Histochem Cell Biol (2012) 137:11–24 (see Lowry et al. 2005). The methods documented in the present study enable further detailed analyses of the entire 5-HTR mRNA expression of NPY-producing neurons particularly in limbic brain areas. These data will provide the basis for electrophysiological and connectivity studies of serotonin-NPY interactions, and may thus further our understanding of the role of these important neuromediator systems in CNS functions. Acknowledgments We wish to thank Brigitte Treffny and Gabriela Ortega for skilfull technical assistance. This work was supported by the Deutsche Forschungsgesellschaft (DFG) RTG 1253/1, SFB 581 (TPZ3, B9) and SFB TRR 58 (TPA5). Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which per- mits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. 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