Sexual Behaviour and Endocrine Changes During Reproductive Maturation and Aging in the Avian Male. In: Balthazart J, Pröve E, Gilles R, editors. Hormones and Behaviour in Higher Vertebrates. Berlin: Springer Berlin Heidelberg; 1983. pp. 350-67. [DOI: 10.1007/978-3-642-69216-1_25]

Induction of circadian rhythm of feeding activity by testosterone implantations in arrhythmic Japanese quail males

Studies in vertebrates have shown that hormones can influence circadian rhythms of behavior. We investigated whether testosterone could induce rhythmicity in arrhythmic Japanese quail, kept in DD. The animals used were 3 1/2-week-old castrated males from a line of quail selected for the lack of the circadian rhythm of feeding activity. After 3 weeks in DD, 8 birds were implanted with an empty implant and 16 others with a testosterone implant. Two weeks later, the operation was repeated. After implantation, we noticed that 15 out of 16 testosterone-treated birds showed a circadian rhythm of feeding activity, in contrast to the control birds, which remained arrhythmic. The clarity of this rhythm increased significantly after each implantation. A positive correlation was found between the indexes of clarity of the rhythm (autocorrelation coefficient ratio and area of the peak of spectrum) and the plasma testosterone level. The period of the induced free-running rhythm was identical to the specific value of the endogenous circadian rhythm in immature quail. The circadian period showed a significant lengthening with the second implantation. This lengthening looks like the variation previously observed in maturing rhythmic or implanted quail. So, it would appear that testosterone can act on rhythmicity on at least two levels: by inducing the circadian rhythm and increasing its clarity and by modulating its period. To explain these results, several hypotheses can be considered. First, the observed arrhythmy may be the consequence of an internal desynchronization of oscillators, responsible for generating the circadian rhythm of feeding activity, and testosterone could play a role in the coupling of these oscillators. Alternatively, we suggest that testosterone could act on the transcription of genes implicated in the control of the rhythmicity or may regulate by rapid signals the cellular rhythmic activity. The possible functional values of the enhancing of circadian rhythmicity by testosterone at different stages of the bird's life were discussed.

The serotoninergic system in the brain of the Japanese quail. An immunohistochemical study

The presence and topographical localization of the serotoninergic system in the brain of the Japanese quail (Coturnix coturnix japonica) have been studied by means of peroxidase-anti-peroxidase immunocytochemistry. The perimeter, diameter, area, and shape factor of immunoreactive cells have been recorded and analyzed morphometrically for intra- and interspecies comparison. The data reported here confirm and extend results previously obtained in the brain of other avian species. Serotonin-immunoreactive neurons of the quail are mainly located in the hypothalamic paraventricular organ and adjacent areas, and in the brainstem where they form three separate groups. The first of these groups consists of small-sized neurons located in the ventro-rostral mesencephalon. The second group is composed of medium-sized neurons located in the dorsal mesencephalo-pontine region. The third group is also formed by medium-sized neurons, and is located ventrally in the ponto-medullary region. In the quail brain, serotoninergic neurons are not restricted to nuclei located in the vicinity of the midsagittal plane, but show some lateralization, especially in the brainstem. The organization of the different groups of immunoreactive neurons based on this topographical distribution and morphometric analysis has been compared with descriptions of the serotoninergic system in other birds. Serotonin-immunoreactive nerve fibers are widely distributed throughout the brain, but appear to be particularly abundant in regions involved in the control of reproductive activities, such as the septal region, the medial preoptic nucleus, the nucleus intercollicularis, and the external zone of the median eminence. The data reported here have allowed the drawing of a map of serotonin-immunoreactive structures.

Comparison of monoamine concentrations in the brains of adult male and female Japanese quail

A fluorometric assay measuring brain tissue concentrations of norepinephrine, dopamine, and serotonin has been validated for Japanese quail. Accuracy, precision, specificity, and parallelism were determined. The sensitivity of the assays was 6 ng/tube, which allowed individual assay of 1 to 2 mg hypothalamic tissue. In Experiment 1, relatively large areas of brain from adult, reproductively active males and females were found to differ significantly in norepinephrine content in optic lobes and for dopamine in right telencephalon. A microdissection technique was used in Experiment 2 to sample small portions of hypothalamic tissue. Sex differences were observed for norepinephrine in the sections containing the lobus paraolfactorius and the preoptic, anterior, and medial hypothalamus. Differences in monoamine content were most apparent when smaller areas dissected by microdissection were analyzed. These results give evidence for sex differences in the monoamine content in specific areas of the brain.

Androgen and estrogen receptors in adult zebra finch brain

Androgens and estrogens have been implicated in the activation of a variety of sexually-dimorphic, hormone-dependent behaviors in the adult zebra finch. In the present report, several biochemical characteristics of two putative sex steroid receptors, androgen- and estrogen-binding activities, were determined by DNA-cellulose chromatography in brain tissues from these birds. High-affinity, limited-capacity receptors for androgens and estrogens were found in cytosolic extracts of telencephalon, diencephalon-mesencephalon, and metencephalon-myelencephalon from adult male and female zebra finches. Androgen-binding activity reproducibly adhered to DNA-cellulose and was eluted within the 110-150 mM NaCl region of a linear salt concentration gradient. Estrogen receptors adhered to DNA-cellulose and exhibited elution maxima between 170 mM and 210 mM NaCl. Collectively these data indicate that brain regions of zebra finches contain steroid receptors that are similar to those found in the brains of other vertebrates and that their biochemical properties are similar in males and females. Quantitatively, males consistently exhibited higher androgen binding than females in both anterior and posterior telencephalic areas. Females treated with estradiol immediately after hatching exhibited adult levels of androgen binding corresponding to those detected in males. Masculinization of the androgen receptor system by early steroid exposure is discussed.