Oviduct contraction in Drosophila is modulated by a neural network that is both, octopaminergic and glutamatergic.

Fertility is a highly complex and regulated phenomenon essential for the survival of any species. To identify Drosophila fertilityspecific neural networks, we used a GAL4/UAS enhancer trap genetic screen that selectively inactivates groups of neurons. We identified a GAL4 line (bwk tqs ) that has a female sterile phenotype only when it expresses the tetanus toxin light chain (TeTxLC). These flies lack oviduct contraction, lay almost no eggs, sperm accumulate in the oviducts, and fewer than normal are seen in the storage organs. In insects, two neuroactive substances are important for oviduct contraction: octopamine (OA), a monoamine that inhibits oviduct contraction, and glutamate (Glu), a neurotransmitter that induces contraction. It is known that octopaminergic neurons of the thoracic abdominal ganglion (TAG) modulate oviduct contraction, however, the glutamatergic neurons that innervate the oviduct have not been identified yet and the interaction between these two neuroactive substances is not well understood. Immunostaining experiments revealed that the bwk tqs line trapped an octopaminergic neural network that innervates the genital tract. We show that wt like oviduct contraction in TeTxLC-inactivated flies can only be rescued by simultaneous application of Glu and OA suggesting that the abdominal bwk tqs neurons are both octopaminergic and glutamatergic, the use of an agonistand anantagonist forGlureceptors aswell astheir directvisualizationconfirmed its participationin thisphenomenon. Our work provides the first evidence that adult abdominal type II visceral innervations co-express Glu and OA and allows us to reevaluate the previous model of neuronal network controlling insect oviduct contraction. J. Cell. Physiol. 209: 183‐198, 2006. 2006 Wiley-Liss, Inc. The properties of neural networks, the functional modules of central nervous systems, are poorly understood because there are few strategies to genetically isolate and manipulate them. In an effort to better understand neural networks, we developed a functional genetic screen using an enhancer trap strategy to identify neuronal groups in the CNS involved in fertility and define their function. We used the bipartite GAL4/ UAS system (Brand and Perrimon, 1993) to target the expression of the tetanus toxin light chain (TeTxLC) to inactivate discrete groups of neurons in the fly CNS. With this approach, we isolated a GAL4 line (bwk tqs ) that presents a female sterile phenotype only when it expresses the TeTxLC. The inactivation of bwk tqs neurons produce a female sterile phenotype caused by defective oviposition and improper sperm storage. Oviposition in insects is mainly regulated by octopamine (OA) and glutamate (Glu). OA is a neurohormone, neuromodulator, and neurotransmitter in invertebrates (Roeder, 1999) that modulates many aspects of physiol