The Chinese black sleeper Bostrychus sinensis belongs

The Chinese black sleeper, Bostrychus sinensis, belongs to the family Eleotridae, suborder Gobioidei. This species is a burrowing animal and inhabits intertidal zones [28]. As a seasonal breeding fish, females and males live in individual burrows during the non-spawning season, but spawn as a pair inside the same burrow during the spawning season [29]. This spawning behavior and burrow-living habit suggest that mature males and females may employ sex pheromones to synchronize gametogenesis, spawning and fertility, since visual communication seems less efficient inside the burrow. Our previous studies showed that the levels of PGE2 were obviously higher than those of PGF2α in ovarian extract and urine at sex maturation stage [32], which suggested that PGE2 may be involved in the ovulatory process, and serves as a sex pheromone in B. sinensis. This hypothesis was further proved by our study which showed that nests with a PGE2-releasing tube attract more males and females and have in a higher spawning rate than control nests [29]. In addition, both mature male and female B. sinensis display greater EOG response to PGE2, compared to immature fish [30], which indicates that PGE2 is a putative sex pheromone in B. sinensis and that the olfactory sensitivity to PGE2 depends on the reproductive status. According to transcriptomic data, three subtypes of PGE2 receptor mRNAs (ep1, ep2 and ep4) were expressed in the B. sinensis olfactory rosette. The ep1 mRNA levels in the olfactory rosette of mature fish were significantly higher than those in immature fish [31], suggesting that the distinct olfactory sensitivities to PGE2 might be due to the changes of Ep1 levels [31]. However, it is not clear if androgens contribute to the up-regulation of ep1 BRD-K4477 synthesis in male fish. In the present study, we first examined the in vivo and ex vivo effects of androgens on ep1 expression in the olfactory rosette of male B. sinensis. Thereafter, we cloned two different B.sinensis ar cDNAs and investigated their roles in the effects of 11-KT on ep1 expression.
Material and methods
Results
Discussion It is well documented that androgens modify olfactory processing in vertebrates. For example, treatment of female mice with androgen on the day of birth is sufficient to produce the male-typical olfactory preference for female-soiled bedding [38]. It has been reported in several teleost species that androgens increase the olfactory sensitivity in response to prostaglandin pheromone [5,15], but the mechanism is still unclear. One possibility may be that androgens increase olfactory epithelium thickness as well as surface area, which results in higher density of OSNs for pheromone detection [39,40]. Besides the number of OSNs, the positions of OSNs within the olfactory epithelium change from deep to superficial throughout the year [41]. The androgen-induced reorganization of OSNs (density and position) might contribute to higher sensitivity to pheromones. Alternatively, androgens may directly bind to androgen receptors in the olfactory epithelium to modulate the expression of receptors for pheromones [20]. The finding in mice supports this hypothesis by showing that T modulates the expression of vomeronasal receptors, thus altering behavioral responses to pheromones [17]. In B. sinensis, mature fish displayed greater EOG response to sex pheromone PGE2 and higher olfactory ep1 transcript levels than immature fish [30,31]. Moreover, Ep1 protein was found in the dendritic knobs of OSNs in the olfactory epithelium, indicating Ep1 is a candidate receptor for pheromone PGE2. In the present study, we found that androgens up-regulated the expression of ep1 in the olfactory rosette of B. sinensis, suggesting that androgens increase the olfactory sensitivity to pheromone PGE2 by modulating the expression of ep1.