Sex differences in brain aromatase activity: genomic and non-genomic controls

in Frontiers in Neuroendocrine Science (in press)

Steroid receptor coactivator 2 modulates steroid-dependent male sexual behavior and neuroplasticity in Japanese quail (Coturnix japonica)

in Journal of Neurochemistry (2011), 119

Effects of social experience on subsequent sexual performance in naïve male Japanese quail (Coturnix japonica)

in Hormones & Behavior (2010), 57

On their first sexual encounter, naïve male Japanese quail will attend to and approach a female; they sometimes mount but they do not always copulate. During the second encounter, most males successfully ... [more ▼]

On their first sexual encounter, naïve male Japanese quail will attend to and approach a female; they sometimes mount but they do not always copulate. During the second encounter, most males successfully copulate. Although sexual experience facilitates subsequent sexual interactions, sensory cues provided by females, independent of any sexual encounter, may also enhance sexual performance. To investigate whether previous exposure to a conspecific affects subsequent sexual behavior, we allowed inexperienced males to observe an empty box, or a conspecific consisting of either an experienced female or male for 2.5 min/day on 7 days. Measures of appetitive sexual behavior were recorded during these tests. On day 8, subjects were allowed to copulate with a novel female for 5 min. On the following days, all subjects were repeatedly provided with visual access to a female and allowed to mate. In the pre-copulatory trials males initially exhibited a high frequency of appetitive responses that dissipated with repetition. Pre-copulatory experience also significantly affected motivation to mate with subjects exposed to females copulating more quickly than other subjects. Post-copulatory appetitive behavior also differed between groups: control subjects showed the highest behavioral frequency followed by males exposed to females and finally males exposed to males. These data indicate that pre-copulatory social experience profoundly influences subsequent sexual behavior and probably reproductive success. This experience effect is independent of any hormonal effect (such as one resulting from changes in secretion following different social interactions) given that the subjects were castrates chronically treated with testosterone. [less ▲]

Sex steroid-induced neuroplasticity and behavioral activation in birds

in European Journal of Neuroscience (2010), 32

Is sexual motivational state linked to dopamine release in the medial preoptic area?

in Behavioral Neuroscience (2010)

The medial preoptic area (mPOA) is a key site for the dopaminergic enhancement of male sexual behavior. Dopamine release increases in the rat mPOA with mating, supporting the critical stimulatory role ... [more ▼]

The medial preoptic area (mPOA) is a key site for the dopaminergic enhancement of male sexual behavior. Dopamine release increases in the rat mPOA with mating, supporting the critical stimulatory role played by preoptic dopamine on male sexual behavior. However, it has been questioned whether dopamine is specifically related to the occurrence of male sexual behavior and not simply involved in general arousal. To address this question, we ask whether dopamine release in the mPOA is linked to the production of male sexual behavior in Japanese quail, a species that exhibits a much shorter temporal pattern of copulation than rats and does not have an intromittent organ, resulting in a very different topography of their sexual response. Extracellular samples from the mPOA of adult sexually experienced male quail were collected every six minutes before, during, and after exposure to a female using in vivo microdialysis and analyzed using HPLC-EC. Extracellular dopamine significantly increased in the presence of a female and returned to baseline after removal of the female. However, subjects who failed to copulate did not display this increased release. These findings indicate that it is not solely the presence of a female that drives dopamine release in males, but how a male responds to her. Further, in subjects that copulated, dopamine release did not change in samples collected during periods of no copulation. Together, these findings support the hypothesis that dopamine action in the mPOA is specifically linked to sexual motivation and not only copulatory behavior or physical arousal. [less ▲]

Behavioral effects of rapid changes in aromatase activity in the central nervous system

in Kordon, C.; Gaillard, R. C.; Christen, Y. (Eds.) Research and perspectives in endocrine action (2004)

Multiple mechanisms control brain aromatase activity at the genomic and non-genomic level

in Journal of Steroid Biochemistry & Molecular Biology (2003), 86

Evidence has recently accumulated indicating that aromatase activity in the preoptic area is modulated in parallel by both slow (hours to days) genomic and rapid (minutes to hours) non-genomic mechanisms ... [more ▼]

Evidence has recently accumulated indicating that aromatase activity in the preoptic area is modulated in parallel by both slow (hours to days) genomic and rapid (minutes to hours) non-genomic mechanisms. We review here these two types of control mechanisms and their potential contribution to various aspects of brain physiology in quail. High levels of aromatase mRNA, protein and activity (AA) are present in the preoptic area of this species where the transcription of aromatase is controlled mainly by steroids. Estrogens acting in synergy with androgens play a key role in this control and both androgen and estrogen receptors (ER; alpha and beta subtypes) are present in the preoptic area even if they are not necessarily co-localized in the same cells as aromatase. Steroids have more pronounced effects on aromatase transcription in males than in females and this sex difference could be caused, in part, by a sexually differentiated expression of the steroid receptor coactivator 1 in this area. The changes in aromatase concentration presumably control seasonal variations as well as sex differences in brain estrogen production. Aromatase activity in hypothalamic homogenates is also rapidly (within minutes) down-regulated by exposure to conditions that enhance protein phosphorylation such as the presence of high concentrations of calcium, magnesium and ATP. Similarly, pharmacological manipulations such as treatment with thapsigargin or stimulation of various neurotransmitter receptors (alpha-amino-3-hydroxy-methyl-4-isoxazole propionic acid (AMPA), kainate, and N-methyl-d-aspartate (NMDA)) leading to enhanced intracellular calcium concentrations depress within minutes the aromatase activity measured in quail preoptic explants. The effects of receptor stimulation are presumably direct: electrophysiological data confirm the presence of these receptors in the membrane of aromatase-expressing cells. Inhibitors of protein kinases interfere with these processes andWestern blotting experiments on brain aromatase purified by immunoprecipitation confirm that the phosphorylations regulating aromatase activity directly affect the enzyme rather than another regulatory protein. Accordingly, several phosphorylation consensus sites are present on the deduced amino acid sequence of the recently cloned quail aromatase. Fast changes in the local availability of estrogens in the brain can thus be caused by aromatase phosphorylation so that estrogen could rapidly regulate neuronal physiology and behavior. The rapid as well as slower processes of local estrogen production in the brain thus match well with the genomic and non-genomic actions of steroids in the brain. These two processes potentially provide sufficient temporal variation in the bio-availability of estrogens to support the entire range of established effects for this steroid. [less ▲]