A comparison of the effects of methyltrienolone (R 1881) and 5 alpha-dihydrotestosterone on sexual behavior of castrated male rats

Genetics and Epigenetics of the X and Y Chromosomes in the Sexual Differentiation of the Brain

For many decades to date, neuroendocrinologists have delved into the key contribution of gonadal hormones to the generation of sex differences in the developing brain and the expression of sex-specific physiological and behavioral phenotypes in adulthood. However, it was not until recent years that the role of sex chromosomes in the matter started to be seriously explored and unveiled beyond gonadal determination. Now we know that the divergent evolutionary process suffered by X and Y chromosomes has determined that they now encode mostly dissimilar genetic information and are subject to different epigenetic regulations, characteristics that together contribute to generate sex differences between XX and XY cells/individuals from the zygote throughout life. Here we will review and discuss relevant data showing how particular X- and Y-linked genes and epigenetic mechanisms controlling their expression and inheritance are involved, along with or independently of gonadal hormones, in the generation of sex differences in the brain.

Post-finasteride syndrome: a surmountable challenge for clinicians

Post-finasteride syndrome (PFS) is a constellation of serious adverse side effects manifested in clinical symptoms that develop and persist in patients during and/or after discontinuing finasteride treatment in men with pattern hair loss (androgenetic alopecia) or benign prostatic hyperplasia. These serious adverse side effects include persistent or irreversible sexual, neurological, physical and mental side effects. To date, there are no evidence-based effective treatments for PFS. Although increasing number of men report persistent side effects, the medical community has yet to recognize this syndrome nor are there any specific measures to address this serious and debilitating symptoms. Here we evaluate the scientific and clinical evidence in the contemporary medical literature to address the very fundamental question: Is PFS a real clinical condition caused by finasteride use or are the reported symptoms only incidentally associated with but not caused by finasteride use? One key indisputable clinical evidence noted in all reported studies with finasteride and dutasteride was that use of these drugs is associated with development of sexual dysfunction, which may persist in a subset of men, irrespective of age, drug dose or duration of study. Also, increased depression, anxiety and suicidal ideation in a subset of men treated with these drugs were commonly reported in a number of studies. It is important to note that many clinical studies suffer from incomplete or inadequate assessment of adverse events and often limited or inaccurate data reporting regarding harm. Based on the existing body of evidence in the contemporary clinical literature, the author believes that finasteride and dutasteride induce a constellation of persistent sexual, neurological and physical adverse side effects, in a subset of men. These constellations of symptoms constitute the basis for PFS in individuals predisposed to epigenetic susceptibility. Indeed, delineating the pathophysiological mechanisms underlying PFS will be of paramount importance to the understanding of this syndrome and to development of potential novel therapeutic modalities.

Finasteride, not tamsulosin, increases severity of erectile dysfunction and decreases testosterone levels in men with benign prostatic hyperplasia

BACKGROUND

5α-reductase inhibitors (5α-RIs) (finasteride and dutasteride) have been proven useful in treatment of lower urinary tract symptoms (LUTS) related to benign prostatic hyperplasia (BPH). However, these inhibitors exert undesirable sexual side effects and, in some cases, these effects are persistent. There is considerable disagreement with regard to whether the adverse side effects resolve with continuous treatment.

AIM

To investigate the long-term adverse effects of finasteride treatment in men with BPH on erectile function and to compare these adverse effects in men treated with the α1-adrenergic receptor blocker, tamsolusin.

METHODS

In this retrospective registry study, a cohort of 470 men aged between 47 and 68 years (mean 57.78±4.81) were treated with finasteride (5 mg/day). A second cohort of 230 men aged between 52 and 72 years (mean 62.62±4.65) were treated with tamsulosin (0.4 mg). All men were followed up for 45 months. At intervals of 3 months and at each visit, plasma testosterone (T) levels and the international index of erectile function (IIEF-EF) questionnaire scores were determined.

RESULTS

Long-term treatment with finasteride therapy is associated with worsening of erectile dysfunction (ED) as shown by the significant decrease in the IIEF-EF scores in men treated with finasteride. No worsening of ED was observed in men treated with tamsulosin. The increase in ED due to finasteride did not resolve with continued treatment with finasteride. Most importantly, long-term finasteride therapy resulted in reduction in total T levels, contributing to a state of hypogonadism. On the contrary, no changes in T levels were noted in men treated with tamsolusin.

CONCLUSION

Our findings suggest that in men with BPH, long-term finasteride therapy but not tamsulosin results in worsening of ED and reduces total T concentrations. Clinicians are urged to discuss the impact of 5α-RIs therapy on sexual function with their patients before commencing this therapy.

Adverse effects of 5α-reductase inhibitors: What do we know, don't know, and need to know?

Steroids are important physiological orchestrators of endocrine as well as peripheral and central nervous system functions. One of the key processes for regulation of these molecules lies in their enzymatic processing by a family of 5α-reductase (5α-Rs) isozymes. By catalyzing a key rate-limiting step in steroidogenesis, this family of enzymes exerts a crucial role not only in the physiological control but also in pathological events. Indeed, both 5α-R inhibition and supplementation of 5α-reduced metabolites are currently used or have been proposed as therapeutic strategies for a wide array of pathological conditions. In particular, the potent 5α-R inhibitors finasteride and dutasteride are used in the treatments of benign prostatic hyperplasia (BPH), as well as in male pattern hair loss (MPHL) known as androgenetic alopecia (AGA). Recent preclinical and clinical findings indicate that 5α-R inhibitors evoke not only beneficial, but also adverse effects. Future studies should investigate the biochemical and physiological mechanisms that underlie the persistence of the adverse sexual side effects to determine why a subset of patients is afflicted with such persistence or irreversible adverse effects. Also a better focus of clinical research is urgently needed to better define those subjects who are likely to be adversely affected by such agents. Furthermore, research on the non-sexual adverse effects such as diabetes, psychosis, depression, and cognitive function are needed to better understand the broad spectrum of the effects these drugs may elicit during their use in treatment of AGA or BPH. In this review, we will summarize the state of art on this topic, overview the key unresolved questions that have emerged on the pharmacological targeting of these enzymes and their products, and highlight the need for further studies to ascertain the severity and duration of the adverse effects of 5α-R inhibitors, as well as their biological underpinnings.

The dark side of 5α-reductase inhibitors' therapy: sexual dysfunction, high Gleason grade prostate cancer and depression

With aging, abnormal benign growth of the prostate results in benign prostate hyperplasia (BPH) with concomitant lower urinary tract symptoms (LUTS). Because the prostate is an androgen target tissue, and transforms testosterone into 5α-dihydrotestosterone (5α-DHT), a potent androgen, via 5α-reductase (5α-R) activity, inhibiting this key metabolic reaction was identified as a target for drug development to treat symptoms of BPH. Two drugs, namely finasteride and dutasteride were developed as specific 5α-reductase inhibitors (5α-RIs) and were approved by the U.S. Food and Drug Administration for the treatment of BPH symptoms. These agents have proven useful in the reducing urinary retention and minimizing surgical intervention in patients with BPH symptoms and considerable literature exists describing the benefits of these agents. In this review we highlight the adverse side effects of 5α-RIs on sexual function, high grade prostate cancer incidence, central nervous system function and on depression. 5α-Rs isoforms (types 1-3) are widely distributed in many tissues including the central nervous system and inhibition of these enzymes results in blockade of synthesis of several key hormones and neuro-active steroids leading to a host of adverse effects, including loss of or reduced libido, erectile dysfunction, orgasmic dysfunction, increased high Gleason grade prostate cancer, observed heart failure and cardiovascular events in clinical trials, and depression. Considerable evidence exists from preclinical and clinical studies, which point to significant and serious adverse effects of 5α-RIs, finasteride and dutasteride, on sexual health, vascular health, psychological health and the overall quality of life. Physicians need to be aware of such potential adverse effects and communicate such information to their patients prior to commencing 5α-RIs therapy.

Epigenetic setting for long-term expression of estrogen receptor α and androgen receptor in cells

Epigenetic regulation of the nuclear estrogen and androgen receptors, ER and AR, constitutes the molecular basis for the long-lasting effects of sex steroids on gene expression in cells. The effects prevail at hundreds of gene loci in the proximity of estrogen- and androgen-responsive elements and many more such loci through intra- and even inter-chromosomal level regulation. Such a memory system should be active in a flexible manner during the early development of vertebrates, and later replaced to establish more stable marks on genomic DNA. In mammals, DNA methylation is utilized as a very stable mark for silencing of the ERα and AR isoform expression during cancer cell and normal brain development. The factors affecting the DNA methylation of the ERα and AR genes in cells include estrogen and androgen. Since testosterone induces brain masculinization through its aromatization to estradiol in a narrow time window of the perinatal stage in rodents, the autoregulation of estrogen receptors, especially the predominant form of ERα, at the level of DNA methylation to set up the "cell memory" affecting the sexually differentiated status of brain function has been attracting increasing attention. The alternative usage of the androgen-AR system for brain masculinization and estrogenic regulation of AR expression in some species imply that the DNA methylation pattern of the AR gene can be established by closely related but different systems for sex steroid-induced phenomena, including brain masculinization.

Activational and organizational effects of estradiol on male behavioral neuroendocrine function

Evidence is reviewed that establishes an essential role for estradiol, synthesized locally via aromatization of testosterone in the adult as well as the developing male nervous system of rats, ferrets, and mice, in both the organization and adult activation of neural circuits that control appetitive as well as consummatory components of masculine sexual behavior. Evidence is also reviewed suggesting that perinatal estradiol biosynthesis and action in the female's nervous system may contribute to the development of female-typical sexual behavior.

Sex differences, laterality, and hormonal regulation of androgen receptor immunoreactivity in rat hippocampus

Sex differences, laterality, and hormonal regulation of androgen receptor (AR) immunoreactivity in rat hippocampal CA1 pyramidal cells were examined using the PG21 antibody. Adult male rats were either castrated or sham-operated at least 2 weeks prior to sacrifice. Gonadally intact females were sacrificed on the day of proestrus. Animals received an injection of either testosterone propionate (TP) or vehicle 2 h prior to sacrifice. Within CA1, both the intensity of staining and the number of AR+ cells were assessed. AR immunostaining was detected in all the groups with marked variation among them. The overall ranking of staining intensity was: gonadally intact males > females given TP > castrated males given TP > females > castrated males given vehicle. The number of AR+cells within subregions of CA1 showed the same basic pattern: among control-treated animals, gonadally intact males have more than females, but castrated males have the least, and acute TP treatment increases the number in both sexes. The increased level of AR immunoreactivity in CA1 of castrated males following acute TP treatment suggests that testicular androgens in adulthood normally increase AR immunoreactivity there, producing a sex difference favoring males in gonadally intact animals. We also found a higher number of AR+ CA1 cells on the left than on the right, but only in gonadally intact males and in females given TP. These results suggest that a laterality of AR distribution in the rat hippocampus may lead to lateralities in hippocampal structure and function.

Hormonal regulation of androgen receptor messenger RNA in the medial preoptic area of the male rat

In the adult male rat, androgen and estrogen synergize in the regulation of male reproductive behaviors. To explore some of the molecular mechanisms underlying this synergism we examined the distribution and hormonal regulation of androgen receptor (AR) and estrogen receptor (ER) mRNAs in the medial preoptic area (MPOA) and bed nucleus of the stria terminalis (BST) of the adult male rat. Using in situ hybridization, AR and ER mRNAs were found to be distributed in overlapping but unique patterns. The highest density of AR mRNA was found in the central part of the medial preoptic n. and the principal n. of the BST. Gonadectomy (GDX) of adult male rats caused an increase in hybridization density in both brain areas after 4 days followed by a decrease after 2 months. In contrast, ER mRNA was increased following GDX and remained high regardless of length of time. Treatment of adult GDX'd males with dihydrotestosterone (DHT) reversed the effects of GDX on AR mRNA at both the short and long-term castrate but had no effect on ER mRNA in both the MPOA and BST. Estrogen treatment increased AR mRNA in the long-term castrate only and decreased ER mRNA in both long- and short-term castrates. Immunocytochemical detection of AR revealed a similar distribution to AR mRNA; however, AR immunoreactivity was reduced in the MPOA and BST after both short- and long-term GDX. In vitro [3H]DHT binding in cytosols of the preoptic area showed appreciable binding but there was no effect of length of time following GDX. These data show that the pattern of regulation of AR mRNA is unique to this receptor type and does not follow the pattern of regulation of the ER mRNA. Furthermore, although the distribution of AR mRNA and AR protein coincide within the MPOA, changes in mRNA levels as a result of castration or hormone treatment do not result in corresponding changes in binding. This mismatch between mRNA and binding suggests a complex regulation of AR beyond simply changes in transcription.

Hormonal regulation of androgen receptor mRNA in the brain and anterior pituitary gland of the male rat

To determine possible cellular mechanisms governing androgen action in the brain, we examined the hormonal regulation of androgen receptor (AR) mRNA in neural tissues by Northern blot hybridization and RNase protection analysis. While a single hybridizable species of AR mRNA of approximately 11 kb was found in the anterior pituitary gland (AP) and ventral prostate gland (VP), an additional species of AR mRNA, approximately 2 kb smaller, was revealed in neural tissues. Furthermore, in these neural tissues, hormonal regulation of the two species of mRNA was coordinated; long-term castration increased levels of both forms, while testosterone replacement reduced them. The same pattern of regulation was observed for the single 11 kb form in the AP. An RNase protection assay was validated and utilized to quantitatively analyze the hormonal regulation of AR mRNA. Castration (4 days) resulted in significantly increased AR mRNA in the AP and hypothalamic-preoptic area, but not the amygdala, which subsequent administration of dihydrotestosterone (DHT; 1 day; 2 mg/animal) significantly decreased. In the AP, administration of estradiol benzoate (EB) for 1 or 5 days also reversed this effect. However, EB treatment increased the amount of total RNA isolated per gland. Consequently, when the data are normalized to RNA content per gland, 5 days of EB treatment resulted in a significant increase in AR mRNA content. These findings suggest that in contrast to the AP and VP, two forms of androgen receptor mRNA exist in the brain. In addition, there appears to be tissue and hormone specific regulation of AR mRNA.

Area-specific hormonal regulation of brain aromatase

In vitro experiments were conducted to compare the steroid regulation of aromatase in preoptic and posterior hypothalamic areas. Kinetic analysis of aromatase activity in the preoptic area (POA) and posterior hypothalamus (AHP) of castrated and intact doves indicate that both areas have a similar, high substrate affinity (apparent Km less than 15 nM), but castration decreases the Vmax to a greater extent in POA than AHP. This differential effect was confirmed using a single substrate (10 nM) concentration representing the Km of the enzyme. Comparison of the effects of non-aromatisable androgens, methyltrienolone (R1881) and 5 alpha-dihydrotestosterone (DHT), on aromatase activity in 20-day castrates showed that neither R1881 nor DHT induced aromatase activity in POA. This was confirmed in 40-day castrates which also showed a reduced inductive effect of testosterone (T) on the brain enzyme activity. R1881 specifically increased aromatase activity in AHP, but DHT did not affect either area. The non-aromatisable androgens influenced androgen-dependent vocal behaviour to the same extent. Oestradiol (E2) increased aromatase activity in both POA and AHP. We conclude that non-aromatisable androgens affect hypothalamic, but not preoptic oestrogen formation. Aromatase activity in the male preoptic area associated with behaviour is specifically sensitive to the aromatisable androgen, T and E2. The results suggest that hormonal regulation of the aromatase differs locally within androgen target areas of the brain.

Steroid control of sexual behavior and brain aromatase in the dove: effects of nonaromatizable androgens, methyltrienolone (R1881), and 5 alpha-dihydrotestosterone

This study examines the effects of nonaromatizable androgens, methyltrienolone (R1881) and 5 alpha-dihydrotestosterone (DHT) on aggressive courtship and vocal behavior in the male ring dove. Since androgens may influence behavior by increasing the formation of estrogen in the brain, the effects of R1881 and DHT on brain aromatase activity were also studied using an in vitro microassay. Under conditions in which testosterone induced aggressive courtship patterns, the nonaromatizable androgens were ineffective. But DHT and R1881 induced vocal behavior with equal efficiency, indicating that androgens can influence mechanisms of vocal behavior without conversion to estrogens. The behavioral effectiveness of both hormones was reduced (approximately 50%) when the period between castration and treatment was doubled. Testosterone propionate increased formation of E2 from 3H-testosterone in both the preoptic (POA) and anterior hypothalamic areas. Neither of the nonaromatizable androgens affected POA aromatase activity. The results suggest that only the aromatizable androgen, testosterone, which is also required specifically for male courtship, increases preoptic formation of estrogen.

Effects of intracranial implants of dihydrotestosterone on the reproductive physiology and behavior of male guinea pigs

An experiment was conducted to determine whether the intracranial application of dihydrotestosterone (DHT), a nonaromatizable androgen, would stimulate male guinea pig mating. Of three castrate groups studied, one was a control group in which subjects were implanted both in the medial preoptic area (MPOA) and under the skin with cannulae containing cholesterol (NoDHT). Males in one of the experimental groups received implants of cholesterol in the MPOA plus subcutaneous implants containing DHT (ScDHT). Members of the other experimental group were subcutaneously implanted with cholesterol and simultaneously given intracranial implants of DHT (IcDHT). Compared to either the NoDHT control group of the ScDHT experimental group, greater numbers of males in the IcDHT group displayed mounts (P less than 0.01), intromissions (P less than 0.01), and ejaculations (P less than 0.001). Additionally, the hypothalamic implants of DHT had no significant effects on peripheral target tissues. These data indicate that androgenic stimulation of the guinea pig brain is sufficient to activate masculine sexual behavior in this species.

Alpha-adrenergic regulation of androgen receptor concentration in the preoptic area of the rat

We examined the effect of the pharmacological disruption of the catecholaminergic system on the concentration of nuclear androgen receptor, as measured by the in vitro binding of methyltrienolone ([3H]R1881) to salt extracts of anterior pituitary (AP), preoptic area (POA) and medial basal hypothalamus (MBH). Treatment of gonadectomized male and female rats with the dopamine-beta-hydroxylase inhibitor, diethyldithiocarbamate (400 mg/kg b. wt.), 30 min before treatment with dihydrotestosterone (1 mg/animal) produced a decrease in the number of nuclear androgen receptor compared with saline-treated controls (P less than 0.05). This effect was specific for the POA and was not present 15 h after DHT treatment. There was no effect on cytosolic androgen receptor nor was there a drug effect on the apparent dissociation constant (Kd) of [3H]R1881 binding to hypothalamus-preoptic area cytosols. Treatment of intact males and castrated, testosterone-treated males with the alpha 1- and alpha 2-adrenergic antagonists, prazosin (5 mg/kg b. wt.) and yohimbine (2 mg/kg b. wt.), respectively, resulted in a significant decrease in the number of nuclear AR 2 h following drug treatment (P less than 0.05). There was no effect of the beta-adrenergic receptor antagonist propranolol (10 mg/kg b. wt.) when given to intact animals, nor was there an effect of idazoxan (5 mg/kg) when given to testosterone-treated animals. The effects of yohimbine and prazosin were restricted to the POA. None of the drugs competed with the binding of [3H]R1881 for the androgen receptor nor did they alter the Kd of cytosol or nuclear androgen receptor. These data provide evidence for an adrenergic interaction with the POA androgen receptor and suggest a role for catecholamines in modulating androgen sensitivity in the rat brain.

Activation of sexual behavior in male rats by combined subcutaneous and intracranial treatments of 5 alpha-dihydrotestosterone

When given peripherally, 5 alpha-dihydrotestosterone, the major androgenic metabolite of testosterone, is relatively less effective than testosterone in activating sexual behavior of castrated male rats. In order to test the possible central nervous system effects of dihydrotestosterone more directly, we castrated Long-Evans rats, gave them a behaviorally subthreshold dose of dihydrotestosterone placed subcutaneously in Silastic capsules (ScDHT), and then additionally treated the rats with intracranial implants of crystalline dihydrotestosterone (IcDHT, N = 12), testosterone (IcT, N = 12), or cholesterol (IcCHOL, N = 10) placed in the medial preoptic area. The peripheral ScDHT treatment maintained sexual organ weights of castrated males at levels comparable to those of intact males, but did not in itself significantly activate mating behavior. The addition of IcT or IcDHT to this treatment regimen significantly increased the number of males displaying mounting behavior, intromissions, and ejaculatory behavior (P less than 0.05) compared to males with IcCHOL implants. There were no significant differences between the group given IcT and the group given IcDHT. Results of this study support the hypothesis that the nonaromatizable androgen 5 alpha-dihydrotestosterone can act in the rat brain to influence male sexual behavior. In addition, these data lead us to suggest that the relative ineffectiveness of dihydrotestosterone versus testosterone when given systemically may reflect differences in bioavailability of these hormones to the brain following such treatment.

Effect of ethanol on androgen receptors in the anterior pituitary, hypothalamus and brain cortex in rats

The purpose of this study was to investigate ethanol-induced changes in androgen receptor sites in the anterior pituitary, hypothalamus, and brain cortex. Young adult male King-Holtzman rats were fed for 5 months a nutritionally complete liquid diet, with ethanol or isocaloric sucrose constituting 36% of the total calories. Androgen receptor sites were measured by sucrose density gradient and charcoal assay using tritiated dihydrotestosterone (DHT). Scatchard plot analysis of the data revealed that apparent dissociation constants of DHT-receptor complex for the anterior pituitary, hypothalamus, and brain cortex from alcohol-fed animals were estimated to be 0.7 +/- 0.13, 0.6 +/- 0.16 and 0.9 +/- 0.15 nM, respectively. These values are identical to those of their isocaloric controls. The concentrations of cytosol androgen receptors of the pituitary, hypothalamus, and brain cortex from alcohol-fed rats were 8.0 +/- 1.2, 6.2 +/- 1.0 and 4.9 +/- 0.7 fmol/mg protein, respectively. This represents about a 34, 24, and 22% reduction when compared to the values of the isocaloric control animals. In contrast to control rats, neither castration nor androgen or LHRH replacement to castrated alcohol-fed rats altered an alcohol-induced reduction of androgen receptor contents. Serum LH and testosterone levels were significantly decreased in alcohol-fed rats but these hormone levels were increased by administration of LHRH or norepinephrine. Such reduction of androgen receptors, serum LH and testosterone, but enhancement of these hormone levels by treatment with neurohormone and neurotransmitter in these animals suggests that ethanol exerts an adverse effect on the hypothalamic-pituitary unit and the neurotransmitter-hypothalamic hormone relationship, resulting in impairment of the androgen-induced sexual events and a suppression of the pituitary gonadotropin secretion.

Gonadal steroid influence upon sexual and aggressive behavior of female rats

The present experiment investigates the activation of aggressive and sexual behaviors by gonadal hormones in female rats of the S3-strain. In the first experiment three doses of testosterone propionate (TP) were chronically injected. In the second experiment effects of TP were compared to those of estradiol benzoate (EB) and methyltrienelone (R1881), a synthetic, unaromatizable androgen. Females of the S3-strain were tested against TP-treated female Wistar rats as opponents, and masculine and feminine sexual responses were assessed in the test for aggression as well as in separate tests with sexually active stimulus animals. The results of the first experiment indicate that TP in all doses, increased aggressive as well as sexual behavior equally, although plasma testosterone levels differed significantly between the groups. In the second experiment, EB significantly decreased overall aggression as compared to control-treatment. TP- and R1881-stimulated fighting, particularly, as the most offensive parameter of aggression, but did not increase overall levels of aggression. Tests for sexual preference in which the choice between a sexually active male or female was given, indicated that TP-treated females stayed near males with longer durations. Scentmarking frequencies, measured in the semiopenfield test, were effectively activated by TP-treatment. EB- and R1881-treatment resulted in intermediate levels of marking behavior.

Behavioral action of estrogen in male hamsters: effect of the aromatase inhibitor, 1,4,6-androstatriene-3,17-dione (ATD)

This study examines three independent behavioral variables known to be activated by testosterone in the male hamster; namely, the tendency to approach the female, the tendency to leave the female, and the amount of sniffing directed to her. Both intact and testosterone-maintained castrated male hamsters were given the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD) in subcutaneous, Silastic capsules. In intact males, there was an ATD dose-dependent increase in the tendency to leave the female and a decrease in the amount of olfactory investigation. The tendency of the male to approach the female was unaffected. The higher doses of ATD also abolished the ability of males to discriminate between females using vaginal odor cues. These results were confirmed in castrated males whose behavior was maintained at the intact level by testosterone implants. In addition, in both intact and castrated males, estradiol or diethylstilbestrol was able to reverse the behavioral changes induced by ATD. Our results indicate that estrogen produced by aromatization of testosterone activates behavior. We conclude that estrogen, by influencing some, but not all, components of masculine behavior, has a specific role in modulating male-female interactions.

Distribution of androgen receptor in microdissected brain areas of the female baboon (Papio cynocephalus)

We measured androgen receptors in the brain and pituitary of 4 female baboons (Papio cynocephalus) by the in vitro binding of methyltrienolone (R1881) to cytosols from 17 brain subregions as well as anterior and posterior pituitaries. High levels of AR were detected in anterior (22.1 +/- 7.1 (S.E.M.) fmol/mg protein) and posterior pituitary (12.6 +/- 3.3 fmol/mg protein). In brain tissue, the highest androgen receptor levels were found in the infundibular nucleus/median eminence (9.4 +/- 2.3 fmol/mg protein), ventromedial nucleus (6.3 +/- 1.7 fmol/mg protein) and periventricular area (4.9 +/- 1.3 fmol/mg protein). Saturation analysis of anterior pituitary and brain tissue (pool of hypothalamic, preoptic area, amygdala and septum remaining after microdissection of brain nuclei) showed that [3H]R1881 binds to the androgen receptor with high specificity and affinity (Kd = 1.25 x 10(-10) M, 0.45 x 10(-10) M, in anterior pituitary and HPA cytosol, respectively). Serum testosterone levels were low in all animals (0.59 +/- 0.26 ng/ml). With these data we described the quantitative distribution of androgen receptor in the pituitary and in specific brain nuclei in a species of nonhuman primate. The distribution is similar in many respects to that described in the male rat and the data suggest a conservation of androgen receptor distribution across species.

Nonaromatizable androgens may stimulate a male mouse reproductive behavior by binding estrogen receptors

Castrated DBA/2J male mice emitted 70 kHz vocalizations to female stimuli in response to 10 days of treatment with either testosterone (T, 300 micrograms/day), diethylstilbestrol (DES, 1 or 3 micrograms/day) or methyltrienolone (R1881, 900 micrograms/day). Lower dosages of R1881 (300 and 600 micrograms/day) and the oil vehicle were relatively ineffective in restoring vocalizations. The effects of these hormones on restoring seminal vesicle weight did not always parallel their effects upon behavior. In general T and R1881 (600 and 900 micrograms/day) were effective in restoring seminal vesicles while DES, the lowest dose of R1881 (300 micrograms/day), and the oil vehicle were ineffective. In receptor competition studies, R1881 pretreatment significantly reduced estrogen binding in hypothalamic-preoptic cytosol. In fact the most effective dose for restoring vocalizations (900 micrograms/day) reduced available estrogen binding sites by 91%. We propose that the male-typical vocalizations of mice may normally be stimulated through the activation of estrogen receptors following androgen aromatization and that the ability of a pharmacological dosage of R1881 (900 micrograms/day) to restore behavior may be due to interaction with estrogen receptors in the brain.

Effects of androgens and estrogens on the vasopressin and oxytocin innervation of the adult rat brain

Recently we reported that castration of rats eliminates vasopressin immunoreactivity in the lateral septum and other areas that appear to receive vasopressin innervation from the bed nucleus of the stria terminalis. Testosterone treatment counteracts this effect of castration. In the present study, we investigated whether this action of testosterone depends on its androgenic or estrogenic metabolites by treating long-term castrated rats with estradiol (E) and/or 5 alpha-dihydrotestosterone (DHT) or testosterone. The brains were then processed for immunocytochemistry or radioimmunoassay. DHT did not increase vasopressin staining in the lateral septum, although it fully restored the size of the seminal vesicles. E did restore the original fiber density, but individual fibers stained more weakly than in sham-operated males. Only treatment with both E and DHT fully restored the vasopressin innervation. This pattern was also reflected in the radioimmunoassay data. The vasopressin content of the lateral septum decreased about 90% after castration but was fully restored by either testosterone or E + DHT treatment. E alone, however, was only half as effective as E + DHT. The treatments had no effect on the oxytocin content of the septum, or on the vasopressin or oxytocin content of the dorsal vagal complex. The results suggest that E mediates most of the effects of testosterone on the vasopressin innervation of the lateral septum. DHT enhances the response to E but has little effect on its own.

Effects of metabolism inhibitors, antiestrogens and antiandrogens on the androgen and estrogen induced sexual behavior in Japanese quail

The relative contribution of androgenic and estrogenic metabolites of testosterone to the activation of sexual behavior was studied in Japanese quail by using inhibitors of testosterone metabolism, antiestrogens and antiandrogens. These compounds were tested in castrated birds whose sexual behavior had been activated by silastic implants of testosterone (T) or daily injections of testosterone propionate (TP) or diethylstilboestrol (DES). The aromatase inhibitor ATD only depressed T-induced behavior when injected at high doses and the 5 alpha-reductase inhibitor, 4MA was inactive in this respect. The antiestrogens, tamoxifen (TAM) and nitromifene citrate (CI-628) strongly depressed sexual behavior but they also drastically reduced the crowing behavior which is typically androgen-dependent which throws some doubts on the specificity of their action. The antiandrogens, flutamide and cyproterone acetate (CA), only had limited inhibitory effects on the copulatory behavior but similarly decreased only marginally the crowing. As they strongly depressed the cloacal gland growth, it can be ascertained that they were injected in sufficient amounts and their lack of action on crowing questions the ability of these compounds to inhibit brain processes even when they are androgen-dependent. Taken together with the results of previous experiments which tested the behavioral effects of the testosterone metabolites, the present data confirm the implication of both androgenic and estrogenic metabolites of testosterone in the activation of behavior. Their interaction remains, however, poorly defined and its understanding will probably require the identification of the biochemical processes which in the brain mediate the behavior.

Hyperprolactinemia and male sexual behavior: effects of steroid replacement with estrogen plus dihydrotestosterone

To determine if alterations in the availability of the active metabolites of testosterone (T) are involved in the inhibition of sexual activity in hyperprolactinemic animals, the effects of four ectopic pituitary grafts on copulatory behavior were examined in castrated male rats given subcutaneous implants of T or estradiol-17 beta (E2) plus 5 alpha-dihydrotestosterone (DHT). Two weeks after implantation of the steroid-filled capsules, half the animals of each group were given pituitary grafts and the remainder were sham-operated. Tests of copulatory behavior were performed prior to, and one, two, and three months following pituitary transplantation. Pituitary grafting caused significant inhibition of copulatory behavior in both T and E2 + DHT treated animals. PRL levels were significantly higher in E2 + DHT treated grafted males than in T treated grafted animals (2000 +/- 140 vs. 395 +/- 26 ng/ml), but did not differ between the corresponding control groups (61 +/- 8 vs. 73 +/- 6 ng/ml). The results of these experiments preclude the possible involvement of alterations in steroid secretion by the testes or modifications of the conversion of T to its active metabolites in the effects of hyperprolactinemia on copulatory behavior.

Dihydrotestosterone stimulates mounting behavior but not lordosis in female rats

The ability of androgens to stimulate masculine sexual behavior is thought to depend on the aromatization of such androgens to estrogens. In this scheme, reduced androgens such as dihydrotestosterone (DHT) which cannot be aromatized, are thought to exert major peripheral but little or no central nervous system influences on the display of masculine sexual behavior. Further, an early report that DHT can induce lordosis, an estrogen (E) dependent behavior, led to a notion that DHT may effect behavior through metabolic intermediates such as 5 alpha-androstane-3 beta, 17 beta-diol (ADIOL) which then binds to estrogen receptors eliciting the E-dependent lordotic response. The present study reexamined and compared the relative effectiveness of a range of DHT dosages in stimulating a characteristic masculine (mounting) and feminine (lordosis) sexual behavior. Adult ovariectomized rats were randomly assigned to either 250 micrograms or 1 mg daily injections of DHT or DHTP. Other animals received OIL injections or crystalline DHT delivered by two different lengths (20 mm or 40 mm) of Silastic capsules. Animals were tested once weekly (for 5 weeks) for mounting behavior (20 minute test). Then animals were tested thrice (once weekly) for lordosis 4 hrs after the addition of 500 micrograms Progesterone (P). Finally, all females were tested for lordotic potential to respond to 10 micrograms EB plus P. 1 mg DHT or DHTP dosages and the 40 mm-Silastic condition significantly increased mounting behavior over that of lower dosages and OIL controls. A significant correlation existed between mounting frequency and circulating level of serum DHT. Treatment with DHTP was not different than DHT in eliciting mounting behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Methyltrienolone (R1881) is not aromatized by placental microsomes or rat hypothalamic homogenates

The in vitro conversion of the synthetic steroidal androgen methyltrienolone (17 beta-hydroxy-17 alpha- methylestra -4,9,11-trien-3-one) to an estrogen was investigated. First, with a placental microsome preparation a 10-fold molar excess of methyltrienolone did not affect the aromatization of testosterone. Therefore, methyltrienolone did not compete with testosterone in this very active aromatase system, nor did it inhibit the aromatization. Second, while the placental aromatase very efficiently converted testosterone to estrogens, it did not convert methyltrienolone [3H] to estrogenic (phenolic) products. Third, homogenates of rat hypothalamic tissue were also unable to aromatize methyltrienolone, although they converted small quantities of testosterone to estradiol and 19-hydroxyandrostenedione to estrone. This lack of aromatization of methyltrienolone is consistent with observations of additional behavioral and in vivo biochemical experiments.

Differential effects of gonadal steroids on dopamine metabolism in mesolimbic and nigro-striatal pathways of male rat brain

Thirty days after castration the concentration of dopamine (DA) was significantly reduced in the septum and n. accumbens septi, but not in the caudate-putamen, of male rat brain. The concentrations of dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), the principle metabolites of DA, also tended to be lower in septum and n. accumbens septi after castration. Chronic s.c. administration of testosterone (T), estradiol (E2), 5 alpha-dihydrotestosterone (DHT), or E2 plus DHT in silastic capsules effectively reversed these effects of castration in septum and n. accumbens septi without affecting concentrations of DA, DOPAC, or HVA in caudate-putamen. The accumulation of DOPA after inhibition of aromatic amino acid decarboxylase activity, which was taken as an in vivo index of tyrosine hydroxylase activity, was not affected in these brain regions by long-term castration or by chronic administration of DHT to castrated males. Acute administration of haloperidol caused equivalent, significant increments in concentrations of DOPAC and HVA in all brain regions studied, regardless of whether castrated rats had been implanted with DHT capsules or no hormone. However, in the absence of haloperidol treatment the concentration of DOPAC in septum and n. accumbens septi, but not in caudate-putamen, was significantly higher in castrated rats implanted with DHT as opposed to no hormone. These results suggest that chronic exposure to T, or to its neural metabolites, E2 and DHT, selectively enhances metabolic activity in mesolimbic DA neurons.