Down-regulation of striatal MSN TrkB leads to specific alterations in expression of MSN-enriched transcripts in male mice. (a) Diagram of dorsal striatal regions (middle level, 4.2 mm rostral to the interaural line) used for quantitation of results of in situ hybridization of Ntrk2, Penk, Tacr1, Ppp1r1b and Pdyn mRNAs. S = striatum, m = medial, c = central, l = lateral, v = ventral. (b) Densitometry of representative autoradiograms of Penk mRNA in situ hybridization on mid-level striatal sections shows a 40% reduction in preproenkephalin mRNA level (N = 3 fB/fB, N = 4 D9ΔTrkB, P < 0.01, t-test). (c) RT-qPCR was performed on samples derived from the dorsal striatum of male mice (N = 4/genotype), confirming a significant decrease in Ntrk2 and Penk mRNAs in D9ΔTrkB mice versus fB/fB mice (*P < 0.01, t-test) and demonstrating greater than 50% decrease in Calb1 mRNA (*P < 0.01, t-test).