Alexandre Mourot

Nicotinic acetylcholine receptors shape diverse brain functions, including reward, aversion, and pain, but dissecting their roles in vivo requires drug delivery with spatiotemporal precision that conventional pharmacology cannot provide. Here we establish in vivo photopharmacology of endogenous nicotinic receptors: two complementary highly-potent agonists, administered systemically in an inactive caged form, are photoreleased locally in target brain circuits of behaving wild-type mice. Despite irreversible photochemistry, photoactivation can be repeated over many trials on a minute timescale, for hours following a single injection. Local uncaging evokes circuit-specific dopamine release, drives place preference from the ventral tegmental area and aversion from the interpeduncular nucleus, and, in pain circuits, reveals a pronociceptive effect masked when the same agonists are given systemically. By controlling where and when nicotinic signaling acts, this approach exposes circuit-specific drug effects invisible to conventional pharmacology, and outlines a general strategy for on-demand control of endogenous receptors in vivo .

Photopharmacology, which enables the precise optical control of endogenous receptor activity, represents a powerful approach in neuroscience. However, photochromic diffusible ligands often exhibit limited subtype specificity, while alternative strategies for controlling specific receptor subtypes require genetic modification. Here, to achieve high subtype selectivity without the need of receptor engineering, we introduce a genetically independent strategy for optical control of endogenous receptors based on highly selective and chemically defined photoswitchable nanobodies. By covalently coupling a light-sensitive azobenzene agonist to a high-affinity nanobody targeting α7 nicotinic acetylcholine receptor (nAChR), we engineered MalAzoCh-C4, an optonanobody that confers reversible, light-dependent activation of native α7 receptors. In Xenopus oocytes, MalAzoCh-C4 enables wavelength-controlled modulation of recombinant α7 receptors, with enhanced activity in trans configuration. In acute hippocampal slices, application of MalAzoCh-C4 produces robust photocontrol of endogenous α7 nAChRs in interneurons, sufficient to modulate action potential firing. This strategy combines nanobody specificity with the temporal resolution of photopharmacology, establishing optonanobodies as a platform for control of native neuronal receptors.

Social organization and division of labour are fundamental to animal societies^1,2,3, yet how these structures emerge from individual interactions and are shaped by neuromodulation remains unclear. Here, using behavioural tracking in a semi-natural environment, neural recordings and computational models that integrate reinforcement learning and social condition, we show that triads of isogenic mice develop specialized roles spontaneously while solving a foraging task under social constraints. Notably, despite minor intra-sex differences in behaviour when mice were tested alone, male triads formed stable worker–scrounger relationships driven by competition, whereas female triads adopted uniform, cooperative strategies. These sex-divergent roles were shaped by dopaminergic activity in the ventral tegmental area. Model analysis revealed how intra-sex and inter-sex parameter differences in resource exploitation, combined with contingent social interactions, drive behavioural specialization and division of labour. Most notably, it highlighted how contingency, amplified by competition, magnifies individual differences and shapes social profiles. The plastic, adaptive nature of social organization was apparent when sex mixing or reintroducing experienced individuals into naive groups reshaped role distribution. Furthermore, dopaminergic manipulations confirmed this plasticity, reshaping roles and altering group structure. Our findings support a multi-scale feedback loop whereby social context shapes neural states, which in turn reinforce behavioural specialization and stabilize social structures.

Photopharmacology which enables the precise optical control of endogenous receptor activity, represents a powerful approach in neuroscience. However, photochromic diffusible ligands often exhibit limited subtype specificity, while alternative strategies for controlling specific receptor subtypes require genetic modification. Here, to achieve high subtype selectivity without the need of receptor engineering, we introduce a genetically independent strategy for optical control of endogenous receptors based on highly selective and chemically-defined photoswitchable nanobodies. By covalently coupling a light-sensitive azobenzene agonist to a high-affinity nanobody targeting α7 nicotinic acetylcholine receptor (nAChR), we engineered MalAzoCh-C4, an optonanobody that confers reversible, light-dependent activation of native α7 receptors. In Xenopus oocytes, MalAzoCh-C4 enables wavelength-controlled modulation of recombinant α7 receptors, with enhanced activity in trans configuration. In acute hippocampal slices, application of MalAzoCh-C4 produces robust photocontrol of endogenous α7 nAChRs in interneurons, sufficient to modulate action potential firing. This strategy combines nanobody specificity with the temporal resolution of photopharmacology, establishing optonanobodies as a platform for control of native neuronal receptors.

The medial habenula–interpeduncular nucleus pathway is a highly conserved and densely innervated brain circuit known for its unique cholinergic transmission and exceptional expression of nicotinic acetylcholine receptors. This pathway plays a critical role in regulating motivational and emotional processes, particularly those related to nicotine consumption, avoidance behaviors, and negative emotional states. Recent advances have revealed the intricate cellular architecture and receptor diversity of this system, highlighting how specific subunits of acetylcholine receptors influence both the rewarding and aversive properties of nicotine. Genetic and functional studies in rodents and humans point to this pathway as a key regulator of nicotine intake, with potential implications for addiction treatment. In this review, we examine the organization and molecular composition of nicotinic receptors within this pathway, describe their functional and behavioral roles, and explore how cholinergic signaling contributes to nicotine dependence, stress responses, and affective states.

The medial habenula to interpeduncular nucleus pathway is a highly conserved and densely innervated brain circuit known for its unique cholinergic transmission and exceptional expression of nicotinic acetylcholine receptors. This pathway plays a critical role in regulating motivational and emotional processes, particularly those related to nicotine consumption, avoidance behaviors, and negative emotional states. Recent advances have revealed the intricate cellular architecture and receptor diversity of this system, highlighting how specific subunits of acetylcholine receptors influence both the rewarding and aversive properties of nicotine. Genetic and functional studies in rodents and humans point to this pathway as a key regulator of nicotine intake, with potential implications for addiction treatment. In this review, we examine the organization and molecular composition of nicotinic receptors within this pathway, describe their functional and behavioral roles, and explore how cholinergic signaling contributes to nicotine dependence, stress responses, and affective states.

Nicotine activates ventral tegmental area (VTA) dopaminergic (DA) neurons projecting to the nucleus accumbens (NAc) to drive its reinforcing effects. Simultaneously, nicotine inhibits those projecting to the amygdala (Amg) to mediate anxiety-like behavior through a process that remains unknown. Here, we show that in male mice, NAc- and Amg-projecting DA neurons respond with similar polarities to ethanol and nicotine, suggesting a shared network-based mechanism underlying the inhibitory effect of these otherwise pharmacologically-distinct drugs. Selective activation of NAc-projecting DA neurons, using genetic or optogenetic strategies, produced inhibition of Amg-projecting DA neurons, through a GABAergic feedback loop. Furthermore, optogenetically silencing this feedback loop prevented nicotine from inducing both inhibition of DA neurons and anxiety-like behavior. Therefore, nicotine-induced inhibition of the VTA-Amg DA pathway results from a VTA-NAc inhibitory feedback loop, mediating anxiety-like behavior.

Summary: Social organization and division of labor are fundamental to animal societies, but how do these structures emerge from individual interactions, and what role does neuromodulation play in shaping them? Using behavioral tracking in a semi-natural environment, neural recordings, and computational models integrating reinforcement and social learning, we show that groups of three isogenic mice spontaneously develop specialized roles while solving a foraging task requiring individual decisions under social constraints. Moreover, these roles are shaped by dopaminergic activity in the ventral tegmental area. Strikingly, despite minor sex-differences in behavior when mice were tested alone, male triads formed stable worker-scrounger relationships driven by competition, whereas female triads adopted uniform, cooperative strategies. Model analysis revealed how intra- and inter-sex parameter differences in resource exploitation, combined with contingent and dynamic social interactions, drive behavioral specialization and labor division. Most notably, it highlighted how contingency, amplified by competition, magnifies individual differences and shapes social profiles. The plastic, adaptive nature of social organization within triads was confirmed by manipulating dopaminergic cell activity, which reshaped social roles and altered group structure. Our findings support a feedback loop where social context shapes neural states, which in turn reinforce behavioral specialization and stabilize social structures.