Given the importance of appropriately interpreting social stimuli in successful adult social interactions, the overall goal of this study is to determine which brain regions and neurotransmitter systems are associated with adolescent changes in the perception of social stimuli. The male Syrian hamster is an ideal animal model for investigating the neural substrates of adolescent maturation of social information processing. Information regarding female reproductive status is conveyed via pheromone-containing vaginal secretions (VS). Appropriate neural processing of VS is required for the performance of male sexual behavior and

is sufficient Romidepsin datasheet to induce a conditioned place preference (CPP) in sexually naïve adult male hamsters, indicating that VS are inherently rewarding to adults (Murphy & Schneider, 1970; Petrulis, 2009; Bell et al., 2010). In contrast, juvenile hamsters are not attracted to VS (Johnston & Coplin, 1979), nor do they mate with a receptive female when primed with exogenous testosterone (Meek et al., 1997; Schulz et al., 2009). Studies using the immediate Opaganib early gene Fos as a proxy for neural activation reveal that juvenile hamsters do detect VS, as

it elicits an increase in Fos expression in brain regions typically associated with processing of chemosensory social stimuli, e.g. the medial amygdala (Romeo et al., 1998). Thus, the behavioral responses to VS change across adolescent development, and this naturally occurring maturation of social information processing is critical for successful reproduction. The neural underpinnings of these age-related changes in responses to VS are unknown. The ability of adults to form a CPP for VS suggests involvement of reward-related neural systems in the processing of this social stimulus. In particular, the rodent mesocorticolimbic dopaminergic and hypothalamic orexin systems are implicated in sexual, food and psychotropic drug reward (Meisel et al.,

1996; Becker et al., 2001; Harris et al., 2005; Muschamp et al., Racecadotril 2007; Ikemoto, 2010; Lajtha & Sershen, 2010; Di Sebastiano et al., 2011), and these systems often operate in concert (Fadel & Deutch, 2002; Korotkova et al., 2003; Narita et al., 2006). Both dopaminergic and orexinergic circuitries undergo functional and structural changes during adolescence (Kuhn et al., 2010; Sawai et al., 2010); however, developmental changes in response to social stimuli, including VS, have not been examined within these circuitries. The present study seeks to determine if juveniles differ from adults in their proclivity to (1) show CPP for VS, and (2) express Fos in response to VS in mesocorticolimbic and hypothalamic reward circuits.