ablate expression of the Grin1 gene, which encodes the obligate GluN1 subunit of NMDARs, in medial PFC neurons of female and male adolescent mice. We assessed synaptic density and function in layer V pyramidal neurons at multiple time points using whole-cell patch-clamp electrophysiology, integrated with confocal imaging of dendritic spine architecture in recorded neurons. NMDAR ablation caused an early decrease in basilar dendritic spine density, followed by a rebound in spine density and corresponding increase in AMPAR-mediated synaptic transmission, suggesting that synaptic compensation maintains an allostatic set point. Our findings demonstrate that NMDAR ablation initially disrupts local PFC networks, followed by recovery via compensatory processes that could be impaired in disease states.

neuroscience↗

bioRxiv2020

Divergent behavioral consequences of manipulations enhancing pyramidal neuron excitability in the prelimbic cortex

BackgroundDrug-induced neuroadaptations in the prefrontal cortex are thought to underlie impaired executive functions that reinforce addictive behaviors. Repeated cocaine exposure increased layer 5/6 pyramidal neuron excitability in the mouse prelimbic cortex (PL), an adaptation attributable to a suppression of G protein-gated inwardly rectifying K+ (GIRK/Kir3) channel activity. GIRK channel suppression in the PL of drug-naive mice enhanced the motor-stimulatory effect of cocaine. The impact of cocaine on PL GABA neurons, key pyramidal neuron regulators, and the behavioral relevance of increased PL pyramidal neuron excitability, remain unclear. MethodsThe effect of repeated cocaine on mouse layer 5/6 PL GABA neurons was assessed using slice electrophysiology. Adaptations enhancing PL pyramidal neuron excitability were modeled in drug-naive mice using persistent viral Cre ablation and acute chemogenetic approaches. The impact of these manipulations on PL-dependent behavior was assessed in motor activity and trace fear conditioning tests. ResultsRepeated cocaine treatment did not impact GIRK channel activity in, or excitability of, layer 5/6 PL GABA neurons. GIRK channel ablation in PL pyramidal neurons enhanced the motor-stimulatory effect of cocaine but did not impact baseline activity or fear learning. In contrast, direct or indirect chemogenetic activation of PL pyramidal neurons increased baseline and cocaine-induced motor activity and disrupted fear learning. These effects were mirrored by chemogenetic activation of PL pyramidal neurons projecting to the ventral tegmental area. ConclusionsManipulations enhancing the excitability of PL pyramidal neurons, including those projecting to the VTA, recapitulate behavioral hallmarks of repeated cocaine exposure.

neuroscience↗