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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 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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