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At least 973 records · Page 54Linked to original sources
PubMed1979

Androgens and brain differentiation. Effects of testosterone on protein synthesis in neonatal rat hypothalamic and cerebral slices.

Protein synthetic activity of anterior hypothalamic and neocortical brain slices from androgenized neonatal female rats was studied in vitro in an attempt to clarify the mechanism of action of testosterone on the developing hypothalamus. The short-term effects of testosterone propionate injections of the animals on the protein synthetic activity of the slices were assayed by means of incorporation of 14C-leucine into acid-insoluble protein. Although a high dose (1 mg/animal) of testosterone propionate stimulated increased incorporation in neocortical and anterior hypothalamic slices, a lower dose and other approaches failed to demonstrate a stimulation regionally specific to the anterior hypothalamus. It is concluded that if testosterone has specific stimulatory effects on protein synthesis in the anterior hypothalamus of neonatally androgenized rats, these are not readily demonstrable by methods used with other steroid target tissues.

Animals↗
PubMed1983

Neonatal testosterone treatment increases neuron and synapse numbers in male rat superior cervical ganglion.

Neonatal treatment with gonadal steroids has been reported to alter morphological as well as functional development in various regions of the brain and spinal cord. Among the observed alterations are changes in numbers of neurons and in the organization and numbers of synapses. These regions have been found to be sexually dimorphic, and the dimorphism dependent upon gender differences in circulating levels of gonadal steroids. Neonatal treatment with testosterone has been shown to produce an increase in the number of neurons in the superior cervical sympathetic ganglion in female rats. The present studies were designed to investigate the possibility of a normally occurring sexual dimorphism in the SCG of the rat, and to characterize the effect of neonatal treatment with testosterone on neurons and synapses in the male rat. We report a sexual dimorphism in the number of neurons but not in the number of preganglionic axons or ganglionic synapses. In addition, neonatal administration of testosterone propionate results in a 40% increase in the number of superior cervical ganglion neurons in treated male rats over the control male number at 15 and 30 days of age. The testosterone propionate treatment results in a 66% increase in the number of synapses in male superior cervical ganglia, without a concomitant increase in the number of preganglionic axons.

Animals↗
PubMed1995

Influence of androgen on tyrosine hydroxylase mRNA in adrenal medulla of spontaneously hypertensive rats.

We investigated the effects of castration and testosterone propionate on tyrosine hydroxylase mRNA, its activity, and catecholamine synthesis in the adrenal medulla of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Four-week-old male rats were castrated. Testosterone propionate (500 micrograms per rat) was administered subcutaneously twice a week to castrated rats (between 14 and 25 weeks of age). Systolic pressure was measured at the age of 25 weeks, and rats were decapitated. The systolic pressure of castrated SHR was significantly lower than that of control and testosterone-replaced SHR. Epinephrine and norepinephrine levels, tyrosine hydroxylase activity, and tyrosine hydroxylase mRNA in the adrenal medulla of castrated SHR were significantly lower than in control and testosterone-replaced SHR. Systolic pressure and epinephrine and norepinephrine levels, tyrosine hydroxylase activity, and tyrosine hydroxylase mRNA levels in the adrenal medulla of WKY showed no significant differences among the control, castrated, and testosterone-replaced groups. These results suggest that androgens contribute to the development and maintenance of hypertension in SHR via sustained enhancement of tyrosine hydroxylase synthesis in the adrenal medulla, leading to increased epinephrine and norepinephrine levels.

Actins↗
PubMed1988

Reproductive hormones control striatal tyrosine hydroxylase activity in the male rat.

The effects of castration, hypophysectomy and testosterone treatment on striatal tyrosine hydroxylase (TOH) activity were examined in male rats. Enzyme activity was measured by means of high-performance liquid chromatography (HPLC) determination of L-3,4-dihydroxphenylalanine (DOPA) formed. Serum levels of both testosterone and luteinizing hormone (LH) were measured by radioimmunoassay (RIA). Castration, but not hypophysectomy, reduced TOH activity in the striatum. The administration of testosterone propionate (TP) to castrated animals in a dose of 10 micrograms/100 g b.wt. during the two days previous to sacrifice, completely prevented the castration-induced reduction of striatal TOH activity. In orchidectomized rats treated with different doses of testosterone propionate (TP) up to 20 micrograms/100 g b.wt., the levels of striatal TOH activity were apparently related to either the dose-related increase of serum testosterone or the decrease of serum LH. Higher doses of the androgen failed to further modify striatal TOH activity, in spite of the dose-related elevation of serum testosterone concentration. These results suggest that circulating levels of gonadal and/or pituitary hormones partially control dopaminergic synthesis in striatal terminals, which in turn may account for some behavioral effects of reproductive hormones.

Animals↗
PubMedDate not supplied

[Brain monoamines and the hypophyseo-gonadal system of adult rats after the androgenization of their mothers during pregnancy].

The brain noradrenaline system and its involvement in the control of the hypothalamic-hypophysial-gonadal complex were studied on 3 month old Wistar rats, which descended from the mothers treated with testosterone propionate on the 16th and 18th day of pregnancy. A season-independent weakening of the activating effect of noradrenaline, introduced into the brain lateral ventricle on the estradiol and testosterone content of the peripheral blood has been shown, compared with the descendants of the mothers treated with oil at the same times of pregnancy. Unlike noradrenaline, the intraventricular introduction of serotonin or dopamine was accompanied by a similar activation of the hypophysial-gonadal system in the descendants from both the androgenized and control mothers. In the descendants from the former, the thermal reaction to the intraventricular introduction of noradrenaline underwent changes as well. A conclusion is reached that testosterone propionate, introduced during the prenatal period, exerts a long-term and to a certain extent, selective and generalized effect on the developing brain noradrenaline system. In the rats, the critical period for the disturbance in androgen balance influence on the noradrenaline mechanisms of brain is timed to no later than the 18th day of prenatal development.

Animals↗
PubMed1992

Sex steroids possess distinct stimulus properties in female and male mice.

Very few studies have investigated the aversive properties of sex steroids in animals. We studied these properties by testing oestradiol-3-benzoate, testosterone-propionate and progesterone in a conditioned taste aversion set-up, in intact female and male mice. Oestradiol-3-benzoate induced a taste aversion in both female and male mice; however, testosterone-propionate and progesterone had an effect only in females. These results show that sex steroids have intrinsic aversive properties. The different effects of the steroids in males and females cannot simply be explained by nausea induction or novelty.

Analysis of Variance↗
PubMed1981

[Mammary tumors in female rats with combined exposure to nitrosoethylurea and sex hormones].

Transplacental treatment with sinestrol and testosterone-propionate reduces the incidence of spontaneous benign mammary tumors in rats. Treatment of immature female rats with nitrosoethylurea is followed by an earlier development of mammary fibroadenomas. A combined treatment with testosterone-propionate and nitrosoethylurea increases the incidence of mammary fibroadenoma and decreases its mean latent period. Fibroadenoma induction is accelerated by treating adult rats with nitrosoethylurea alone, while combined treatment induces primary mammary tumors at an earlier stage. The morphology of tumors induced by different schemes of combined treatment remains identical.

Adenofibroma↗
PubMed1978

Calusterone.

Androgens are effective therapeutic agents in postmenopausal women with metastatic breast cancer. Early studies with testosterone propionate showed objective regression rates of slightly more than 20%. Subsequent work with synthetic androgens has failed to show a significant reduction in toxicity or an increase in therapeutic efficacy over testosterone propionate. Calusterone (7 beta,17 alpha-dimethyltestosterone), in early clinical trials, showed both of these qualities and was believed by some to be the "ideal androgen." As with many new drugs, subsequent work failed to confirm these early findings, and most of the later data gathered on calusterone are inconsistent. We conclude from our knowledge at present that calusterone offers no real advantages or disadvantages over other androgens in the treatment of breast cancer.

Breast Neoplasms↗
PubMed1990

Differential responses of hypothalamic LHRH-I and -II to castration and gonadal steroid or tamoxifen treatment in cockerels.

Changes in the hypothalamic contents of LHRH-I and LHRH-II were determined in intact and castrated cockerels injected i.m. with gonadal steroids or tamoxifen. An increase in the plasma concentration of LH after castration was accompained by a significant increase in the content of LHRH-I in the posterior hypothalamus (including the mediobasal hypothalamus and median eminence) which was reversed by oestradiol benzoate given on days 14 and 15 after castration. Under similar circumstances, testosterone propionate did not modify the hypothalamic content of LHRH-I, even though both steroids reduced the plasma concentrations of LH to levels below those of intact cockerels. Treatment of intact cockerels with oestradiol benzoate significantly increased the content of LHRH-I in the posterior hypothalamus, whilst testosterone propionate was again without effect. Tamoxifen significantly raised the plasma concentration of LH in intact cockerels and partially antagonized the suppressive effect of oestradiol benzoate and testosterone on LH secretion in castrated cockerels. However, an anti-oestrogenic effect of tamoxifen on the hypothalamic content of LHRH-I was not demonstrated. There was no evidence of any changes in the hypothalamic content of LHRH-II after castration, with or without gonadal steroid replacement. A change in the hypothalamic content of LHRH-I in response to manipulation of the steroid environment would imply an involvement of this peptide in the mechanism by which gonadal steroids regulate the release of LH. The absence of changes in the hypothalamic content of LHRH-II in the same circumstances suggest that it is not directly involved in the control of LH secretion by the gonadal steroid negative feedback loop.

Animals↗
PubMed1975

Effects of C21 steroids on sex accessory organs and testes of mature hypophysectomized rats.

Adult hypophysectomized male rats were treated with 2 mg/day of testosterone propionate, pregnenolone, 17alpha-hydroxypregnenolone, progesterone or 17alpha-hydroxyprogesterone. The treatment commenced on the day of surgery and was continued for 4 weeks. In all steroid treated animals, spermatogenesis was qualitatively maintained. Sex accessory organs were maintained only in testosterone propionate treated animals. In C21 steroid-treated rats the sex accessory organs showed atrophy similar to untreated hypophysectomized animals suggesting lack of peripheral conversion to androgens. However, administration of 3H-pregnenolone with the last injection of pregnenolone resulted in the isolation of a considerable amount of 3H-testosterone from testicular tissue of the experimental animals. This finding suggests that maintenance of spermatogenesis in pregnenolone treated animals could have been due to testosterone formed in the testes from the exogenously administered pregnenolone.

17-alpha-Hydroxypregnenolone↗
PubMed1979

Effects of aromatizable androgens on aggressive behaviour among rats (rattus norvegicus).

Three experiments were used to tests the applicability of the aromatization hypothesis of androgen action to aggressive behaviour among Norway rats. In Expt 1, administration of testosterone propionate was highly effective in restoring aggressive behaviour to castrated rats while 17 beta-hydroxy-5 alpha-androstan-3-one was of intermediate effectiveness. Of the steriods tested in Expt 2, androstenedione and testosterone were highly effective, 17 beta, 19-dihydroxyandrost-4-en-3-one was of intermediate effectiveness and cholesterol was ineffective. The results of Expt 3 indicated that treatment with testosterone or oestradiol both resulted in increased aggression while treatment with (5 alpha,17 beta)-17,19-bis(acetyloxy)-andostan-3-one diacetate (5 alpha-19-hydroxytestosterone) was without effect. Androgens which were aromatizable and could be 5 alpha reduced, i.e. testosterone, testosterone propionate and androstenedione, were highly effective in restoring aggressive behaviour; however, two other steroids, 5 alpha,19-hydroxytestosterone which is 5 alpha reduced, and 19-hydroxytestosterone, which can be aromatized, were respectively of low or medium effectiveness on behaviour. However, oestradiol, which did not maintain sexual development of accessory glands, was highly effective in the restoration of aggressive behaviour. Since the behaviourally active steroids in the present experiments were not only those predicted by the aromatization hypothesis, it is proposed that several steroids are capable of activating aggressive behaviour and that the aromatization hypothesis does not adequately explain the hormonal basis of aggressive behaviour among Norway rats.

Aggression↗
PubMed1984

Alteration of free sulphydryl content of rat sperm heads by suppression of intratesticular testosterone.

Subcutaneous injections of testosterone propionate to adult male rats at a dose of 2.5 or 10 mg/kg body weight, 3 times per week for 7 weeks, resulted in a 75% reduction in serum LH and more than 50% reduction in intratesticular testosterone concentration, but serum FSH levels remained unchanged. The free -SH content, measured as iodo[14C]acetamide binding, increased by 70-100% in testicular sperm heads after suppression of testicular testosterone, and by 25-30% in caput epididymal sperm heads but was decreased by 70-80% in cauda epididymal sperm heads. These results demonstrate an alteration in the oxidative state of sperm nuclear basic proteins, suggesting incomplete nuclear maturation. These changes may be specific for the suppression of intratesticular testosterone, thus illustrating the androgen dependency of sperm head maturation. The contrast effects noted between the iodo[14C]iodoacetamide binding by the caput and the cauda epididymal sperm heads indicate that testosterone propionate treatment may affect the mechanisms regulating the oxidation of the sulphydryl residues in sperm heads during epididymal transit. This alteration may not directly relate to the tissue androgen concentrations.

Animals↗
PubMed1997

Sex differences in EEG in adult gonadectomized rats before and after hormonal treatment.

EEG activity was recorded from the left and right parietal cortex in adult male and female Wistar rats that were gonadectomized (GNX) after puberty during 2 days without and 3 days with hormonal treatment (either testosterone propionate, 5 alpha-DHT or vehicle in males and progesterone, estradiol benzoate or vehicle in females). In contrast to EEG characteristics reported for intact rats, GNX abolished right over left parietal activation in both sexes and, sex differences in EEG interhemispheric correlation and in theta and delta relative power in the right parietal; additionally GNX males showed higher absolute power than females. Hormonal treatment reestablished interparietal asymmetry in both sexes and a lack of sex differences in absolute power, however, it was not enough to reestablish sex differences in delta and theta proportion in the right parietal nor in interhemispheric correlation. Differential effects were obtained with testosterone propionate and 5 alpha-DHT in males suggesting that activational effects of testosterone on EEG are probably exerted through testosterone or its aromatized metabolites. The results of our study indicate that the activational effects of gonadal steroids after puberty are necessary for maintaining sex differences in the EEG of the adult rat.

Animals↗
PubMed1985

Testosterone and muscle hypertrophy in female rats.

The effects of chronic treatment with testosterone propionate on compensatory muscle hypertrophy secondary to synergist removal were studied in female rats. Synergist removal resulted in a significant (2-fold) increase in muscle wet weight, with no changes in protein concentration. As reported previously, oxidation of [2-14C]pyruvate to 14CO2 was significantly decreased in hypertrophic muscles. In addition, malate dehydrogenase and lactate dehydrogenase activities were significantly decreased in overloaded muscles on a wet weight basis but not on the basis of noncollagen protein. These data suggest that specific metabolic adaptations may occur in response to overload of muscle. Administration of testosterone propionate in subcutaneously implanted Silastic capsules resulted in a 20-fold increase in serum testosterone levels. This treatment had no effect on body weight, muscle weight, pyruvate oxidation, or malate and lactate dehydrogenase activities in both control and hypertrophic muscles, although there was an effect on the noncollagen protein content of overloaded muscles. These results do not support the hypothesis that androgens, in conjunction with weight-bearing exercise in female subjects, are effective in increasing muscle mass or function in female subjects.

Animals↗
PubMed1979

Effects of neonatal steroids on male sex tissues.

The effects of neonatally administered sex hormones on the growth and hormone responsiveness of the sex accessory tissues of the adult male rat were investigated. If intact neonatal male rats are treated with estradiol diproprionate, the size of the ventral prostate in the adult animal at day 70 of age is less than 10 per cent of the untreated control value. If androgens are administered to intact neonates, the size of the ventral prostate at day 70 is one-third to one-half of the untreated control values. The androgenic response of these abnormally small prostates was tested by treating these adult animals with testosterone propionate daily from day 70 to day 83. Toward ventral prostates of the animals treated with estrogens in the neonatal period show a very limited response to exogenous androgens at adulthood. In contrast, the ventral prostates of the animals receiving testosterone propionate or dihydrotestosterone propionate in the neonatal period were fully responsive to exogenous androgens. In addition, the ability of the adult prostate to respond fully to androgens requires the presence of the testes in the neonatal period. Comparing neonatal castrates with intact neonates, it was shown that the administration of androgen in the neonatal period was only partially effective in restoring the androgenic responsiveness of the adult ventral prostate. This suggests that other testicular factors, or the presence of testosterone at other time periods before the onset of puberty, may be necessary for the normal androgenic induced response of the adult sex accessory tissues.

Animals↗
PubMed1982

Induction of ovulation and cyclic activity in anestrous ewes with testosterone treated wethers and ewes.

An experiment was conducted to evaluate the effectiveness of wethers and ewes treated with testosterone preparations to induce ovulation and breeding activity in anestrous ewes. The testosterone was administered three times at weekly intervals. Wethers and ewes treated with 105 mg testosterone propionate and wethers treated with 100 mg testosterone from testosterone cyclopentyl propionate were as successful as vasectomised rams in inducing ovulation and cyclic activity in ewes. Seven days after the last injection the concentrations of testosterone in peripheral bloods were not significantly different from that in the vasectomised rams. By day 28 the concentrations were significantly lower than in the rams. The testosterone preparations tested are suitable for the induction of male sexual behavior and are rapidly excreted by sheep.

Journal Article↗