Thermogenetic activation (using TrpA1UAS.(B).cKa at 28[o]C) of Scer\GAL4alrm.PD cells in adults significantly reduces the amplitude and slope of excitatory postsynaptic potentials in antennal lobe projection neurons in response to activation of the antennal nerve, compared to controls, with no effect on onset latency.
Expression of hid in Scer\GAL4alrm.PD expressing neurons (limited to late metamorphosis using Scer\GAL80ts.αTub84B and shifting pupae to 25[o]) induces astrocyte ablation. A ~50% reduction in astrocyte numbers is seen in the antennal lobe, mushroom body, subesophageal ganglion (SOG) and abdominal segments of the thoracic ganglion (TGab), but the remaining astrocytes are able to infiltrate most of the neuropil with membrane processes. No lethality is observed and the adult flies do not display any obvious behavioral defects. Shifting the pupae to 30[o]C leads to more dramatic astrocyte reduction, with the remaining astrocyte processes appearing sparsely distributed and unable to cover the neuropil space. 41% of pupae are unable to eclose, 32% die during eclosion and only 27% survive as adults. These surviving adults are highly uncoordinated, cannot walk or fly, and die within a few days.
Gross synaptic morphology is unaffected by severe astrocyte ablation. Postsynaptic density length is unchanged and the percentage of synapses with T-bars is unaltered. Synaptic density is reduced in the antennal lobe, mushroom body and superior posterior slope. The astrocyte-ablated tissue is also marked by an increased frequency of ruptured mitochondria. At 84h after pupal formation, synapse numbers are significantly reduced, but several immature synaptic structures are seen. Gross morphology of the adult brain appears unaffected by severe ablated depletion: antennal lobe glomerular organisation appears normal, as are the neuronal projections of second-order antennal lobe projection neurons and pigment dispersing factor (pdf) neurons. The number of projection neurons is comparable in control and astrocyte ablated animals, as are pdf neurons. The membranes of cortex and ensheathing glia in the adult brain exhibit normal morphology.