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

Yohimbine hydrochloride inhibits benign prostatic hyperplasia by downregulating steroid 5α-reductase type 2

Benign prostatic hyperplasia (BPH) is a frequently encountered disease in older men that affects sexual function and is capable of causing lower urinary tract dysfunction. Unfortunately, current treatment options for BPH primarily seek to address the lower urinary tract dysfunction aspect of the disease and do not improve sexual function. Yohimbine has been effectively used for decades to treat erectile dysfunction. Therefore, the objective of this study was to evaluate the inhibitory effect of yohimbine on BPH and explore the associated underlying mechanisms. Thirty-six rats were randomly divided into the control, BPH, finasteride (1 mg/kg), and yohimbine (2, 4, and 8 mg/kg) groups. Except for the rats in the control group, those in the other groups were subcutaneously injected testosterone propionate (5 mg/kg/day) daily for a period of 4 weeks to establish BPH models. They were also administration the corresponding drug daily for a period of 6 weeks. After the treatments, in addition to determining prostate wet weight and index, the histopathological status of the prostate was observed, and the levels of testosterone, dihydrotestosterone, prostatic acid phosphatase, the prostate-specific antigen, proliferating cell nuclear antigen, and steroid 5α-reductase were determined. Specifically, the administration of 2, 4, and 8 mg/kg yohimbine inhibited prostatic index increase by 46.7, 55.1, and 69.3%, respectively, in BHP rats. Further, yohimbine significantly reduced the levels of dihydrotestosterone, prostatic acid phosphatase, prostate-specific antigen, proliferating cell nuclear antigen, and steroid 5α-reductase, suggesting that it exerts beneficial effects against BPH by modulating the steroid 5α-reductase pathway.

Rauwolfia vomitoria extract suppresses benign prostatic hyperplasia by reducing expression of androgen receptor and 5α-reductase in a rat model

OBJECTIVE

Herbal medicine is an important therapeutic option for benign prostatic hyperplasia (BPH), a common disease in older men that can seriously affect their quality of life. Currently, it is crucial to develop agents with strong efficacy and few side effects. Herein we investigated the effects of the extract of Rauwolfia vomitoria, a shrub grown in West Africa, on BPH.

METHODS

Rats with testosterone-induced BPH were treated with R. vomitoria. Prostates were histologically analyzed by Hematoxylin and eosin staining. Proliferation index and the expression levels of androgen receptor and its associated proteins were quantified through immunohistochemistry and immunoblotting. Androgen receptor target genes were examined by quantitative real-time polymerase chain reaction. The sperm count and body weight of rats were also measured.

RESULTS

The oral administration of R. vomitoria extract significantly reduced the prostate weight and prostate weight index in BPH rats, supported by the decreased thickness of the prostate epithelial layer and increased lumen size. Similar effects were observed in the BPH rats treated with the reference drug, finasteride. R. vomitoria extract significantly reduced the testosterone-induced proliferation markers, including proliferating cell nuclear antigen and cyclin D1, in the prostate glands of BPH rats; it also reduced levels of androgen receptor, its associated protein steroid 5α-reductase 1 and its downstream target genes (FK506-binding protein 5 and matrix metalloproteinase 2). Notably, compared with the finasteride group, R. vomitoria extract did not significantly reduce sperm count.

CONCLUSION

R. vomitoria suppresses testosterone-induced BPH development. Due to its milder side effects, R. vomitoria could be a promising therapeutic agent for BPH.

Distribution of alpha 2-adrenergic binding sites in the parabrachial complex of the rat

The present study describes the distribution of alpha 2-adrenoceptors in the parabrachial and Kölliker-Fuse nucleus of the rat by employing the tritium-labeled alpha 2-receptor antagonist rauwolscine ([3H]-RAUW) as a ligand. The [3H]-RAUW binding was densitometrically quantified in five nuclei of the parabrachial (PB) complex in serial coronal sections. We found that cytoarchitectonically and anatomically distinct nuclei of the PB complex exhibit different numbers of [3H]-RAUW-binding sites. The largest number of binding sites was observed over the external lateral PB and caudally over the waist area of the PB. Lower numbers of binding sites were found in the remaining lateral PB nuclei, followed by the medial PB and the Kölliker-Fuse nucleus. In addition we disclosed that the internal lateral PB contains a very low number of binding sites while the external medial PB is marked by dense [3H]-RAUW binding. Also, the affinities of the binding sites differed between the PB areas. High affinities were observed in the external lateral PB, the remaining lateral PB nuclei and in the waist area of the PB, while the medial PB and the Kölliker-Fuse nucleus exhibited only low affinities for the ligand. Furthermore, saturation curves demonstrated non-linear profiles, indicating the presence of more than one population of binding sites in the PB nuclei for the radioligand. Our data demonstrate that the PB exhibits a distinct distribution of alpha 2-adrenergic binding sites. These correlate well with the cytoarchitectonically defined nuclei of the PB complex and with the pattern of ascending axons from the medial nucleus of the solitary tract and the area postrema terminating in the PB. Since a large number of these projection neurons utilize adrenaline or noradrenaline as their transmitters, we conclude that solitary-parabrachial neurotransmission to the forebrain is, at least in part, mediated via alpha 2-adrenoceptors.

Neonatal prazosin exposure reduces ovarian weight and estrogen receptor binding in adult female rats

Exposure of estrogen treated adult female guinea pigs to the alpha-1 antagonist prazosin has been shown to reduce levels of estrogen binding in the hypothalamus and preoptic area. To further investigate this interaction between the noradrenergic and neuroendocrine axes, newborn female rat pups received an s.c. implant of prazosin (0.0125 mg/day for 5 days) or placebo. In adulthood, subjects were sacrificed by perfusion with DMSO on the morning of proestrous. Tissue analysis of the medial preoptic area, corticomedial amygdala, and mediobassal hypothalamus revealed that cytosolic estrogen binding was significantly reduced in all three areas for the prazosin treated group as compared to controls. Ovarian weight was also significantly reduced in the prazosin treated group, although uterine weight was unaffected. Interestingly, prazosin treated females showed a post-pubertal increase in body weight characteristic of ovariectomized females, while controls showed no such increase. These results support the existence of a significant developmental interaction between the noradrenergic system and the neuroendocrine axis as measured by ovarian weight and estrogen binding in the brain.

Estradiol increases the duration of nuclear androgen receptor occupation in the preoptic area of the male rat treated with dihydrotestosterone

Androgens and estrogens interact in neural tissues to regulate behavioral and neuroendocrine responses. As an initial attempt to identify the cellular level at which these steroids interact, we characterized the time course of nuclear androgen receptor (ARn) occupation in the preoptic area of the hypothalamus (POA) after chronic dihydrotestosterone (DHT) administration and determined whether it was modified by concurrent treatment with estradiol benzoate (EB). We found that ARn levels peaked (47.1 +/- 12.6 fmol/mg DNA) by 12 h after castrated rats were treated with Silastic capsules filled with crystalline DHT and remained significantly elevated for at least an additional 12 h. When EB was injected (2 micrograms/rat) at the same time the DHT capsules were inserted, peak levels of ARn in POA were reached sooner (6 h) and retained longer (48 h). Comparisons with other central and peripheral tissues suggested that this response was unique to the POA. These results suggest that estrogens may modify the response of POA neurons to androgens by altering the duration of ARn occupation.

Estrogen receptor binding in regions of the rat hypothalamus and preoptic area after inhibition of dopamine-beta-hydroxylase

Previous studies have shown that administration of diethyldithiocarbamate (DDC), a dopamine-beta-hydroxylase inhibitor, results in a decreased concentration of estrogen receptors measured in the rodent hypothalamus and preoptic area. To determine if this modulation of receptor content is region-specific, in vitro estrogen binding assays were performed on cytosol and cell nuclear extracts of microdissected brain regions from female rats treated with DDC. For cytosol binding comparisons, ovariectomized (OVX) rats were treated with 550 mg DDC/kg b. wt. or the saline vehicle 12 h before sacrifice. For cell nuclear binding comparisons, OVX rats received a maximal dose of estradiol 12 h after DDC or saline treatment and 1 h before sacrifice. No region-specific decreases in estrogen binding were observed in either cytosol or nuclear extracts. To further examine possible regional specificity, quantitative autoradiographic analysis of the in vivo hypothalamic uptake of an iodinated analog of estradiol, 11 beta-methoxy-16 alpha-[125I]iodoestradiol (MIE2), in OVX rats treated with DDC was conducted. Animals received a saturating dose of [125I]MIE2 12 h after DDC or saline treatment and 1 h before sacrifice. DDC treatment resulted in higher background levels of radioactivity and a trend toward higher uptake levels in all brain regions, but with no evidence of marked regional specific effects in any area of the brain. In tissue uptake studies, DDC treatment resulted in higher levels of radioactivity recovered from serum and neural tissues of [125I]MIE2-injected rats, suggesting that DDC slows the clearance of MIE2.(ABSTRACT TRUNCATED AT 250 WORDS)