Fig. 1

Fig. 1 Pituicytes, Axons, and Blood Capillaries Form Multiple Neurovascular Interfaces (A) Scheme describing functional labeling of pituicytes in vivo. Injection of the fluorescent aminomethylcoumarin-(AMCA) conjugated diamino acid peptide β-Ala-Lys-Nɛ intraperitoneally (IP) into adult zebrafish leads to active uptake of β-Ala-Lys-Nɛ-AMCA by pituicytes. 3 hr following injection, the hypophysis was dissected and imaged. (B) Whole-mount imaging of hypophysis dissected from 3-month-old transgenic reporter zebrafish allowing simultaneous visualization of neurohypophyseal axons, labeled by Tg(oxt:EGFP), and blood capillaries, labeled by Tg(kdrl:mCherry-caax), shows β-Ala-Lys-Nɛ-AMCA-labeled pituicytes. Scale bar, 5 μm. The axo-glial-vasal interface is seen in both the rostral (Bʹ) and caudal (Bʹʹ) pars nervosa of the neurohypophysis. Scale bar: 10 μm. (C) High magnification of a neurovascular unit showing pituicytes and neurohypophyseal axon termini interfacing with a single blood capillary. Scale bar: 5 μm. (D–G) Inverted gray scale high-magnification images of morphologically distinct pituicyte subtypes. Four major subtypes were identified: long processes connecting multiple pituicytes (D), pituicytes forming Rosenthal fibers (E), amoeboid pituicytes (F), and basket pituicytes (G). Scale bar: 5 μm. (H) Schematic three-dimensional model of the adult zebrafish neurohypophysis. Hypophyseal axons (green), blood capillaries plexus (red), and pituicytes (magenta) are the main components of the neurohypophysis. Axo-glial-vasal contacts are mainly present in the rostral and caudal pars nervosa. Inset: enlarged scheme of an axo-glio-vasal neurovascular unit depicting engulfment of axon swellings by pituicytes that also contact the perivascular space of blood capillaries.