A sexually dimorphic nucleus in the quail preoptic area.

in Neuroscience Letters (1986), 64(2), 129-34

The cytoarchitectural analysis of the preoptic-anterior hypothalamic region of the Japanese quail reveals a sexual dimorphism in the total volume of the medial preoptic nucleus (significantly larger in ... [more ▼]

The cytoarchitectural analysis of the preoptic-anterior hypothalamic region of the Japanese quail reveals a sexual dimorphism in the total volume of the medial preoptic nucleus (significantly larger in males than in females). Different nuclei of the region (dorsal preopticus, suprachiasmaticus) do not show any statistically significant difference. The sex-related difference is more consistent comparing the distribution of dark volume. This last is due to a larger number of cells containing high amount of Nissl's substance in male than in female. Present findings represent the first example of sexual dimorphism in the avian hypothalamus. [less ▲]

Diurnal variations of sexual receptivity in the female Japanese quail (Coturnix coturnix japonica).

in Hormones and Behavior (1986), 20(1), 13-33

A series of experiments was performed to study the changes during the day of female receptivity in Japanese quail. In each experiment, the frequency of squatting and the percentage of male approaches ... [more ▼]

A series of experiments was performed to study the changes during the day of female receptivity in Japanese quail. In each experiment, the frequency of squatting and the percentage of male approaches which were followed by squatting increased at the end of the day, approximately 11 to 13 hr after lights on (in a photoperiod of 16L:8D). In some cases this increased receptivity was associated with a significant decrease of the long-avoid frequency. Analyses are presented which demonstrate that the increased receptivity at the end of the day is not directly caused by the oviposition and does not result directly from changes in the behavior of the male stimuli. This is strongly supported by the observation that the increase in receptivity was observed at the same time after lights on (but different clock times) in two groups of females which were raised in two different photoperiods shifted by 6 hr and tested with the same group of males raised in one of the two photoperiods. The increase in receptivity coincides with an increase in plasma estradiol and progesterone. Considering that this behavior is suppressed by ovariectomy, it is argued that the daily changes in receptivity could be controlled by the hormonal changes associated with the ovulatory cycle. [less ▲]

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

in Poultry Science (1986), 65(7), 1413-20

A fluorometric assay measuring brain tissue concentrations of norepinephrine, dopamine, and serotonin has been validated for Japanese quail. Accuracy, precision, specificity, and parallelism were ... [more ▼]

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. [less ▲]

Brain testosterone metabolism during ontogeny in the zebra finch.

in Brain Research (1986), 378(2), 240-50

The testosterone metabolism in different parts of the brain and in the syrinx was studied by an in vitro radioenzyme assay in male and female zebra finch (Taeniopygia guttata castanotis) at various ages ... [more ▼]

The testosterone metabolism in different parts of the brain and in the syrinx was studied by an in vitro radioenzyme assay in male and female zebra finch (Taeniopygia guttata castanotis) at various ages between 1 day post-hatch and adulthood. The 5 beta-reductase appeared in all experiments as the main enzyme involved in testosterone metabolism. Two experiments allowed to determine the kinetic parameters of the 5 beta-reductase. It was shown that the Vmax of the 5 beta-reduction is much higher in very young animals than in adults but that the Km of the enzyme is smaller (higher affinity) in the latter than in the former. A major decrease of 5 beta-reductase activity is observed during the ontogeny of both males and females in all the tissue samples which were studied including the hypothalamus and brain regions containing nuclei of the song system. This high reductase activity which produces behaviorally inactive compounds is likely to play a protective role during the sexual differentiation of the birds and in this way prevent the masculinization in females of the song system by the relatively high levels of circulating androgens. [less ▲]

Interaction of androgens and estrogens in the control of sexual behavior in male Japanese quail.

in Physiology & Behavior (1985), 35(2), 157-66

A series of 4 experiments was performed to study the relative contribution of androgens and estrogens in the activation of sexual behavior in castrated male quail. The synthetic androgen methyltrienolone ... [more ▼]

A series of 4 experiments was performed to study the relative contribution of androgens and estrogens in the activation of sexual behavior in castrated male quail. The synthetic androgen methyltrienolone (R 1881) which is not metabolized in androgen target tissues activated sexual behavior in castrated birds and at the dose level of 0.5-1 mg/day/animal had the same potency as testosterone (T). However R 1881 was much more active than T in the induction of cloacal gland growth and activation of crowing, two typically androgen-dependent responses. This suggests that sexual behavior is not controlled by exactly the same mechanism as crowing or cloacal gland growth. In another experiment, estradiol (E2) alone activated sexual behavior but it is only at very high doses which had clear toxic effects that a significant behavioral activation could be observed. This questions the role of E2 as the physiological agent stimulating copulation in intact birds unless it is assumed that centrally administered E2 would be much more active compared to peripheral E2 which is exposed to a very intense peripheral catabolism. In the last two experiments, a clear synergism could be detected between 5 alpha-dihydrotestosterone (5 alpha-DHT) and E2 in the activation of sexual activity and doses of hormones could be defined which had almost no activity by themselves but significantly stimulated sexual behavior when given simultaneously. It was however impossible to define a hormonal treatment with T metabolites which restored behavior to its precastration level, a result very easily achieved with T treatments. Taken together, these data suggest that activation of sexual behavior in quail does not depend only on E2, nor 5 alpha-DHT nor even on their combined action. Considering that specific T receptors which probably do not bind 5 alpha-DHT are present in the brain, it would seem justified to reconsider the possible role played by T itself in the activation of behavior. [less ▲]

Estradiol contributes to the postnatal demasculinization of female Japanese quail (Coturnix coturnix japonica).

in Hormones and Behavior (1984), 18(3), 287-97

Two experiments were performed to characterize the process of postnatal demasculinization in Japanese quail. In the first experiment, it was shown that estradiol (E2) can complete female demasculinization ... [more ▼]

Two experiments were performed to characterize the process of postnatal demasculinization in Japanese quail. In the first experiment, it was shown that estradiol (E2) can complete female demasculinization during the first 4 weeks of life. By contrast, E2 did not demasculinize sexual behavior and cloacal gland in neonatally castrated males. Neonatally gonadectomized females preferentially performed mount attempts when tested in their home cage by comparison to a test arena. In Experiment 2, E2 Silastic implants (40-mm) maintained full copulatory behavior in castrated males but not in females. This large dose of E2 did not demasculinize adult sexually active birds (males or females) even if treatment lasted for 1 month. It is concluded that E2 can demasculinize sexual behavior only in females and only if treatment is performed in very young birds. [less ▲]

Hormonal control of the gonadal regression and recovery observed in short days in male and female doves.

in Journal of Endocrinology (1981), 89(1), 79-89

Sexually mature ring doves (Streptopelia risoria) maintained from hatch on a photoperiod of 14 h light : 10 h darkness (14L : 10D) and kept in isolation were transferred to 8L : 16D. This treatment ... [more ▼]

Sexually mature ring doves (Streptopelia risoria) maintained from hatch on a photoperiod of 14 h light : 10 h darkness (14L : 10D) and kept in isolation were transferred to 8L : 16D. This treatment resulted in a partial regression of the ovaries and testes and a fall in the concentration of plasma LH but not of plasma FSH. After 2--3 months exposure to 8L : 16D, the gonads regrew to their original size: this regrowth was accompanied by a parallel increase in the concentration of plasma LH. The responsiveness of the pituitary gland to LH releasing hormone in both sexes after 5 weeks of exposure to 8L : 16D (when the gonads were partially regressed) was similar to the response observed after 15 weeks exposure to this lighting schedule (when the gonads had regrown). It was concluded that the spontaneous recovery of gonadal size in ring doves exposed to 8L : 16D is controlled by the hypothalamus and does not involve changes in the functional capacity of the pituitary gland or of the gonads. [less ▲]

Changes in pituitary responsiveness to luteinizing hormone-releasing hormone during an annual cycle in the domestic duck, Anas platyrhynchos L.

in Journal of Experimental Zoology (The) (1980), 211(1), 113-23

On four occasions during an annual cycle, 5--7 male domestic ducks were injected with two different doses (5 and 20 micrograms) of synthetic luteinizing hormone-releasing hormone (LHRH) to study the ... [more ▼]

On four occasions during an annual cycle, 5--7 male domestic ducks were injected with two different doses (5 and 20 micrograms) of synthetic luteinizing hormone-releasing hormone (LHRH) to study the possible changes in responsiveness of the pituitary. The luteinizing hormone (LH) and the follicle-stimulating hormone (FSH) were measured in the plasma samples collected after these injections. The induced release of LH changes from one period of the year to another, being minimum in March at the height of the reproductive season. The LHRH injection also induces the release of some FSH but only in limited amounts. The changes in pituitary responsiveness to LHRH are negatively correlated to changes in the circulating LH level (it is high when the plasma LH is low and vice versa). This suggests that the hypothalamic synthesis and release of LHRH must also change during the year. [less ▲]

Short day induced gonadal regression in ring doves (Streptopelia risoria): a case for seasonal variation.

in Chronobiologia (1980), 7(3), 357-70

Changes in follicular size (in diameter) were studied by laparotomy under various photoperiodic regimes in the domesticated ring doves that have been kept under standard laboratory conditions for ... [more ▼]

Changes in follicular size (in diameter) were studied by laparotomy under various photoperiodic regimes in the domesticated ring doves that have been kept under standard laboratory conditions for generations. Follicular response shows two distinct patterns: 1. a shift from standard laboratory photoperiodic regime (LD 14:10) to extra long day (LD 20:4) accelerated the follicular development in the spring as well as in the autumn; 2. a shift from the standard laboratory photoperiodic regime (LD 14:10) to short day (LD 8:16 or LD 1/2:23 1/2) induced follicular regressions in the autumn but not in the spring. We propose that there is a responsive phase (spring) and nonresponsive phase (autumn) of hypothalamo-hypophyseal-ovarian system in the ring doves. Comparison of radioimmunoassay of pituitary and plasma LH value suggests that the responsive and non-responsive phase involves mainly release mechanisms. In the autumn, the release mechanism becomes insensitive to stimuli below certain thresholds. Our ring doves are kept in responsive phase throughout the year under the long photoperiodicity (LD 14:10). However, the effect of long day does not appear to override completely the seasonal effect. [less ▲]

Pheromones are involved in the control of sexual behaviour in birds.

in Naturwissenschaften (Die) (1979), 66(1), 55-6