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See detailAromatase inhibition blocks the expression of sexually-motivated cloacal gland movements in male quail
Taziaux, Mélanie ULg; Cornil, Charlotte ULg; Balthazart, Jacques ULg

in Behavioural Processes (2004), 67(3), 461-469

In Japanese quail (Coturnix japonica), activation of appetitive and consummatory aspects of male sexual behavior requires aromatization of testosterone (T) into estrogens. Appetitive male sexual behavior ... [more ▼]

In Japanese quail (Coturnix japonica), activation of appetitive and consummatory aspects of male sexual behavior requires aromatization of testosterone (T) into estrogens. Appetitive male sexual behavior (ASB) is usually assessed with the use of a learned social proximity procedure. In the present experiment, we investigated the role of estrogens in the activation of an another index of ASB. the female-induced activation of rhythmic cloacal sphincter movements (RCSMs) that are produced in reaction to the visual presentation of a female. Consummatory sexual behavior (CSB) was also assessed by the frequency and latency of copulatory behaviors. Castrated male quail were treated with Silastic implants filled with T in association with chronic injections of the aromatase inhibitor Vorozole(TM) (R83842; 1 mg/kg twice a day; CX + T + VOR group). Control birds were implanted with T capsules only (CX + T group). CSB was almost completely blocked by injections of the aromatase inhibitor. The RCSM frequency decreased progressively in the CX + T + VOR group by comparison with the CX + T group and was therefore significantly reduced at the end of the experiment. These results demonstrate that the frequency of RCSM, a second measure of ASB is, like the social proximity response and CSB, blocked by inhibition of estrogen production. It was shown previously that lesions of the preoptic area inhibit both aspects of the appetitive sexual behavior (proximity response and RCSM). It is therefore, likely that both responses are controlled, like copulation, by aromatase-containing neurons of the preoptic area. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailPreoptic aromatase modulates male sexual behavior: slow and fast mechanisms of action
Balthazart, Jacques ULg; Baillien, M.; Cornil, Charlotte ULg et al

in Physiology & Behavior (2004), 83(2), 247-270

In many species, copulatory behavior and appetitive (anticipatory/motivational) aspects of male sexual behavior are activated by the action in the preoptic area of estrogens locally produced by ... [more ▼]

In many species, copulatory behavior and appetitive (anticipatory/motivational) aspects of male sexual behavior are activated by the action in the preoptic area of estrogens locally produced by testosterone aromatization. Estrogens bind to intracellular receptors, which then act as transcription factors to activate the behavior. Accordingly, changes in aromatase activity (AA) result from slow steroid-induced modifications of enzyme transcription. More recently, rapid nongenomic effects of estrogens have been described and evidence has accumulated indicating that AA can be modulated by rapid (minutes to hour) nongenomic mechanisms in addition to the slower transcriptional changes. Hypothalamic AA is rapidly down-regulated in conditions that enhance protein phosphorylation, in particular, increases in the intracellular calcium concentration, such as those triggered by neurotransmitter (e.g., glutamate) activity. Fast changes in brain estrogens can thus be caused by aromatase phosphorylation as a result of changes in neurotransmission. In parallel, recent studies demonstrate that the pharmacological blockade of AA by specific inhibitors rapidly (within 15-45 min) down-regulates motivational and consummatory aspects of male sexual behavior in quail while injections of estradiol can rapidly increase the expression of copulatory behavior. These data collectively support an emerging concept in neuroendocrinology, namely that estrogen, locally produced in the brain, regulates male sexual behavior via a combination of genomic and nongenomic mechanisms. Rapid and slower changes of brain AA match well with these two modes of estrogen action and provide temporal variations in the estrogen's bioavailability that can support the entire range of established effects for this steroid. (C) 2004 Elsevier Inc. All rights reserved. [less ▲]

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See detailHormonal regulation of brain circuits mediating male sexual behavior in birds
Ball, G. F.; Balthazart, Jacques ULg

in Physiology & Behavior (2004), 83(2), 329-346

Male sexual behavior in both field and laboratory settings has been studied in birds since the 19th century. Birds are valuable for the investigation of the neuroendocrine mechanisms of sexual behavior ... [more ▼]

Male sexual behavior in both field and laboratory settings has been studied in birds since the 19th century. Birds are valuable for the investigation of the neuroendocrine mechanisms of sexual behavior, because their behavior can be studied in the context of a large amount of field data, well-defined neural circuits related to reproductive behavior have been described, and the avian neuroendocrine system exhibits many examples of marked plasticity. As is the case in other taxa, male sexual behavior in birds can be usefully divided into an appetitive phase consisting of variable behaviors (typically searching and courtship) that allow an individual to converge on a functional outcome, copulation (consummatory phase). Based primarily on experimental studies in ring doves and Japanese quail, it has been shown that testosterone of gonadal origin plays an important role in the activation of both of these aspects of male sexual behavior. Furthermore, the conversion of androgens, such as testosterone, in the brain to estrogens, such as 17beta-estradiol, is essential for the full expression of male-typical behaviors. The localization of sex steroid receptors and the enzyme aromatase in the brain, along with lesion, hormone implant and immediate early gene expression studies, has identified many neural sites related to the control of male behavior. The preoptic area (POA) is a key site for the integration of sensory inputs and the initiation of motor outputs. Furthermore, prominent connections between the POA and the periaqueductal gray (PAG) form a node that is regulated by steroid hormones, receive sensory inputs and send efferent projections to the brainstem and spinal cord that activate male sexual behaviors. The sensory inputs regulating avian male sexual responses, in contrast to most mammalian species, are primarily visual and auditory, so a future challenge will be to identify how these senses impinge on the POA-PAG circuit. Similarly, most avian species do not have an intromittent organ, so the projections from the POA-PAG to the brainstem and spinal cord that control sexual reflexes will be of particular interest to contrast with the well characterized rodent system. With this knowledge, general principles about the organization of male sexual circuits can be elucidated, and comparative studies relating known species variation in avian male sexual behaviors to variation in neural systems can be pursued. (C) 2004 Elsevier Inc. All rights reserved. [less ▲]

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See detailThe effects of aromatase inhibition on testosterone-dependent conditioned rhythmic cloacal sphincter movements in male Japanese quail
Cornil, Charlotte ULg; Holloway, K. S.; Taziaux, Mélanie ULg et al

in Physiology & Behavior (2004), 83(1), 99-105

Male Japanese quail produce a foam that, along with semen, is transferred to the quail hen during copulation. This foam has been reported to increase fertility, prolong sperm motility, and enhance sperm ... [more ▼]

Male Japanese quail produce a foam that, along with semen, is transferred to the quail hen during copulation. This foam has been reported to increase fertility, prolong sperm motility, and enhance sperm competition. Action of the cloacal sphincter muscles in response to visual exposure to a female produces the foam. The rhythmic cloacal sphincter movements (RCSM) responsible for foam production in male quail is elicited by a conditioned stimulus (CS) previously paired with access to a quail hen. These conditioned RCSM are testosterone-dependent. The present experiment was conducted to explore whether, as is the case with most other testosterone-dependent male sexual behaviors in the quail, conditioned RCSM are mediated by the aromatization of testosterone. Castrated, testosterone-treated male quail were presented with paired presentations of an arbitrary focal CS and visual access to a female. Once conditioned RCSM had developed, subjects received twice daily injections of the aromatase inhibitor Vorozole(TM) (R083842) during a series of extinction test presentations of the CS. Injections of Vorozole(TM) significantly decreased the number of RCSM elicited by a sexual CS. This decrease was specific to sexual RCSM; cloacal sphincter movements that occurred following defecation were not affected by Vorozole. Conditioned sexual RCSM are therefore mediated by the aromatization of testosterone, most likely due to effects on central aromatase activity related to sexual motivation. (C) 2004 Elsevier Inc. All rights reserved. [less ▲]

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See detailRapid regulation of pain by estrogens synthesized in spinal dorsal horn neurons
Evrard, H. C.; Balthazart, Jacques ULg

in Journal of Neuroscience (2004), 24(33), 7225-7229

In addition to exerting genomic actions via nuclear receptors within hours to days, estrogens also regulate neuronal activity much faster (within seconds) by activating neuronal membrane receptors coupled ... [more ▼]

In addition to exerting genomic actions via nuclear receptors within hours to days, estrogens also regulate neuronal activity much faster (within seconds) by activating neuronal membrane receptors coupled to intracellular second-messenger pathways. To date, the origin of estrogens inducing rapid effects in the brain remains unclear, although it is often ascribed to the gonads. We report here that an acute blockade of the endogenous synthesis of estrogens in the quail spinal dorsal horn markedly reduced, within 1 min, the behavioral responsiveness to a thermal painful stimulus. Similar rapid effects in the opposite direction were induced by estradiol. This finding identifies a new paracrine and nongenomic mechanism for the regulation of pain by estrogens. Such regulation was assumed previously to result only from slow genomic actions of estrogens arising from the ovaries. Also, quite importantly, this finding suggests that the numerous rapid nongenomic effects of estrogens in the CNS could depend on their immediate local production by the enzyme aromatase, independently from the gonads. [less ▲]

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See detailCatecholaminergic inputs to aromatase cells in the canary auditory forebrain
Appeltants, D.; Ball, G. F.; Balthazart, Jacques ULg

in Neuroreport (2004), 15(11), 1727-1730

The caudomedial nidopallium in songbirds is a specialized forebrain auditory region involved in the processing of species-typical vocalizations. It receives a prominent catecholaminergic projection with ... [more ▼]

The caudomedial nidopallium in songbirds is a specialized forebrain auditory region involved in the processing of species-typical vocalizations. It receives a prominent catecholaminergic projection with many fibers forming basket-like structures around non-immunoreactive cells. We investigated in male canaries the anatomical relationship between tyrosine hydroxylase and cells immunoreactive for the steroid metabolizing enzyme, aromatase, in the caudomedial nidopallium using double-label immunocytochemistry. Fibers immunoreactive for tyrosine hydroxylase established numerous close contacts with aromatase-immunoreactive cells and often encircled these cells to form basket-like structures. Aromatase containing cells in the caudomedial nidopallium are therefore a major target of catecholaminergic inputs in canary. Interactions between catecholaminergic systems and aromatase in the caudomedial nidopallium may provide one mechanism for the regulation of estrogens involved in song perception and memorization. [less ▲]

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See detailOestrogen-deficient female aromatase knockout (ArKO) mice exhibit 'depressive-like' symptomatology
Dalla, C.; Antoniou, K.; Papadopoulou-Daifoti, Z. et al

in European Journal of Neuroscience (2004), 20(1), 217-228

We recently found that female aromatase knockout (ArKO) mice that are deficient in oestradiol due to a targeted mutation in the aromatase gene show deficits in sexual behaviour that cannot be corrected by ... [more ▼]

We recently found that female aromatase knockout (ArKO) mice that are deficient in oestradiol due to a targeted mutation in the aromatase gene show deficits in sexual behaviour that cannot be corrected by adult treatment with oestrogens. We determined here whether these impairments are associated with changes in general levels of activity, anxiety or 'depressive-like' symptomatology due to chronic oestrogen deficiency. We also compared the neurochemical profile of ArKO and wild-type (WT) females, as oestrogens have been shown to modulate dopaminergic, serotonergic and noradrenergic brain activities. ArKO females did not differ from WT in spontaneous motor activity, exploration or anxiety. These findings are in line with the absence of major neurochemical alterations in hypothalamus, prefrontal cortex or striatum, which are involved in the expression of these behaviours. By contrast, ArKO females displayed decreased active behaviours, such as struggling and swimming, and increased passive behaviours, such as floating, in repeated sessions of the forced swim test, indicating that these females exhibit 'depressive-like' symptoms. Adult treatment with oestradiol did not reverse the behavioural deficits observed in the forced swim test, suggesting that they may be due to the absence of oestradiol during development. Accordingly, an increased serotonergic activity was observed in the hippocampus of ArKO females compared with WT, which was also not reversed by adult oestradiol treatment. The possible organizational role of oestradiol on the hippocampal serotonergic system and the 'depressive-like' profile of ArKO females provide new insights into the pathophysiology of depression and the increased vulnerability of women to depression. [less ▲]

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See detailThe roles of testosterone and singing in the regulation of seasonal neuroplasticity in songbirds
Sartor, Jennifer J.; Balthazart, Jacques ULg; Riters, L. V. et al

in Hormones & Behavior (2004, June), 46(1), 121

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See detailAssessment of olfactory function in male and female aromatase knockout (ArKO) mice
Pierman, S.; Douhard, Quentin ULg; Balthazart, Jacques ULg et al

in Hormones & Behavior (2004, June), 46(1), 99

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See detailAromatase activity modulates conditioned cloacal sphincter movements, an appetitive sexual behavior, in Japanese quail
Holloway, K. S.; Cornil, Charlotte ULg; Taziaux, Mélanie ULg et al

in Hormones & Behavior (2004, June), 46(1), 92

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See detailActivational effects of estradiol on the arginine-vasopressin immunoreactive system in the forebrain of male mice
Allieri, F.; Sica, M.; Bakker, Julie ULg et al

in Hormones & Behavior (2004, June), 46(1), 84

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See detailSocial modulation of testosterone-induced singing in canaries
Boseret, Géraldine ULg; Ball, G. F.; Balthazart, Jacques ULg

in Hormones & Behavior (2004, June), 46(1), 108

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See detailSeasonal development of song control nuclei HVC and RA preceeds peaks in plasma testosterone and singing activity in male Corsican blue tits
Caro, S.; Lambrechts, M. M.; Balthazart, Jacques ULg

in Hormones & Behavior (2004, June), 46(1), 108

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See detailRestoration of male sexual behavior by adult exogenous estrogens in male aromatase knockout mice
Bakker, Julie ULg; Honda, S.; Harada, N. et al

in Hormones & Behavior (2004), 46(1), 1-10

We previously found that male aromatase knockout (ArKO) mice that carry a targeted mutation in exons 1 and 2 of the CYP 19 gene and as a result cannot aromatize androgen to estrogen show impaired sexual ... [more ▼]

We previously found that male aromatase knockout (ArKO) mice that carry a targeted mutation in exons 1 and 2 of the CYP 19 gene and as a result cannot aromatize androgen to estrogen show impaired sexual behavior in adulthood. To determine whether this impairment was due to a lack of activation of sexual behavior by estradiol, we studied here male coital behavior as well as olfactory investigation of sexually relevant odors in male ArKO mice following adult treatment with estradiol benzoate (EB) or dihydrotestosterone propionate (DHTP). Again, we found that gonadally intact ArKO males show pronounced behavioral deficits affecting their male coital behavior as well as their olfactory investigation of volatile body odors but not that of soiled bedding. Deficits in male coital behavior were largely corrected following adult treatment with EB and the androgen DHTP, suggesting that estradiol has prominent activational effects on this behavior. By contrast, adult treatment with EB to either castrated or gonadally intact ArKO males did not stimulate olfactory investigation of volatile body odors, suggesting that this impairment may result from a lack of proper organization of this behavior during ontogeny due to the chronic lack of estrogens. In conclusion, the present studies suggest that the behavioral deficits in sexual behavior in male ArKO mice result predominantly from a lack of activation of the behavior by estrogens. This is in contrast with earlier pharmacological studies performed on rats and ferrets that have suggested strong organizational effects of estradiol on male sexual behavior. (C) 2004 Elsevier Inc. All rights reserved. [less ▲]

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See detailRapid regulation of brain aromatase activity by afferent inputs: Behavioral implications
Balthazart, Jacques ULg; Baillien, M.; Cornil, Charlotte ULg

in Hormones & Behavior (2004, June), 46(1), 127

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See detailRapid and correlated changes in brain aromatase activity and aggressive behavior are socially-mediated in Lythrypnus dalli
Black, M.; Balthazart, Jacques ULg; Baillien, M. et al

in Hormones & Behavior (2004, June), 46(1), 107-108

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See detailEstrogen-deficient female but not male aromatase knockout (ArKO) mice exhibit "depressive-like" symptoms
Bakker, Julie ULg; Dalla, C.; Antoniou, K. et al

in Hormones & Behavior (2004, June), 46(1), 127

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See detailRelationships between aromatase activity in the brain and gonads and behavioural deficits in homozygous and heterozygous aromatase knockout mice
Bakker, Julie ULg; Baillien, M.; Honda, S. et al

in Journal of Neuroendocrinology (2004), 16(5), 483-490

The present study was carried out to determine whether aromatase knockout (ArKO) mice are completely devoid of aromatase activity in their brain and gonads and to compare aromatase activity in wild-type ... [more ▼]

The present study was carried out to determine whether aromatase knockout (ArKO) mice are completely devoid of aromatase activity in their brain and gonads and to compare aromatase activity in wild-type and ArKO mice, as well as in heterozygous (HET) mice of both sexes that were previously shown to display a variety of reproductive behaviours; at levels intermediate between wild-type and ArKO mice. Aromatase activity was extremely low, and undetectable by the tritiated water assay, in homogenates of the preoptic area-hypothalamus of adult wild-type mice, but was induced following a 12-day treatment with testosterone. The induction of aromatase activity by testosterone was significantly larger in males than in females. Even after 12 days exposure to testosterone, no aromatase activity was detected in the brain of ArKO mice of either sex whereas HET mice showed intermediate levels of activity between ArKO and wild-type. Aromatase activity was also undetectable in the ovary of adult ArKO females but was very high in the wildtype ovary and intermediate in the HET ovary. In wild-type mice, a high level of aromatase activity was detected on the day of birth even without pretreatment with testosterone. This neonatal activity was higher in males than in females, but females nevertheless appear to display a substantial level of oestrogen production in their brain. Aromatase activity was undetectable in the brain of newborn ArKO males and females and was intermediate between wild-type and ArKO in HET mice. In conclusion, the present study confirms that ArKO mice are unable to synthesize any oestrogens, thereby validating the ArKO mouse as a valuable tool in the study of the physiological roles of oestradiol. In addition, it demonstrates that the intermediate behaviour of HET mice presumably reflects the effect of gene dosage on aromatase expression and activity, that aromatase activity is sexually differentiated in mice during the neonatal period as well as in adulthood and, finally, that the neonatal female brain produces substantial amounts of oestrogens that could play a significant role in the sexual differentiation of the female brain early in life. [less ▲]

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