Octopamine in Sexual Behavior
Octopamine is a biogenic amine neuromodulator present in neuronal and non-neuronal tissues in invertebrates (Roeder, 1999). It modulates numerous physiological processes such as motivation, pheromone response, olfaction, ovulation, learning and memory. Octopamine together with its precursor tyramine have roles restricted only to invertebrates (Roeder, 1999). It is believed that octopamine is the invertebrate homolog of norepinephrine, a catecholamine present in mammals that acts as a neuromodulator in the sympathetic and central nervous systems. Both octopamine and norepinephrine are derived from the same amino acid tyrosine and are monoamine neurotransmitters. The main objective of this study is to understand the role of octopamine and its receptors in sexual behavior in Drosophila melanogaster, an organism widely used in research, as a model system. This invertebrate is amenable for genetic manipulation and has a relatively short life cycle, making it ideal to investigate large sample sizes. There are four known receptors involved in octopamine signaling in Drosophila: OAMB with two different isoforms OAMB-AS and OAMB-K3, Octβ1R, Octβ2R, and Octβ3R. These are G-protein coupled receptors that activate second messengers when octopamine binds to them. OAMB-K3, Octβ1R, Octβ2R, and Octβ3R elevate cAMP levels while OAMB-AS and OAMB-K3 increase intracellular calcium levels (Han et al., 1998; Maqueira et al., 2005). To understand the mechanism by which octopamine regulates sexual behavior, this study focused on the octopamine receptors OAMB, Octβ1R, and Octβ2R. Here we demonstrated octopamine’s importance in male sexual behavior and that its site of action might be OAMB receptors in the mushroom bodies. This study advanced the mechanism that the octopamine system regulates different aspects of sexual behavior including courtship, copulation and courtship memory. Identification of the octopamine receptors important for these aspects of sexual behavior will aid in pest control of harmful insect population. These findings may also offer insight into the role that the mammalian adrenergic system have in sexual behavior.
Fernandez, Ana Isabel, "Octopamine in Sexual Behavior" (2017). ETD Collection for University of Texas, El Paso. AAI10687053.