In their classic experiments, Olds and Milner showed that rats learn to lever press to receive an electric stimulus in specific brain regions. This led to the identification of mammalian reward centers. Our interest in defining the neuronal substrates of reward perception in the fruit fly Drosophila melanogaster prompted us to develop a simpler experimental approach wherein flies could implement behavior that induces self-stimulation of specific neurons in their brains. The high-throughput assay employs optogenetic activation of neurons when the fly occupies a specific area of a behavioral chamber, and the flies' preferential occupation of this area reflects their choosing to experience optogenetic stimulation. Flies in which neuropeptide F (NPF) neurons are activated display preference for the illuminated side of the chamber. We show that optogenetic activation of NPF neuron is rewarding in olfactory conditioning experiments and that the preference for NPF neuron activation is dependent on NPF signaling. Finally, we identify a small subset of NPF-expressing neurons located in the dorsomedial posterior brain that are sufficient to elicit preference in our assay. This assay provides the means for carrying out unbiased screens to map reward neurons in flies.reward circuit | high-throughput two-choice assay | optogenetics | neuropeptide F | Drosophila

Highlights d Mating non-ejaculatory males induce a copulation effect reducing female receptivity d Activity of LSAN neurons is necessary and sufficient for copulation effect d Neurons expressing mechanosensory channel Piezo relay copulation effect to LSANs d Neurons expressing MIP mediate copulation effect downstream of LSANs

The dysfunction of multiple neurotransmitter systems is a striking pathophysiological feature of many mental disorders, schizophrenia in particular, but delineating the underlying mechanisms has been challenging. Here we show that manipulation of a single schizophrenia susceptibility gene, dysbindin, is capable of regulating both glutamatergic and dopaminergic functions through two independent mechanisms, consequently leading to two categories of clinically relevant behavioral phenotypes. Dysbindin has been reported to affect glutamatergic and dopaminergic functions as well as a range of clinically relevant behaviors in vertebrates and invertebrates but has been thought to have a mainly neuronal origin. We find that reduced expression of Drosophila dysbindin (Ddysb) in presynaptic neurons significantly suppresses glutamatergic synaptic transmission and that this glutamatergic defect is responsible for impaired memory. However, only the reduced expression of Ddysb in glial cells is the cause of hyperdopaminergic activities that lead to abnormal locomotion and altered mating orientation. This effect is attributable to the altered expression of a dopamine metabolic enzyme, Ebony, in glial cells. Thus, Ddysb regulates glutamatergic transmission through its neuronal function and regulates dopamine metabolism by regulating Ebony expression in glial cells.dystrobrevin binding protein 1 | glutamate | glia

The reward system is a collection of circuits that reinforce behaviors necessary for survival [1, 2]. Given the importance of reproduction for survival, actions that promote successful mating induce pleasurable feeling and are positively reinforced [3, 4]. This principle is conserved in Drosophila, where successful copulation is naturally rewarding to male flies, induces long-term appetitive memories [5], increases brain levels of neuropeptide F (NPF, the fly homolog of neuropeptide Y), and prevents ethanol, known otherwise as rewarding to flies [6, 7], from being rewarding [5]. It is not clear which of the multiple sensory and motor responses performed during mating induces perception of reward. Sexual interactions with female flies that do not reach copulation are not sufficient to reduce ethanol consumption [5], suggesting that only successful mating encounters are rewarding. Here, we uncoupled the initial steps of mating from its final steps and tested the ability of ejaculation to mimic the rewarding value of full copulation. We induced ejaculation by activating neurons that express the neuropeptide corazonin (CRZ) [8] and subsequently measured different aspects of reward. We show that activating Crz-expressing neurons is rewarding to male flies, as they choose to reside in a zone that triggers optogenetic stimulation of Crz neurons and display conditioned preference for an odor paired with the activation. Reminiscent of successful mating, repeated activation of Crz neurons increases npf levels and reduces ethanol consumption. Our results demonstrate that ejaculation stimulated by Crz/Crz-receptor signaling serves as an essential part of the mating reward mechanism in Drosophila. VIDEO ABSTRACT.

SignificanceTo survive, an organism must adjust its behavior based upon past experiences. In Drosophila, aggression affects fitness as it ensures access to food and mating resources. Here, we show that upon repeated aggressive encounters, males adopt a winner or loser state that shows the qualities of persistence and generalization. Winning is perceived as rewarding, while losing is aversive. We also demonstrate that the activity of specific dopamine neurons is needed for males to avoid an odor previously paired with losing. Although the effects of losing and winning have been extensively studied in other species, our work advances the use of Drosophila as a model for circuit dissection of internal states that promote behavioral changes associated with winning or losing fights.

Although the genetic contribution is under debate, biological studies in multiple mouse models have suggested that the Disrupted-in-Schizophrenia-1 (DISC1) protein may contribute to susceptibility to psychiatric disorders. In the present study, we took the advantages of the Drosophila model to dissect the molecular pathways that can be affected by DISC1 in the context of pathology-related phenotypes. We found that three pathways that include the homologs of Drosophila Dys, Trio, and Shot were downregulated by introducing a C-terminal truncated mutant DISC1. Consistently, these three molecules were downregulated in the induced pluripotent stem cell-derived forebrain neurons from the subjects carrying a frameshift deletion in DISC1 C-terminus. Importantly, the three pathways were underscored in the pathophysiology of psychiatric disorders in bioinformatics analysis. Taken together, our findings are in line with the polygenic theory of psychiatric disorders.

The Drosophila homolog of schizophrenia susceptibility gene dysbindin (Ddysb) affects a range of behaviors through regulation of multiple neurotransmitter signals, including dopamine activity. To gain insights into mechanisms underlying Ddysb-dependent regulation of dopamine signal, we investigated interaction between Ddysb and Ebony, the Drosophila β-alanyl-monoamine synthase involved in dopamine recycling. We found that Ddysb was capable of regulating expression of Ebony in a bi-directional manner and its subcellular distribution. Such regulation is confined to glial cells. The expression level of ebony and its accumulation in glial soma depend positively on Ddysb activity, whereas its distribution in glial processes is bound to be reduced in response to any alterations of Ddysb from the normal control level, either an increase or decrease. An optimal binding ratio between Dysb and Ebony might contribute to such non-linear effects. Thus, Ddysb-dependent regulation of Ebony could be one of the mechanisms that mediate dopamine signal. Dysbindin, ebony, glial cell, subcellular distribution, dopamine Citation:Lu BY, Shao LS, Feng SX, Wang T, Zhong Y. The β-alanyl-monoamine synthase ebony is regulated by schizophrenia susceptibility gene dysbindin in

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