SPR decreases sensitivity of olfactory neurons to polyamines after mating.

<p>(A) Schematic diagram of a fly brain and its antennal appendages with olfactory sensory neurons (OSNs). OSNs project into the antennal lobe (AL), where they innervate a specific glomerulus (green). Projection neurons (PN) send the information mainly to two higher brain centers, the mushroom body (MB) and the lateral horn (LH) (top). Illustrative confocal image stack showing the IR41a and IR76b OSN innervation in the AL (bottom). VC5 is the glomerulus innervated by the polyamine-responding IR41a/IR76b sensory neurons. (B) Illustration of the in vivo calcium imaging setup. (C–E) In vivo calcium imaging of <i>IR41-Gal4;UAS-GCaMP6f</i> flies stimulated with water and 10 ppm putrescine, respectively. Mated females’ OSN axon terminals show a significant reduction in their sensitivity to putrescine at 1–6 h post-mating. (C) Quantification of peak ΔF responses (in %ΔF/F) in virgin and mated females. Boxes show median and upper/lower quartiles, and whiskers show minimum/maximum values. *<i>p <</i> 0.05, unpaired <i>t</i> test (<i>n</i> = 8). (D) Representative pseudo-color images showing the response to water and 10 ppm putrescine in virgin and mated flies at 1–6 h and 1 wk post-mating. (E) Average response trace (in %ΔF/F) of the VC5 glomerulus peak response at 1–6 h and 1 wk post-mating compared to traces from virgin females. The dark colored line in the middle presents the average value and the light shade presents the SEM. (F–H) In vivo calcium imaging of test (<i>IR41a-Gal4</i>,<i>UAS-SPRi;UAS-GCaMP5</i>) and control (<i>IR41a-Gal4;UAS-GCaMP5)</i> mated female flies. OSN axon terminals of <i>IR41a>SPRi</i> females show significantly enhanced responses to putrescine compared to control females. (F) Representative pseudo-color images showing the response to water and 10 ppm putrescine in <i>IR41a>SPRi</i> and control females, respectively. (G) Average response trace of the VC5 glomerulus in <i>IR41a>SPRi</i> and control females at 1–6 h post-mating for 10 ppm putrescine. (E,G) The gray column represents the 0.5 s stimulation period. Dark colored line is the average response and the light shade is the SEM. (H) Quantification of peak ΔF responses (in %ΔF/F) in <i>IR41a>SPRi</i> and control females for 0 ppm, 6 ppm, 8 ppm, and 10 ppm putrescine, respectively (<i>n</i> = 7 ± SEM). All <i>p</i>-values were calculated using an unpaired <i>t</i> test (*<i>p</i> ≤ 0.05, **<i>p</i> ≤ 0.01, ***<i>p</i> ≤ 0.001).