Polµ^−/− mice brain presents an altered endocrine network.

<p>(<b>A</b>) Hierarchical clustering of the differential mRNA expression between wild-type and Polµ^−/− old (18 months) mice. (<b>B</b>) Schematic representation of the expression network detected using the software Ingenuity. (<b>C</b>) qRT-PCR analysis of genes belonging to the previously described network (<b>B</b>) and others found in DNA expression arrays carried out with brain of acutely treated animals (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053243#pone.0053243.s010" target="_blank">Figure S10</a>). Black bars denote values for wild-type animals and white bars correspond to Polµ^−/− animals. (<b>D</b>) Circulating levels of IGF1 and GH (ng/mL) were monitored by ELISA in old (21–24 months) animals. (<b>E, F</b>) qRT-PCR expression (<b>E</b>) and immunoconfocal analysis (<b>F</b>) of Igf1 and Igf1R in the hippocampal CA1area from wild-type and Polμ^−/− young adult (4 months) mice. Igf1 immunoreactivity-labeled non-pyramidal cells (short arrows) of <i>stratum oriens</i> (so), <i>stratum pyramidale</i> (sp), and <i>stratum radiatum</i> (sr; not shown); no differences in labeling frequency or labeling intensity were found between Polμ^−/− and wild-type mice. Igf1R-immunostaining delineated cell processes in the stratum radiatum (sr) of Polμ^−/− but not of wild-type mice. As compared with the case of aged mice, unspecific punctate labeling (long arrows) was infrequent in these tissue sections. Slight differences were found, however, in the occurrence of Igf1-immunoreactive cells in the CA1 area of aged mice, and in the expression of Igf1R between young wild-type and Polμ^−/− mice. Scale bar, 25 µm.