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J Balthazart

Publications and source records attributed to J Balthazart.

At least 145 records · Page 8Linked to original sources
PubMed1991

Effects of in ovo estradiol benzoate treatments on sexual behavior and size of neurons in the sexually dimorphic medial preoptic nucleus of Japanese quail.

In male Japanese quail, the injection of estradiol benzoate (EB) in the egg causes a complete loss of the testosterone (T)-induced copulatory behavior (behavioral demasculinization). This treatment is only effective if performed before day 12 of incubation. This suggests that embryonic estrogens affect in a permanent way brain structures controlling sexual behavior. The medial preoptic nucleus (POM) is the only sexually dimorphic brain nucleus identified in quail and it is a key center for the action of T on behavior. Recent morphometric studies revealed that the dorsolateral population of neurons in the POM is sensitive to variations of plasma T levels in adult males but not in females. These effects are not observed in the medial part of the POM. This sexually differentiated feature might therefore be organized by the embryonic hormonal environment. Quail embryos of both sexes were treated with EB or received a control injection either on day 9 or on day 14 of egg incubation and the cell size in the dorsolateral and medial POM was evaluated by classical morphometric techniques. EB treatment on day 9 decreased cell size in the dorsolateral POM neurons of males but had no effect in females. No effect was also observed when the treatment was performed on day 14. The medial POM neurons were not affected. The decrease in neuronal size observed in the dorsolateral POM of males treated with EB on day 9 was correlated with their behavioral demasculinization. Some of these males showed a weak sexual behavior during the tests and in parallel had significantly larger neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Testosterone metabolism in the avian hypothalamus.

Many central actions of testosterone (T) require the transformation of T into several metabolites including 5 alpha-dihydrotestosterone (5 alpha-DHT) and estradiol (E2). In birds as in mammals, 5 alpha-DHT and E2, alone or in combination, mimic most behavioral effects of T. The avian brain is, in addition, able to transform T into 5 beta-DHT, a metabolite which seems to be devoid of any behavioral or physiological effects, at least in the context of reproduction. By in vitro product-formation assays, we have analyzed the distribution, sex differences and regulation by steroids of the 3 main T metabolizing enzymes (aromatase, 5 alpha- and 5 beta-reductases) in the brain of the Japanese quail (Coturnix c. japonica) and the zebra finch (Taeniopygia guttata castanotis). In the hypothalamus of quail and finches, aromatase activity is higher in males than in females. It is also decreased by castration and increased by T. The activity of the 5 alpha-reductase is not sexually differentiated nor controlled by T. The 5 beta-reductase activity is often higher in females than in males but this difference disappears in gonadectomized birds and no clear effect of T can be observed at this level. The zebra finch brain also contains a number of steroid-sensitive telencephalic nuclei [e.g. hyperstriatum ventrale, pars caudale (HVc) and robustus archistriatalis (RA)] which play a key role in the control of vocalizations. These nuclei also contain T-metabolizing enzymes but the regulation of their activity is substantially different from what has been observed in the hypothalamus. Aromatase activity is for example higher in females than in males in HVc and RA and the enzyme in these nuclei is not affected by castration nor T treatment. In these nuclei, the 5 alpha-reductase activity is higher in males than in females and the reverse is true for the 5 beta-reductase. These sex differences in activity are not sensitive to gonadectomy and T treatment and might therefore be organized by neonatal steroids. We have been recently able to localize aromatase-immunoreactive (AR-ir) neurons by ICC in the brain of the quail and zebra finch. Positive cells are found in the preoptic area, ventromedial and tuberal hypothalamus. AR-ir material is found in the perikarya of cells and fills the entire cellular processes including axons. At the electron microscope level, immunoreactive material can clearly be observed in the synaptic boutons. This observation raises questions concerning the mode of action of estrogens produced by central aromatization of T.

Animals↗
PubMed1991

A sex-dependent influence of testosterone on the dorso-medial neuronal population of the Japanese quail intercollicular nucleus.

The nucleus intercollicularis in quail is implicated in the control of a number of vocalizations. It is also a target structure for steroids and includes high numbers of cells containing androgen and estrogen receptors. We recently demonstrated that in another steroid target, the medial preoptic nucleus, the effects of testosterone are paralleled by significant changes in the neuronal size. A morphometrical analysis of the nucleus intercollicularis was therefore undertaken in male and female Japanese quail that were either gonadectomized or gonadectomized and treated with testosterone or left intact as controls. This showed that, in males, testosterone increases the cellular size in the dorso-medial part of the nucleus: the mean neuronal area was larger in intact and testosterone-treated males than in castrated. Such an effect was not observed in females nor in the adjacent nucleus mesencephalicus dorso-lateralis which was taken as control structure because it is devoid of steroid receptors. The changes observed in the nucleus intercollicularis of males represent a morphological marker for the cellular actions of the steroid. They could provide a useful tool to analyze the mechanisms by which testosterone activates vocalizations in male quail.

Animals↗
PubMed1991

Testosterone effects on staining density and autoradiographic investigations of the alpha 2-adrenergic receptor in the medial preoptic nucleus of the Japanese quail: relationship to the activation of reproductive behavior.

The effects of gonadectomy combined or not with testosterone (T) therapy on the sexual behavior, cloacal gland area, staining density and alpha 2-adrenergic receptors in the medial preoptic nucleus (POM) were studied in male and female Japanese quail. In castrated males, T increased the cloacal gland size and activated copulatory behavior. In agreement with previous reports, these effects were sexually differentiated: under the influence of T, cloacal gland growth was smaller and this treatment did not activate masculine sexual behavior in females. The optical density of the medial preoptic nucleus stained with thionein blue (Nissl stain) was decreased by castration and increased by T in both males and females. This suggests that T has a profound effect on the synthesis of proteins in the POM and, since POM is a critical site in the activation by T of masculine sexual behavior, these induced proteins are, in all probability, a part of the causal chain of biochemical events giving rise to copulatory behavior. The treatment with T had, by contrast, no clear effect on the number of binding sites and on the affinity of the alpha 2-adrenergic receptors in the POM. Therefore, if the noradrenergic transmission is involved in the induction by T of copulatory behavior, it is probably acting either through the alteration of another adrenergic receptor subtype or through the modulation of the baseline levels or turnover of the transmitter itself.

Animals↗
PubMed1990

Distribution of aromatase in the brain of the Japanese quail, ring dove, and zebra finch: an immunocytochemical study.

An immunocytochemical peroxidase-antiperoxidase procedure using a purified polyclonal antibody raised against human placental aromatase was used to localize aromatase-containing cells in the brain of three avian species: the Japanese quail, the ring dove, and the zebra finch. In quail and dove, immunoreactive cells were found only in the preoptic area and hypothalamus, with a high density of positive cells being present in the medial preoptic area, in the septal area above the anterior commissure, in the ventromedial nucleus of the hypothalamus, and in rostral part of the infundibulum. Immunoreactivity was weaker in zebra finches, and no signal could therefore be detected in the ventromedial and tuberal hypothalamus. The positive material was localized in the perikarya and in adjacent cytoplasmic processes, including the full length of axons always leaving a clear unstained cell nucleus. These features could be observed in more detail on sections cut from perfused brains and stained with an alkaline phosphatase procedure. The distribution of aromatase immunoreactivity was similar in the three species although minor differences were observed in the preoptic area. The localization of labelled neurons coincided with the distribution of aromatase activity as studied by in vitro radioenzyme assays on brain nuclei dissected by the Palkovits punch method. There was one striking exception to this rule: no immunoreactivity was detected in the zebra finch telencephalon, while assays had shown the presence of an active enzyme in several nuclei such as the robustus archistriatalis, the hyperstriatum ventrale pars caudale, and the hippocampus and area parahippocampalis. The origins of this discrepancy and the functional role of the aromatase observed in the axons are discussed.

Animals↗
PubMed1990

Muscarinic cholinergic receptors in the songbird and quail brain: a quantitative autoradiographic study.

In order to clarify the neuroanatomical basis for postulated muscarinic cholinergic control of a wide array of physiological processes in birds, the distribution of muscarinic cholinergic receptors in the brain of three avian species was investigated by quantitative autoradiography. The species consisted of two passerines (songbirds), the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia), and one galliform, the Japanese quail (Coturnix coturnix japonica). [3H]N-methyl scopolamine (NMS), a muscarinic cholinergic antagonist was used as the ligand to label the receptors. Initial experiments demonstrated that the binding of this ligand in the three species is saturable in the nanomolar range and has a high affinity (Kd = +/- 0.6 nM). Displacement experiments revealed that three muscarinic ligands competed in an order of potency characteristic of the mammalian muscarinic receptor (i.e., atropine greater than oxotremorine greater than carbachol) for NMS binding in the avian brain. In all three species, portions of the basal ganglia, such as the parolfactory lobe and the paleostriatum augmentatum, exhibited the highest density of binding. On the other hand, the paleostriatum primitivum, the avian homologue of the mammalian globus pallidus, contained very few binding sites. Other telencephalic sites, such as the ventral and dorsal hyperstriatum, also revealed relatively high receptor density. However, the neostriatum and especially the ectostriatum showed much lower levels. In the hypothalamus, in all three species, specific binding could be observed in the ventromedial nucleus and adjacent areas. The paraventricular nucleus also showed moderate levels of binding density, especially in the two songbird taxa. At a more rostral level, the preoptic area showed low levels of binding. In the quail, the sexually dimorphic nucleus of the preoptic area was clearly outlined in the autoradiograms by the low level of binding sites compared to the surrounding areas. In the two passerine species, nuclei of the song system were identified by either high or low levels of NMS binding. High binding defined area X and the mesencephalic nucleus, intercollicularis (ICo). In contrast, the robust nucleus of the archistriatum and the magnocellular nucleus of the anterior neostriatum showed low levels of binding in comparison with the surrounding tissue. None of these nuclei were visible in the quail autoradiograms except for ICo, which appeared as in the passerines as a heavily labelled area surrounding the lightly labelled nucleus mesencephalicus lateralis pars dorsalis. In all three species, the hippocampal complex was devoid of NMS binding except for two lateral dark bands that were present along the entire rostral to caudal extent of the hippocampus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Immunocytochemical localization of aromatase in the brain.

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.

Animals↗
PubMed1990

Sex- and age-related differences in the activity of testosterone-metabolizing enzymes in microdissected nuclei of the zebra finch brain.

Many effects of testosterone (T) in the zebra finch (Taeniopygia guttata) can be mimicked by T-metabolites, mainly estradiol and 5 alpha-dihydrotestosterone. We have therefore studied the neuroanatomical distribution of testosterone-metabolizing enzymes by means of the Palkovits punch technique combined with radioenzyme assay in the brain of adult and young male and female zebra finches. The activity of these enzymes was studied by a one-point assay in 5 nuclei of the song system (X, MAN, HVc, RA, ICo), 2 nuclei of the visual system (ectostriatum, nucleus rotundus) and in limbic and hypothalamic areas. Very noticeable was the presence of a very high aromatase activity in the hippocampal and parahippocampal region and in the nucleus taeniae and the absence of this enzyme in ICo. We found a higher aromatase activity in female than male HVc and RA and a higher 5 alpha-reductase activity in MAN, HVc, RA and ICo of males compared to females. The 5 alpha-reductase was more active in the preoptic area of females. A few sex-related differences in the activity of the 5 beta-reductase were also observed (higher activity in females than in males for area X and RA, but difference in the opposite direction for the ectostriatum). The statistical significance of these differences depended, to some extent, on the statistical technique used to demonstrate them, with the sex differences in RA being by far the most robust ones. Many age-related metabolic differences were also detected but these do not have a clear interpretation since the Km of these enzymes also changes with age. Extremely low levels of 5 beta-reductase activity were found in the nuclei of the visual system in adult birds while this enzymatic activity was very high in young birds. The biological significance of this change with age remains obscure. Correlations are thus observed between the neuroanatomical distribution of T-metabolizing enzymes and of androgen and estrogen receptors with the important exception of ICo which has no aromatase but contains high concentrations of estrogen receptors. Testosterone-metabolizing enzymes are however also present in areas which are not known as steroid targets.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1990

Effects of castration and testosterone treatment on the activity of testosterone-metabolizing enzymes in the brain of male and female zebra finches.

Recently, we described the distribution of testosterone-metabolizing enzymes (i.e., aromatase, 5 alpha- and 5 beta-reductases) in the zebra finch (Taeniopygia guttata) brain using a sensitive radioenzyme assay combined to the Palkovits punch method. A number of sex-differences in the activity of these enzymes were observed especially in nuclei of the song-control system. The hormonal controls of these differences have now been analyzed by gonadectomizing birds of both sexes and by giving them a replacement therapy with silastic implants of testosterone (T). Five nuclei of the song system (Area X [X], nucleus magnocellularis of the anterior neostriatum [MAN], nucleus robustus archistriatalis [RA], nucleus intercollicularis [ICo], hyperstriatum ventrale, pars caudalis [HVc]) and three preoptic-hypothalamic areas (preoptic anterior [POA], periventricular magnocellular nucleus [PVM], and posterior medial hypothalamic nucleus [PMH]) were studied as well as other limbic and control non-steroid-sensitive areas. The activity of the 5 alpha-reductase was higher in males than in females for the five song-control nuclei and was not affected by the hormonal treatments. The overall activity of this enzyme was not sexually dimorphic in POA and PVM. It was higher in males than in females in intact birds only, and was reduced by gonadectomy and enhanced by T. The activity of the 5 beta-reductase was higher in females than in males in all nuclei of the song system and in POA, but was not influenced by the changes in T level. Both sex and treatment effects were observed in the control of aromatase. The production of estrogens was dimorphic (females greater than males) in RA and PMH. It was increased by T in POA, PVM, and PMH, and also in RA. These data show that some of the sex differences in T-metabolizing enzymes result from the exposure to different levels of T in adulthood (e.g., 5 alpha-reductase in POA and PVM or aromatase in PVM), whereas others persist even if birds are exposed to the same hormonal conditions. These are presumably the result of organizational effects of steroids. The steroid modulation of the aromatase might be related directly to the activation of sexual, aggressive, and nest-building behaviors, whereas the stable dimorphism in 5 alpha- and 5 beta-reductase observed in the nuclei of the song system might be one of the neurochemical bases of the sex differences in the vocal behavior of the zebra finch.

Animals↗
PubMed1990

Effects of the nonsteroidal inhibitor R76713 on testosterone-induced sexual behavior in the Japanese quail (Coturnix coturnix japonica).

A new triazole derivative, R76713 (6-[4-chlorophenyl)(1H-1,2,4-triazol-1-yl)methyl]-1-methyl-1H- benzotriazole), was recently shown to inhibit aromatase selectively without affecting other steroid-metabolizing enzymes and without interacting with estrogen, progestin, or androgen receptors. This compound was tested for its capacity to intefere with the induction of copulatory behavior by testosterone (T) in castrated Japanese quail (Coturnix coturnix japonica). In a first experiment, R76713 inhibited (range 0.01 to 1 mg/kg) the activation of sexual behavior by T silastic implants and hypothalamic aromatase activity in castrated male quail in a dose-dependent manner. The 5 alpha- and 5 beta- reductases of T were not systematically affected. Stereotaxic implantation of R76713 in the medial preoptic area similarly blocked the behavior activated by systemic treatment with T, demonstrating that central aromatization of androgen is implicated in the activation of behavior. These inhibiting effects of R76713 on behavior were observed when implants were placed in the medial part of the nucleus preopticus medialis, confirming the implication of this brain area in the control of male copulatory behavior. Finally, the behavioral inhibition produced by R76713 could be reversed by simultaneous treatment with a dose of estradiol, which was not behaviorally effective by itself. This suggests that the behavioral deficit induced by the inhibitor was specifically due to the suppression of estrogen production. This also shows that the activation of copulatory behavior probably results from the interaction of androgens and estrogens at the brain level, as the two treatments separately providing these hormonal stimuli (T with the aromatase inhibitor on one hand and a low dose of estradiol on the other hand) had almost no behavioral effects but they synergized to activate copulation when given concurrently. These data confirm the critical role of preoptic aromatase in the activation of reproductive behavior and demonstrate that R76713 is a useful tool for the in vivo study of estrogen-dependent processes.

Animals↗
PubMed1990

The induction by testosterone of aromatase activity in the preoptic area and activation of copulatory behavior.

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.

Androstatrienes↗
PubMed1990

Androgen and estrogen action in the preoptic area and activation of copulatory behavior in quail.

The sites of androgen and estrogen action on sexual behavior were studied in the preoptic area of castrated male Japanese quail by stereotaxic implantation of hormones, antihormones and metabolism inhibitors. The first experiment demonstrated that bilateral implantation of the aromatase inhibitor, androstatrienedione (ATD), in the sexually dimorphic nucleus (POM) of the preoptic area can completely suppress the behavioral activation produced by a systemic treatment with testosterone. The effects of ATD were only observed if the implants were located in the POM. In the second experiment, implants in the POM of the synthetic estrogen, diethylstilbestrol, restored copulatory behavior in castrated males while implants of the synthetic nonaromatizable androgen, methyltrienolone, were almost ineffective. During the third experiment, the activating effects of a systemic treatment with testosterone were blocked by stereotaxic implants in the POM of the antiestrogen, tamoxifen, or the antiandrogen, flutamide. The effects of tamoxifen were more pronounced than those of flutamide. In addition, tamoxifen was active in all parts of the POM while a behavioral inhibition was observed only for flutamide implants which were located in the caudal part of the nucleus. Taken together, these results demonstrate that the sexually dimorphic POM is the area where the behaviorally active estrogenic metabolites of T have to be produced. The estradiol derived from T aromatization presumably acts within the POM to activate copulation as demonstrated by the effectiveness of DES implanted in this region. Androgens also have a direct action on sexual behavior as suggested by the partial inhibition observed in flutamide-treated birds. It is, however, suggested that androgens and estrogens do not act in the same brain area to activate behavior.

Androgens↗
PubMed1990

Copulatory behavior is controlled by the sexually dimorphic nucleus of the quail POA.

The medial preoptic nucleus (POM) of the quail preoptic area is sexually dimorphic and testosterone sensitive. Stereotaxic implantation of needles filled with crystalline testosterone demonstrated that the POM is a critical site of steroid action in the control of copulatory behavior. Only implants located in the POM reliably restored the behavior in castrated birds. Implants around the nucleus weakly activated the behavior; those which were distant by more than 200 microns were totally inactive. Electrolytic lesions confirmed the role of the POM in the control of copulatory behavior. The percentage of the POM which was lesioned was highly correlated to the behavioral deficit while the absolute size of the lesion was not. Electrolytic lesions in or around POM also significantly decreased the volume of the nucleus suggesting that the afferents and efferents of the nucleus are required for its full development. The total volume of the POM was correlated with the sexual behavior of the birds. The morphological changes in POM observed following exposure to testosterone probably represent the signature of the behavioral effects of the steroid. The sexually dimorphic testosterone-sensitive POM is therefore an excellent animal model to study the brain-steroid interactions which mediate the activation of male reproductive behavior.

Animals↗
PubMed1989

Distribution of estrogen receptors in the brain of the Japanese quail: an immunocytochemical study.

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.

Animals↗
PubMed1989

Effects 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.

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.

Adrenergic alpha-Agonists↗
PubMed1989

Distribution of alpha 2-adrenergic receptors in the brain of the Japanese quail as determined by quantitative autoradiography: implications for the control of sexually dimorphic reproductive processes.

With the use of [3H]p-aminoclonidine (PAC), alpha 2-adrenergic binding sites were mapped in the brain of the Japanese quail (Coturnix coturnix japonica). The sites were labeled with the use of in vitro quantitative autoradiography. Special attention was given to areas implicated in the control of sexually dimorphic reproductive processes including sexual behavior. Preliminary competition experiments found that [3H]PAC binding on tissue sections exhibited a pharmacology appropriate to the alpha 2 receptor. Binding sites were found to be heterogeneously distributed throughout the brain. Some of the highest levels of specific binding were found in several areas regulating reproductive function such as the preoptic area, the supraoptic nucleus, the infundibulum, and the medial mammillary nucleus of the infundibulum. [3H]PAC labeled precisely the morphologically dimorphic preoptic medial nucleus but no sexual dimorphism in density of receptor binding was identified. However, dimorphism in density of receptor binding was identified in two areas: the medial mammillary nucleus and the mesencephalic intercollicular nucleus. The former area appears to be involved in the regulation of gonadotrophin secretion and the latter area has been implicated in the control of vocal behavior. These neurochemical dimorphisms may contribute to the regulation of two sexually dimorphic reproductive processes, gonadotropin secretion and courtship vocalizations.

Adrenergic alpha-Agonists↗
PubMed1989

An autoradiographic study of alpha 1-adrenergic receptors in the brain of the Japanese quail (Coturnix coturnix japonica).

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.

Animals↗