Fig. 5: Type II and III SG acini are innervated by cholinoceptive peptidergic axons, while agranular type I acini are targets for synaptic ACh.
Double immunolabelling of anti-Ir-mAChR-A with anti-orcokinin (a) and anti-Ir-mAChR-B with anti-SIFa (b) in synganglial neurons and their axonal projections to the SG of an unfed female. Co-localisation of anti-Ir-mAChR-A with anti-orcokinin marks OsSG1,2 neurons (yellow) and their axon terminals (yellow, arrowheads) targeting type II acini, while anti-Ir-mAChR-B co-localises with anti-SIFa in PcSG cells (yellow) and their axon terminals (yellow, arrowheads) innervating type II and III acini. c Double immunolabelling of SG acini from an unfed female with anti-Ir-mAChR-A (red, open arrowheads) and anti-Ir-mAChR-B (green, filled arrowheads) showing that type II acini receive both inputs, whereas type III acini are labelled exclusively with anti-Ir-mAChR-B. d Association of anti-Ir-mAChR-A- and anti-Ir-mAChR-B-positive axon terminals (green, arrowheads) with a single myoepithelial cell visualised with anti–βIII-tubulin (red, arrows) across feeding stages, showing acinar enlargement from unfed to fully engorged females. e Number of female SGs positive for anti-Ir-mAChR-A and anti-Ir-mAChR-B immunoreactivity in axon terminals in type II and III acini. Tick numbers (n) are shown in the figure. f Double labelling of type I acini with anti-Ir-mAChR-A or anti-Ir-mAChR-B with anti-ChAT shows scattered Ir-mAChR-type-positive immunoreactivity (green, arrowheads) in acinar cells adjacent to ChAT-positive axon terminals (red, arrows). DAPI, blue. A schematic of SG-innervating neurons and their axons is shown in Fig. 6a, b. Validation of anti-Ir-mAChR-A and anti-Ir-mAChR-B antibodies is provided in Supplementary Fig. 4. Scale bars, 50 µm.
