Regulation Of Reproductive Behavior Research Articles

Exogenous Progesterone: A Potential Therapeutic Candidate in CNS Injury and Neurodegeneration

The role of progesterone (PROG) in the regulation of reproductive behavior is well understood, but a large and growing body of evidence indicates that this hormone also exerts neuroprotective effects on the central nervous system (CNS), i.e. in spinal cord injuries, traumatic brain injuries and in the age-related pathological process. Its neuroprotective actions, now well documented by experimental studies, make it a particularly promising therapeutic agent for neuroinjury and neurodegenerative diseases. The purpose of this article is to review recent preclinical and epidemiological evidences that exogenous administration of PROG or its metabolites plays an important role in the CNS. The diverse signaling mechanisms and the dose- dependent neuroprotective actions of PROG are also summarized. Awareness of the pleiotropic effects of PROG may open a novel perspective for the treatment of injuries and diseases in the nervous system. PROG could be produced in the brain by neurons and glial cells in the CNS of both male and female. Laboratories around the world have reported that administering relatively large doses of PROG during the first few hours or even days after injury significantly limits CNS damage, reduces loss of neuronal tissue and improves functional recovery. PROG appears to exert its protective effects by protecting or rebuilding the blood-brain barrier, decreasing the development of cerebral edema, down-regulating the inflammatory cascade, and limiting cellular necrosis and apoptosis. All these are plausible mechanisms of neuroprotection.

Brain and gonadal aromatase activity and steroid hormone levels in female and polymorphic males of the peacock blenny Salaria pavo

In the peacock blenny Salaria pavo large males with well-developed secondary sexual characters establish nests and attract females while small “sneaker” males mimic female sexual displays in order to approach the nests of larger males and parasitically fertilize eggs. These alternative reproductive tactics are sequential, as sneakers irreversibly switch into nesting males. This transition involves major morphologic and behavioral changes and is likely to be mediated by hormones. This study focuses on the role of aromatase, an enzyme that catalyses the conversion of androgens into estrogens, in the regulation of male sexual polymorphism in S. pavo. For this, sex steroid plasma levels and aromatase activity (AA) in gonads, whole brain and brain macroareas were determined in sneakers, transitional males (i.e. sneakers undergoing the transition into nesting males), nesting males and females collected in the field. AA was much higher in ovarian tissue than in testicular tissue and accordingly circulating estradiol levels were highest in females. This supports the view that elevated AA and estradiol levels are associated with the development of a functional ovary. Transitional males are in a non-reproductive phase and had underdeveloped testes when compared with sneakers and nesting males. Testicular AA was approximately 10 times higher in transitional males when compared with sneakers and nesting males, suggesting high AA has a suppressive effect on testicular development. Nesting males had significantly higher plasma levels of both testosterone (T) and 11-ketotestosterone when compared with the other male morphs and previous studies demonstrated that these androgens suppress female-like displays in sneakers. In the brain, AA was highest in macroareas presumably containing hypothalamic nuclei traditionally associated with the regulation of reproductive behaviors. Overall, females presented the highest levels of brain AA. In male morphs AA increased from sneakers, to transitional males, to nesting males in all brain macroareas. These results suggest that the transition into the nesting male tactic is accompanied both by an increase in testicular androgen production and by a higher conversion of androgens into estrogens in the brain. The increase in androgen production is likely to mediate the development of male secondary sexual characters while the increase in brain AA may be related to the behavioral changes associated with tactic transition.

Sex-steroidal regulation of aromatase mRNA expression in adult male rat brain: a quantitative non-radioactive in situ hybridization study

Neuronal aromatase, the enzyme that catalyzes the conversion of androgens to estrogens, is involved in brain sexual differentiation, the regulation of reproductive behavior, and gonadotropin secretion. We have previously reported that aromatase P450 (AromP450) protein expression is enhanced by both androgens and estrogens in the principal nucleus of the bed nucleus of the stria terminalis (prBST) and posterodorsal part of the medial amygdaloid nucleus (pdMAm) of the adult rat but is not altered in the central amygdaloid nucleus (CeAm) even after sex-steroid withdrawal or supplementation. Here, we have evaluated, via in situ hybridization with digoxigenin-labeled cRNA probes, the sex-steroidal regulation of brain AromP450 mRNA in the prBST, pdMAm, and CeAm of orchidectomized and adrenalectomized adult male rats treated with sesame oil, testosterone (1 mg/rat/day), dihydrotestosterone (1 mg/rat/day), or 17beta-estradiol (2 microg/rat/day) for 6 days. AromP450-mRNA expression in the prBST and pdMAm was markedly reduced in orchidectomized/adrenalectomized rats treated with sesame oil but strongly enhanced by testosterone or dihydrotestosterone and significantly reinstated by 17beta-estradiol. These results are essentially consistent with those of AromP450 protein expression and thus indicate that enhanced AromP450-protein expression in the prBST and pdMAm reflects transcriptional upregulation and/or post-transcriptional stabilization of its mRNA by sex steroids. In the CeAm, despite moderate AromP450-protein expression, the mRNA has never been detected with or without sex-steroidal manipulations, indicating that the putative sex-steroid-insensitive AromP450 mRNA in the CeAm may be distinct from that in the prBST and pdMAm or, if it occurs at all, expressed at much lower levels.

1408 POSTER Identification of bipotential cells in both neuroblastic primary tumours and neuroblastoma bone marrow metastasis

Sexual behavior in female rats depends on the action of estradiol on estrogen receptors (ERs) found in particular brain regions. While hormonal regulation of female sexual behavior requires ERα, the possible functions of ERβ remain to be clarified. Mating stimulation has several behavioral and physiological consequences and induces Fos expression in many brain areas involved in the regulation of reproductive behavior and physiology. In addition, some cells in which mating induces Fos expression coexpress ERα. To determine whether cells in which Fos is induced by a particular mating stimulus coexpress ERα, ERβ, or both, we used a triple-label immunofluorescent technique to visualize ERα-, ERβ-, and mating-induced Fos-immunoreactivity (Fos-ir) in neurons in which mating stimulation reliably increases Fos expression. Ovariectomized, hormone-primed rats were either unmated, received 15 mounts, or received 15 intromissions. In the rostral medial preoptic area, Fos-ir was induced by mounts alone primarily in cells coexpressing ERα-ir, while Fos-ir was induced by intromissions mainly in cells coexpressing both ERα-ir and ERβ-ir (ERα/ERβ-ir). In the dorsal part of the posterodorsal medial amygdala, Fos-ir was induced by intromissions in cells coexpressing ERα-ir and ERα/ERβ-ir. However, in the ventral part of the posterodorsal medial amygdala, Fos-ir was induced by intromissions primarily in cells coexpressing only ERβ-ir. These data suggest that qualitatively different sexual stimuli may be integrated through distinct ER-containing circuits in the rostral medial preoptic area and posterodorsal medial amygdala. The diversity in coexpression of type of ER in cells in different brain areas after various mating stimuli suggests a role for both ERα and ERβ in the integration of hormonal information and information related to mating stimuli.

Biphasic expression of phosphorylated cAMP response element binding protein in hypothalamic and limbic nuclei of mated female rats

In many rodent species, such as Syrian hamsters, reproductive behavior requires neural integration of chemosensory information and steroid hormone cues. The medial amygdala (MA) processes both of these signals through anatomically distinct sub-regions; the anterior region (MeA) receives substantial chemosensory input, but contains few steroid receptor-labeled neurons, whereas the posterodorsal region (MePD) receives less chemosensory input, but contains a dense population of steroid receptors. Importantly, these sub-regions have considerable reciprocal connections, and the goal of this experiment was therefore to determine whether interactions between MeA and MePD are required for male hamsters' preference to investigate female over male odors. To functionally disconnect MeA and MePD, males received unilateral lesions of MeA and MePD within opposite brain hemispheres. Control males received either unilateral lesions of MeA and MePD within the same hemisphere or sham surgery. Odor preferences were measured using a 3-choice apparatus, which simultaneously presented female, male and clean odor stimuli; all tests were done under conditions that either prevented or allowed contact with the odor sources. Under non-contact conditions, males with asymmetrical lesions investigated female and male odors equally, whereas males in both control groups preferred to investigate female odors. Under contact conditions, all groups investigated female odors longer than male odors, although males with asymmetrical lesions displayed decreased investigation of female odors compared to sham males. These data suggest that MeA–MePD interactions are critical for processing primarily the volatile components of social odors and highlight the importance of input from the main olfactory system (MOS) to these nuclei in the regulation of reproductive behavior. More broadly, these results support the role of the MA in integrating chemosensory and hormone information, a process that may underlie social odor processing in a variety of behavioral contexts.

Inhibition of Steroid Receptor Coactivator-1 Blocks Estrogen and Androgen Action on Male Sex Behavior and Associated Brain Plasticity

Studies of eukaryotic gene expression demonstrate the importance of nuclear steroid receptor coactivators in mediating efficient gene transcription. However, little is known about the physiological role of these coactivators in vivo. In Japanese quail, the steroid receptor coactivator-1 (SRC-1) is broadly expressed in steroid-sensitive brain areas that control the expression of male copulatory behavior, and we investigated the role of this coactivator by antisense technology. Daily intracerebroventricular injections of locked nucleic acid (LNA) antisense (AS) oligonucleotides targeting SRC-1 significantly reduced the expression of androgen- and estrogen-dependent male-typical sexual behaviors compared with control animals that received the vehicle alone or scrambled oligonucleotides. Sexual behavior was restored and even enhanced within 48 h after interruption of LNA injections. Western blot analysis confirmed the decrease of SRC-1 expression in AS animals and suggested an overexpression 48 h after the end of injections. The effects of SRC-1 knock-down on behavior correlated with a reduction in volume of the preoptic medial nucleus (POM) when its borders were defined by Nissl staining or by aromatase immunohistochemistry. The amount of aromatase-immunoreactive material in POM was also reduced in the AS compared with the control group. Previous work on SRC-1 knock-out mice raised questions about the importance of this specific coactivator in the regulation of reproductive behavior and development of sexually dimorphic structures in the CNS. Together, the present findings indicate that SRC-1 modulates steroid-dependent gene transcription and behavior and highlight the rapid time course of steroid-induced brain plasticity in adult quail.

Response of ERα-IR and ERβ-IR cells in the forebrain of female rats to mating stimuli

Sexual behavior in female rats depends on the action of estradiol on estrogen receptors (ERs) found in particular brain regions. While hormonal regulation of female sexual behavior requires ERα, the possible functions of ERβ remain to be clarified. Mating stimulation has several behavioral and physiological consequences and induces Fos expression in many brain areas involved in the regulation of reproductive behavior and physiology. In addition, some cells in which mating induces Fos expression coexpress ERα. To determine whether cells in which Fos is induced by a particular mating stimulus coexpress ERα, ERβ, or both, we used a triple-label immunofluorescent technique to visualize ERα-, ERβ-, and mating-induced Fos-immunoreactivity (Fos-ir) in neurons in which mating stimulation reliably increases Fos expression. Ovariectomized, hormone-primed rats were either unmated, received 15 mounts, or received 15 intromissions. In the rostral medial preoptic area, Fos-ir was induced by mounts alone primarily in cells coexpressing ERα-ir, while Fos-ir was induced by intromissions mainly in cells coexpressing both ERα-ir and ERβ-ir (ERα/ERβ-ir). In the dorsal part of the posterodorsal medial amygdala, Fos-ir was induced by intromissions in cells coexpressing ERα-ir and ERα/ERβ-ir. However, in the ventral part of the posterodorsal medial amygdala, Fos-ir was induced by intromissions primarily in cells coexpressing only ERβ-ir. These data suggest that qualitatively different sexual stimuli may be integrated through distinct ER-containing circuits in the rostral medial preoptic area and posterodorsal medial amygdala. The diversity in coexpression of type of ER in cells in different brain areas after various mating stimuli suggests a role for both ERα and ERβ in the integration of hormonal information and information related to mating stimuli.

Evidence for Conservation of the Vasopressin/Oxytocin Superfamily in Annelida

Annetocin is a structurally and functionally oxytocin-related peptide isolated from the earthworm Eisenia foetida. We present the characterization of the annetocin cDNA. Sequence analyses of the deduced precursor polypeptide revealed that the annetocin precursor is composed of three segments: a signal peptide, an annetocin sequence flanked by a Gly C-terminal amidation signal and a Lys-Arg dibasic processing site, and a neurophysin domain, similar to other oxytocin family precursors. The proannetocin showed 37.4-45.8% amino acid homology to other prohormones. In the neurophysin domain, 14 cysteines and amino acid residues essential for association of a neurophysin with a vasopressin/oxytocin superfamily peptide were conserved, suggesting that the Eisenia neurophysin can bind to annetocin. Furthermore, in situ hybridization experiments demonstrated that the annetocin gene is expressed exclusively in neurons of the central nervous system predicted to be involved in regulation of reproductive behavior. These findings confirm that annetocin is a member of the vasopressin/oxytocin superfamily. This is the first identification of the cDNA encoding the precursor of an invertebrate oxytocin-related peptide and also the first report of the identification of an annelid vasopressin/oxytocin-related precursor.

Sex differences in estrogenic regulation of preproenkephalin mRNA levels in the medial preoptic area of prepubertal rats

Opioids have been implicated in sexual differentiation of the brain and in the regulation of reproductive behavior and endocrinology of mammals. Previous studies have indicated that estrogen administration in adults regulates preproenkephalin MRNA levels in several hypothalamic brain nuclei. We have determined preproenkephalin mRNA levels in estrogen-treated juvenile male and female rats to investigate the developmental pattern of estrogenic regulation of enkephalinergic neurons in the medial preoptic area. Rats were treated with estradiol benzoate (20 μg/kg/day) or oil from day 21 to 23. Sections of the medial preoptic area (mPOA) were studied by in situ hybridization histochemistry at the single cell level and quantified with the assistance of an image analysis system. Our data indicate that males contain higher levels of preproenkephalin mRNA per neuron than females. In addition, our results indicate that estrogen causes an upward shift in the amount of mRNA expressed per cell, females demonstrating a greater response to estrogen than males. An increase in soma cell area following estrogen treatment was observed only in female mPOA enkephalinergic neurons. Taken together, these results indicate a sex difference in total preproenkephalin levels and in estrogenic regulation of preproenkephalin mRNA in the POA of juvenile rats. These results are discussed in relation to the differential role opioids may play in male and female reproductive physiology.

Estrogen regulation of μ-opioid receptor mRNA in the forebrain of female rats

Previous studies have suggested that opioids play a role in the regulation of reproductive behaviors in the female rat. The present study examined whether estrogen treatment alters μ-opioid receptor mRNA levels in different areas of the forebrain of ovariectomized (OVX) female rats using the in situ hybridization technique. We observed an increase in μ-opioid receptor mRNA levels in the ventromedial nucleus of the hypothalamus (VMH) and arcuate nucleus (ARN) after 48 h of 10 μg of 17- β-estradiol-3-benzoate treatment when compared to OVX females. No effects of estrogen were observed on μ-opioid receptor mRNA levels in the posterior medial nucleus of the amygdala (MeAmyg), hippocampus, caudate-putamen (CPu) or the medial habenula. Our result suggests that the estrogenic regulation of μ-opioid receptor in the CNS may in part be mediated by de novo synthesis and/or stability of the μ-opioid receptor message.

Aromatase-immunoreactive neurons in the adult female chicken brain detected using a specific antibody

Estrogen formation in the brain catalysed by the cytochrome P450 arom is required for the control of estrogen-dependent neural mechanisms regulating reproductive behaviour. A polyclonal antibody was raised against a 15-amino acid fragment of the chicken ovarian P450 arom protein, to localise aromatase-immunoreactive (AR-IR) cells in the adult female chicken brain. Specificity of antibody reaction was established by Western blot and by inhibition of aromatase activity in homogenates of chicken ovarian follicles determined by a radiometric assay. The AR-IR material in the brain was localised in the perikarya and some of their adjacent cytoplasmatic processes. Intense immunoreactivity was observed in the preoptic region as well as in other hypothalamic nuclei. AR-IR cells were also found in extrahypothalamic areas; in particular, in the area entorhinalis and hippocampus. These results confirm histologically that aromatization of testosterone in the adult female chicken brain occurs in preoptic nuclei closely associated with the regulation of reproductive behaviour. The mapping of AR-IR cells in the female chicken brain now allows study of its regulation under different physiological and environmental conditions, and its relation to classic target areas expressing estrogen receptors.

Steroid priming promotes oxytocin-induced norepinephrine release in the ventromedial hypothalamus of female rats

In vivo microdialysis was used to detect norepinephrine (NE) release in the ventromedial hypothalamus of estradiol (E 2)- or E 2 plus progesterone (P)-treated female rats injected with 1.0 IU of oxytocin (OXY). Dialysates were collected before and after OXY administration on 3 consecutive days and analyzed for NE content by high performance liquid chromatography with electrochemical detection. After the last sample was collected on day 1, animals were injected with 3 μg E 2 benzoate or oil. On day 3, E 2-primed animals received 200 μg of P and control females received oil prior to OXY administration. OXY administration did not induce NE release on day 1. When OXY was administered to animals that received E 2 approximately 20 h earlier, increased release of NE was not consistently seen. In contrast, E 2-primed animals that received P on day 3 displayed significant increases in the release of NE after OXY administration compared to their own basal levels and to NE levels in control animals. To distinguish whether E 2 priming is sufficient to promote OXY-induced release of NE without the addition of P, NE content of VMH dialysates in a second group of animals was examined following exposure to vehicle or E 2 alone. When OXY was administered 24 or 48 h after estrogen priming, only 1 of 4 E 2-primed females had modestly elevated dialysate NE levels. To evaluate the interactions between OXY and NE in the regulation of reproductive behavior, lordosis responses were observed in hormone-primed female rats receiving systemic injections of OXY, the α 1-adrenoceptor antagonist prazosin, or both OXY and prazosin. OXY enhanced lordosis behavior in females primed with subthreshold doses of E 2 and P. Prazosin abolished lordosis behavior in rats primed with behaviorally effective doses of E 2 and P and significantly inhibited lordosis in steroid-primed females given OXY. These data suggest that after priming with both E 2 and P together, but not with E 2 alone, OXY may facilitate lordosis behavior through activation of NE transmission.

Relationship of Population Density, Territorial Interaction and Plasma Levels of Gonadal Steroids in Spawning Male Demoiselles Chromis dispilus (Pisces: Pomacentridae)

Territorial male demoiselles Chromis dispilus were captured and bloodsampled underwater by scuba divers, from reef areas of low, medium, and high population density, over five spawning seasons. Measurements of densities of territory-holding males and the water-column population (females and nonterritory-holding males) were made from the same sites. Behavior of territory-holding males was assessed in relation to phase of the reproductive cycle and population density, using a remote underwater video system. Plasma levels of testosterone, 11-ketotestosterone (11KT), and 17α,20β-dihydroxy-4-pregnen-3-one (17.2βP) were measured by RIA. Territory density was found to be proportional to population size. Males from high density sites spent more time chasing conspecifics and spawning during the phase of courtship display and spawning (spawning phase), but there were no differences in behavior between males from different density sites during periods of egg-brooding and defence (nesting phase). Plasma levels of all three steroids were elevated during the spawning phase, and low during the nesting phase. Absolute levels of gonadal steroids were higher in fish from areas of high population density during the spawning phase, than in fish from lower population densities. In one case, plasma 11KT and 17.20βP were also elevated at high density during the nesting phase. The results of the study indicate that steroid hormone levels are labile in response to changes in population density, and frequency of territorial interaction. Changes in levels of plasma androgens are consistent with the "challenge" hypothesis of social regulation of territorial aggression. Changes in plasma levels of 17,20βP also occur in association with behavioral events but there is no direct evidence of a role for 17,20βP in the regulation of reproductive behavior.

Multiple molecular actions for steroids in the regulation of reproductive behaviors

Steroid hormones control brain functions and behaviors by several molecular actions that include the well-known genomic mechanism, in which intracellular steroid receptors regulate gene expression, and mechanisms that involve cell-surface receptors for steroids. Examples of the latter include the steroid modulation of the GABA A receptor complex and the recently discovered corticosteroid receptor in neuronal membranes from an amphibian (Taricha granulosa). This cortico steroid receptor meets the major criteria for being a bona fide receptor, is neuroanatomically and pharmacologically distinct from intracellular glucocorticoid receptors and seems to be coupled to G proteins. Furthermore, this membrane receptor seems to be physiologically relevant, functioning in the inhibitory pathways that control reproductive behaviors in Taricha.

Effects of cholecystokinin on male copulatory behavior and lordosis behavior in male rats

Because the distribution of cholecystokinin octapeptide (CCK-8) within the hypothalamus and limibc system overlaps with steroid concentrating regions, and because these areas are involved in the regulation of reproductive behaviors, we examined the effects of exogenous CCK-8 on male copulatory behavior and lordosis behavior in the male rat. Peripheral administration of a dose of CCK-8 that altered lordosis behavior in females (3 μg/kg, intraperitoneal) was ineffective in altering male copulatory behavior in males, either before or after gonadectomy, and was also ineffective in altering lordosis behavior after estrogen priming. In a separate experiment, CCK-8 injected into the lateral ventricle also did not affect male copulatory behavior, but lordosis behavior was increased dramatically after gonadectomy and estrogen priming. Although these results do not answer the question whether CCK-8 is acting to inhibit a neural system that normally suppresses lordosis behavior or is acting to stimulate a facilitatory circuit, these results do indicate the existence of an estrogen sensitive neural substrate in males on which CCK can act to facilitate lordosis behavior.

Regulation of Reproductive Behaviors in Amphibians by LHRH

Regulation of Reproductive Behaviors in Amphibians by LHRH

The Importance of Androgen Metabolism in the Regulation of Reproductive Behavior in the Avian Male

INTRODUCTIONIn a wide variety of vertebrate species, the repertoire of social behaviors associated with reproduction in the male, including heightened intermale aggression, courting of the female, and copulation, is dependent on gonadal hormones (Leshner, 1978). Because the effects of castration can be countered by treatment with testosterone (T) and because T is the primary androgen secreted by the testes in all species examined, it was assumed for many years that endogenous T was the hormone controlling reproductive activities in the male. Recent research in a variety of mammalian and avian species has cast doubt on this assumption. It now appears likely that T serves primarily as a prehormone, being metabolized to other hormones to exert its effects. The general schema seems to be that the testes produce T, which is released into the bloodstream and circulated throughout the body. Hormone-dependent tissues, such as the sexual accessory tissues and specific .

Regulation of reproductive behaviour and egg maturation in the tobacco hawk moth, Manduca sexta

ABSTRACT. The virgin female tobacco hawk moth, Manduca sexta, flies during the early scotophase in an LD 16:8 cycle at 24d̀C then begins ‘calling’ within 2h. Mating lasts 3–4 h. Oviposition occurs in the succeeding scotophases if a tobacco plant is present. The switch from virgin ‘calling’ behaviour to mated ovipositional behaviour is mediated by the presence of sperm and/or associated testicular fluids in the bursa copulatrix. The corpora allata, which are necessary for egg maturation in this species, are activated via the NCC I and II around the time of eclosion. Feeding increases the activity of the corpora allata in the virgin female (as judged by the number of eggs matured in 4 days) but mating brings about a further stimulation of the activity of the corpora allata. The stretching of the bursa copulatrix by the insertion of the spermatophore during mating is probably the trigger for this response. Continued neural input from the bursa copulatrix to the brain is necessary to maintain the increased activity of the corpora allata.

The role of the basal hypothalamus in the regulation of reproductive behavior in the lizard, Anolis carolinensis: Lesion studies

Bilateral radiofrequency lesions in the anterior and posterior basal hypothalamus decreased courtship and agonistic behaviors in both intact, sexually active, and castrated, androgen treated male Anolis carolinensis. Intact males receiving lesions in the anterior basal hypothalamus had atrophied testes, aspermia, and decreased epithelial cell height of the renal sex segment. Lesions of the posterior basal hypothalamus had no effect on testicular activity or the development of accessory organs. All animals demonstrating behavioral changes had lesion destruction in the ventromedial nucleus and the accompanying periventricular system. It is concluded that the basal hypothalamus in male A. carolinensis is involved both in the regulation of reproductive behavior and pituitary function.

The role of estrogen and progesterone in the regulation of reproductive behaviour in female ring doves (Streptopelia risoria) under long vs. short photoperiods

Female ring doves held under long (16 h per day) or short (8 h per day) photoperiods were treated daily for 15 days with saline, estrogen, or progesterone, alone or in combination. Seven days after the start of hormone therapy females were placed with reproductively active males for 4 h per day for 9 days. There was no difference in egg-laying, courtship, and nest-building by control birds under the two photoregimes.Ovarian follicles remained small in all birds receiving hormone treatment. Oviducts of birds receiving progesterone alone remained small in the short-photoperiod group, but at long photoperiods oviducts became enlarged. Estrogen stimulated oviduct growth at both photoperiods. The combined hormone treatment resulted in considerably greater oviduct development than estrogen alone, and in this case the oviducts of birds under long photoperiod were significantly heavier than those of short-photoperiod birds.Female soliciting and nest-building activity remained low in progesterone-treated females under short photoperiod, but increased rapidly under long photoperiod. Birds treated with estrogen and estrogen and progesterone performed considerable soliciting and nest-building. There was a marked tendency for birds under long-photoperiod conditions to be more active in nest-oriented behaviour. Copulatory behaviour by the female (begging and sexual crouch) occurred infrequently in all hormone-treated birds.