AgRP2 preoptic neurons project towards the pituitary and terminate at the pituitary vasculature.
(a) A cross between agrp2:mCherry and Tg(oxt:EGFP)wz01 shows that AgRP2 neurons (magenta) are localized to the preoptic area, adjacent to oxytocin neurons (green), dorsal view of a 5-dpf larva head. (b) Higher-gain imaging of a 5-dpf agrp2:mCherry larva reveals projections of the AgRP2 preoptic neurons towards the pituitary (arrows). (c) Pituitary of a 12-dpf agrp2:mCherry, Tg(pomc:EGFP)zf44 larva, showing AgRP2 projections (magenta) terminating at the adenohypophysis, in close proximity to anterior POMC neurons (green). (d) Pituitary of a 12-dpf agrp2:mCherry, Tg(oxt:EGFP)wz01 larva, showing that projections from AgRP2 (magenta) and oxytocin (green) neurons share the same axonal tracts (arrows) but terminate at different locations within the pituitary: AgRP2 axons terminate at an anterior region whereas oxytocin axons terminate at a posterior region. (e) Pituitary of a 7-dpf agrp2:mCherry, Tg(UAS:SYP-EGFP)biu5 larva expressing synaptophysin (SYP)-EGFP fusion protein and mCherry in AgRP2 neurons. SYP-EGFP protein aggregates in pre-synaptic vesicles at the adenohypophysial AgRP2 terminals. (f) Z-stack projection of a 12-dpf agrp2:mCherry, Tg(kdrl:EGFP)s843 larval pituitary, showing that AgRP2 preoptic projections (magenta) form an interface with the pituitary vasculature (green). (g−g”) show higher magnification of (f). (g) A single focal plane of the pituitary vasculature. (g’) AgRP2 terminals form an arc along the pituitary artery. (g”) Merged image of (g) and (g’). The observed overlap between AgRP2 terminals and the pituitary artery demonstrates a neurovascular interface of AgRP2 terminals with the pituitary vasculature. Anterior to top. AH, adenohypophysis; NH, neurohypophysis; Pit, pituitary; POA, preoptic area. Scale bar, 20 μm.