Effects of photostimulation,castration, and testosterone replacement on daily patterns of calling and locomotor activity in Japanese quail

To record calling (crowing) of Japanese quail continuously and automatically, an electronic device was developed. With this device, one call by Japanese quail triggers a pen deflection on a event recorder and also a count on a counter. Locomotor activity was also recorded automatically on the event recorder and the counter. Photostimulation induced calling and enhancement of activity in intact quails, and castration abolished calling and reduced locomotor activity. Silastic capsule implants containing testosterone restored both behaviors to the precastration levels in a week or so. There were daily rhythms of calling and locomotor activity in fully matured birds. These patterns also reappeared in testosterone-implanted birds, even though the release rate of the steroid hormone from the implanted capsules was expected to be constant. These results indicate that testosterone is required to induce calling and enhancement of locomotor activity and that a circadian oscillatory mechanism is possibly involved in daily rhythms of the behaviors.     

Organization and activation of behavior in quail: role of testosterone metabolism

In quail, the hypothalamus enzymatically transforms testosterone (T) into estradiol (E2), 5 alpha-dihydrotestosterone (5 alpha-DHT), and 5 beta-dihydrotestosterone (5 beta-DHT). During the embryonic life, the 5 beta-reductase activity is very high, which probably protects the brain of males from being behaviorally demasculinized by their endogenous T. 5 beta androstanes are inactive androgens. The decrease of 5 beta reductase with age during sexual maturation corresponds to a potentiation of the effects of T as shown by experiments that compared the effects of T and 5 alpha-DHT in adult and young quail. T metabolism is also involved in the activation of male behavior in the adult. T aromatization is probably essential for behavioral activation, but nonaromatizable androgens such as methyltrienolone, and to some extent 5 alpha-DHT, can also stimulate sexual behavior in castrates. These enzymatic activities show a clear neuroanatomical localization and are sexually dimorphic. Males produce more active metabolites (E2, 5 alpha-DHT) than females, which could explain the male's greater sensitivity to T treatments. It thus appears that T metabolism is involved in the differentiation and activation of behavior in quail.     

Circadian rhythms of testosterone-dependent behaviors,crowing and locomotor activity,in male Japanese quail

Summary An apparatus was devised to record crowing (mate calling by males) together with locomotor activity and recorded data was analyzed by several methods for rhythm analysis. Crowing and locomotor activity of Japanese quail held on long days were recorded during sexual development as estimated from circulating gonadotropins and testosterone. Both behaviors were testosterone-dependent but commencement of crowing preceded the increase in locomotor activity. When the two behaviors attained their maximum levels, crowing showed consistent daily rhythms in which two peaks were apparent, a major one at the onset of light and a broader one 8 hours later. Locomotor activity also showed a clear daily rhythm with a peak between the two peaks of crowing rhythm suggesting a fixed phase relationship between the two rhythms.Both rhythms free-ran under constant dim light with periods shorter than 24 h. They persisted in birds which had been castrated and then supplied with exogenous testosterone via implanted Silastic capsules. The durations of both rhythms were quite comparable to each other and they maintained a fixed phase relationship similar to that found under LD cycles.The results indicate that testosterone is essential for the induction of crowing and for the enhancement of locomotor activity but the formation of the rhythms in behavior was strictly dependent on a circadian oscillatory mechanism.Abbreviations LH luteinizing hormone - FHS follicle-stimulating hormone - LD light-dark - LDim light-dim light     

Effects of androgens and estrogens on crowings and distress callings in male Japanese quail, Coturnix japonica

In male Japanese quail, crowing behavior is considered to be strictly androgen-dependent. It was previously shown that in chicks, treatment with either testosterone or 5alpha-dihydrotestosterone (5alpha-DHT; a non-aromatizable androgen) induced crowing with motivation for distress calling in acutely isolated conditions. Many studies, however, have shown that the potencies of testosterone and 5alpha-DHT in activating crowing in castrated males are different. To clarify the effects of androgenic and estrogenic actions on the production of crows and distress calls, we injected quail daily from 11 to 42 days after hatching (Day 11 to 42) with testosterone propionate (TP), 5alpha-DHT, estradiol benzoate (EB) or vehicle and examined their calling behaviors both in a recording chamber (acutely isolated conditions) and in their home-cages (well-acclimated conditions). Both TP- and 5alpha-DHT-treated birds began to crow by Day 13 when isolated in the recording chamber. The TP-treated birds, however, crowed less frequently than 5alpha-DHT-treated ones. This, combined with the observations that distress calling was strongly inhibited in EB-treated birds, suggests that estrogen converted from testosterone may inhibit the motivation for distress calling. On the other hand, after chronic treatment of TP, but not of 5alpha-DHT, birds began to crow intensely in their home-cages earlier than vehicle treated controls, suggesting that estrogen is needed to initiate crowing behavior in sexually active males. Taken together, it is suggested that estrogenic actions affect the motivation underlying vocal behaviors, while the androgenic action is indispensable in generating crowing.     

Effects of sex steroids on calling,locomotor activity,and sexual behavior in castrated male Japanese quail

Castrated male Japanese quail were implanted with Silastic capsules containing testosterone (T), estradiol-17β (E₂), 5β-dihydrotestosterone (5β-DHT), Δ₄-androstenedione (Δ₄) 5α-androstanedione (A), 5α-dihydrotestosterone (5α-DHT) or with empty capsules. Calling, monitored continuously and automatically, was induced significantly by T and Δ₄. Locomotor activity, also monitored continuously by floor deflection, was enhanced by T, Δ₄, and E₂. Additional data concerning heterosexual and homosexual behavior were obtained from castrated quails after implantation of T, Δ₄, E₂, or 5α-DHT. T and Δ₄ restored hetero- and homosexual behavior as did E₂ but to a lesser extent. 5α-DHT did not induce either sexual behavior. Growth of the cloacal protrusion was induced in birds implanted with T, Δ₄, A, and 5α-DHT but not with 5β-DHT and E₂. These results indicate that calling and locomotor activity enhancement (including sexual behavior) are two different components of reproductive behavior which require different androgens or their metabolites to be activated.     

Estradiol Mediates Effects of Testosterone on Vasotocin Immunoreactivity in the Adult Quail Brain

In adult male quail, the activation of sexual behavior by testosterone (T) is mediated at the cellular level by the interaction of T metabolites with intracellular steroid receptors. In particular, the aromatization of T into an estrogen plays a key limiting role. Nonaromatizable androgens such 5alpha-dihydrotestosterone (DHT) synergize with estradiol (E2) to activate the behavior. Given that the density of vasotocin (VT) immunoreactive structures is increased by T in adult male quail and that VT injections affect male behavior, we wondered whether the expression of VT is also affected by T metabolites such as E2 and DHT. We analyzed here, in castrated male quail, the effects of a treatment with T, E2, DHT, or E2 + DHT on sexual behavior and brain VT immunoreactivity. The restoration by T of the VT immunoreactivity in the medial preoptic nucleus, bed nucleus striae terminalis, and lateral septum of castrated male quail could be fully mimicked by a treatment with E2. The androgen DHT had absolutely no effect on the VT immunoreactivity in these conditions and, at the doses used here, DHT did not synergize with E2 to enhance the density of VT immunoreactive structures. These effects of T metabolites in the brain were not fully correlated with their effects on the activation of male copulatory behavior, suggesting that the increase in VT expression in the brain does not represent a necessary step for the activation of behavior. Although VT expression in the medial preoptic nucleus and bed nucleus striae terminalis is often tightly correlated with the expression of male copulatory behavior, VT presumably does not represent simply one step in the biochemical cascade of events that is induced by T in the brain and leads to the expression of male sexual behavior.     

The postnatal demasculinization of sexual behavior in the Japanese quail (Coturnix coturnix japonica)

Three experiments were performed to analyze the time course of demasculinization in the Japanese quail and to test the activating and organizing effects of estradiol (E2) in adult sexually active birds. In Experiment 1, males and females were castrated at the age of 1 day or 1, 2, 4, and 6 weeks and treated as adults with testosterone (T). The age of castration had no effect on behavior and morphology in males. Plasma gonadotrophins (LH and FSH) were, however, higher in males castrated at or before than in those castrated after 2 weeks of age. This suggests that postnatal testicular secretions have organizing effects on the pituitary activity. Females which were castrated before 1 week of age were less sensitive to the activating effects of T than males, but were not fully demasculinized. The demasculinization of different reproductive characteristics such as male sexual behavior, cloacal gland size, and weight of the syringeal muscles is achieved in females at different times posthatching. In Experiment 2, castration of male and female quail at the ages of 4 days or 4 weeks confirmed that postnatal ovarian secretions contribute to the full behavioral and morphological demasculinization of females. It is easier to elicit mounting in T-treated females when they are tested in their home cage instead of a test arena. This difference was not observed in males. During Experiment 3, it was impossible to demasculinize sexually active adult males or females by treatment with Silastic implants of E2. E2 did not maintain sexual behavior in ovariectomized females showing male sexual behavior when treated with T but maintained the behavior in males.     

Testosterone implanted in the preoptic area of male Japanese quail must be aromatized to activate copulation

Intracranial implantation of minute pellets of gonadal steroids was combined with aromatase inhibitor treatment to determine if aromatization within the preoptic area (POA) is necessary for androgens to activate sexual behavior in the Japanese quail (Coturnix japonica). In this species, implantation of pellets of testosterone propionate (TP) or estradiol benzoate (EB) in the POA of castrated males restores male-typical copulatory behavior. In Experiment 1, adult male castrated quail were implanted intracranially with 200-micrograms pellets of equimolar mixtures of crystalline TP + cholesterol (CHOL), TP + 1,4,6-androstatriene-3,17-dione (ATD, an aromatase inhibitor), EB + ATD, or CHOL and behavior-tested with intact males and females. Copulation was stimulated by POA implants containing TP or EB (three of six CHOL + TP males and two of seven ATD + EB males copulated vs zero of four CHOL males), but copulation was not inhibited by combining ATD with TP (three of four ATD + TP males copulated). In Experiment 2, adult male castrated quail were injected systemically with ATD or oil for 6 days prior to and 14 days after intracranial implantation of 200-micrograms pellets containing the same amounts of TP or EB as in Experiment 1. The ATD injections completely blocked copulatory behavior in males with TP implants in the POA such that ATD/TP and Oil/TP mount frequencies differed significantly, but failed to block copulation in males with EB implants in the POA (proportions of males copulating were ATD/EB, 6/8; ATD/TP, 0/6; Oil/TP, 4/7). The cloacal foam gland, an androgen-sensitive secondary sex character, was unaffected by the dose of ATD used. We conclude that activation of copulatory behavior by TP implants in the POA is not due to nonspecific effects of high local testosterone concentrations but rather to aromatization. These results support the hypothesis that cells within the POA aromatize testosterone to estrogens, which directly stimulate the cellular processes leading to activation of male-typical copulatory behavior.     

Cocaine-induced sensitization correlates with testosterone in male Japanese quail but not with estradiol in female Japanese quail

Research has indicated that gonadal hormones may mediate behavioral and biological responses to cocaine. Estrogen, in particular, has been shown to increase behavioral responding to cocaine in female rats relative to male rats. The current study investigated the effect of cocaine on locomotor activity and hormonal correlates in male and female Japanese quail (Coturnix japonica). In Japanese quail, circulating hormone levels can be manipulated without surgical alterations via modifying the photoperiod. Male and female quail were housed on either 8L:16D (light:dark) or 16L:8D (light:dark) cycle for 21 days. Blood samples were taken prior to the beginning of the experiment and assays were performed to determine the levels of testosterone (T) and estradiol (E2). Quail were given injections of saline or cocaine (10 or 20 mg/kg) once a day for 10 days. Immediately after each injection, birds were placed in open field arenas and distance traveled was measured for 30 min. Results showed that male quail housed under long-light conditions exhibited cocaine-induced sensitization to 10 mg/kg cocaine which was correlated with the high levels of plasma T. Female quail housed under short-light conditions demonstrated sensitization to 10 mg/kg cocaine, but this was not correlated with the levels of plasma E2. The current findings suggest that cocaine-induced locomotor activity was associated with T in males but not with E2 in females.     

Steroidal control of sexual behavior in the rough-skinned newt (Taricha granulosa): effects of testosterone, estradiol, and dihydrotestosterone

Adult, sexually mature, male rough-skinned newts (Taricha granulosa) obtained from a wild population were castrated and received Silastic capsules containing testosterone (T), estradiol (E), or 5 alpha-dihydrotestosterone (DHT). The newts received three capsules of T, either one or three capsules of E or DHT, or combined treatments with these two steroids. When tested for sexual responsiveness after 32 and 34 days of steroid treatment, no group differed from the castrated controls (C). After 74 and 75 days of treatment, more T-implanted than C newts were sexually responsive, but the newts treated with E, DHT, or these two steroids in combination did not differ behaviorally from the C group. The diameter of the vas deferens was greater in the T- and DHT-treated males than in the C males, indicating that the implants adequately replaced testicular androgens. Together with other studies on this and other species, these results confirm the participation of testosterone in the regulation of sexual behaviors in male amphibians. Furthermore, these results indicate that in this amphibian, the behavioral effects of T are mediated directly by this steroid, not indirectly by enzymatic conversion to DHT or E.     

Infradian rhythmics of markers of physiologic and metabolic processes in Wistar male rats

This work presents the results of the amplitude-phase structure of the physiological rhythms (locomotor activity) and steroid hormones production (common testosterone and cortisole) in gelded and intact Wistar male rats as well as rats exposed to an information load. The markers have been shown to depend on the social state of the animal. It was proved that there was a phase coincidence of the periods of the biological rhythms of common testosterone (intact rats), cortisole and locomotor activity for animals with different individualand typological features. It was shown that the oscillation period of infradian rhythms of the measured markers of physiologic and metabolic processes in the animals of all groups amounted to 4 days. It was found that infradian rhythms were not sensitive to factors of various genesis.     

Photoperiodic and gonadal steroid regulation of pineal hydroxyindole-O-methyl transferase and N-acetyl transferase in Coturnix quail.

The activities of the melatonin-synthesizing enzymes were determined in pineals of Coturnix quail in response to photoperiodicity and gonadal hormones. Both hydroxyindole-O-methyl transferase (HIOMT) and N-acetyl transferase (NAT) were two-fold higher during exposure to darkness in female and male Coturnix maintained in a gonad-stimulating photoperiod (16L:8D). Castration decreased HIOMT activity in both female and male Coturnix. Administration of diethylstilbestrol, estradiol benzoate and progesterone into castrated females, and testosterone propionate and androstenedione into castrated males, restored HIOMT activity similar to that of intact controls. NAT was not affected by castration or gonadal steroids. These results suggest that the activity of pineal NAT is regulated primarily by photoperiodicity, while HIOMT activity is a consequence of photoperiodic and gonadal steroid regulation.     

Suppression of nocturnal increases in levels of melatonin elicits an anticipatory behavior in male quail

Abstract

During the reproductive development of male Japanese quail the duration of daily activity is prolonged and the onset of the rhythm of activity is advanced relative to the light‐dark cycle. The neuroendocrine basis for these changes was investigated with focusing on plasma levels of melatonin and testosterone. By means of 4 additional hours of photic stimulation of the brain, after the environmental lights (8L: 16D, lights on at 1000 hr) were turned off, the increase in levels of melatonin after lights‐off was suppressed for a few days. Thereafter the early onset of daily locomotor activity was observed and the gonads began to develop. Similar behavioral changes occurred in castrated quail following direct brain‐illumination or testosterone implants. The testosterone implants also suppressed the increases in levels of melatonin after lights‐off, for a few days. Treatment with an antiserum raised against melatonin (anti‐M) for the first 3 days, to suppress the increases in levels of melatonin after lights‐off, elicited such an anticipatory behavior. These results suggest that suppression of the nocturnal rise in melatonin levels is important for the first steps toward reproductive activity in male Japanese quail.     

Social Context Influences Androgenic Effects on Calling in the Green Treefrog (Hyla cinerea)

Courtship behavior in frogs is an ideal model for investigating the relationships among social experience, gonadal steroids, and behavior. Reception of mating calls causes an increase in androgen levels in listening males, and calling, in turn, depends on the presence of androgens. However, previous studies found that androgen replacement does not always restore calling to intact levels, and the relationship between androgens and calling may be context dependent. We examined the influence of androgens on calling behavior in the presence and the absence of social signals in male green treefrogs (Hyla cinerea). We categorized calling during an acoustic stimulus (mating chorus or tones) as evoked and calling in the absence of a stimulus as spontaneous. Intact males received a cholesterol implant, castrated males were castrated and received a cholesterol implant, and T-implanted males were castrated and received a testosterone implant. The androgen levels (mean +/- SE ng/ml of plasma) achieved by the implants were as follows: castrated males, 1.2 +/- 0.2; intact males 21.9 +/- 7.0; T-implanted males, 254.6 +/- 39.5. As in other frogs, calling depends on the presence of androgens, as castration abolished and T replacement maintained calling. However, among intact and T-implanted males, the influence of androgens on calling differed between spontaneous and evoked calling. There was a positive effect of androgen treatment on spontaneous call rate and a positive correlation between spontaneous call rate and androgen levels. The influence of androgen levels on evoked call rate was more complex and interacted with acoustic treatment. Surprisingly, T implants suppressed the chorus-specific increase in calling that is evident in intact males. In addition, in response to the chorus, T-implanted males called less than did intact males, in spite of higher androgen levels. Furthermore, variation in androgens did not explain variation in evoked call rate. These data indicate that androgens influence the motivation to call, but that, when socially stimulated, androgens are necessary but insufficient for calling.     

Effect of steroid milieu on gonadotropin-releasing hormone-1 neuron firing pattern and luteinizing hormone levels in male mice

GnRH neuronal function is regulated by gonadal hormone feedback. In males, testosterone can act directly or be converted to either dihydrotestosterone (DHT) or estradiol (E2). We examined central steroid feedback by recording firing of green fluorescent protein (GFP)-identified GnRH neurons in brain slices from male mice that were intact, castrated, or castrated and treated with implants containing DHT, E2, or E2 + DHT. Castration increased LH levels. DHT or E2 alone partially suppressed LH, whereas E2 + DHT reduced LH to intact levels. Despite the inhibitory actions on LH, the combination of E2 + DHT increased GnRH neuron activity relative to other treatments, reflected in mean firing rate, amplitude of peaks in firing rate, and area under the curve of firing rate vs. time. Cluster8 was used to identify peaks in firing activity that may be correlated with hormone release. Castration increased the frequency of peaks in firing rate. Treatment with DHT failed to reduce frequency of these peaks. In contrast, treatment with E2 reduced peak frequency to intact levels. The frequency of peaks in firing rate was intermediate in animals treated with E2 + DHT, perhaps suggesting the activating effects of this combination partially counteracts the inhibitory actions of E2. These data indicate that E2 mediates central negative feedback in males primarily by affecting the pattern of GnRH neuron activity, and that androgens combined with estrogens have a central activating effect on GnRH neurons. The negative feedback induced by E2 + DHT to restore LH to intact levels may mask an excitatory central effect of this combination.     

Intracranial androgenic and estrogenic stimulation of male-typical behaviors in house mice (Mus domesticus).

Two experiments in house mice (Mus domesticus) examined the neural sites at which steroid hormones activate the following male-typical behaviors: 70 kHz ultrasonic mating vocalizations in response to stimulus females or their urine, urinary marking in response to stimulus males or stimulus females, mounting of estrous females, and intermale aggression. In the first experiment, four groups of castrated males received bilateral intracranial implants of testosterone (T) into either the septum (SEPTUM), medial preoptic area (MPO), anterior hypothalamus (AHA), or ventromedial hypothalamus (VMH). Two control groups received subcutaneous silastic capsules of T (TSIL) or empty silastic capsules (BSIL). The TSIL males performed all behaviors at male-typical levels while the BSIL males were unresponsive. MPO males emitted ultrasonic mating vocalizations at high levels while few vocalizations were seen in males of the other brain implant groups. The VMH, AHA, and MPO males urine marked at higher levels than the BSIL males but did not exhibit the high levels of the TSIL males. Mounting was observed only in MPO and TSIL males. Aggression was rare in males from any of the brain implant groups. In the second experiment, the hormone activity of the implants was increased by using testosterone propionate (TP) or a 50% mixture of estradiol (E2) and cholesterol. The six groups were SEPTUMTP, SEPTUME2, MPOTP, MPOE2, TPSIL, and BSIL. The TPSIL males performed all behaviors at male-typical levels while the BSIL males were unresponsive. TP was effective at restoring vocalizations and urine marking only when placed in the MPO; however, E2 was effective at both sites. Again aggression and mounting were less evident in the brain implanted males. In conclusion, implants of T or TP were effective in restoring ultrasonic mating vocalization when placed into the MPO. MPO implants of T and TP were also effective in stimulating urine marking, although VMH and AHA implants also showed some effectiveness. The restorative effects of E2 were not localized which is probably related to the greater hormonal activity of this treatment. Comparisons of the properties of the various brain implants to restore more than one behavior were discussed.     

The relationship between locomotor activity rhythm and burying behavior in the wrasse,Suezichthys gracilis

The wrasse,Suezichthys gracilis, is a diurnal fish which buries itself in sand during the night-time. The present paper deals with the locomotor activity rhythms ofS. gracilis, examined by using an actograph with infra-red photo-electric switches in a dark room. The fish were kept in eight experimental tanks (each 30l in capacity), with three different bottom conditions: sand (grain size about 1 mm in diameter and 5 cm deep); 1 or 2 stones (about 10cm in diameter) without sand; and transparent acrylic pellets (2 × 2 × 3 mm in size, 5 cm deep). The light intensities were 550–700 lux just above the water surface, decreasing to 21.3% under the acrylic pellets at a water depth of 20cm. The water temperatures were kept at 22.0–25.0°C during the experiments for 7 to 14 days. In the aquarium with bottom sand, diel activity rhythms ofS. gracilis were mostly synchronized to LD (LD12:12; 06:00–18:00 light, 18:00–06:00 dark), free-running activity rhythms continued distinctly under LL (constant illumination), and locomotor activity was greatly suppressed, with disappearance of the activity rhythm, under DD (constant darkness). In the aquarium without sand, locomotor activity ofS. gracilis could be summarized as follows. The fish moved throughout almost the entire period under LD, though more frequent movements were observed in light conditions than in dark ones. Under LL they showed continuous locomotor activity during the experiment, with no obvious periodicity. Under DD the activity of the species was somewhat suppressed, but irregular movement or indistinct periodicity was observed. In the aquarium with transparent acrylic pellets, locomotor activity under LD and DD, respectively, bore a close resemblance to activity patterns under the same light conditions with sand, whilst activity under LL was identical to that under LL without sand. Accordingly, it seems that maintenance of normal activity rhythms in the wrasse was due not only to the darkness, but also to the presence of bottom sand. It therefore seems that the biological clock inS. gracilis is not related to locomotor activity, but to burying behavior.     

Ultradian and circadian compartmentalization of respiratory and metabolic exchanges in small laboratory vertebrates

Carbon dioxide emission (VCO2) taken as an index of respiratory and metabolic exchanges, was continuously recorded during 4-30 consecutive days in 100 quail, 87 chicks, 347 rats, 665 mice and 70 guinea-pigs which were under controlled environmental parameters. Harmonic analysis, fast Fourier transform, chi-square periodograms, peak and trough intervals were computed with VCO2 values obtained with CO2 concentrations sampled every 20 min on the CO2 recordings. In LD 12:12 alternation, circadian rhythms were observed in all quail, chicks, rats and mice, but only in 80% of the guinea-pigs. Ultradian VCO2 rhythms, with periods which show statistically significant interspecies differences, were assessed. For each of the 5 species these computed periods, which were the same in LL and DD, were: 1.17 h for quail and chickens, 1.25 h for rats, 1.50 h for mice and 1.0 h for guinea-pigs. In LD 12:12 these periods were different during L and D in quail, chicks, rats and mice, but not in guinea-pigs. The amplitudes of these ultradian variations were, according to the species, 10-20% of their mean VCO2 levels. These ultradian rhythms persist in the absence (or masking) of circadian rhythms, e.g. in LD 12:12 in 20% of guinea-pigs and in LL in 87% of Japanese quail and in 23% of Sprague-Dawley rats. Moreover, these ultradian rhythms persist during starvation, locomotor activity restraint and ageing. These ultradian VCO2 cycles which are related to rest-activity variations appear to be basic physiological rhythms with a genetic origin.     

Behavioral characteristics of freemartins administered estradiol, estrone, testosterone, and dihydrotestosterone

Eighteen genetic females born co-twin with males and diagnosed as being sterile intersexes (freemartins) were studied from birth to 79 weeks of age. Testosterone (T) and estrone (EI) were administered in Silastic capsules of two groups from birth to 50 weeks of age and other animals were left untreated. At 50 weeks the two treated groups had larger implants installed and the untreated animals were assigned to a new estrone (EII) and estradiol (E2) treatment. Later a dihydrotestosterone (DHT) group was formed in comparison with new E2 and testosterone propionate-enanthate (TP-TE) groups, plus untreated controls. Vulvar interest, Flehmen lip curl, mounting, and agonistic behavior were recorded daily for 30 min while animals were allowed social interaction. Agonistic behavior, interest in the genital area, and mounting were induced or stimulated by T, TP-TE, and E2, but not by DHT or estrone (EI or EII). Also, only animals in the T, TP-TE, and E2 groups induced to mount displayed the standing type of behavioral estrus. Flehmen lip curl was stimulated only by T or TP-TE. The evidence is interpreted to indicate that T, per se, evokes the lip curl, but it probably stimulates other responses at the neural level by conversion to E2. Also, the freemartin response, the response of castrates to steroid hormones, and current knowledge of circulating steroid hormones in male and female cattle could be interpreted to indicate that the neural tissue responsible for sexual behavior in both sexes of this species may respond similarly in several respects.     

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.