Sex-Specific Modulation of Cell Proliferation by Socially Relevant Stimuli in the Adult Green Treefrog Brain <i>(Hyla cinerea)</i>

Abstract

Social experience plays an important role in regulating the neural, physiological and hormonal changes that accompany the expression of reproductive behavior in vertebrates. This suite of functions is sexually dimorphic, with different neural control areas preeminent in males and females. In anuran amphibians, social experience comes in the form of acoustic communication, which is central to their reproductive behavior. We sought to determine whether acoustic cues regulate cell proliferation in the brain of adult green treefrogs (Hyla cinerea). Our results show that both male and female treefrogs that heard a conspecific chorus during the breeding season exhibited increased brain cell proliferation compared to animals that heard random tones. Increased cell proliferation, as assessed by the number of 5-bromo-2′-deoxyuridine-immunoreactive (BrdU+) cells, were found near the ventricles of acoustically sensitive brain regions such as the preoptic area (POA) and the infundibular hypothalamus (IF). Sex differences emerged in the location of this socially modulated cell proliferation: increases occurred primarily in the male POA and the female IF. In addition, gonadal steroid hormones might have played a role in the social modulation of cell proliferation: by statistically control- ling for hormone level, we revealed that androgens might influence socially induced increases in BrdU+ cells in the male POA, but estrogen did not contribute to socially induced increases in the female IF. These results indicate that the reception of social cues increases cell proliferation in brain regions mediating sexual behavior and endocrine regulation, and moreover that social modulation of cell proliferation occurs in a sexually differentiated fashion.

Environmental complexity, seasonality and brain cell proliferation in a weakly electric fish, Brachyhypopomus gauderio

“…In this frog, exposure to conspecific acoustic stimuli elevates cell proliferation rates in brain regions involved with calling behavior, but not in control regions that are unrelated to calling behavior (Almli and Wilczynski, 2009). Together, these results indicate that cell proliferation in brain regions involved with communication behavior is particularly responsive to social stimuli and may contribute to adaptive changes in social behavior.…”

Influence of long-term social interaction on chirping behavior, steroid levels and neurogenesis in weakly electric fish

“…In the 1980s, Fernando Nottebohm and colleagues showed that changes in the songs of canaries correlated with addition of neurons in a brain region (the high vocal center) that controls vocal behavior (Goldman and Nottebohm, 1983;Alvarez-Buylla et al, 1988). Since then, many studies in vertebrates have shown that social interaction influences cell proliferation and neurogenesis in the brain (Lieberwirth and Wang, 2012;Gheusi et al, 2009;Font et al, 2012;Almli and Wilczynski, 2009;Barnea and Pravosudov, 2011). However, given the complexity of social signaling in most species, it is often difficult to identify specific features of social interaction that are effective for influencing neurogenesis.…”

Socially Modulated Cell Proliferation Is Independent of Gonadal Steroid Hormones in the Brain of the Adult Green Treefrog <i>(Hyla cinerea)</i>

“…Our previous study [Almli and Wilczynski, 2009] demonstrated that the number of proliferating cells, as labeled by 5-bromo-2 -deoxyuridine (BrdU) incorporation, can be modulated in adult animals in naturally cycling reproductive condition via acoustic social stimuli in a region-and sex-specific manner. In males, social stimulation increased proliferating cell numbers in the preoptic area (POA), whereas in females this increase occurred in the infundibular hypothalamus (IF).…”

“…Because social stimulation affects both gonadal steroid levels and cell proliferation in frogs, we could not determine with certainty if the hormone change mediated or influenced the increase in cell proliferation, or if they were two separate phenomena related to the stimulation. Although androgen changes co-occurred with increases in cell proliferation following exposure to conspecific calls, and therefore might have contributed to the social modulation of cell proliferation in males, estrogens did not seem to modulate socially induced cell proliferation in females [Almli and Wilczynski, 2009]. In this study, we sought to determine experimentally the role of gonadal steroid hormones in cell proliferation in general and specifically whether they are important for socially modulated cell proliferation.…”