Steroid profiles in quail brain and serum: Sex and regional differences and effects of castration with steroid replacement.

Both systemic and local production contribute to the concentration of steroids measured in the brain. This idea was originally based on rodent studies and was later extended to other species, including humans and birds. In quail, a widely used model in behavioural neuroendocrinology, it was demonstrated that all enzymes needed to produce sex steroids from cholesterol are expressed and active in the brain, although the actual concentrations of steroids produced were never investigated. We carried out a steroid profiling in multiple brain regions and serum of sexually mature male and female quail by gas chromatography coupled with mass spectrometry. The concentrations of some steroids (eg, corticosterone, progesterone and testosterone) were in equilibrium between the brain and periphery, whereas other steroids (eg, pregnenolone (PREG), 5α/ß-dihydroprogesterone and oestrogens) were more concentrated in the brain. In the brain regions investigated, PREG sulphate, progesterone and oestrogen concentrations were higher in the hypothalamus-preoptic area. Progesterone and its metabolites were more concentrated in the female than the male brain, whereas testosterone, its metabolites and dehydroepiandrosterone were more concentrated in males, suggesting that sex steroids present in quail brain mainly depend on their specific steroidogenic pathways in the ovaries and testes. However, the results of castration experiments suggested that sex steroids could also be produced in the brain independently of the peripheral source. Treatment with testosterone or oestradiol restored the concentrations of most androgens or oestrogens, respectively, although penetration of oestradiol in the brain appeared to be more limited. These studies illustrate the complex interaction between local brain synthesis and the supply from the periphery for the steroids present in the brain that are either directly active or represent the substrate of centrally located enzymes.

A role for Src kinase in progestin facilitation of estrous behavior in estradiol-primed female rats.

This study tested the hypothesis that the Src/Raf/MAPK signaling pathway is involved in the facilitation of the lordosis and proceptive behaviors induced by progesterone (P) and its ring A-reduced metabolites in ovariectomized, estradiol-primed rats. Intraventricular (icv) infusion of PP2 (7.5, 15 and 30 microg), a Src kinase inhibitor, significantly depressed P-dependent estrous behavior (lordosis and proceptivity) in estradiol-primed rats. Icv infusion of 30 microg of PP2 also significantly attenuated estrous behavior induced by the ring A-reduced P metabolites 5 alpha-dihydroprogesterone (5 alpha-DHP) and 5 alpha-pregnan-3alpha-ol-20-one (allopregnanolone). PP2 did not inhibit estrous behavior induced by administration of high doses of estradiol alone to ovariectomized rats. We also assessed if the ventromedial hypothalamus (VMH) is one of the neural sites at which progestins activate Src signaling to facilitate estrous behavior. Bilateral administration of 15 microg of PP2 into the VMH inhibited the stimulation of both lordosis and proceptive behaviors elicited by subcutaneous P administration to estradiol-primed rats. These results suggest that progestins act through Src/Raf/MAPK signaling to initiate estrous behaviors in estrogen-primed rats. This event is one component of the cellular pathways leading to the display of estrous behaviors induced by P and its ring A-reduced metabolites in female rats.

Corticosteroid and neurosteroid dysregulation in an animal model of autism, BTBR mice.

Autism spectrum disorders (ASD) are a constellation of neurodevelopmental disorders associated with disruptions in social, cognitive, and/or motor behaviors. ASD are more prevalent among males than females and characterized by aberrant social and language development, and a dysregulation in stress-responding. Levels of progesterone (P(4)) and its metabolite 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) are higher and more variable in females compared to males. 3alpha,5alpha-THP is also a neurosteroid, which can be rapidly produced de novo in the brain, independent of peripheral gland secretion, and can exert homeostatic effects to modulate stress-responding. An inbred mouse strain that has demonstrated an ASD-like behavioral and neuroendocrine phenotype is BTBR T +tf/J (BTBR). BTBR mice have deficits in cognitive and social behaviors and have high circulating levels of the stress hormone, corticosterone. We hypothesized that central 3alpha,5alpha-THP levels would be different among BTBR mice compared to mice on a similar background C57BL/6J (C57/J) and 129S1/SvlmJ (129S1). Tissues were collected from BTBR, C57/J and 129S1 male mice and levels of corticosterone, P(4), and 3alpha,5alpha-THP in plasma and in the hypothalamus, midbrain, hippocampus, and cerebellum were measured by radioimmunoassay. Circulating levels of corticosterone, P(4), and 3alpha,5alpha-THP were significantly higher among BTBR, than C57/J and 129S1, mice. Levels of P(4) in the cerebellum were significantly higher than other brain regions among all mouse strains. Levels of 3alpha,5alpha-THP in the hypothalamus of BTBR mice were significantly higher compared to C57/J and 129S1 mice. These findings suggest that neuroendocrine dysregulation among BTBR mice extends to 3alpha,5alpha-THP.

Role of progesterone receptor isoforms in female sexual behavior induced by progestins in rats.

Progesterone and its ring A reduced metabolites regulate female sexual behavior through the direct or indirect activation of progesterone receptor (PR) which has two isoforms with different function and regulation: PR-A and PR-B. The contribution of each PR isoform to the regulation of lordosis in rats is unknown. We explored the role of PR isoforms in lordosis display induced by progesterone and two of its ring A reduced metabolites: 5alpha-pregnan-3,20-dione (5alpha-DHP), and 5beta,3beta-pregnan-20-one (5beta,3beta-Pgl) in adult ovariectomized rats. Two weeks after ovariectomy, the animals were injected subcutaneously with 5 microg of estradiol benzoate (EB), and 40 h later, progestins were injected intracerebroventricularly. PR-B and total PR (PR-A + PR-B) sense or antisense oligonucleotides were administered intracerebroventricularly immediately before EB injection and 24 h later. Lordosis was evaluated 30, 120 and 240 min after progestin administration. Western blot analysis of both PR isoforms was performed in the hypothalamus and preoptic area 24 h after lordosis tests. All progestins induced maximal lordosis 120 min after administration, and antisense oligonucleotides against both PR isoforms inhibited lordosis in all animals. PR-B antisense oligonucleotides also inhibited lordosis induced by progesterone and 5alpha-DHP although with less efficacy than total PR antisense oligonucleotides, but the former inhibited lordosis induced by 5beta,3beta-Pgl in a similar manner as total PR antisense oligonucleotides. In the hypothalamus and preoptic area, the content of both PR isoforms or PR-B alone was diminished by the administration of total or PR-B antisense oligonucleotides, respectively. These results suggest that the PR-B isoform is essential for the display of the lordosis behavior in rats.