Abstract
Neuropeptides are a group of neuronal signalling molecules that modulate a wide range of physiological processes and behaviors. The Drosophila neuropeptide F (NPF), a homolog to human NPY, is involved in a wide range of brain functions, especially hunger-induced motivational response which can facilitate the Long-term memory (LTM) formation. To understand how NPF signals are transmitted and regulate motivational and memory behaviors, it is critical to know the circuitry wiring and connectome of NPF neurons. Here, we analysed NPF positive neurons and their receptor NPFR1 neurons. A pair of NPF-positive dorsal-anterior-lateral2 (DAL2) neurons was demonstrated also NPFR1 and NMDAR positive have structured connections with LTM neuron-DAL in superior dorsofrontal protocerebrum (SDFP) region. We postulated that the DAL2 releases NPF signals received by NPFR1 in the DAL neuron to regulate long-term memory. Polarity analysis showed the DAL2 neurons could receive NPF signal through an autocrine feedback mechanism to increase the activity of themselves and their downstream DAL neurons. In the adult brain, subsets of dopaminergic neurons expressed NPFR1 that might conduct the NPF signals into the dopaminergic (DA) system which involve in appetitive and aversive memory behaviour. And the NPF-positive DAL2 neuron also have structured connections with DA neurons in the SDFP region. These findings suggested three information flowing pathways from NPF to NPFR1, (i) DAL2 (NPF) --> DA neurons, (ii) DAL2 (NPF) --> DAL (NPFR1), and (iii) DAL2 (NPF) --> DAL2 (NPFR1), all connection major in the SDFP region to modulate relative behaviours.