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Synaptic depression induced by postsynaptic cAMP production in the Drosophila mushroom body calyx
Author(s) -
Sato Shoma,
Ueno Kohei,
Saitoe Minoru,
Sakai Takaomi
Publication year - 2018
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jp275799
Subject(s) - mushroom bodies , calyx , neuroscience , postsynaptic potential , antennal lobe , biology , stimulation , synapse , synaptic plasticity , long term potentiation , drosophila melanogaster , monocular deprivation , parvalbumin , sensory system , anatomy , visual cortex , ocular dominance , biochemistry , gene , receptor
Key points Synaptic potentiation in Drosophila is observed at cholinergic synapses between antennal lobe (AL) and mushroom body (MB) neurons in the adult brain; however, depression at the AL–MB synapses has not yet been identified. By ex vivo Ca 2+ imaging in an isolated cultured Drosophila brain, we found novel activity‐dependent depression at the AL–MB synapses. The degree of Ca 2+ responses after repetitive AL stimulation is significantly reduced in the dendritic region of MB neurons (calyx) compared with those before AL stimulation, and this reduction of Ca 2+ responses remains for at least 30 min. The expression of rutabaga , which encodes Ca 2+ /calmodulin‐dependent adenylyl cyclase, is essential in the MB neurons for the reduction of Ca 2+ responses in the calyx. Our study reveals that elevation of cAMP production in the calyx during repetitive AL stimulation induces the depression at the AL–MB synapses.Abstract Synaptic plasticity has been studied to reveal the molecular and cellular mechanisms of associative and non‐associative learning. The fruit fly Drosophila melanogaster can be used to identify the molecular mechanisms of synaptic plasticity because vast genetic information or tools are available. Here, by ex vivo Ca 2+ imaging of an isolated cultured Drosophila brain, we examined the novel activity‐dependent synaptic depression between the projection neurons of the antennal lobe (AL) and mushroom body (MB). Ex vivo Ca 2+ imaging analysis revealed that electrical stimulation of AL elicits Ca 2+ responses in the dendritic (calyx) and axonal (α lobe) regions of MB neurons, and the responses are reduced after repetitive AL stimulation. Since the cAMP signalling pathway plays an important role in synaptic plasticity in invertebrates and vertebrates, we examined whether the reduction of Ca 2+ responses is also regulated by the cAMP signalling pathway. The expression of rutabaga ( rut ), which encodes Ca 2+ /calmodulin‐dependent adenylyl cyclase, was essential for the reduction of Ca 2+ responses in the calyx and α lobe. Furthermore, imaging analysis using a fluorescence resonance energy transfer‐based cAMP indicator revealed that the cAMP level increased in the wild‐type calyx during repetitive AL stimulation, whereas it decreased in rut 1 mutant flies with a loss‐of‐function mutation of rut . Thus, our study suggests that an increase in postsynaptic cAMP level during repetitive AL stimulation contributes to the attenuation of inputs at AL–MB synapses.