2002; Zhao et al. 2003; Cooper and Isacson 2004; Frielingsdorf et al. 2004; Chen et al. 2005; Yoshimi et al. 2005; Shan et al. 2006; Aponso et al. 2008; Peng et al. 2008; Hermann et al. 2009) or at very low rates (Zhao et al. 2003; Shan et al. 2006) in adult mouse SNc; and (3) evidence indicates similar changes in hypothalamus are due to DA neurotransmitter “switching,” not neurogenesis or apoptosis (Dulcis et al. 2013). Blockade of GABAA receptors in EE mice (Table ​(Table3)3) supports this hypothesis by providing Inhibitors,research,lifescience,medical instances of reciprocal

changes in the number of TH+ and TH− SNc neurons. However, while the number of TH+ SNc neurons changed in mated and environment-enriched mice without drug infusion, the number of TH− SNc neurons did not (Tables ​(Tables1,1, ​,2).2). Nevertheless this could be due to an artifact of the stereological method rather than evidence against DA neurotransmitter switching. We noted in the present study that many “new” TH+ neurons

Inhibitors,research,lifescience,medical lay just outside the perimeter of SNc http://www.selleckchem.com/DNA-PK.html following behavioral manipulation. Therefore, in these mice the borders of SNc (defined by the stereologist as the area circumscribing TH+ SNc cells) would expand compared Inhibitors,research,lifescience,medical to control mice (e.g., SH). Intermingled among these “new” TH+ neurons are TH− neurons which would otherwise be considered outside SNc and therefore not be counted. These additional TH− neurons would offset any decrease in TH− neurons brought about by acquisition Inhibitors,research,lifescience,medical of the DA phenotype. In the case of DA phenotype loss (e.g., mated females in Fig. ​Fig.1A),1A), the opposite might occur (i.e., the Inhibitors,research,lifescience,medical borders of SNc contract and any increase in TH− neurons due to DA phenotype loss would be offset by exclusion of perimeter TH− neurons from the counts). Further, we have previously shown that reciprocal changes in TH+ and TH− SNc neurons occur in almost every instance of drug infusion only (i.e., without concurrent EE) (e.g., SH + bicuculline in the present study [Table ​[Table3]3]

or [Aumann et al. 2011, 2008]), indicating that SNc borders remain stable in this context. Taken together, these data indicate that the environment or behavior has access to a broader pool click here of “switchable” SNc neurons than drug infusion, and most of these are located on the perimeter of SNc. When we subject mice to environmental manipulations alone (e.g., mating or EE in the present study), we do not see reciprocal changes in the number of TH+ and TH− SNc neurons for the reasons just discussed. However, when we infuse drugs alone (e.g., SH + bicuculline in the present study [Table ​[Table3]3] or [Aumann et al. 2008, 2011]), or combine environmental manipulations with drug infusions (e.g.