Figure 1:

Neural circuit pathways mediating mating and aggression behaviors in male Drosophila.

The schematic illustrates neurons regulating male courtship, aggression, and copulation discussed in this review. For clarity, sensory inputs to P1 neurons are not illustrated. Male courtship song is generated by a circuit consisting of fru⁺ neuronal clusters: P1 neurons, descending interneurons (P2b/plP10), and central pattern generators (“CPG”, dPR1/vPR6/vMS11). GABAergic LC1 neurons, via indirect or direct actions on P1 or pC1, shift behavior towards aggression. DA-SMPa neurons encode mating drive and desensitize P1 neurons to GABAergic inhibition from mAL neurons. A positive recurrent NPF-pCd circuit sustains motivation for courtship, which is inhibited by copulation reporting neurons (CRNs). An indirect action of P1 neurons on pCd neurons also promotes persistent courtship singing. For copulation, dsx⁺ glutamatergic motor neurons promote genital coupling, and this is suppressed by dsx⁺ GABAergic neurons. A small subset of these dsx⁺ GABAergic cells terminates copulation, while dopamine tone in the ventral nerve cord conversely maintains copulation. A cell-autonomous molecular timer (CaMKII) in corazonin (Crz)-releasing neurons also sustains copulation duration. Signals from P1 and octopaminergic (OA) neurons converge in aSP2 to promote aggression. Similar to courtship singing, an indirect action of P1 neurons on pCd neurons plays an important role for persistence of aggression. Data sources: aSP2 [56], CPGs [40], CRNs [47], Crz [52,53], DA [51], DA-SMPa [43,46,47], dsx⁺/Gad1 [50,51], dsx⁺/Glut [50], LC1 [55], mAL [55], NPF [47], OANs [56], P1 [34,43,45–47,54–56,58], P2b [34], pC1 [55], pCd [47,58], plP10 [40].