Mating proximity blinds threat perception

Animals constantly balance opportunities and risks, yet the neural mechanisms that resolve conflict between survival and reproduction remain unclear. Courtship is a key context in which the trade-off is acute: avoiding threats can save life, but excessive caution may forfeit mating opportunities. Prior work identified partially separate neural substrates for sex drive and threat avoidance across species, but how these competing needs are prioritized during conflict is unknown. Dopamine is implicated in motivation, reward, and the valuation of sensory input, suggesting a role in dynamically modulating sensory valence and decision-making. The authors hypothesized that a state-dependent sensory filter could shut down competing sensory inputs as animals near a crucial goal. They set out to define how, in male Drosophila, neural circuits prioritize between courtship and escape, and whether dopaminergic signalling filters threat perception based on proximity to mating.

The study builds on a broad literature on risk–reward trade-offs in humans, rodents, fish, and invertebrates, and on Drosophila circuits for courtship and threat detection. Previous work showed: (1) separate signalling of sex drive and threat avoidance; (2) dopamine’s roles in reward prediction, motivation, and state-dependent modulation of sensory processing; (3) serotonergic involvement in stress and predator-associated responses in vertebrates; and (4) visual projection neurons (e.g., lobular columnar LC cells) linking visual features such as looming to behavior. Prior Drosophila studies identified P1 as a central courtship hub, plP10 descending neurons as essential for courtship song, and state-dependent gating of visual processing by sexual arousal. Mammalian literature reports dopaminergic ramping as goal proximity increases. These studies motivated testing whether dopaminergic ramping with courtship progress could act as a sensory filter to down-weight threats when mating is imminent.

• Established a sex–danger conflict assay: courting male Drosophila paired with an immobile virgin female were challenged with a predator-like moving shadow visual threat. Defensive behaviors and courtship indices were quantified.
• Genetic manipulations of visual projection neurons LC16: synaptic silencing with UAS-TNT; optogenetic activation with CsChrimson; in vivo two-photon calcium imaging (GCaMP6f) of LC16 responses to threats and control stimuli.
• Identified serotonergic neurons implicated in threat responses using TRH-GAL4 and a split-GAL4 (TRHR23E12) targeting the posterior medial dorsal (PMPD) cluster. Manipulations included pan-5-HT neuron silencing and TRH RNAi; TRHR23E12>TNT or TRH knockdown; optogenetic activation (CsChrimson); and GCaMP6s imaging in 5-HTPMPD neurons. Assessed solitary and courting males.
• Tested central courtship nodes: optogenetic activation of P1 neurons to assess override of threat; receptor-specific RNAi in P1 (5-HT1, 5-HT1A, 5-HT1B, 5-HT2B) and G protein knockdowns (Gαi, Gαo) to determine inhibitory mechanisms; ex vivo bath application of 100 μM 5-HT during P1 calcium imaging.
• Examined plP10 descending neurons: optogenetic activation (to test sufficiency to sustain courtship), optogenetic inhibition (GtACR1) to suppress courtship; receptor RNAi screens in plP10 with focus on 5-HT2B; calcium imaging with 100 μM 5-HT; G protein knockdown tests (Gαi vs Gαo).
• Stage-dependent behavioral assays: delivered visual threats at early (≈7–30 s), middle (≈120 s), and late (≈240 s) courtship; analyzed dependence on advanced steps (abdomen bending). Manipulated OvAbg neurons to induce or block abdomen bending (CsChrimson activation; TNT silencing) and assessed threat responsiveness.
• Dopaminergic components: targeted TH-C1-GAL4 dopamine neurons (including PPM1/2 subset). Optogenetic activation during early courtship. Developed tethered preparation for two-photon imaging of PPM1/2 (GCaMP7b/6s) during live courtship progression; compared female vs male targets; removed female; immobilized specific body parts; mechanically prevented abdomen bending to dissociate proprioceptive vs efference copy contributions.
• Measured dopamine release onto LC16 axon terminals using GRABDA sensor during pairing with female vs male.
• Tested dopamine effects on LC16: bath application of 500 μM dopamine during LC16 GCaMP6f imaging with threat; focal dopamine microinjection onto LC16 terminals; optogenetic activation of PPM1/2 while imaging LC16 responses.
• Receptor identity: Dop2R involvement tested by LC16-specific Dop2R RNAi; verified Dop2R localization in LC16 axon terminals via split-GFP reconstitution (endogenous Dop2R::spGFP11 with LC16-driven spGFP1-10). Behaviorally tested late-stage threat response after LC16 Dop2R knockdown.
• Tested whether dopamine suppression of 5-HTPMPD threat responses depends on LC16: recorded 5-HTPMPD GCaMP6s responses to threats with/without dopamine, and with LC16 Dop2R knockdown.
• Behavioral metrics reported as courtship and defensive indices; calcium imaging quantified as ΔF/F%; numerous controls included (non-threat light controls, mechanical threats, solitary males).

• LC16 visual projection neurons detect the moving shadow threat and suppress courtship: silencing LC16 (LC16>TNT) prevented threat-induced courtship interruption, while LC16 activation (CsChrimson) without threat halted courtship, mimicking threat. LC16 robustly responded to visual threat but not to non-threat light or female cues (two-photon GCaMP6f).
• Serotonergic 5-HTPMPD neurons mediate threat-induced inhibition of courtship: LC16 activation drove calcium increases in 5-HTPMPD; blocking 5-HT neurons or TRH synthesis reduced defensive responses and prevented threat-induced courtship cessation; activating 5-HT neurons or TRHR23E12 neurons alone suppressed courtship. Thus, 5-HT neurons act downstream of LC16 to promote escape over courtship.
• Central courtship nodes are inhibited by 5-HT: activating P1 overrode the threat. 5-HT application decreased P1 activity; P1 knockdown of 5-HT1 abolished this inhibition and reduced threat effects on behavior. In plP10, 5-HT application decreased activity via 5-HT2B; RNAi of 5-HT2B in plP10 reduced threat-induced courtship suppression. In both P1 and plP10, inhibition required Gαi signalling, indicating an inhibitory 5-HT1/5-HT2B–Gαi mechanism.
• As courtship progresses, males become less responsive to visual threats: delivering threats at later stages (≈240 s) produced minimal suppression of courtship relative to early stages (≈30 s). Copulating males ignored visual threats, even post–sperm transfer. Execution of advanced steps (abdomen bending) predicted reduced threat responsiveness; optogenetic induction of abdomen bending (OvAbg activation) reduced threat responses, and OvAbg silencing restored late-stage threat sensitivity.
• Dopaminergic PPM1/2 neurons ramp activity with courtship progression: TH-C1 activation during early courtship caused males to ignore threats without altering threat detection per se. Two-photon imaging showed gradual ramping of PPM1/2 calcium during courtship with females, correlated with abdomen bending; absent with male targets and reversed when the female was removed.
• Proprioceptive feedback from abdomen bending drives the dopamine ramp: preventing abdomen bending abolished the ramp (PPM1/2 activity decreased over time), while inducing bending (OvAbg activation) increased PPM1/2 signals in a dose-dependent manner and only when physical bending was possible.
• Dopamine filters visual threat responses at LC16 via Dop2R: GRABDA reported a steady increase in dopamine at LC16 terminals during pairing with a female. Bath-applied dopamine (500 μM) suppressed LC16 baseline and eliminated threat-evoked responses; focal dopamine at LC16 terminals reduced LC16 calcium. Optogenetic activation of PPM1/2 decreased LC16 calcium and reduced LC16 threat responses. LC16-specific knockdown of Dop2R prevented dopamine-induced suppression, restored LC16 threat responses, and behaviorally reinstated defensive responses to late threats.
• Dopamine also prevents activation of serotonergic threat responses by shutting down LC16: dopamine blocked threat-evoked 5-HTPMPD activation; this block required Dop2R in LC16. Overall: Early courtship—threat via LC16 → 5-HTPMPD inhibits P1 and plP10 to abort courtship. Late courtship—abdomen bending drives PPM1/2 dopamine ramp → Dop2R at LC16 axon terminals suppresses visual threat detection, enabling continued courtship.

The study resolves how Drosophila males arbitrate between escape and mating by dynamically re-weighting sensory inputs based on goal proximity. Early in courtship, visual threats activate LC16, which via 5-HTPMPD inhibits central courtship nodes (P1 and plP10), ensuring survival priority. As courtship advances, proprioceptive feedback from abdomen bending ramps PPM1/2 dopaminergic activity, which directly suppresses LC16 output via Dop2R at LC16 axon terminals. This dopaminergic filter thus down-weights external threat signals when mating is imminent, shifting behavioral selection toward reproduction. The mechanism integrates well with ethological observations of reduced risk aversion near high-value rewards and extends the role of dopamine ramping beyond motivation/reward prediction to top-down sensory filtering. The work suggests conserved principles: D2-like receptor–mediated modulation of sensory pathways may be a general strategy across species for prioritizing goal-directed behavior under conflict.

Main contributions: (1) Identification of an LC16→5-HTPMPD→(P1, plP10) pathway that inhibits courtship in response to visual threats; (2) Discovery that courtship progression, specifically abdomen bending, ramps PPM1/2 dopaminergic activity; (3) Demonstration that dopamine release onto LC16 axon terminals via Dop2R suppresses visual threat detection, enabling persistence of courtship at late stages; (4) Establishment of a state-dependent dopaminergic sensory filter that biases perception by goal proximity. Future directions: obtain direct synaptic confirmation among 5-HTPMPD, P1, and plP10 in males; dissect the biophysical mechanisms underlying dopaminergic ramp integration (e.g., intrinsic excitability, neuromodulatory control); test whether recurrent P1-supporting circuits are modulated by PPM1/2; explore parallel modulatory pathways that reduce 5-HT threat signalling or decrease sensitivity of courtship nodes; examine whether similar dopaminergic sensory filtering via D2-like receptors generalizes across modalities and species.

• Connectomic links among 5-HTPMPD, P1, and plP10 are inferred from the female connectome and functional data; direct male synaptic confirmation is pending.
• PPM1/2 activation prevents threat responses in courting but not solitary males, implying additional parallel mechanisms and state dependence that were not fully delineated.
• Use of immobilized virgin females and specific threat paradigms (moving shadow) may limit generalization to other female states or threat modalities; though some mechanical threats were tested, broader ethological contexts were not exhaustively examined.
• Pharmacological dopamine application (500 μM) and optogenetic stimulations, while informative, may not precisely match endogenous dynamics.
• Equal contribution and present-address notes indicate author mobility; affiliations do not affect results but may reflect collaborative multi-lab methodologies.