Figure 1: Selective targeting of striatal cholinergic interneurons results in enhancement of reversal learning.
From: Enhanced flexibility of place discrimination learning by targeting striatal cholinergic interneurons
(a) Transgene construct for generating rats expressing the human IL-2Rα/mVenus fusion protein under the control of the ChAT gene promoter. Exons 1–4 of the rat ChAT gene are shown. Open and closed boxes indicate the 5′-noncoding region and coding regions, respectively. Restriction enzyme abbreviations: E, EcoRI; H, HindIII. pA; polyadenylation signal from the SV40 early gene. (b) Expression of IL-2Rα/mVenus products in the dorsal striatum of Tg rats revealed by in situ hybridization analysis for IL-2Rα sequence (upper panel) and immunohistochemical staining for mVenus (lower panel). Scale bars, 200 μm. (c) Double immunofluorescence histochemistry for mVenus and ChAT. mVenus- and ChAT-positive signals are shown in green and red, respectively. In a merged image, green signals overlap with red signals, and thus emit yellow signals. Scale bar, 200 μm. (d) Intrastriatal injection by stereotaxic surgery. Right panel indicates coordinates for the injection (sites 1–6). The anteroposterior coordinates (mm) from bregma are shown. Scale bar, 2 mm. (e) Immunohistochemical staining of the striatal section for ChAT, showing selective loss of ChAT-positive neurons in the IT-injected Tg rats. Lower panels are fourfold magnified view of the squares in the upper panels. Scale bar, 200 μm. (f) Cell counts of ChAT-positive cells. n=4 per group. *P<0.05, relative to the PBS- and IT-injected non-Tg and the PBS-injected Tg rats (Bonferroni method). (g) Strategy of a place discrimination task for evaluating the performance of reversal learning. The entrance to one of the arms in the cross maze was prevented. The positions of the start arms were changed in a pseudorandom order. (h,i) Place discrimination task of the rats bilaterally injected with IT solution (h) or PBS (i) into the dorsal striatum. The performance in the acquisition and reversal learning phases were tested. n=8 per group. *P<0.05, relative to the IT-injected non-Tg rats (Bonferroni method). An inset shows the number of perseverative (Per) and regressive (Reg) errors in the reversal learning phase in the IT-injected rats. *P<0.01, relative to the non-Tg rats (Student’s t-test). Data are presented as mean±s.e.m.
