Appetitive learning requires the alpha1-like octopamine receptor OAMB in the Drosophila mushroom body neurons.
Associative learning is a fundamental form of behavioral plasticity. Octopamine plays central roles in various learning types in invertebrates; however, the target receptors and underlying mechanisms are poorly understood. Drosophila provides a powerful system to uncover the mechanisms for learning and memory. Here, we report that OAMB in the mushroom body neurons mediates the octopamine's signal for appetitive olfactory learning. The octopamine receptor OAMB has two isoforms (OAMB-K3 and OAMB-AS), differing in the third cytoplasmic loop and downstream sequence. The activation of each OAMB isoform increases intracellular Ca(2+) similar to the alpha1 adrenergic receptor, while OAMB-K3 additionally stimulates cAMP production. The oamb-null mutants showed severely impaired learning in appetitive olfactory conditioning that tests flies' capacity to learn and remember the odor associated with sugar reward. This deficit was also seen in the hypomorphic mutant with reduced OAMB expression in the mushroom bodies, the brain structure crucial for olfactory conditioning. Consistently, the oamb mutant's learning phenotype was fully rescued by conditional expression of either OAMB isoform in the mushroom body αβ and γ neurons. These results indicate that the OAMB receptor is a key molecule mediating the octopamine's signal for appetitive olfactory learning and its functional site is the mushroom body αβ and γ neurons. This study represents a critical step forward in understanding the cellular mechanism and neural circuit mediating reward learning and memory.
Department of Biological Sciences, Border Biomedical Research Center Neuroscience and Metabolic Disorders Project, University of Texas at El Paso, El Paso, Texas 79968, USA.
Young-Cho
YC
Kim
Hyun-Gwan
HG
Lee
Junghwa
J
Lim
Kyung-An
KA
Han
D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D004330:Drosophila; D029721:Drosophila Proteins / Q000378:metabolism*; D007150:Immunohistochemistry; D024521:Mushroom Bodies / Q000166:cytology* / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D017981:Receptors, Neurotransmitter / Q000378:metabolism*
D029721:Drosophila Proteins; C480734:OAMB protein, Drosophila; D017981:Receptors, Neurotransmitter