Clitoral Blood Flow Research Articles

Diabetes induced alteration of clitoral hemodynamics and structure in the rabbit.

We investigated the effect of diabetes on clitoral hemodynamics and structures in the rabbit. A total of 25 New Zealand White female rabbits weighing 3 to 3.5 kg. were divided into 2 groups, including 5 in the control and 20 in the experimental group. Experimental animals received intravenous injection of alloxan hydrochloride (Sigma Chemical Co., St. Louis, Missouri) (100 mg./kg.). The development of diabetes was verified by measuring body weight and blood glucose levels. After 12 weeks clitoral cavernous blood flow in ml. per minute per 100 gm. tissue was measured with a laser Doppler flowmeter. Cross sections of the clitoris were used for histochemistry and histomorphometric image analysis. After 12 weeks 5 animals were included in the diabetes group. Mean baseline flaccid and peak clitoral cavernous blood flow plus or minus standard deviation significantly decreased in the diabetic group compared with the control group (3.9 +/- 1.6 and 5.8 +/- 2.2 versus 7.2 +/- 2.5 and 12.9 +/- 5.8 ml. per minute per 100 gm. tissue, respectively, p <0.05). Histology revealed diffuse clitoral fibrosis in the diabetic group. On histomorphometry the mean proportion of clitoral cavernous smooth muscle in the diabetic group was significantly decreased compared with the control group (51.9% +/- 4.9% versus 62.3% +/- 3.1%, p < 0.05). These results show that diabetes mellitus produces significant adverse effects on the hemodynamic mechanism of clitoral engorgement and leads to diffuse clitoral cavernous fibrosis. It implies that decreased sexual arousal in diabetic women may result from structural changes in the clitoris.

Clitoral blood flow as a measure of sexual arousal

Clitoral blood flow as a measure of sexual arousal

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.

Clitoral Artery Blood Flow in Healthy Young Women: Preliminary Report on Menstrual Cycle and Hormonal Contraception

The aim of the present study was to measure clitoral artery blood flow throughout the menstrual cycle and in oral contraceptive users. We recruited healthy young women ( n = 19, age range: 21-28 years; body-mass index: 18-23 kg/m 2 ) without sexual dysfunction (Female Sexual Functioning Index criteria; Rosen et al., 2000). Clitoral arterial peak systolic velocity (PSV) in at least two phases of the same ovulatory cycle or during the second week of the pill was measured by doppler ultrasonography. Clitoral arterial PSV measures (cm/s) were superimposable during the follicular and the luteal phase of the menstrual cycle (10.4 - 1.2 versus 10.2 - 1.6), whereas a slight but significant increase (12.2 - 1.2, f = 3.99; p < 0.04) was evident at the time of ovulation. In addition, PSV measures were significantly higher in women taking hormonal contraception compared to women studied throughout the menstrual cycle (14.2 - 2.7 versus 10.8 - 1.5; p < .001). Whether or not these preliminary data may be of any significance to female sexual arousal throughout the menstrual cycle remains to be established.

Hemodynamic Evaluation of the Female Sexual Arousal Response in an Animal Model

The goal of this study was to assess the utility of existing and new techniques for characterizing and measuring hemodynamic changes in the vagina and clitoris in response to pelvic nerve stimulation (PNS) in an animal model. Using female New Zealand White rabbits, we measured the following parameters before, during, and after PNS at 4, 16, and 32 hertz (Hz): clitoral hemoglobin (Hb) content by laser oximetry, clitoral blood flow by laser Doppler flowmetry, vaginal luminal pressure of upper and lower segments, and clitoral intracavernosal pressure. Clitoral tissue concentrations of total and oxygenated hemoglobin (oxy-Hb) increased in a frequency-dependent manner while deoxygenated hemoglobin (deoxy-Hb) concentration decreased. The duration of the responses at 16 and 32 Hz were significantly greater than at 4 Hz. Clitoral blood flow increased significantly only at 32 Hz with a prolonged response duration, relative to 4 Hz. PNS caused vaginal luminal pressure changes that were highly variable, but qualitatively different, between the upper and lower regions. Clitoral intracavernosal pressure did not change significantly in response to PNS. Measurement of changes in tissue Hb content by the novel technique of laser oximetry provides a direct assessment of blood flow in a noninvasive manner and may prove to be a powerful tool in evaluating hemodynamic aspects of the female genital sexual response.

Decreased circulating levels of estrogen alter vaginal and clitoral blood flow and structure in the rabbit.

Aging and menopause related decline in circulating levels of estrogen has been shown to adversely affect female sexual arousal function. Our aim was to study the effects of circulating levels of estrogen on the hemodynamic mechanism of vaginal and clitoral engorgement and on the structure of the vaginal and clitoral cavernosal tissue in the rabbit. New Zealand White female rabbits (3.5-4 kg) were randomly divided into three groups with five rabbits in each group: control; bilateral oophorectomy; bilateral oophorectomy undergoing subcutaneous injection of estrogen (40 microg/kg/day). After 6 weeks, the serum levels of 17 beta-estradiol were measured and systemic blood pressure was monitored. Vaginal and clitoral cavernosal blood flows were measured with laser Doppler flowmeter before and after pelvic nerve stimulation. Cross sections of the clitoris and vagina were processed for histologic examination and histomorphometric image analysis. Serum level of 17 beta-estradiol (pg/ml; mean+/-s.d.) revealed a significant decrease in the oophorectomy group (25.4+/-5.1) compared with the control (38.5+/-7.6) and estrogen replacement (115.9+/-57.3) groups (P<0.05). Nerve stimulation-induced peak vaginal and clitoral intracavernosal blood flows in the oophorectomy group (28.9+/-16.3 and 6.1+/-1.4, respectively) were significantly less than those recorded in the control (48.9+/-6.5 and 11.0+/-2.4, respectively) or estrogen replacement (48.7+/-12.2 and 10.1+/-2.8, respectively) group (P<0.05). In histology, marked thinning of the vaginal epithelial layers, decreased vaginal submucosal microvasculature, and diffuse clitoral cavernosal fibrosis were evident in the oophorectomy group but not in the estrogen supplement and control groups. In histomorphometry, the percentage of clitoral cavernosal smooth muscle in the oophorectomy group (49.6+/-6.2) was significantly decreased compared with the control (56.8+/-2.6) and estrogen replacement (58+/-3.0) groups (P<0.05). Our studies show that decline in circulating levels of estrogen impairs the hemodynamic mechanism of vaginal and clitoral engorgement and leads to histopathologic changes in the vagina and clitoral cavernosal tissue. These observations suggest that decreased circulating levels of estrogen, a physiologic change in the menopausal state, may play a role in the development of female sexual arousal dysfunction.

Sildenafil augments pelvic nerve-mediated female genital sexual arousal in the anesthetized rabbit.

The NO-cGMP pathway has been implicated in clitoral and vaginal smooth muscle relaxation based on previous immunochemical, biochemical and physiologic studies. There are limited data from in vivo studies demonstrating enhancement of the genital sexual arousal response by pharmacologic agents influencing the NO-cGMP pathway. The goal of this study was to investigate if sildenafil, a phosphodiesterase type-5 inhibitor, facilitated female genital sexual arousal in an animal model in response to pelvic nerve stimulation (PNS). Using female New Zealand White rabbits, we measured the following parameters before, during and after PNS at 4, 16, and 32 Hz: a) hemoglobin concentration and oxygen saturation in female genital (vaginal, labial, clitoral) tissues by laser oximetry; b) clitoral blood flow by laser Doppler flowmetry; c) vaginal luminal pressure by a balloon catheter pressure transducer; d) vaginal lubrication by tampon. Sildenafil was administered intravenously (0.21 microg/kg, 0.42 microg/kg, 2.1 microg/kg) to achieve a systemic concentration of 5, 10 and 50 nM, respectively. After 20 minutes, physiologic measurements were repeated. Sildenafil (50 nM) caused a significant increase in genital oxyhemoglobin concentration and a significant decrease in genital deoxyhemoglobin concentration. Sildenafil also increased the duration of response following PNS, relative to genital hemoglobin concentration and mean clitoral blood flow. Sildenafil caused a decrease in vaginal luminal pressure and resulted in an increase in vaginal lubrication. These data indicate that the NO-cGMP pathway is involved in the physiologic mechanism of female genital arousal and that sildenafil facilitates this response in an in vivo animal model.

Evaluation of Clitoral Blood Flow by Color Doppler Ultrasonography

The feasibility of reliably measuring clitoral blood flow using standard color Doppler ultrasonography was evaluated by two independent assessors in a sample of 40 pre- and post-menopausal women. High positive correlations with no significant mean differences between examiners were found for three major standard blood flow measures including maximum velocity, resistance, and pulsatility indices. With further methodological refinements, ultrasonographic evaluation of clitoral blood flow will be adaptable for clinical and research use and is likely to become the standard physiological measure of female sexual arousal.

Increases in clitoral and vaginal blood flow following clitoral and pelvic plexus nerve stimulations in the female rat.

The objective of this present study is to establish a model in the rat for the study of female clitoral and vaginal vascular changes during sexual excitation. A laser Doppler was used to measure blood flow changes following clitoral and pelvic plexus nerve stimulations. Results show an increase in clitoral blood flow following clitoral nerve (df1 = 12, df2 = 108, F = 21.4, P < 0.001) and pelvic plexus nerve stimulations (n = 3). A vaginal blood flow increase is also observed following pelvic plexus nerve stimulations (df1 = 12, df2 = 108, F = 4.75, P < 0.001). The female rat can therefore be used as a model for the study of the physiology, pharmacology and sexual dysfunction relating to blood flow in clitoral and vaginal tissue.

Vasculogenic female sexual dysfunction: the hemodynamic basis for vaginal engorgement insufficiency and clitoral erectile insufficiency.

Organic female sexual dysfunction may be related in part to vasculogenic impairment of the hypogastric-vaginal/clitoral arterial bed. The aim was to develop an animal model of vaginal engorgement insufficiency and clitoral erectile insufficiency. Pelvic nerve stimulated vaginal engorgement and clitoral erection were achieved in control (normal diet, n = 8) and atherosclerotic (balloon injury of aorto-iliac arteries and 0.5% cholesterol diet, n = 7) New Zealand White female rabbits. After 16 weeks, novel hemodynamic variables including vaginal wall and clitoral blood flow, vaginal wall and clitoral intracavernosal pressure, vaginal length, vaginal luminal pressure, blood levels of cholesterol and triglycerides, aorto-iliac angiography and vaginal wall and clitoral erectile tissue histology were recorded in the two groups. Concerning pelvic nerve stimulated vaginal hemodynamic changes, there was significantly less increase in blood flow (ml/min/100 gm tissue), wall pressure (mmHg) and length changes (mm) in atherosclerotic (9.3 +/- 3.7, 4.8 +/- 3.8, 67.3 +/- 8.3) compared to control (13.9 +/- 4.5, 5.5 +/- 2.6, 74.1 +/- 10.0) animals respectively. Histologic examination of clitoral erectile tissue demonstrated cavernosal artery atherosclerotic changes and diffuse vaginal and clitoral fibrosis. Aorto-iliac angiography in atherosclerotic animals revealed diffuse moderate to severe atherosclerotic occlusion. Vaginal engorgement and clitoral erection depend on increased blood inflow. Atherosclerosis is associated with vaginal engorgement insufficiency and clitoral erectile insufficiency.

Clitoral blood flow increases following vaginal pressure stimulation

The vascular responses of clitoral arteries to vaginal pressure stimulation in 10 volunteer women were evaluated by Doppler ultrasonography. Pressure stimulations (20-160 mm Hg) along the lower third of the vagina increased blood velocity and flow into clitoral arteries in 9 of the 10 women. The latency and duration of the Doppler responses ranged from 0.1 to 1.6 sec and from 3.2 to 9.5 sec, respectively, and the response was associated with a blood flow increase of 4 to 11 times the baseline prestimulation level. This response parallels that recorded in the cavernous arteries in men when a similar range of pressure stimulations are applied to the glans penis. Similar responses evoked in the male and female suggest a sexual synergy that may occur during intercourse in that such physiological responses and reflexes may be reciprocally reinforced.