Horm Behav. isotocin. synthesis of estrogens (Diotel et al., 2010). Second, goldfish are a highly sociable varieties (Kavaliers, 1989; Magurran and Pitcher, 1983) in which behavior has been well analyzed in the context of sex steroid modulation. During the breeding time of year, as testosterone levels rise, olfactory cues play a predominant part in eliciting courtship-related behaviours (examined in Stacey and Sorensen, 2009), although visual cues are used for sexual discrimination (Thompson et al., 2004) and may help males maintain proximity to ovulating females and thus better compete with additional males during spawning (Thompson and Mangiamele, 2013). In goldfish males, rapid raises in sociable approach in response to the visual stimuli of females (in the absence of additional cues) can be induced within 30C45 moments of peripheral testosterone (T) injection, an effect that is clogged by aromatase inhibition, and within 10C25 moments of peripheral estradiol injection (Lord et al., Demeclocycline HCl 2009). Although olfactory cues are critical for initiating courtship in male goldfish, we have no evidence to suggest that E2 rapidly modulates responses to olfactory signals in this species. E2 could rapidly influence pathways that mediate visually guided approach responses of males to females via actions in limbic structures associated with the interpersonal brain network (SBN), a collection of highly conserved, interconnected nuclei that respond to sex steroids and mediate multiple interpersonal behaviors, including sexual responses, across Demeclocycline HCl vertebrates (Newman, 1999; Goodson, 2005; OConnell and Hofmann, 2011; Demeclocycline HCl OConnell and Hofmann, 2012). In goldfish, proposed homologous regions include the supracommissural nucleus of the ventral telencephalon (Vs), the putative fish homolog of the medial extended amygdala, and/or the preoptic area (POA). Both the Vs and the POA are areas that express aromatase in goldfish (Gelinas and Callard, 1993; Gelinas and Callard, 1997) and are involved in the regulation of courtship behavior (Kyle and Peter, 1982). The preoptic area receives direct retinal projections (Springer and Gaffney, 1981), as well as olfactory input (Levine and Dethier, 1985; Lado et al., 2014), so it could play a critical role in integrating sexual stimuli processed in multiple sensory modalities into behavioral output. Interestingly, isotocin produced in the preoptic area can, like E2, stimulate approach responses to the visual stimuli of conspecifics within 5C20 moments in goldfish males (Thompson and Walton, 2004), raising the possibility that estrogenic effects on these peptidergic neurons, perhaps through GPR30 signaling mechanisms, could also play some role in E2s behavioral effects. Alternatively, or in addition, rapid estrogenic effects on male goldfish interpersonal approach behavior could be mediated through actions in visual processing areas, Demeclocycline HCl including the retina, where increased visual sensitivity could help males detect potential mates, and/or its main target, the optic tectum (OT), which F2r plays a critical role in visual orienting (Springer et al., 1977). Notably, both the retina and one of its major main targets, the OT, contain high levels of the enzyme aromatase in goldfish (Gelinas and Callard, 1997), thereby supporting the hypothesis that local synthesis of estrogens in this main visual pathway could play a particularly important role in mediating visually guided behaviors. Estrogens could also stimulate approach responses to females through influences on the processing of visual information in ascending visual pathways that ultimately reach the dorsal telencephalon, including the lateral, medial, and central divisions (Dl, Dm, and Dc, respectively) via a relay in the preglomerular complex (Northcutt, 2006; Yamamoto and Ito, 2008), although the precise role these pathways play.