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See detailImmunocytochemical Localization of Aromatase in the Brain
Balthazart, Jacques ULg; Foidart, Agnès ULg; Harada, N.

in Brain Research (1990), 514(2), 327-33

An immunocytochemical peroxidase-antiperoxidase procedure using a purified polyclonal antibody raised against human placental aromatase was used to localize aromatase-containing cells in the Japanese ... [more ▼]

An immunocytochemical peroxidase-antiperoxidase procedure using a purified polyclonal antibody raised against human placental aromatase was used to localize aromatase-containing cells in the Japanese quail brain. Immunoreactive cells were found only in the preoptic area and hypothalamus, with a high density of positive cells being present in the sexually dimorphic medial preoptic nucleus, in the ventromedial nucleus of the hypothalamus and in the infundibulum. The positive material was localized in the perikarya and in adjacent cytoplasmic processes. Aromatase-containing cells were a specific marker for the sexually dimorphic preoptic nucleus. Treatment with testosterone produced a 6-fold increase in the aromatase activity of the preoptic area and a 4-fold increase in the number of immunoreactive cells in the medial preoptic nucleus. Thus, the increase in aromatase activity observed after testosterone administration is caused by a change in enzyme concentration. [less ▲]

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See detailThe Induction by Testosterone of Aromatase Activity in the Preoptic Area and Activation of Copulatory Behavior
Balthazart, Jacques ULg; Foidart, Agnès ULg; Hendrick, J. C.

in Physiology & Behavior (1990), 47(1), 83-94

A series of 4 experiments was designed to study the relationships between the activity of the aromatase (AA) in the preoptic area (POA) and the activation by testosterone (T) of copulatory behavior in ... [more ▼]

A series of 4 experiments was designed to study the relationships between the activity of the aromatase (AA) in the preoptic area (POA) and the activation by testosterone (T) of copulatory behavior in gonadectomized male and female Japanese quail. The induction of AA by T in the POA is dose- and time-dependent. Levels of AA seen in sexually mature males are restored in castrated birds by a treatment with 20 to 40 mm silastic T capsules which produce physiological levels of steroid in the plasma. The minimal dose of T (10 mm implant) which reliably restores copulatory behavior approximately doubles the AA in the POA. The induction of AA is significantly larger in males than in females. A significant increase in AA is observed within 16 hours after the start of the treatment with T and the induction is maximal after 48 hours. Activation of copulatory behavior follows a similar time course but occurs with a delay of 24-48 hours. These results thus suggest that, in male quail, the activity of the aromatase in the POA is a limiting factor in the activation of copulatory behavior. This idea is confirmed by direct experimentation using an aromatase inhibitor, androstatrienedione (ATD). If T-treated birds receive at the same time silastic implants filled with ATD, the activation of behavior is suppressed for at least one week. This behavioral inhibition is, as expected, accompanied and very probably caused by the inhibition of the aromatase activity in the preoptic area and anterior hypothalamus. No increase of enzyme activity over the level seen in castrates was actually detected during the first 8 days of exposure to T. A moderate increase in AA was seen on day 16 and is probably responsible for the behavioral activation which was observed at the end of the experiment. [less ▲]

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See detailAn Autoradiographic Study of Alpha 1-Adrenergic Receptors in the Brain of the Japanese Quail (Coturnix Coturnix Japonica)
Balthazart, Jacques ULg; Ball, G. F.; McEwen, B. S.

in Cell & Tissue Research (1989), 258(3), 563-8

The neuroanatomical distribution of alpha 1-adrenergic receptors was studied in Japanese quail by quantitative in vitro autoradiography using the specific antagonist [3H]prazosin as the ligand. The ... [more ▼]

The neuroanatomical distribution of alpha 1-adrenergic receptors was studied in Japanese quail by quantitative in vitro autoradiography using the specific antagonist [3H]prazosin as the ligand. The presence of saturable (Bmax less than 200 fmol/mg protein) high affinity (Kd less than 0.12 nM) binding sites was detected by saturation analysis. High concentrations of [3H]prazosin binding sites were detected in the archistriatum/pars ventralis, the hippocampus, the cortex piriformis, the area corticoidea dorsolateralis, the dorsal thalamus, and the nucleus praetectalis. Lower concentrations were seen in the intercollicular nucleus, the lateral septum, and the posterior and tuberal hypothalamus. Very little binding was seen in the preoptic and anterior hypothalamic areas. The relatively high number of binding sites identified in the telencephalic structures agrees well with previous mammalian studies. This is in contrast with the pattern in the anterior hypothalamus where, in mammals, a number of nuclei have been reported to contain a high receptor density. [less ▲]

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See detailCorrelation between the Sexually Dimorphic Aromatase of the Preoptic Area and Sexual Behavior in Quail: Effects of Neonatal Manipulations of the Hormonal Milieu
Balthazart, Jacques ULg

in Archives Internationales de Physiologie et de Biochimie (1989), 97(6), 465-81

The aromatase of the preoptic area is significantly more active in males than in females. This sex dimorphism in enzyme activity is still found in birds that have been gonadectomized and treated with a ... [more ▼]

The aromatase of the preoptic area is significantly more active in males than in females. This sex dimorphism in enzyme activity is still found in birds that have been gonadectomized and treated with a same dose of testosterone. This suggests that the sex difference is not the result of a differential activation by the adult hormonal environment but rather is organized neonatally by steroid hormones. As the central aromatization of testosterone is a limiting step in the activation of copulatory behavior by testosterone, the lower aromatase activity in the preoptic area of females might be responsible, at least in part, for their lower sensitivity to the activating effects of testosterone on behavior. Three experiments were carried out to determine whether early manipulations of the hormonal environment, which are known to differentiate sexual behavior, also affect in a permanent way the aromatase activity in the preoptic area. Injection of estradiol benzoate into male embryos on day 9 of incubation decreased the preoptic aromatase activity in parallel to its demasculinizing effect on behavior. Unexpectedly the same treatment tended to increase enzyme activity in females so that the physiological relevance of the observed enzymatic change remains questionable. In two independent experiments, we confirmed that neonatal ovariectomy of female quail interferes with their behavioral differentiation. Females gonadectomized at 4 days post-hatch showed significantly more male-type sexual behavior as adult in response to testosterone than females gonadectomized at the age of 5 weeks. These experiments also confirmed that the preoptic aromatase activity is higher in males than in females but no evidence for an effect of the age of gonadectomy on the enzyme activity could be obtained. The sex difference and experimental modifications observed in the aromatase activity of the preoptic area were not seen in the posterior hypothalamus demonstrating that these effects are specific. The mechanisms controlling the sex difference in aromatase activity are discussed. The difference might be organized by the action of embryonic steroids as suggested by the changes observed in males injected with estradiol benzoate in egg. Alternatively, activational mechanisms cannot be ruled out at present. In one experiment, the activity of the preoptic aromatase was positively correlated with the sexual activity of the birds.(ABSTRACT TRUNCATED AT 400 WORDS) [less ▲]

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See detailDistribution of Estrogen Receptors in the Brain of the Japanese Quail: An Immunocytochemical Study
Balthazart, Jacques ULg; Gahr, M.; Surlemont, C.

in Brain Research (1989), 501(2), 205-14

The distribution of estrogen receptors in the quail brain was investigated by immunocytochemistry using the monoclonal antibody H222SPy raised against estrogen receptors that had been isolated from a ... [more ▼]

The distribution of estrogen receptors in the quail brain was investigated by immunocytochemistry using the monoclonal antibody H222SPy raised against estrogen receptors that had been isolated from a human mammary tumor. Nuclei which contained cells labeled for estrogen receptor were identified in the telencephalon, diencephalon and mesencephalon. In particular, a high percentage of labeled cells was observed in the lateral septum, the nucleus accumbens, the preoptic medial nucleus, the supraoptic nuclei, the anterior medial hypothalamus, the paraventricular magnocellular nucleus, the caudal parts of the lateral hypothalamus and in the whole tuberal and infundibular area. A small number of weakly labeled cells was also observed in the ventromedial nucleus of the hypothalamus. Although most of the positive cells were observed in the hypothalamic and preoptic area, a few areas were also labeled in other brain regions. This was particularly the case for the nucleus taeniae, the nucleus intercollicularis and the central gray. The distribution of labeled cells in this study closely matched with the distribution of cells which accumulated radioactivity following injection of tritiated estradiol in a previous study. The distribution of cells labeled by immunocytochemistry was similar in males and females and no evidence for a quantitative dimorphism in the percentage of labeled cells could be obtained. All nuclei containing cells labeled for estrogen receptors also contain significant levels of aromatase with the exception of the ICo. [less ▲]

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See detailEffects of the Noradrenergic Neurotoxin Dsp-4 on Luteinizing Hormone Levels, Catecholamine Concentrations, Alpha 2-Adrenergic Receptor Binding, and Aromatase Activity in the Brain of the Japanese Quail
Balthazart, Jacques ULg; Ball, G. F.

in Brain Research (1989), 492(1-2), 163-75

Previous investigations have established that DSP-4 reliably enhances the activating effects of testosterone on copulatory behavior in adult male quail. In the present study, we wanted to clarify the ... [more ▼]

Previous investigations have established that DSP-4 reliably enhances the activating effects of testosterone on copulatory behavior in adult male quail. In the present study, we wanted to clarify the neurochemical changes that parallel these behavioral effects and to determine whether DSP-4 also affects non-behavioral steroid-dependent sexually dimorphic reproductive processes. We first showed using the Palkovits microdissection technique combined with assay by high-performance liquid chromatography (HPLC) that DSP-4 specifically depletes norepinephrine in several nuclei of the brain such as the medial preoptic nucleus, the ventromedial nucleus of the hypothalamus or the intercollicular nucleus but leaves intact the noradrenergic innervation in other areas such as the infundibulum or nucleus accumbens. Other amines such as dopamine and serotonin were not affected by the drug. Surprisingly DSP-4 did not decrease the binding of tritiated p-aminoclonidine in any of the brain areas which were studied by quantitative autoradiography. This suggests that most of the alpha 2-adrenergic receptors are located at the postsynaptic level but alternative interpretations are discussed. Testosterone treatment of castrated birds specifically reduced the density of alpha 2-adrenergic receptors in the dorsal infundibulum and in the medial mammillary nucleus. The possible relations of this receptor change to the control of luteinizing hormone (LH) secretion are discussed. Finally it was shown that DSP-4 treatment decreases plasma LH levels (which reveals the stimulatory effect of norepinephrine on LH secretion) but increases the testosterone-induced aromatase activity in the preoptic area. This latter effect could be one of the mechanisms by which DSP-4 potentiates copulatory behavior in testosterone-treated quail. [less ▲]

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See detailA Dorsomedial Subdivision within the Nucleus Intercollicularis Identified in the Japanese Quail (Coturnix Coturnix Japonica) by Means of Alpha 2-Adrenergic Receptor Autoradiography and Estrogen Receptor Immunohistochemistry
Ball, G. F.; Foidart, Agnès ULg; Balthazart, Jacques ULg

in Cell & Tissue Research (1989), 257(1), 123-8

The nucleus intercollicularis is an important site in the control of vocalization in birds. In oscines, a subregion of the nucleus intercollicularis called the dorso-medial intercollicular nucleus appears ... [more ▼]

The nucleus intercollicularis is an important site in the control of vocalization in birds. In oscines, a subregion of the nucleus intercollicularis called the dorso-medial intercollicular nucleus appears to play a key role in this process because it receives the majority of the projections from the nucleus robustus archistriatalis and sends most of the projections to the motor nucleus of the hypoglossal nerve. In this paper, we present neurochemical studies of the nucleus intercollicularis in the Japanese quail which suggest the presence of heterogeneity within this structure. One rostral band contains high densities of cholinergic muscarinic receptors identified by quantitative autoradiography using tritiated N-methylscopolamine as the ligand. A caudal dorso-medial region is specifically labeled by estrogen receptors identified using immunocytochemistry and by alpha 2-adrenergic receptors which were quantified by autoradiography using tritiated para-amino-clonidine. This latter subregion is possibly equivalent to the dorso-medial intercollicular nucleus of oscines. Additional track-tracing studies should be performed to confirm this homology. The coexistence of estrogen and alpha 2-adrenergic receptors within the same structure suggests important functional connections between steroid action and catecholaminergic systems in the brain. [less ▲]

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See detailSexual Differentiation in Quail: Critical Period and Hormonal Specificity
Schumacher, M.; Hendrick, J. C.; Balthazart, Jacques ULg

in Hormones & Behavior (1989), 23(1), 130-49

There is a discrepancy between results showing that male quail are demasculinized by exogenous estrogens only if the treatment is given before Day 12 of egg incubation and results showing that ovariectomy ... [more ▼]

There is a discrepancy between results showing that male quail are demasculinized by exogenous estrogens only if the treatment is given before Day 12 of egg incubation and results showing that ovariectomy of females after hatching still affects their sexual differentiation which leads to the conclusion that female demasculinization by ovarian estrogens is a continuing process extending into posthatching life. The first experiment was performed to test different models which have been proposed to reconcile these apparently contradictory results. Male and female quail were treated with 0, 5, or 25 micrograms of estradiol benzoate (EB) on either Day 9 or Day 14 of embryonic life. Birds were castrated at the age of 4 days to avoid the confounding effects of postnatal gonadal hormones and were treated as adults with testosterone (T). Whereas EB-treatment demasculizined sexual behavior and cloacal gland growth of males when administered on Day 9, it was without effect on Day 14. This result confirms the presence of a "critical period" for sexual differentiation of behavior in embryonic life. However, the time course of sexual differentiation and the sensitivity to the demasculinizing actions of estrogens were not the same for different behavioral and morphological characteristics. Some dependent variables such as plasma levels of luteinizing hormone and crowing were still affected by the EB treatment on Day 14. These results show that the whole process of demasculinization is not retricted to the "critical period" ending on Day 12 of incubation. A second experiment was performed to determine if 5 beta-dihydrotestosterone (5 beta-DHT), a metabolite of testosterone, also exerts demasculinizing effects during embryonic life. A large dose of 5 beta-DHT (2 mg/egg) had no effects on behavior and morphology in males if administered on Day 9 of egg incubation. This suggests that 5 beta-DHT, which is a steroid devoid of behavioral effects in the adult bird, is also an inactive compound as far as sexual differentiation of the quail is concerned. The high 5 beta-reductase activity which was previously identified in the hypothalamus of the embryonic quail thus probably plays a protective role. By transforming testosterone into inactive nonaromatizable androgens, it prevents male embryos from being demasculinized by their endogenous testosterone acting through aromatization. [less ▲]

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See detailChanges in Progesterone Metabolism in the Chicken Hypothalamus During Induced Egg Laying Stop and Molting
Balthazart, Jacques ULg; Verheyen, G.; Schumacher, M. et al

in General and Comparative Endocrinology (1988), 72(2), 282-95

In the present study, we have established and validated a radioenzyme assay which permits us to quantify progesterone metabolism in the chicken brain. Progesterone metabolism was then studied in five ... [more ▼]

In the present study, we have established and validated a radioenzyme assay which permits us to quantify progesterone metabolism in the chicken brain. Progesterone metabolism was then studied in five brain areas obtained by microdissection from the telencephalon (part of the lobus paraolfactorius immediately rostral to the preoptic area), the preoptic area, and the hypothalamus. Three metabolites of progesterone were produced in large amounts in these brain regions and were quantified in this study: 5 beta-pregnane-3,20-dione (5 beta-DHP) as well as its metabolite 3 alpha-hydroxy-5 beta-pregnane-20-one (5 beta,3 alpha-ol) and 5 alpha-pregnane-3,20-dione (5 alpha-DHP). The unmetabolized progesterone was also recovered and quantified. The 5 beta-reduction of progesterone (production of 5 beta-DHP and 5 beta,3 alpha-ol) was very active but its 5 alpha-reduction (production of 5 alpha-DHP) was almost absent in the lobus paraolfactorius. An opposite pattern of metabolism was found in the preoptic area and the hypothalamus (higher 5 alpha- but lower 5 beta-reductase activity). The changes in progesterone metabolism in these brain areas were then studied in groups of hens submitted to induced egg laying stop and molting. A significant decrease in progesterone 5 alpha-reduction was found in the median hypothalamus of hens during the period of molt. Simultaneously, the experimental procedures induced significant decreases in the production of 5 beta-DHP by the lobus paraolfactorius, anterior, and medial hypothalamus but induced a significant increase in the production of this metabolite in the preoptic area. These changes are likely to be involved in the control of reproductive functions including sexual behavior and secretion of luteinizing hormone-releasing hormone, and a number of possible causal mechanisms are presented. These should now be tested experimentally especially in view of the very limited information which is now available on the biological effects of the metabolites of progesterone. [less ▲]

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See detailChanges in Serum Concentrations of Steroids During Embryonic and Post-Hatching Development of Male and Female Japanese Quail (Coturnix Coturnix Japonica)
Schumacher, M.; Sulon, Joseph ULg; Balthazart, Jacques ULg

in Journal of Endocrinology (1988), 118(1), 127-34

Serum concentrations of testosterone, 5 alpha-dihydrotestosterone, oestradiol and progesterone were measured by radioimmunoassay combined with Celite chromatography in male and female Japanese quail ... [more ▼]

Serum concentrations of testosterone, 5 alpha-dihydrotestosterone, oestradiol and progesterone were measured by radioimmunoassay combined with Celite chromatography in male and female Japanese quail (Coturnix coturnix japonica) during the second half of embryonic life (days 9-17 of incubation) and during the first 5 weeks after hatching. The mean level of each of the four steroids was significantly affected by the age of the birds. An overall effect of sex was detected by analysis of variance only on oestradiol concentrations, with females having higher serum concentrations than males during most of the age range studied. Significant peaks of testosterone and progesterone were also detected around hatching time. These results are consistent with the view that oestradiol is the major hormone implicated in the sexual differentiation of reproductive behaviour in the quail. The relationships between the circulating concentrations of oestradiol during ontogeny and the critical period of differentiation as postulated by currently accepted models is also discussed. [less ▲]

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See detailNeuroanatomical Distribution of Testosterone-Metabolizing Enzymes in the Japanese Quail
Schumacher, M.; Balthazart, Jacques ULg

in Brain Research (1987), 422(1), 137-48

We describe a very sensitive and precise assay which allows one to study the metabolism of testosterone (T) in small brain nuclei dissected out according to the method of Palkovits and Brownstein. With ... [more ▼]

We describe a very sensitive and precise assay which allows one to study the metabolism of testosterone (T) in small brain nuclei dissected out according to the method of Palkovits and Brownstein. With this method, the neuroanatomical distributions of aromatase, and 5 alpha- and 5 beta-reductase activities were studied in adult male quail (Coturnix coturnix japonica). The different enzymes show different neuroanatomical distributions. Production of estradiol-17 beta (E2) was highest in the sexually dimorphic nucleus preopticus medialis (POM). We showed previously that the preoptic aromatase activity is higher in male than in female quail. As the POM is a central and very large structure within the preoptic area, the present results suggest a relationship between the neuroanatomical and the biochemical sex differences. By contrast, the production of 5 alpha-DHT was highest in the lateral hypothalamic area (LHY), the bed nucleus of the pallial commissure (BPC) and the lateral septum (SL). The 5 beta-reductase activity was highest in the lateral septum and in the ventral part of the archistriatum (AV). Moreover, there was a rostral to caudal decrease in 5 beta-reductase activity in the hypothalamus. [less ▲]

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See detailCentral and Peripheral Metabolism of 5 Alpha-Dihydrotestosterone in the Male Japanese Quail: Biochemical Characterization and Relationship with Reproductive Behavior
Deviche, P.; Delville, Y.; Balthazart, Jacques ULg

in Brain Research (1987), 421(1-2), 105-16

An in vitro radioenzymatic assay and purification procedure by thin-layer chromatography were used to study the metabolism of dihydrotestosterone (DHT) into 3 alpha- and 3 beta-androstanediols by the ... [more ▼]

An in vitro radioenzymatic assay and purification procedure by thin-layer chromatography were used to study the metabolism of dihydrotestosterone (DHT) into 3 alpha- and 3 beta-androstanediols by the brain and cloacal gland of Japanese quail. Kinetic studies showed that these 2 metabolites are produced in a linear fashion with respect to time of incubation for up to 15 min but that they continue to accumulate for up to 4 h. The maximum velocity of these reactions is high (nmol/mg protein/15 min), but the affinities of the enzymes for DHT are low (in the microM range). The enzymatic activities are not evenly distributed in the brain: they are high in the tuberal hypothalamus and lobus parolfactorius but low in the preoptic area and anterior hypothalamus. Enzyme activities are not markedly affected by treatment of the birds with either testosterone or DHT. The activity of these enzymes is lower in the preoptic area and tuberal hypothalamus of DHT-treated birds which display female-directed sexual behavior than in the same brain areas of birds which are sexually inactive. We discuss the relationships between this reductive metabolism of DHT and the activational effects of the steroid on sexual behavior. [less ▲]

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See detailSteroid Hormones, Behavior and Sexual Dimorphism in Animals and Men: The Nature-Nurture Controversy
Schumacher, M.; Legros, Jean-Jacques ULg; Balthazart, Jacques ULg

in Experimental & Clinical Endocrinology (1987), 90(2), 129-56

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See detailHormonal Control of Female Sexual Behavior in the Japanese Quail
Delville, Y.; Balthazart, Jacques ULg

in Hormones & Behavior (1987), 21(3), 288-309

Four experiments were carried out to study the hormonal control of female receptivity and proceptivity in Japanese quail. Both aspects of reproductive behavior can be activated in a dose-dependent manner ... [more ▼]

Four experiments were carried out to study the hormonal control of female receptivity and proceptivity in Japanese quail. Both aspects of reproductive behavior can be activated in a dose-dependent manner by injections of estradiol benzoate (EB). Progesterone (P) given in addition to suboptimal doses of EB has little additional stimulatory effect. Other aspects of the reproductive physiology such as enlargement of the cloacal diameter and growth of the oviduct also seem to be controlled primarily by estrogens with little or no additive effect of P. These conclusions were confirmed by injecting egg-laying females with an antiestrogen, tamoxifen, or an antiprogestin, RU38486. Only the former had marked effects on sexual receptivity, cloacal diameter, and oviduct weight. The inhibiting effects of tamoxifen could easily be reversed by injecting females with large doses of estrogen, which demonstrates that tamoxifen acts on an estrogen-dependent mechanism and not through nonspecific effects. [less ▲]

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See detailEffect of the injection solvent on steroid activity.
Deviche, P.; Balthazart, Jacques ULg

in General and Comparative Endocrinology (1987), 65(2), 199-202

The effects of testosterone, 5 alpha-dihydrotestosterone, and androstenedione on cloacal gland and sternotracheal muscle growth and on luteinizing hormone plasma levels were studied in Japanese quail. The ... [more ▼]

The effects of testosterone, 5 alpha-dihydrotestosterone, and androstenedione on cloacal gland and sternotracheal muscle growth and on luteinizing hormone plasma levels were studied in Japanese quail. The steroids were given to the animals in daily intramuscular injections and were dissolved either in propylene glycol or in ethanol:saline (1:1). The three steroids had significant effects on the responses which were measured, but the magnitude of this effect was clearly related to the type of vehicle in which the steroids were dissolved. Furthermore there was a significant interaction between the effects of solvents and of steroid; for example, testosterone was much less androgenic than 5 alpha-dihydrotestosterone when dissolved in propylene glycol, but both had similar effects when dissolved in ethanol:saline. The effects of the mode of administration of different steroids on a given physiological response should be taken into consideration. [less ▲]

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See detailInteractions des androgenes et des oestrogenes dans le controle de la reproduction
Schumacher, M.; Alexandre, Corine; Balthazart, Jacques ULg

in Comptes Rendus de l'Académie des Sciences. Série III, Sciences de la Vie (1987), 305(14), 569-74

Castrated male quail were injected with the synthetic oestrogen, diethylstylbestrol (DES) or the synthetic androgen, methyltrienolone (R 1881) or both compounds simultaneously. Both R 1881 and DES ... [more ▼]

Castrated male quail were injected with the synthetic oestrogen, diethylstylbestrol (DES) or the synthetic androgen, methyltrienolone (R 1881) or both compounds simultaneously. Both R 1881 and DES activated male sexual behaviour, inhibited LH and FSH secretion and increased hypothalamic aromatase activity. Additive effects between R 1881 and DES were observed for the induction of brain aromatase and for the inhibition of FSH secretion. As a consequence, mechanisms mediated by androgen and estrogen receptors must be involved in the control of these reproductive characteristics. [less ▲]

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See detailInhibition of testosterone metabolism in the brain and cloacal gland of the quail by specific inhibitors and antihormones.
Alexandre, Corine; Balthazart, Jacques ULg

in Journal of Endocrinology (1987), 112(2), 189-95

The effects of antioestrogens, antiandrogens and of various inhibitors of testosterone metabolism on testosterone metabolism in the quail hypothalamus and cloacal gland were studied by an in-vitro ... [more ▼]

The effects of antioestrogens, antiandrogens and of various inhibitors of testosterone metabolism on testosterone metabolism in the quail hypothalamus and cloacal gland were studied by an in-vitro radioenzymatic assay. It was found that antioestrogens and antiandrogens generally had little or no effect on aromatase and 5 alpha- and 5 beta-reductases of testosterone, except when used at very high doses. The 5 alpha-reductase inhibitor, 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one, inhibited both 5 alpha- and 5 beta-dihydrotestosterone production without markedly affecting aromatase activity. Surprisingly, the aromatase inhibitor, 1,4,6-androstatriene-3,17-dione, inhibited not only the production of oestradiol but also that of 5 beta-dihydrotestosterone and, to a lesser extent, 5 alpha-dihydrotestosterone. These unexpected properties should be taken into account when interpreting the results of in-vivo experiments using these compounds. [less ▲]

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See detailSexual differentiation and hormonal control of the sexually dimorphic medial preoptic nucleus in the quail.
Panzica, G. C.; Viglietti-Panzica, C.; Calacagni, M. et al

in Brain Research (1987), 416(1), 59-68

We recently identified a sexually dimorphic nucleus in the preoptic region of the Japanese quail, the medial preoptic nucleus (POM), which is significantly larger in males than in females. In the present ... [more ▼]

We recently identified a sexually dimorphic nucleus in the preoptic region of the Japanese quail, the medial preoptic nucleus (POM), which is significantly larger in males than in females. In the present study, we investigated the hormonal control of this morphological neuroanatomical difference and the possible relationships between the sexual dimorphism in POM volume and in copulatory behavior. Treatments which are known to affect sexual behavior were thus applied to different groups of birds and the POM volume was then measured. In one experiment, male and female quails were either gonadectomized, gonadectomized and treated with testosterone or left intact. The larger size of the POM in males was confirmed and treatments significantly affected the nucleus size which was decreased by gonadectomy and restored by testosterone treatment in both sexes to a level similar to that seen in intact males. In two other experiments, eggs were injected with estradiol benzoate on day 9 of incubation and the POM volume was measured in adulthood either in intact birds or in gonadectomized birds receiving a replacement therapy with testosterone. Despite the fact that estradiol benzoate treatment completely suppressed copulatory behavior, it did not affect the volume of the POM or slightly increased it. These data thus show that the POM volume is controlled by testosterone levels in adulthood and could thus be an interesting model for the study of the effects of steroids on the brain. [less ▲]

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See detailSeasonal changes in some plasma hormones in pigeons: diurnal variation under natural photoperiods with constant or seasonally changing ambient temperature.
Rintamaki, H.; Hissa, R.; Etches, R. J. et al

in Comparative Biochemistry and Physiology (1986), 84(1), 33-8

The diurnal variations of several plasma hormones and free fatty acids (FFA) were studied during periods in summer and winter for pigeons reared either outdoors or indoors. The latter were subjected to ... [more ▼]

The diurnal variations of several plasma hormones and free fatty acids (FFA) were studied during periods in summer and winter for pigeons reared either outdoors or indoors. The latter were subjected to constant temperature and naturally varying photoperiods. A significant seasonal variation in the mean daily levels of triiodothyronine (T3), thyroxine (T4), corticosterone (B), lutropin (LH) and FFA was seen in the outdoor birds and in the T4 and B levels of indoor birds. The diurnal variation of hormone levels was generally more pronounced in winter in both groups. Cold ambient temperature significantly decreased the plasma LH level and potentiated the increasing effect of short photoperiod on plasma B level. Diurnal variation of plasma FFA level seems to be under the control of photoperiod, without any effects due to the ambient temperature. No significant correlation was found between FFA and GH concentrations. [less ▲]

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See detailSeasonal changes in some plasma hormones in pigeons from different environments.
Saarela, S.; Hissa, R.; Etches, R. et al

in Comparative Biochemistry and Physiology (1986), 84(1), 25-31

Seasonal variation in the plasma concentration of lutropin (LH), follitropin (FSH), prolactin (PRL), thyroxine (T4), triiodothyronine (T3) and corticosterone (B) were measured in the pigeon by RIA methods ... [more ▼]

Seasonal variation in the plasma concentration of lutropin (LH), follitropin (FSH), prolactin (PRL), thyroxine (T4), triiodothyronine (T3) and corticosterone (B) were measured in the pigeon by RIA methods. Pigeons were maintained indoors under constant ambient temperature (Ta) and simulated natural daylight (LD), 12:12 L:D regimens or outdoors exposed to seasonal variations in temperature and photoperiod at Oulu, Finland. Only slight changes of gonadotropins (LH, FSH) were observed throughout the year, without any clear photosensitive or photorefractory period. In the indoor (natural LD) group, LH stayed elevated from May until October. Interdependence between the circannual hormonal fluctuation and photoperiod could not be shown, although the amplitude of FSH, T4 and T3 fluctuation of pigeons maintained in laboratory conditions were greater than that of natural LD and outdoor pigeons, whose circannual rhythms were similar. A high concentration of plasma PRL in autumn and the peak value of B in winter for all groups are thought to be correlated to lipid metabolism. Two peaks, the first in winter and the second in autumn, observed in T4 and T3 hormone profiles, may be due to molting of the pigeons. [less ▲]

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