, 2010; Kuhn et al., 2010). The apparent lack of involvement of the hypothalamic cluster cell groups in mediating adolescent change in social information processing is surprising, given their roles

in expression of social behaviors and reward. The VMH is involved in sexual behavior (Harding & McGinnis, 2005) and shows increased Fos expression in response to estrous odors in adult male rats (Kippin et al., 2003). However, the rats in their study were sexually experienced, whereas hamsters in the current study were sexually naïve, suggesting that a VMH response to estrous odors may be conditioned as a result of previous selleck chemicals llc experience. Hypothalamic orexin is involved in expression of sexual behavior and reward (Muschamp et al., 2007; Di Sebastiano et al., 2011), but the finding that orexinergic neurons were not responsive to VS suggests that the rewarding value of VS is somehow distinct from Lumacaftor manufacturer general sexual reward. The number of single-labeled Tail VTA TH-ir and orexin-ir neurons was greater in juveniles than in adults. These results are somewhat difficult to interpret

because a reduction in cytoplasmic immunoreactivity could be indicative of either reduced protein expression or reduced cytoplasmic levels of protein secondary to enhanced protein transport to the axon terminal. The current study also found that, compared

with juveniles and independent of VS exposure, adults had greater numbers of Fos-expressing TH-ir and orexin-ir cells in Tail VTA and DM/PeF, respectively. These results may be indicative of heightened Cyclooxygenase (COX) vigilance or sensitivity to non-specific stimuli in adulthood (e.g. a clean cotton swab in this study), as both dopamine and DM/PeF orexin have been implicated in general arousal as reviewed by Harris & Aston-Jones (2006), Ikemoto (2007) and Boutrel et al. (2010). Previous studies have documented adolescent changes in the rewarding properties of drugs of misuse in animals, but less attention has been paid to natural or social rewards (Doremus-Fitzwater et al., 2010). The present study demonstrates an experience-independent gain in the unconditioned rewarding value of a social stimulus over the course of adolescent development, and provides a neuroanatomical basis for the hypothesis that maturational changes within the mesocorticolimbic system mediate this shift in behavioral responses to VS.