Fig. 4: Newborn neurons in the adult NAc become mature MSNs.

a Experimental schematic: P4-day-old pups were injected with a RFP-expressing retrovirus in the V-SVZ and analyzed 4–8 weeks later. b Coronal section of P56 wild-type mouse brain immunostained for RFP, DARPP-32, and NeuN. Inset: schematic of the anatomical region in a coronal section. The red rectangle denotes the area in the picture. c, d High-magnification images from the area indicated with the yellow dashed rectangle in b. d1, d2 Magnifications show segments of a dendrite bearing spines. d3 High-magnification image of the retrovirus-infected soma, indicating that this cell expresses typical markers for mature MSNs in the NAc (DARPP-32 and NeuN). e Top: morphological reconstruction of a biocytin-filled virus-infected neuron in the NAc. Bottom: representative firing patterns of virus-infected neurons recorded in the NAc. f Schematic of the experimental protocol. g Overview of the NAc immunostained for DAPI, biocytin, DARPP-32, and YFP. Inset: low-magnification image of a coronal brain section of a P130 wild-type mouse immunostained for DAPI. h High-magnification image of the yellow dashed rectangle. h1–h4 Enlargement of the areas indicated in the picture, showing dendritic spines. h5 High-magnification image of the biocytin-filled cell body, showing positive expression for YFP and DARPP-32. i Left: morphological reconstruction of biocytin-filled YFP-expressing neuron shown in h. Right: representative firing pattern of the YFP-labeled MSN recorded in the NAc. Abbreviations: ac, anterior commissure; NAc, nucleus accumbens; lv, lateral ventricle; Sp, septum. Scale bars in µm: 500 (onset in g), 200 (g) 50 (b, e, i), 20 (c, d, h), 5 (d3, h1–h5), 1 (d1, d2). See also Supplementary Fig. 9 and Supplementary Movie 6.