Biology subjects

TADROSS, M. R.

Publications and source records attributed to TADROSS, M. R..

4 recordsLinked to original sources

bioRxiv2026

Connectomic dopamine-neuron disinhibition accelerates behavioral extinction

Animals must balance persistence with flexibility when outcomes change. Behavioral extinction--the reduction in responding to cues that no longer predict reward--is widely thought to be driven by pauses in dopamine-neuron firing upon omission of expected rewards. However, whether these pauses are necessary remains unknown. We used a connectomic intervention to weaken inhibitory synapses onto dopamine neurons in the ventral tegmental area, attenuating electrophysiologically defined pauses while sparing tonic and burst firing. Contrary to canonical accounts, this intervention accelerated rather than delayed behavioral extinction, demonstrating that these synapses normally postpone behavioral extinction. Learning about a newly rewarded cue was spared, arguing against a general disruption of learning. Dopamine photometry showed that the intervention attenuated reward-omission dopamine dips, whose dissipation preceded and predicted behavioral extinction across mice. These findings show that pause-generating inhibitory inputs to dopamine neurons sustain behavioral persistence. This mechanism may protect established associations from premature abandonment as outcomes fluctuate.

neuroscience↗

bioRxiv2026

Subunit selective modulation of GABAA receptors using pharmacogenetically tethered neurosteroids

Neurosteroids are powerful endogenous modulators of inhibition and emerging therapeutics for anxiety, epilepsy, and mood disorders, yet their actions at defined receptor subtypes and within specific neuronal populations remain poorly resolved. Here, we engineer a neurosteroid DART (Drug Acutely Restricted by Tethering) platform to deliver neuroactive steroid (NAS) activity with cellular precision and receptor-subunit selectivity. From a screen of seventeen NAS analogs, we identified seven scaffolds suitable for further engineering, and we discovered that linker attachment at the steroid C11 position uniquely preserves NAS positive allosteric modulation of GABAA receptors, whereas C2 and C17 attachment abolished activity. C11-linked NAS-DARTs slowed IPSC decay kinetics and showed variable off-target modulation of NMDA and AMPA EPSCs. The lead DART compound, YX85.1DART.2, enhanced GABA-evoked currents in neurons expressing engineered 4/{delta}-containing GABAA receptors but spared {gamma}2-containing receptors. A complementary benzodiazepine DART BZP.1DART.2 showed the opposite selectivity. Together, these tools enable cell-restricted, subunit-resolved interrogation of neurosteroid action on inhibitory microcircuits and provide a strategy to dissect how distinct GABAA receptor subclasses contribute to circuit function and therapeutic outcomes.

neuroscience↗

bioRxiv2024

Reward perseveration is shaped by GABAA-mediated dopamine pauses

When animals unexpectedly fail, their dopamine neurons undergo phasic inhibition that canonically drives extinction learning--a cognitive-flexibility mechanism for discarding outdated strategies. However, the existing evidence equates natural and artificial phasic inhibition, despite their spatiotemporal differences. Addressing this gap, we targeted a GABAA-receptor antagonist precisely to dopamine neurons, yielding three unexpected findings. First, this intervention blocked natural phasic inhibition selectively, leaving tonic activity unaffected. Second, blocking natural phasic inhibition accelerated extinction learning--opposite to canonical mechanisms. Third, our approach selectively benefitted perseverative mice, restoring rapid extinction without affecting new reward learning. Our findings reveal that extinction learning is rapid by default and slowed by natural phasic inhibition--challenging foundational learning theories, while delineating a synaptic mechanism and therapeutic target for cognitive rigidity.

neuroscience↗

bioRxiv2022

Thousandfold Cell-Specific Pharmacology of Neurotransmission

Cell-specific pharmaceutical technologies promise mechanistic insight into clinical drugs[-]those that treat, and often define, human disease. In particular, DART (drug acutely restricted by tethering) achieves genetically programmable control of drug concentration over cellular dimensions. The method is compatible with clinical pharmaceuticals and amenable to studies in behaving animals. Here, we describe DART.2, comprising three advances. First, we improve the efficiency of chemical capture, enabling cell-specific accumulation of drug to [~]3,000-times the ambient concentration in 15 min. Second, we develop tracer reagents, providing a behavior-independent measure of cellular target engagement in each animal. Third, we extend the method to positive allosteric modulators and outline design principles for this clinically significant class. We showcase the platform with four pharmaceuticals[-]two that weaken excitatory (AMPAR) or inhibitory (GABAAR) chemical neurotransmission, and two that strengthen these forms of synaptic communication. Across four labs, we tested reagents in the mouse cerebellum, basal ganglia, visual cortex, and retina. Collectively, we demonstrate robust, bidirectional editing of chemical neurotransmission. We provide for distribution of validated reagents, community design principles, and synthetic building blocks for application to diverse pharmaceuticals.

neuroscience↗