Investigation of octopamine-glutamate dual transmission neurons

Abstract

Dual transmission, or the ability of a neuron to signal with more than one neurotransmitter, is now a well-established phenomenon in the field of neuroscience. However, many questions about this type of signaling process still remain with regards to its mechanisms and its impacts on neural circuitry and organism behavior. In particular, the mode of neurotransmitter release from synaptic vesicles can have significant profoundly affects elements on neural circuitry and, subsequently, on behaviors of an organism. In Drosophila melanogaster, a particular subset of neurons important for the behaviors of courtship and aggression signal with the neuromodulator octopamine and the excitatory neurotransmitter glutamate. Whether these two neurotransmitters are released simultaneously (co-release) or are housed for separate synaptic release (cotransmission) is unknown. The mechanism of release for these neurotransmitters in this population of neurons is investigated here through the development of synaptic vesicle visualization tools, synaptic vesicle isolation, and an examination of the expression of octopamine and glutamate receptors; I explored the hypothesis that receptor expression downstream of dual transmitting neurons will provide information about the co-release or co-transmission of octopamine and glutamate. Results from these experiments demonstrated release of octopamine and glutamate from the same synaptic site, with some variation, and a significant amount of presynaptic receptor expression. The results indicate these dual transmission neurons may release octopamine and glutamate at the same synapse for both post-synaptic signaling as well as pre-synaptic signal modulation.