Differential Effects of Testosterone and Estradiol on Clitoral Function: An Experimental Study in Rats.

INTRODUCTION: Female sexual response is a complex phenomenon in which psychological, neurologic, and vascular mechanisms and hormonal factors interact. During the arousal phase, they cooperate to increase genital blood flow, thus inducing engorgement of the clitoris and lubrication of the vagina. Regulation of vascular and non-vascular smooth muscle tone is the crucial event in the erectile process. Preclinical studies have suggested that nitric oxide (NO) is the main vasodilator neurotransmitter modulating, through the second messenger cyclic guanosine monophosphate (cGMP), clitoral flow vessels. AIM: To investigate the effects of sexual steroid hormones on pro-erectile and relaxant (mediated by NO and cGMP) and anti-erectile and contractile (mediated by ras homolog gene family member A [RhoA] and Rho-associated protein kinase [ROCK]) mechanisms in the clitoris using a validated animal model of female ovariectomized Sprague-Dawley rats. METHODS: Subgroups of ovariectomized rats were treated with 17ß-estradiol, progesterone, testosterone, or testosterone and letrozole for 6 weeks. The experimental groups were compared with a control group of intact rats. MAIN OUTCOME MEASURES: Sex steroids plasma levels were assessed and in vitro contractility studies were carried out in order to investigate the effect of ovariectomy and in vivo treatments on clitoris smooth muscle activity. Smooth muscle cells (SMCs) from rat clitoral biopsies were isolated and characterized. RhoA activity was determined in SMCs cell cultures. RNA from tissues and cells was analyzed by quantitative real-time RT-PCR. RESULTS: Using real-time polymerase chain reaction, testosterone treatment upregulated the expression of NO-mediated pathway genes (endothelial and neuronal NO synthase, guanylate cyclase soluble subunit-α3, guanylate cyclase soluble subunit-ß3, cGMP-dependent protein kinase 1, and phosphodiesterase type 5). Conversely, estrogen replacement upregulated the expression of calcium-sensitizing RhoA-ROCK pathway genes. In vitro contractility studies were performed on phenylephrine pre-contracted clitoris strips. Ovariectomy resulted in a decreased responsiveness to Y-27632, a ROCK inhibitor, which was fully restored by 17ß-estradiol supplementation. To further examine the effect of 17ß-estradiol on the RhoA-ROCK pathway, smooth muscle cells were isolated from rat clitoris and their migration capacity was evaluated. CONCLUSION: Collectively, these data demonstrate that testosterone improves the relaxation of vascular smooth muscle cells through the NO-cGMP pathway, and that testosterone and 17ß-estradiol are necessary to maintain a functional contractile and relaxant machinery in the clitoris. This new concept might provide support for the concomitant use of estrogen and testosterone during the treatment of sexual arousal disorders related to hormonal imbalance or insufficiency.

Genistein supplements might not induce clitoral modifications in postmenopausal women: a prospective, pilot study.

INTRODUCTION: Vaginal dryness, low sexual desire, and low sexual arousability are critical issues for many postmenopausal women. Hormone therapy seems to improve vaginal lubrication and dyspareunia. AIM: To evaluate, in postmenopausal women who refused hormonal therapy, the role of genistein in the treatment of vasomotor symptoms and its capacity to induce clitoral volumetric and vascular modifications independently from sexual stimulation. METHODS: Twenty-nine postmenopausal women who refused hormonal therapy were submitted to oral daily treatment with genistein 45 mg (Group I; N = 15); or no treatment (Group II; N = 14). The Group II patients served as controls. The patients were not randomly assigned to the two groups. The patients were studied before and after 3 months. MAIN OUTCOMES MEASURES: Endometrial and clitoral ultrasonographic analysis; color Doppler evaluation of the dorsal clitoral artery; evaluation of hormonal plasma concentrations; administration of the two-factor Italian McCoy Female Sexuality Questionnaire; compilation of a monthly diary reporting the number of hot flashes. The ultrasound, color Doppler and psychometric tests were performed by examiners blinded to the participant's group assignment. RESULTS: In the genistein-treated patients the vasomotor symptoms ameliorated at the end of the study. The use of genistein did not influence any other parameter. CONCLUSIONS: Postmenopausal women submitted to a 3-months treatment with genistein showed an improvement of vasomotor symptoms. However, isoflavones seem to not induce any modification in the clitoral structures.

The effects of dehydroepiandrosterone (DHEA)/DHEA-sulfate (DHEAS) on the contraction responses of the clitoral cavernous smooth muscle from female rabbits.

INTRODUCTION: Dehydroepiandrosterone (DHEA) is a multifunctional steroid that is increasingly available as a supplement aimed at improving libido and well-being in postmenopausal women in the recent times. Together with its sulfate version, DHEA-sulfate (DHEAS), it is the most abundant steroid in humans. The clitoris is an important component of the female sexual response, with its increased vascular response during sexual arousal that results in erection. AIMS: To elucidate the direct effects of DHEA/DHEAS on the vasomotor reactivity of the rabbit clitoral cavernosum. METHODS: Twenty New Zealand white female rabbits weighing approximately 2.5-3 kg were used in the study. MAIN OUTCOME MEASURES: The contractile response of clitoral cavernous smooth muscle strips in response to phenylephrine (PE; 10(-9)-10(-4) M) were observed in rabbits. Additionally, DHEA/DHEAS effects on phenylephrine-induced contraction and/or acetylcholine-induced relaxation of phenylephrine-induced contraction were measured. RESULTS: DHEA/DHEAS did not elicit any remarkable response in the resting state. However, both DHEA and DHEAS evoked dose-dependent relaxations of PE-induced contraction. The contractile responses to high potassium were significantly decreased in the DHEA/DHEAS-pretreated strips, compared with the DHEA/DHEAS-nontreated strips. Additionally, contractions by Bay K 8644 (10(-7)-10(-6) M) treatment were also significantly inhibited by DHEA/DHEAS. DHEA-induced relaxation responses were stronger than DHEAS-induced relaxation responses. Various K channel blockers, tetraethylammonium (TEA; 1 mM, 10 mM), 4-aminopyridine (10 microM) and glibenclamide (10 microM) did not affect the DHEA/DHEAS-induced relaxation on muscle strips contracted by PE. Relaxation responses by acetylcholine or sodium nitroprusside (SNP) were not changed after DHEA/DHEAS pretreatment. CONCLUSIONS: DHEA/DHEAS was found to induce a relaxation response in rabbit clitoral cavernosal smooth muscle, and this is thought to be mediated by direct inhibition of a voltage-dependent calcium channel.

Possible improvement of the clitoral and vaginal blood flow using a somatostatin analog in chronic spinalized Sprague-Dawley rats.

We evaluated the effect of a somatostatin analog (octreotide) on clitoral and vaginal blood flow following suprasacral spinal cord injury (SCI) in rats. Twenty-four spinalized female Sprague-Dawley rats were randomized into 4 equal groups. The first group served as control paraplegics. The other three groups received octreotide (60 micrograms/day/4 weeks) immediately, 2 weeks, and 4 weeks following SCI. At the end of the experiment, a laser Dopper was used to measure blood flow changes following clitoral and pelvic nerve plexus stimulations. Marked decreases in both clitoral and vaginal blood flow in the control paraplegics were recorded. Significant increases (p < 0.05) in both clitoral and vaginal blood flow were recorded in animals that received octreotide; however, the increase was marked in the animals that received the drug immediately following SCI. Improvement in the clitoral and vaginal blood flow of spinalized rats using octreotide indicates that octreotide may be helpful for patients with SCI.

A 280-day tolerance-efficacy study with mibolerone for suppression of estrus in the cat.

Mibolerone, a synthetic anabolic steroid, prevented estrus in domesticated cats when orally given a daily dose of 50 microng over a 180-day period. Doses of 20 microng daily and 50 microng given once a week failed to prevent estrus. Treatment with the 50-microng dose each day for 6 months had no apparent effects on subsequent estrus, mating, queening, or litter size. Kittens born to queens which had been treated did not have obvious developmental defects. Systemic metabolic changes produced by treatment were detected only in thyroid function, as revealed in dose- and time-related changes in serum cholesterol concentrations, thyroid gland weights, and thyroid histology. Clinical evidence of thyroid dysfunction was not apparent during the 6 months of treatment. Clinical and microscopic evidence of slight masculinization was apparent in cats after 3 months of treatment with 20 or 50 microng per day. Masculinizing changes consisted of thickening of the cervical dermis and clitoral hypertrophy. Behavioral changes were not observed. The apparent mechanism of action of mibolerone in the cat is the suppression of the release of pituitary luteinizing hormone.

The effects of implanting testosterone propionate into the central nervous system on the sexual behaviour of adrenalectomised female rhesus monkeys.

Bilateral adrenalectomy rendered ovariectomised, oestrogen-treated female rhesus monkeys sexually unreceptive. Small unilateral implants of testosterone propionate (mean weight 140 mug) into the anterior hypothalamus/preoptic area restored receptivity in 7 out of 8 of these monkeys. Cholesterol implanted into the same area, or similar amounts of testosterone propionate implanted into the posterior hypothalamus/pretectal area (4 females) or cerebral cortex/dorsal thalamus (5 monkeys) had no consistent effect on behaviour. It therefore seems likely that androgens regulate sexual receptivity in female monkeys by acting on some part of the anterior hypothalamus. Thus, though the hormonal control of receptivity in female primates differs from non-primates, the site on which hormones act to regulate this behaviour may be similar in both.