Changes in central steroid receptor expression, steroid synthesis, and dopaminergic activity related to the reproductive cycle of the ring dove

Abstract

This review examines possible neural mechanisms involved in the expression of parental behavior in the ring dove, Streptopelia risoria. This avian species has proved an excellent animal model for studies concerning endocrine-behavior interactions for many years. Studies were performed to localize the expression of central androgen and progesterone receptor in both sexes. Expression of androgen receptor (androgen receptor immunoreactivity, AR-ir) was widespread but increased, similarly in both sexes, with increasing day-length. Progesterone receptor-immunoreactivity (PR-ir) was more localized in several discrete areas of the hypothalamus. Similarly, no sex differences were observed in PR-ir, and expression increased in birds maintained on long days. AR-ir demonstrated dramatic changes over the breeding cycle, being greatest in courting birds and almost undetectable in parenting birds of both sexes brooding their young. PR-ir showed a differential expression over the breeding cycle relative to its hypothalamic localization. PR-ir decreased in the tuberal hypothalamic area in brooding birds of both sexes; whereas in the preoptic area, PR-ir was maintained. Significant increases in dopaminergic activity during the parenting phase of the breeding cycle occurred in specific neural regions including the PVM and DMA. Studies demonstrated the ability of the diencephalon of both sexes of the ring dove brain to synthesize progesterone, with indications that in the male brooding dove, synthesis is increased. Finally, a model is presented that proposes a mechanism whereby these central systems may interact to result in the expression of full parental behavior in both sexes of the ring dove.

Seasonal changes in the expression of the androgen receptor in the testes of the domestic goose (Anser anser f. domestica)

“…The relation between season and AR protein expression in bird testes still remains explored. Our findings corroborate the results of previous studies focused on central AR seasonal protein expression in songbirds [9,10,21,39]. Moreover, there is growing evidence that photoperiod induces changes in AR protein levels in various organisms and tissues, including the testes of bank vole [4,43] and brushtail possum (Trichosurus vulpecula) [26], the brain of Syrian hamster (Mesocricetus auratus) and electric fish (Brachyhypopomus gauderio) [34,35].…”

Winning territorial disputes selectively enhances androgen sensitivity in neural pathways related to motivation and social aggression

“…36 for example). Indeed, activation of AR in adult animals plays a critical role in aspects of reproduction and parenting (37,38), which implies that these behaviors might be adjusted in winners as a result of changes to neural AR expression.…”

Endocrine and neuroendocrine regulation of fathering behavior in birds

“…Thus, in these species, uninterrupted care of young may be enabled by (1) a decoupling of testosterone secretion from social challenges, which could reduce the incidence of transient elevations in testosterone once breeding is underway, and (2) a reduced behavioral sensitivity to any elevations in testosterone that do occur (e.g., in the presence of fertile females) (Goymann et al, 2007;Lynn, 2008;Lynn and Wingfield, 2008). In terms of underlying mechanisms, some evidence suggests that changes in androgen receptor levels and/or rapid changes in expression or activity of the androgen-metabolizing enzyme aromatase in the brain may mediate at least some aspects of changing sensitivity to testosterone during breeding (Foidart et al, 1998;Lea et al, 2001;Pintér et al, 2011;Riters et al, 2001;Silverin et al, 2004;Silverin and Deviche, 1991;Soma et al, 1999). However, mechanisms of behavioral insensitivity to testosterone during the parental phase specifically remain understudied.…”