Mounting behavior and lordosis behavior in castrated male rats treated with testosterone propionate, or with estradiol benzoate or dihydrotestosterone in combination with testosterone propinonate.

Treatment of prepuberally castrated male rats with testosterone propionate (TP, 50, 200, 500, or 1000 μg for 30 days) in adulthood stimulated the display of both mounting behavior and lordosis behavior. No correlation between mounting and lordosis behavior could be detected at any TP dose level. Treatment of prepuberally castrated male rats with either 1 μg estradiol benzoate (EB) or 500 μg dihydrotestosterone (DHT) for 60 days stimulated the display of mounting behavior in three of eight and four of eight rats, respectively. Treatment with 200 μg TP for the last 30 days of rats receiving either EB or DHT for 60 days resulted in an abrupt onset on mounting behavior as compared to rats treated with oil for 60 days. These results show additive effects of EB or DHT and TP upon mounting behavior by male rats and are interpreted as a support for the suggestion that testosterone to estrogen as well as testosterone to DHT conversion may be involved in the mechanism whereby testosterone activates the mounting behavior of castrated rats.     

Serum estradiol, testosterone and dihydrotestosterone in male monkeys treated with testosterone propionate.

Serum estradiol (E2), testosterone (T) and dihydrotestosterone (DHT) were measured in juvenile (pre-pubertal) male rhesus monkeys injected with either 8 mg or 80 mg of testosterone propionate (TP). After one week, the three steroids were elevated and remained essentially unchanged for the duration of the study. There was little difference in serum E2 or DHT when comparing the two groups of steroid-treated monkeys. In contrast, T levels were consistently greater in the animals given the high dosage of TP.     

Lordosis behavior in castrated male rats treated with estradiol benzoate or testosterone propionate in combination with an estrogen antagonist, MER-25, and in intact male rats

Lordosis behavior could be elicited by manual stimulation in castrated male rats after treatment with estradiol benzoate (15 μg for 10 days) or testosterone propionate (1 or 3 mg for 10 days). The effect was antagonized by treatment with the estrogen antagonist MER-25 (10mg for 10 days). Prolonged treatment with testosterone propionate (1 mg for 26 days) resulted in display of male (nine of ten rats) as well as female (seven of ten rats) sexual behavior. Eleven of 32 intact male rats (age 120 days) and 22 of 37 other intact males (age 75 days) displayed lordosis in response to manual stimulation without hormonal treatment. Seven intact males which showed lordosis without hormone treatment were injected with MER-25 (10 mg/day × 10 days) and lordosis was abolished in six cases. The results suggest that estrogen is involved in the regulation of lordosis behavior in TP-treated and intact male rats.     

Testosterone,androstenedione and dihydrotestosterone: Effects on mating behavior of male rats

The relative effectiveness of testosterone, androstenedione, and dihydrotestosterone in maintaining mating behavior following castration of male rats was studied. In Experiment 1 testosterone, but not dihydrotestosterone, was found to maintain mating. In Experiment 2 testosterone and androstenedione were found to be equally effective in maintaining mating. Dihydrotestosterone failed to maintain mating and was no more effective than no treatment at all. Testosterone, androstenedione, and dihydrotestosterone significantly enhanced seminal vesicle and penis weight. In Experiment 3 castrated male rats were administered radiolabeled testosterone, androstenedione, or dihydrotestosterone. Radioactivity was found in hypothalamic and seminal vesicle samples indicating that these steroids can be accumulated by brain as well as peripheral androgen-sensitive tissues. It was concluded that the peripherally active steroid dihydrotestosterone probably plays no role in the maintenance of sexual behavior.     

Induction of male sex behavior in pony mares with testosterone propionate

Two pony mares were administered 150 mg of testosterone propionate every other day for 20 days (ten injections) and every ten days there-after. An additional two mares and one stallion were not treated and served as controls. Testosterone propionate was dissolved in absolute ethanol and administered subcutaneously. Sex behavior tests were conducted 26 and 40 days after the first injection. Control mares exhibited very little male sex behavior. Both testosterone propionatetreated mares, however, exhibited mounting, sniffing, flehmen, biting and vocalization behavior in the presence of an estrous mare. The testosterone propionate-treated mares mounted and bit estrous mares more frequently than the stallion but exhibited less sniffing, flehmen and vocalization behavior in the presence of an estrous mare than the stallion. Testosterone propionate-treated mares and the stallion mounted an estrous mare 23.3 +/- 9.7 seconds and 172.5 +/- 22.5 seconds, respectively, after being introduced into the pen. Mares in estrus were mounted by the testosterone propionate-treated mares and the stallion an average of 4.0 +/- 1.3 and 1.0 +/- 0 times, respectively, during a ten-minute test. None of the non-estrous mares was ever mounted by the testosterone propionate-treated mares. In summary, testosterone propionate induced male sex behavior in intact mares and the testosterone propionate-treated mares effectively detected estrous mares.     

Activation of sexual behavior by implantation of testosterone propionate and estradiol benzoate into the preoptic area of the male Japanese quail (Coturnix japonica)

Intracranial implantation of minute pellets of gonadal steroids was performed to determine neuroanatomical loci at which steroids activate sexual behavior in the Japanese quail (Coturnix japonica). In this species, systemic treatment of castrated males with either testosterone propionate (TP) or estradiol benzoate (EB) restores male-typical copulatory behavior (head grabbing, mounting, and cloacal contact movements). In addition, EB activates female-typical receptive behavior (crouching). Adult male castrated quail were implanted intracranially with 300-micrograms pellets containing TP, EB, or cholesterol (CHOL) and behavior was tested with intact males and females. Either TP or EB pellets in the preoptic area (POA) activated male-typical copulatory behavior. Mounting was specifically activated without concomitant activation of other steroid-sensitive sexual and courtship behaviors. TP and EB implants in adjacent nuclei containing receptors for these steroids and CHOL implants in POA had no effect on male-typical copulatory behavior. Eighteen percent of all males tested for female-typical receptivity crouched, but no specific effect of EB was seen at any site. The similarity of the POA sites for activation of mounting by TP and EB is consistent with the hypothesis that cells within the POA aromatize testosterone to estrogens, which directly stimulate the cellular processes leading to behavioral activation.     

Effects of dihydrotestosterone and estradiol benzoate pretreatment upon testosterone-induced sexual behavior in the castrated male rat

Three groups of inexperienced castrated male rats were treated daily for 15 days with oil, estradiol benzoate (1 μg), or dihydrotestosterone (1 mg), and thereafter injected daily with testosterone (1 mg) for 21 days. Sexual behavior was tested every third day after the start of the pretreatment until day 36. Estradiol benzoate or dihydrotestosterone failed to elicit sexual behavior. Pretreatment with dihydrotestosterone, but not estradiol benzoate, significantly shortened the intervals to initiation of mounting and intromission in response to testosterone. The results suggest that fully developed genitals (penis and/or sexual accessories) facilitate initiation of copulatory behavior in response to testosterone administration.     

Synergistic effect of estradiol benzoate and dihydrotestosterone on aggression in mice

Orchiectomized CD-1 mice were treated with several steroids, alone and in combination, and then tested for aggressiveness against group-housed, intact “stimulus” mice. Estradiol benzoate (EB) in combination with dihydrotestosterone (DHT) elicited aggression equivalent to that shown by intact, sham-operated animals and by testosterone-treated subjects. EB alone was less effective than EB with DHT. DHT alone elicited no more aggression than that observed in control animals. The data suggest a synergism between EB and DHT within the central nervous system in the induction of aggressive behavior.     

Actions of esters of testosterone, dihydrotestosterone, or estradiol on sexual behavior in castrated male guinea pigs

Prepuberally castrated male guinea pigs were treated in adulthood with estradiol benzoate, testosterone propionate, dihydrotestosterone propionate or corn oil (vehicle control). Both corn oil and estradiol benzoate were ineffective in augmenting or inducing any aspect of adult male sexual behavior. Dihydrotestosterone propionate and testosterone propionate were both effective in establishing the complete male sexual behavior pattern, although they differed in the manner in which they affected specific components. For example, males treated with testosterone propionate showed more non-intromissive but not more intromissive mounts than males treated with dihydrotestosterone propionate. In addition, the average frequency of thrusts per intromission was greater for males treated with dihydrotestosterone propionate than for males treated with testosterone propionate.     

Effects of testosterone propionate and dihydrotestosterone on penile morphology and sexual reflexes of spinal male rats

Testosterone propionate (TP) has a quantitative influence on sexual reflexes mediated at the spinal level in male rats. The possibility that this influence reflects the direct action of androgen on neural elements in the cord, rather than on sensory receptors in the penis was examined indirectly by the use of dihydrotestosterone (DHT). Spinal castrated male rats maintained initially on TP and then switched to DHT showed a significant decline in sexual reflexes paralleling the decline of another group of spinal rats receiving no hormone after initial TP treatment. Yet the number of penile papillae and weight of the penile shaft for the DHT subjects were not significantly different from these measures of penile morphology in a third group of subjects receiving continuous TP and in which reflexes did not decline. These and other observations are consistent with the hypothesis that neural elements within the spinal cord, related to the mediation of the ejaculatory pattern in intact male rats, are directly influenced by gonadal androgen.     

Induction of male sex behavior in ewes with silastic implants containing testosterone propionate

In the first of two experiments, ovariectomized ewes with silastic implants containing testosterone propionate had higher concentrations of plasma testosterone than ovariectomized ewes with silastic implants containing testosterone (4.0 +/- .2 vs .8 +/- .1 ng/ml). In the second experiment, one or two 10 cm silastic implants filled with testoster-one propionate increased concentrations of plasma testosterone and induced male sex behavior in ovariectomized ewes similar to plasma testosterone levels and male sex behavior in rams. The interval from initiation of the treatment to the first behavior test in which mounting was consistently observed was 14.4 +/- 2.9 days and once mounting behavior was consistently induced, the testosterone treated ewes mounted estrous ewes an average of 10.7 +/- 1.3 times during a 10-minute test.     

Effects of estradiol benzoate in combination with dihydrotestosterone on postejaculatory vocalization and refractory period in castrated male rats

The objective of this experiment was to compare the effects of estradiol ben-zoate (EB) treatment with those of testosterone propionate (TP) on the postejaculatory vocalization and refractory period in castrated dihydrotestosterone (DHT)-treated male rats. Twelve reliable maters were tested, castrated, and then treated with subcutaneous implants of DHT and daily injections of either 200 μg of TP (N = 6) or 200 μg of EB (N = 6). Testing continued weekly for 9 weeks with treatments interchanged after the fourth week. EB treatment resulted in: (1) a reduction in the number of males that vocalized, (2) a reduction in the duration of vocalization, and (3) the exhibition of extraordinarily abbreviated postejaculatory refractory periods by a few males. It was suggested that high doses of estradiol act to counter inhibitory processes during the refractory period.     

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.     

The effects of testosterone, estradiol, and dihydrotestosterone on male mouse (Mus musculus) ultrasonic vocalizations

Two experiments examined the effects of the free forms of testosterone (T), dihydrotestosterone (DHT), and estradiol (E₂) upon male mouse (Mus musculus) courtship vocalizations and seminal vesicle weight. In the first experiment, administration of T to castrated males was associated with a large number of vocalizations and large seminal vesicle weights, DHT was associated with large seminal vesicle weights but very few vocalizations, whereas E₂ was associated with low measures of both vocalization and seminal vesicle weight. In the second experiment, T and DHT had effects highly similar to those of the previous experiment; however, in contrast to the previous experiment, both low and high dosages of E₂ were associated with large numbers of ultrasonic vocalizations but small seminal vesicles. A mixture of E₂ and DHT was very similar to T in its effect upon both measures. We suggest from these results that hormonal mechanisms similar to those reported for rat sex behavior may interact with situational variables to determine the expression of male mouse courtship.     

The effects of testosterone propionate and estradiol benzoate on the vitro synthesis of FSH.

The effects of estradiol benzoate (EB) and testosterone propionate (TP) on pituitary and plasma concentrations of follicle stimulating hormone (FSH) and the in vitro synthesis of FSH in pituitary tissue was studied in mature male rats. By the 4th day of treatment with EB, pituitary content and concentration of FSH had declined, and content had fallen to 6% and concentration to 3% of pretreatment values. Similar results occurred during in vitro synthesis. However, serum levels of FSH did not show any decline until the 21st and 28th days of treatment. Administration of TP produced a progressive increase in pituitary content and concentration of FSH, though serum levels remained unchanged for the 1st 7 days, after which they fell slightly. The effect of TP on the in vitro synthesis of FSH showed no consistent pattern, though in no case was a decrease in the uptake of labeled leucine into immunoprecipitable FSH observed. The results suggest that EB and TP have different effects on pituitary FSH in normal adult male rats.     

Effects of estrone, estradiol and estriol combined with dihydrotestosterone on mounting and lordosis behavior in castrated male rats

Prepuberally castrated male rats were injected with estrone (1 or 5 μg), estradiol (1 or 5 μg) or estriol (1, 5, or 25 μg) either alone or in combination with dihydrotestosterone, (0.5 mg). Each of these steroids, when given alone, had no or only weak stimulatory effects on male sexual behavior. When combined with dihydrotestosterone all estrogens stimulated full copulatory behavior, the order of potency being estradiol, estrone, and estriol. Lordosis behavior in response to male mounting or manual stimulation was facilitated by all estrogens. All estrogens caused a slight weight increase of the seminal vesicles, ventral prostate and glans penis.     

Differential effect of testosterone and dihydrotestosterone on the sexual behavior of prepuberally castrated male rabbits

The effect of testosterone propionate (Tp) and dihydrotestosterone propionate (DHTp) at doses of 1, 3 and 9 mg daily for 30 days on the copulatory behavior of prepuberally castrated male New Zealand white rabbits was studied. Tp was significantly more effective than DHTp in eliciting copulatory behavior at each dose level tested. Three milligrams Tp was the minimal dose required to elicit mounting consistently. DHTp at the high dose level (9 mg) only elicited sexual activity comparable to that observed with the low dose of Tp (1 mg). The results suggest that T does not need to be reduced to DHT to stimulate sexual behavior in the male rabbit.     

Implantation of dihydrotestosterone propionate into the lateral septum or medial amygdala facilitates copulation in castrated male rats given estradiol systemically

Two experiments were conducted to determine whether unilateral implantation of dihydrotestosterone propionate (DHTP) into different brain regions of castrated rats, bearing silastic capsules containing estradiol, could augment sexual behavior without appreciable leakage of androgen into the peripheral circulation. In Experiment 1 implanation of pulverized crystalline DHTP (via 25-gauge, 1-mm-long pellets) facilitated mating significantly without stimulating penile spine growth, provided the pellets were positioned in the lateral septum or medial amygdala. Insertion of DHTP pellets into the preoptic area-anterior hypothalamus, caudate-putamen, or the border of the substantia nigra and ventral tegmental nucleus or of cholesterol pellets into lateral septum or medial amygdala had no behavioral effects. Implanation of DHTP into the lateral septum also failed to activate penile erections in rats restrained in a supine position. In Experiment 2 implantation of different bone wax dilutions of DHTP (via 25-gauge, 1-mm-long pellets) into the preoptic area-anterior hypothalamus augmented males' sexual performance only in that group in which penile spine growth was also significantly stimulated. The results sugggst that 5α-reduced androgen is capable of activating mating in the male rat by acting locally in the lateral septum and/ or medial amygdala.