Medroxyprogesterone acetate, aggression, and sexual behavior in male cynomolgus monkeys (Macaca fascicularis).

Medroxyprogesterone acetate (MPA) is used clinically to treat male sex offenders, but there are conflicting reports about its effects on aggression. To investigate these matters in a nonhuman primate, four intact male cynomolgus monkeys were studied in a testing paradigm that involved the presence of a caged, aggression-arousing stimulus male either immediately before or during a pair-test with an ovariectomized, untreated female partner. After two 4-week periods of pretreatment baseline, males received weekly injections of 40 mg MPA either alone (two 4-week treatment periods) or in combination with testosterone replacement with sc implants (one period) and additional daily injections of 2 mg testosterone propionate (two periods). MPA was then withdrawn while testosterone replacement continued (three periods). The testing paradigm was effective in maintaining aggression, especially male-male aggression, for many months. Male-male aggression increased with MPA treatment, and increased further with testosterone replacement, whereas male-female aggression tended to change in the opposite direction. As in earlier studies, MPA decreased both plasma testosterone and male sexual activity, but restoring plasma testosterone levels in treated males failed to restore their sexual activity. MPA therefore has behavioral effects that are not mediated primarily by its suppression of circulating androgens.     

Identification of radioactivity in cell nuclei from brain, pituitary gland and genital tract of male rhesus monkeys after the administration of [3H]testosterone

Enzymes are present in the primate brain that convert testosterone into 17 beta-hydroxy-5 alpha-androstan-3-one (dihydrotestosterone), estradiol-17 beta and 4-androstene-3,17-dione. To identify the metabolites of testosterone that accumulate in cell nuclei obtained from different regions of the brain, 9 adult castrated male rhesus monkeys were injected with 5 mCi [3H]testosterone as an intravenous bolus. After 1 h, brains were rapidly removed and the left halves were used for autoradiography while the right halves were dissected to provide 14 samples. Radioactive metabolites in cell nuclei were identified by high-performance liquid chromatography (HPLC) and by repeated recrystallization. In autoradiograms of brain, most of the labeled neurons were in the hypothalamus, preoptic area and amygdala. These three regions also had the highest levels of radioactivity. The major form of this radioactivity was [3H]estradiol-17 beta (Type I tissues) and the major radioactive androgen present was [3H]testosterone. In all other brain regions and pituitary gland, the major form of radioactivity was unchanged [3H]testosterone (Type II tissues). In genital tract structures, [3H]dihydrotestosterone predominated (Type III tissues). These results suggested that, in contrast to its actions on genital tract structures, testosterone acts on neuronal nuclei mainly in unmetabolized form or after conversion to estradiol-17 beta.     

Localization and identification of nuclear radioactivity in the pituitary gland and genital tract after administering 3H-testosterone, 3H-dihydrotestosterone,or 3H-estradiol to male rhesus monkeys

Summary Target cells for testosterone, dihydrotestosterone, and estradiol in the pituitary gland and genital tract of the male primate were localized by thaw-mount autoradiography, and high performance liquid chromatography was used to identify the metabolites of these steroids in cell nuclei. Castrated rhesus monkeys were injected with ³H-testosterone, ³H-dihydrotestosterone, or ³H-estradiol and killed 60 min later. In the anterior pituitary gland, fewer cells were labeled and less radioactivity was taken up by cell nuclei following the administration of either ³H-testosterone (4% of pars distalis cells and 5 dpm/g DNA) or ³H-dihydrotestosterone (5% of cells and 13 dpm/g DNA) than following the administration of ³H-estradiol (43% of cells and 214 dpm/g DNA). Most of the radioactivity in nuclei was in the form of the unmetabolized parent compound (78–94%). In prostate, seminal vesicles, and penis, ³H-dihydrotestosterone was the predominant form of nuclear radioactivity following both ³H-testosterone (67–90%) and ³H-dihydrostestosterone (94–97%) administration, and both androgens labeled epithelial and smooth muscle cells. In contrast, ³H-estradiol was taken up in unchanged form, by cell nuclei of the genital tract and it labeled connective tissue fibroblasts, but not epithelial cells. Thus, the distributions of target cells for androgens and estrogens were clearly different in all these tissues, and the uptake of testosterone resembled that of its androgenic rather than that of its estrogenic metabolite.     

Characterization by high performance liquid chromatography of nuclear metabolites of testosterone in the brains of male rhesus monkeys

Testosterone (T) restores the potency of castrated male rhesus monkeys, and our autoradiographic data have demonstrated that ³H-T or its metabolites concentrate in cell nuclei in the corticomedial amygdala, bed nucleus of stria terminalis, preoptic area, and hypothalamus. In rat, ³H-estradiol (³H-E₂) is a major nuclear metabolite of ³H-T in areas of the limbic system, but comparable data are lacking for the primate. We have therefore developed an improved technique using high performance liquid chromatography for investigating metabolites of ³H-T that accumulate in cell nuclei in small amounts of tissue obtained from the brain of the rhesus monkey. Two castrated male rhesus monkeys were injected with 5 mCi of ³H-T and were killed 30 min later. In amygdala, preoptic area-bed nucleus of stria terminalis, and hypothalamus, 48–70% of the nuclear radioactivity was in the form of ³H-E₂ (Type I tissues). In six other brain areas and in pituitary, 35–85% of the nuclear radioactivity was in the form of ³H-T (Type II tissues), whereas in genital tract tissues, 86–99% of the nuclear radioactivity was in the form of ³H-dihydrotestosterone (³H-DHT) (Type III tissues). In plasma and in supernatants from both Type I and Type II tissues, the proportions of ³H-T were high, and ³H-E₂ did not exceed 10% of the total extractable radioactivity. These data suggest that, as in rodents, some of the central actions of T in primates may be mediated by estrogen target neurons.     

The uptake and metabolism of labelled testosterone by the brain and pituitary of the male rhesus monkey (Macaca mulatta)

The ventricular systems of three male rhesus monkeys (one castrate) were infused over a one hour period with a small volume of labelled testosterone of high specific activity. The pituitary and various areas of the brain and samples of blood and spinal fluid were secured following infusion. Radioactive steroids were extracted from the tissues, separated chromatographically, and identified by recrystallization to constant specific activity. Radioactive testosterone (T), 5α-dihydrotestosterone (5α-DHT), 5α-androstane-3α, 17β-diol (5α-A-diol) and δ₄-androstenedione (δ₄-A) were found in all samples of pituitary and brain and at a much higher concentration per unit weight than that noted in blood. The spinal fluid samples contained primarily unchanged T. Uptake of labelled T appeared to be greater in the pituitary and hypothalamus than in other areas of the brain. It is concluded that (1) ventricular infusion of labelled testosterone under the conditions of these experiments provided a suitable means of supplying deep structures of monkey brain and pituitary with a high concentration of steroid with relatively little reaching the systemic circulation, and (2) steroidal 5α-reductase and 17β-dehydrogenase activity was present throughout the brain.     

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.     

Pre-optic and hypothalamic neurons accumulate [3H]medroxyprogesterone acetate in male cynomolgus monkeys

Medroxyprogesterone acetate (MPA) is a synthetic progestin that is reported to be effective in the treatment of paraphilic behavior, including paraphilic aggression, in men. The mechanisms and sites of action for its behavioral effects are not known. Thaw-mount autoradiography was used to help identify sites in the brain at which MPA may act in a male primate. Two adult, castrated male cynomolgus monkeys were administered [3H]MPA and killed one hour later. Radioactivity was concentrated in the nuclei of many neurons in the medial preoptic nucleus (n.), anterior hypothalamic area, ventromedial hypothalamic n., and arcuate n. Virtually no labeled cells were observed in the bed n. of the stria terminalis, lateral septal n., or amygdala. Analysis by high performance liquid chromatography of brain samples from the same animals demonstrated that 84% of the extractable radioactivity in cell nuclei from the hypothalamus and preoptic area was in the form of unmetabolized [3H]MPA. The localization of MPA-concentrating neurons in regions of the brain known to be implicated in regulating both sexual behavior and pituitary function suggests that, among other sites of action, MPA may act directly upon the brain.     

Effects of testosterone on the behavior of male cynomolgus monkeys (Macaca fascicularis)

To determine the threshold doses of testosterone propionate (TP) that cause clear-cut behavioral changes in the sexual behavior of castrated male cynomolgus monkeys, observations were made on three males during successive 5-week treatment periods while they received daily subcutaneous doses of 100 μg TP increasing in octaves to 25.6 mg TP. Males were tested with each of the same two ovariectomized, estrogen-treated females (6 pairs, 330 1-hr behavior tests). To mimic the diurnal plasma testosterone rhythm, TP injections were given at 1600 hr and blood samples were obtained at 0800 hr (141 samples). Male ejaculatory activity increased at the threshold dose of 200 μg TP per day giving plasma testosterone levels of 830 ng/100 ml, which is in the physiological range of 600–1600 ng/100 ml for intact males. This threshold dose was eight times higher than in rhesus monkeys on a dose per kilogram body weight basis. There was a further marked increase in ejaculatory performance at higher doses (6.4 to 25.6 mg) giving supraphysiological plasma levels of 4000–9000 ng/100 ml. There were individual differences in the behavioral changes occurring with TP treatment, and the female partner modulated the effects. These findings were generally similar to those obtained with male rhesus monkeys, but certain species differences were noted.     

Androgen metabolism in the male hamster--1. Metabolism of testosterone in the pituitary gland and in the brain of animals exposed to different photoperiods

It is known that the metabolism of testosterone in the brain and in the anterior pituitary is different in mammalian and in photoperiodic avian species. In many mammalian species, testosterone is mainly metabolized to 5-alpha-reduced compounds (e.g. 17-beta-hydroxy-5-alpha-androstan- 3-one, 5 alpha-DHT and 3-alpha,17-beta-dihydroxy-5-alpha-androstane, 5-alpha,3-alpha-diol) and, to a smaller extent, to 4-androstene-3,17-dione (androstenedione), while in birds, androstenedione is the main testosterone metabolite and the conversion to the 5-alpha-reduced compounds is quantitatively negligible. In avian species, testosterone is also converted to 5-beta-reduced steroids (mainly 17-beta-hydroxy-5-beta-androstan-3-one, 5-beta-DHT and 3-alpha,17-beta-dihydroxy-5-beta-androstane, 5-beta,3-alpha-diol), and there is also evidence that in these species testosterone metabolism in the central structures may be influenced by the photoperiod. Since the hamster is a mammal whose reproductive cycle is controlled by day length, it has been analyzed whether: (a) the central structures of the hamster (cerebral cortex, hypothalamus and anterior pituitary) metabolize testosterone in vitro following a mammalian (5-alpha-reduced derivatives) or an avian (androstenedione and 5-beta-reduced compounds) pattern; and (b) the metabolism of testosterone in the same structures may be modified by the exposure to different photoperiods (LD 14:10 or LD 8:16). The present data indicate that no one of the hamster structures examined produces the 5-beta-reduced derivatives. Moreover, the formation of the 5 alpha-DHT is quantitatively low, and is not affected by the photoperiod. In contrast, androstenedione is formed in quite high yields and the exposure of the animals to 60 days of short photostimulation increases the formation of this steroid in the pituitary gland, but not in the brain structures. From these data, it appears that the central structures of the hamster metabolize testosterone with a pattern which is intermediate between that of birds and mammals.     

Pretreatments with 5 alpha-dihydrotestosterone and the uptake of testosterone by cell nuclei in the brains of male rhesus monkeys

An in vivo competition method was used in adult male rhesus monkeys to determine if testosterone binds to high affinity binding agents, notably androgen receptors, in brain cell nuclei. Castrated males received 5 alpha-dihydrotestosterone propionate (DHTP, 20 mg, N = 6), testosterone propionate (TP, 100 mg, N = 3) or oil vehicle (controls, N = 6) followed 3 h later by 5 mCi [3H]testosterone [( 3H]T) as an intravenous bolus. Brain and peripheral tissue samples were removed after 60 min, homogenized and separated into supernatant and purified nuclear fractions. Radioactive metabolites of [3H]T [( 3H]estradiol, [3H]DHT) and unchanged [3H]T were identified by high performance liquid chromatography (HPLC). Androgen pretreatments reduced the nuclear uptake of [3H]T by 67-98% in hypothalamus (HYP), preoptic area (POA) and pituitary gland (PIT). This blockade was presumed to be due to prior occupation of nuclear androgen receptors by unlabeled androgens because pretreatments had no effects on levels of [3H]T in supernatants. Since [3H]T was the major radioactive androgen present in brain cell nuclei, results strongly suggested that the principal nuclear androgen receptor ligand in HYP, POA and PIT was unchanged [3H]T rather than [3H]DHT as occurs in the genital tract. In the amygdala the situation was quite different. Here, nuclear concentrations of [3H]T were reduced by 67% following TP pretreatment but were not changed following DHTP pretreatment, indicating a different uptake mechanism in this region that could have particular relevance for testosterone's central actions on behavior.     

Effect of neonatal injections of estradiol, testosterone and cryproterone acetate on plasma and testicular testosterone and on the genital system in adult male mice]

On day old male mice received a single injection of oestradiol benzoate, testosterone propionate or cyproterone acetate in order to study their action on testicular development, particularly testosterone secretion. Oestrogenization of newborn males leads, when the animals mature, to a high proportion or cryptorchidism, to atrophy of testes and seminal vesicles, and inhibition of spermatogenesis. Testosterone levels were reduced in the plasma. Testosterone propionate produced moderate reduction of testicular weight but spermatogenesis was not impaired. Plasma testosterone level was reduced. Cyproterone acetate increased significantly testicular testosterone level.