On the etiology of the electric activity of the external anal and urethral sphincters.

UNLABELLED: In a previous study, the external anal sphincter (EAS) in dogs, known to consist of skeletal muscle fibers, was proved to contain bundles of smooth muscle fibers in between as well. OBJECTIVE: Cause of electric activity in the external anal and urethral sphincters is not known; the current study investigated this point. MATERIAL AND METHODS: Slices from external anal and urethral sphincters of 21 cadavers (12 male, 9 female). Eighth were fully and mat wide neonates, 13 were adults, were stained with hematoxylin and eosin, Masson's trichrome and succinic dehydrogenase, and examined microscopically. Eighteen healthy volunteers, electromyography activity of their external anal and urethral sphincters was recorded at rest, on coughing, after pudendal nerve block and after drotaverine administration, (a smooth muscle relaxant). Anal and urethral pressures were also measured. RESULTS: Microscopic studies have shown that both external anal and urethral sphincters were formed of bundles of smooth muscle fibers present in between the skeletal muscle fibers. Bilateral pudendal nerve block did not abolish the external anal or the urethral sphincters electromyography activity at rest, or on coughing, and did not cause significant anal or urethral pressure changes (p > .05). Drotaverine administration lead to disappearance of the electromyography activity and significant decline of the anal and urethral pressures (p < .05). The results were reproducible when the tests were repeated in the same subject. CONCLUSION: Histologic examination revealed the presence of smooth muscle fibers, between the skeletal fibers of the external anal and urethral sphincters. Evidence suggests that the smooth muscle fibers are the source of the electric activity of the sphincters and might explain some physiologic phenomena such as the external anal contraction on rectal distension or on coughing.

Tunica albuginea reefing: a novel technique for the treatment of erectile dysfunction.

BACKGROUND: "Tunica albuginea (TA) reefing" is a modification of Shafik's "TA overlapping" operation. Both techniques are based on the fact that in venogenic erectile dysfunction patients, the TA exhibits degenerative and atrophic collagen and elastic fibers causing its subluxation and flabbiness. This had led to loss of the veno-occlusive mechanism of the TA and venous leakage during erection. AIM: Reefing of the redundant tissue by bilateral excision of an ellipse of the TA provides a more effective correction of the TA and achieves a good support of the corpora cavernosa during tumescence. MATERIAL AND METHODS: The study included 24 patients with a mean age of 33.5 ± 1.7 SD years. Intracorporal pressure was measured preoperatively and postoperatively. After penile degloving, an ellipse was excised from both lateral aspects of the penile shaft, extending from the glans penis to its root, and the two edges of each wound were reefed by continuous Dexon suture. RESULTS: The TA ellipses were taken as biopsies and revealed degenerative changes when stained with hematoxylin and eosin and Masson's trichrome stain. Postoperatively, there was an intracorporal pressure increase (p < .01) in 20 out of 24 patients of the study and a decrease in 4 out of 24. Six months after operation, the patients showed significantly (p < .01) improved scores for the domain of erectile function over the preoperative scores. CONCLUSION: The reefing operation corrects the TA flabbiness to a greater extent, lends more support to corporal tissue, and improves the veno-occlusive mechanism.

Effect of severe stress on the gastric motor activity: canine study of mechanism of action.

BACKGROUND: Increased gastric motility was observed during restraint stress in animals; however, mechanism of action could not be traced in literature. We investigated the hypothesis that high levels of stressful cutaneous stimuli induce increase of gastric motor activity through a reflex action. METHODS: Gastric tone (GT) was assessed in 14 dogs by barostat system consisting of balloon-ended tube connected to strain gauge and air-injection system. Tube was introduced into stomach and its balloon inflated with 150 mL of air. Thermal cutaneous stimulation (TCS) was performed by thermal plate applied to skin. Temperature was raised in increments of 5 degrees C up to 107 degrees C and GT was simultaneously assessed by recording balloon volume variations expressed as percentage change from baseline volume. Test was repeated after separate anesthetization of skin and stomach. RESULTS: TCS up to mean temperature of 48.7 +/- 1.1 degrees C effected significant decrease of GT, but significant increase beyond this temperature. Twenty minutes after individual anesthetization of skin and stomach, TCS produced no significant change in GT. CONCLUSION: TCS up to certain degree effected GT decrease, whereas TCS beyond this degree augmented the GT. These effects seem to be mediated through reflex action as evidenced by their absence on individual anesthetization of the suggested 2 arms of the reflex arc: skin and stomach; we call this reflex "cutaneo-gastric reflex." The reflex may have the potential to serve as an investigative tool in diagnosis of gastric motor disorders provided further studies are performed to reproduce current results.

An electrophysiologic study of female ejaculation.

Opinions vary over whether female ejaculation exists or not. We investigated the hypothesis that female orgasm is not associated with ejaculation. Thirty-eight healthy women were studied. The study comprised of glans clitoris electrovibration with simultaneous recording of vaginal and uterine pressures as well as electromyography of corpus cavernous and ischio- and bulbo-cavernosus muscles. Glans clitoris electrovibration was continued until and throughout orgasm. Upon glans clitoris electrovibration, vaginal and uterine pressures as well as corpus cavernous electromyography diminished until a full erection occurred when the silent cavernosus muscles were activated. At orgasm, the electromyography of ischio-and bulbo-cavernosus muscles increased intermittently. The female orgasm was not associated with the appearance of fluid coming out of the vagina or urethra.

Percutaneous perineal electrostimulation induces erection: clinical significance in patients with spinal cord injury and erectile dysfunction.

OBJECTIVES: Approximately one third to one half of the penis is embedded in the pelvis and can be felt through the scrotum and in the perineum. The main arteries and nerves enter the penis through this perineal part of the penis, which seems to represent a highly sensitive area. We investigated the hypothesis that percutaneous perineal stimulation evokes erection in patients with neurogenic erectile dysfunction. METHODS: Percutaneous electrostimulation of the perineum (PESP) with synchronous intracorporeal pressure (ICP) recording was performed in 28 healthy volunteers (age 36.3 +/-7.4 y) and 18 patients (age 36.6 +/- 6.8 y) with complete neurogenic erectile dysfunction (NED). Current was delivered in a sine wave summation fashion. Average maximal voltages and number of stimulations delivered per session were 15 to 18 volts and 15 to 25 stimulations, respectively. RESULTS: PESP of healthy volunteers effected an ICP increase (P < 0.0001), which returned to the basal value upon stimulation cessation. The latent period recorded was 2.5 +/- 0.2 seconds. Results were reproducible on repeated PESP in the same subject but with an increase of the latent period. Patients with NED recorded an ICP increase that was lower (P < 0.05) and a latent period that was longer (P < 0.0001) than those of healthy volunteers. CONCLUSION: PESP effected ICP increase in the healthy volunteers and patients with NED. The ICP was significantly higher and latent period shorter in the healthy volunteers than in the NED patients. PESP may be of value in the treatment of patients with NED, provided that further studies are performed to reproduce these results.

Vaginal response to clitoral stimulation: identification of the clitorovaginal reflex.

OBJECTIVE: To investigate the hypothesis that glans clitoris (GC) penile buffeting effects contraction of the vaginal musculature and seems to increase arousal of the penis during coitus. STUDY DESIGN: The response of the vaginal wall to GC electrical and mechanical stimulation was recorded in 26 healthy women (aged 36.8 +/- 6.7 years). The test was repeated after individual anesthetization of the GC and vagina using lidocaine gel and after application of bland gel instead of lidocaine. RESULTS: The 2 vaginal electrodes recorded, at rest, slow waves followed or superimposed by action potentials. Wave parameters were similar from the 2 electrodes. Electrical or mechanical GC stimulation effected a significant increase in vaginal electromyographic (EMG) activity and pressure (p < 0.01). GC stimulation, while the vagina or GC had been separately anesthetized, produced no significant change, but there was a response following application of bland gel. CONCLUSION: GC stimulation effected an increase in vaginal EMG activity and pressure and presumably indicated vaginal wall contraction. This action seems to be a reflex and is mediated through the clitorovaginal excitatory reflex. Vaginal wall contraction during coitus appears to effect penile arousal and, consequently, female sexual stimulation.

Study of the response of the penile corporal tissue and cavernosus muscles to micturition.

BACKGROUND: The reaction of the corpora cavernosa (CC), the corpus spongiosum (CS), the bulbocavernosus (BCM) and ischiocavernosus (ICM) muscles to passage of urine through the urethra during micturition is not known. We investigated the hypothesis that the passage of urine through the urethra stimulates the corporal tissue and cavernosus muscles. METHODS: In 30 healthy men (mean age 42.8 +/- 11.7 years), the electromyographic activity (EMG) of the CC, CS, BCM, and ICM were recorded before and during micturition, and on interruption of and straining during micturition. These tests were repeated after individual anesthetization of urethra, corporal tissue, and cavernosus muscles. RESULTS: During micturition, the slow wave variables (frequency, amplitude, conduction velocity) of the CC and CS decreased while the motor unit action potentials of the BCM and ICM increased; these EMG changes were mild and returned to the basal values on interruption or termination of micturition. Micturition after individual anesthetization of urethra, corporal tissue and cavernosal muscles did not effect significant EMG changes in these structures, while saline administration produced changes similar to those occurring before saline administration. CONCLUSION: The decrease of sinusoidal and increase of cavernosus muscles' EMG activity during micturition apparently denotes sinusoidal relaxation and cavernosus muscles contraction. Sinusoidal muscle relaxation and cavernosus muscles contraction upon micturition are suggested to be mediated through a 'urethro-corporocavernosal reflex'. These sinusoidal and cavernosus muscle changes appear to produce a mild degree of penile tumescence and stretch which might assist in urinary flow during micturition.

Inguinal canal dilatation: a novel technique for the repair of failed testicular descent despite hormonal treatment.

Treatment of the undescended testicle (UT) after it failed to descend on hormonal therapy is surgical. Spermatic cord elongation may impair testicular function, particularly in cases in which cord integuments or veins have to be divided to provide an extra cord length. A factor that might impede testicular descent is presence of a narrowed or obliterated inguinal canal. We investigated the hypothesis that dilatation of a narrowed or obliterated inguinal canal might assist spontaneous testicular descent. Twenty-six boys (age 3.6 +/- 0.8 years) with unilateral UT and failed hormonal treatment, whose UT was located at deep inguinal ring, were included in the study. Through an inguinal incision, the inguinal canal was dilated, spermatic cord adhesions divided, hernial sac, if present, excised, and skin closed. Testicular descent into the scrotum occurred in 22 patients within 4.2 +/- 1.3 months. The remaining four patients were reoperated on by Fowler-Stephens orchiopexy after 14 months. A technique is presented for the treatment of the UT after failure to respond to hormonal treatment. It consisted of clearing the testicular pathway of any adhesions and dilating the narrowed inguinal canal. The technique is simple, easy, and does not interfere with the testicle or spermatic cord.

Effect of micturition on clitoris and cavernosus muscles: an electromyographic study.

We investigated the hypothesis that passage of urine through urethra stimulates corporal tissue and cavernosus muscles. Electromyographic (EMG) activity of corpora cavernosa (CC), bulbocavernosus muscle (BCM), and ischiocavernosus muscle (ICM) was recorded in 27 healthy women before and during micturition. These tests were repeated after individual anesthetization of urethra, corporal tissue, and cavernosus muscles. During micturition, slow wave variables of CC decreased and motor unit action potentials of the BCM and ICM increased. These EMG changes returned to basal values on micturition interruption or termination. Micturition after individual anesthetization of the urethra, corporal tissue, and cavernosus muscles did not effect significant changes in these structures. Decreased EMG activity of CC and increased activity of cavernosus muscles during micturition apparently denotes corporal tissue relaxation and cavernosus muscles' contraction. The latter two actions occurring on micturition are suggested to be mediated through a reflex called "urethro-corporocavernosal reflex" and effect a mild degree of clitoral tumescence.

The electromyographic activity of the external and internal urethral sphincters and urinary bladder on vaginal distension and its role in preventing vaginal soiling with urine during sexual intercourse.

BACKGROUND/AIM: We investigated the hypothesis that external (EUS) and internal (IUS) urethral sphincters and urinary bladder (UB) respond to penile thrusting (PT) of vagina in a way that prevents urinary leakage during coitus. METHODS: Vaginal condom was inflated with air in increments of 50-300 ml and EMG of EUS and IUS and vaginal pressure were recorded; test was repeated after anesthetization of vagina, UB, EUS, and IUS. RESULTS: Vaginal distension effected reduction of vesical pressure but increase of IUS EMG until the 150 ml distension was reached, beyond which more vaginal distension caused no further effect; EUS EMG showed no response. Vaginal distension while vagina, UB, EUS, and IUS had been separately anesthetized, produced no change. CONCLUSION: Vaginal balloon distension appears to effect vesical relaxation and increased IUS tone. This seems to provide a mechanism to avoid urine leakage during coitus and to occur through a reflex we term 'vagino-urethrovesical reflex'.

Effect of urethral stimulation on vesical contractile activity.

BACKGROUND: We investigated the hypothesis that urethral stimulation effects vesical contraction. METHODS: Vesical pressure response to urethral balloon distension with normal saline in increments of 1 mL was recorded in 26 healthy volunteers (17 men, 9 women; mean age, 36.9 +/- 9.7 SD years) before and after individual anesthetization of the urinary bladder and urethra. Urethral distension was effected by a 6F balloon-ended catheter introduced per urethra. Vesical pressure was measured by means of a microtip catheter. RESULTS: Vesical pressure recorded gradual increase on increase of urethral balloon distension. Bladder response was maintained as long as urethral distension was continuous. The response showed no significant difference when we distended different parts of the male or female urethrae. Urethral distension after individual vesical and urethral anesthetization effected no change in the vesical pressure. CONCLUSIONS: Urethral distension produced a vesical pressure increase that presumably denotes vesical contraction. Vesical contraction on urethral stimulation by distension is suggested to be mediated through a "urethrovesical stimulating reflex" that seems to facilitate vesical contraction. Provided further studies to be performed in this respect, the reflex may prove to be of diagnostic significance in micturition disorders.

Duodeno-jejunal junction: a histoanatomical study with the concept of the existence of an "anatomical" sphincter.

BACKGROUND: Duodenojejunal junction (DJJ) pressure decreased on duodenal contraction and increased on jejunal contraction. These findings postulated potential existence of anatomical sphincter at DJJ. METHODS: DJJ was studied by direct dissection in 34 cadavers and histologically in 24. Transverse and longitudinal sections across DJJ were cut and stained. RESULTS: DJJ was narrower than duodenum or jejunum and had one or two grooves occupied by arterial branch derived from superior mesenteric artery and we call it "duodenojejunal junction artery". DJJ was thicker on palpation than duodenum or jejunum. Its mucous membrane was crowded into "DJJ rosette". DJJ length varied in adults from 0.75 to 0.9 cm. Microscopically, circular muscle layer was thickened at DJJ. CONCLUSION: The thickened circular muscle, mucosal rosette and narrowing at DJJ point to possible existence of anatomical sphincter at DJJ. Together with presence of high-pressure zone at DJJ, these findings would support such postulation.

Physiological considerations of the morphologic changes of the testicles during erection and ejaculation: a canine study.

PURPOSE: We investigated the hypothesis that testicles and scrotal skin undergo morphologic changes that would serve the mechanism of erection and ejaculation. MATERIALS AND METHODS: Testicular and scrotal skin changes during erection and ejaculation were studied in 9 dogs. Testicular volume was measured by ultrasound, testicular temperature by digital thermometer and testicular vascularity by color duplex Doppler ultrasonography. Dartos muscle activity was studied by electromyography. RESULTS: Testicular volume increased during erection and diminished at ejaculation. Testicular consistency became softer during erection and firmer at ejaculation. During erection and ejaculation the testicles were elevated closer to abdominal wall. Testicular temperature increased in the erectile phase followed by reduction during ejaculation. Doppler ultrasonography recorded increased testicular vascularity during erection and diminished vascularity at ejaculation. A dartos muscle electromyogram exhibited increased activity in the erectile and ejaculatory phases. CONCLUSION: During erection and ejaculation, testicles underwent changes which apparently serve the erectile and ejaculatory functions of penis.

On the pathogenesis of penile venous leakage: role of the tunica albuginea.

BACKGROUND: Etiology of venogenic erectile dysfunction is not exactly known. Various pathologic processes were accused but none proved entirely satisfactory. These include presence of large venous channels draining corpora cavernosa, Peyronie's disease, diabetes and structural alterations in fibroblastic components of trabeculae and cavernous smooth muscles. We investigated hypothesis that tunica albuginea atrophy with a resulting subluxation and redundancy effects venous leakage during erection. METHODS: 18 patients (mean age 33.6 +/- 2.8 SD years) with venogenic erectile dysfunction and 17 volunteers for control (mean age 31.7 +/- 2.2 SD years) were studied. Intracorporal pressure was recorded in all subjects; tunica albuginea biopsies were taken from 18 patients and 9 controls and stained with hematoxylin and eosin and Masson's trichrome stains. RESULTS: In flaccid phase intracorporal pressure recorded a mean of 11.8 +/- 0.8 cm H2O for control subjects and for patients of 5.2 +/- 0.6 cm, while during induced erection recorded 98.4 +/- 6.2 and 5.9 +/- 0.7 cmH2O, respectively. Microscopically, tunica albuginea of controls consisted of circularly-oriented collagen impregnated with elastic fibers. Tunica albuginea of patients showed degenerative and atrophic changes of collagen fibers; elastic fibers were scarce or absent. CONCLUSION: Study has shown that during erection intracorporal pressure of patients with venogenic erectile dysfunction was significantly lower than that of controls. Tunica albuginea collagen fibers exhibited degenerative and atrophic changes which presumably lead to tunica albuginea subluxation and floppiness. These tunica albuginea changes seem to explain cause of lowered intracorporal pressure which apparently results from loss of tunica albuginea veno-occlusive mechanism. Causes of tunica albuginea atrophic changes and subluxation need to be studied.

The effect of gastric overfilling on the pharyngo-esophageal and lower esophageal sphincter: a possible factor in restricting food intake.

BACKGROUND: How afferent activity in the gut achieves the required ingestion control has not been established. The authors hypothesized that gastric overdistension effects an increase in pharyngo-esophageal and lower esophageal sphincter activity aimed at inhibiting ingestion. MATERIAL/METHODS: The study comprised 16 mongrel dogs. Under anesthesia, one balloon-tipped catheter was placed in the stomach, another within the lower esophageal sphincter (LES), and a third within the pharyngo-esophageal sphincter (PES). The gastric balloon was filled with H(2)O in increments of 10 ml and LES and PES pressures were recorded. The test was repeated after individual gastric, LES, and PES anesthetization. RESULTS: Gastric balloon filling with more than 20 ml of H(2)O showed progressively increasing LES pressure up to 110-120 ml of gastric filling, beyond which the pressure exhibited no further increase upon incrementally increased gastric filling volume. PES pressure increased only with a gastric filling volume exceeding 100-110 ml and continued to increase with increasing gastric filling. Gastric filling as above while the stomach, LES, and PES were separately anesthetized produced no LES or PES pressure response. CONCLUSIONS: LES and PES appear to contract on gastric filling; PES responds only to excess gastric filling. It seems that LES and PES response to gastric filling is mediated through a reflex which the authors call the "gastro-esophagopharyngeal reflex" (GEPR). Changes in the evoked response would indicate a defect in the reflex pathway. GEPR might thus serve as an investigative tool in the diagnosis of gastroesophageal disorders, although further studies are required.

Duodeno-jejunal junction dyssynergia: description of a novel syndrome.

AIM: To investigate the hypothesis that duodeno-jejunal dyssynergia existed at the duodeno-jejunal junction. METHODS: Of 112 patients who complained of epigastric distension and discomfort after meals, we encountered nine patients in whom the duodeno-jejunal junction did not open on duodenal contraction. Seven healthy volunteers were included in the study. A condom which was inserted into the 1st duodenum was filled up to 10 mL with saline in increments of 2 mL and pressure response to duodenal distension was recorded from the duodenum, duodeno-jejunal junction and the jejunum. RESULTS: In healthy volunteers, duodenal distension with 2 and 4 mL did not produce pressure changes, while 6 and up to 10 mL distension effected significant duodenal pressure increase, duodeno-jejunal junction pressure decrease but no jejunal pressure change. In patients, resting pressure and duodeno-jejunal junction and jejunal pressure response to 2 and 4 mL duodenal distension were similar to those of healthy volunteers. Six and up to 10 mL 1st duodenal distension produced significant duodenal and duodeno-jejunal junction pressure increase and no jejunal pressure change. CONCLUSION: Duodeno-jejunal junction failed to open on duodenal contraction, a condition we call 'duodeno-jejunal junction dyssynergia syndrome' which probably leads to stagnation of chyme in the duodenum and explains patients' manifestations.

Electromyographic activity of the anterolateral abdominal wall muscles during rectal filling and evacuation.

BACKGROUND: The role of the anterolateral abdominal wall muscles (AAWMs) at defecation has not received sufficient attention in the literature. We investigated the hypothesis that the AAWMs exhibit increased electromyographic (EMG) activity on rectal distension, which presumably assists in rectal evacuation. MATERIALS AND METHODS: The effect of rectal balloon distension on the AAWMs EMG and on anal and rectal pressure was examined in 23 healthy volunteers (37.2 +/- 9.4 SD years, 14 men, 9 women); this effect was tested before and after rectal and AAWMs anesthetization. RESULTS: The rectal and anal pressures increased gradually upon incremental rectal balloon distension starting at 70 mL balloon distension until, at a mean of 113.6 +/- 5.6 mL, the balloon was expelled to the exterior. The AAWMs showed no EMG activity at rest or on rectal distension up to the time of balloon expulsion when they exhibited significant increase of EMG. This effect was abolished on individual rectal or AAWMs anesthetization but not with saline administration. CONCLUSIONS: AAWMs appear to contract simultaneously with rectal contraction; this action seems to increase the intra-abdominal pressure and assist rectal evacuation. The AAWMs contraction upon rectal contraction appears to be mediated through a reflex, which we call the "recto-abdominal wall reflex". Further studies are required to investigate the role of this reflex in defecation disorders.

Study of the duodenal contractile activity during antral contractions.

AIM: To investigate the hypothesis that duodenal bulb (DB) inhibition on pyloric antrum (PA) contraction is reflex. METHODS: Balloon (condom)-tipped tube was introduced into 1(st) duodenum (DD) and a manometric tube into each of PA and DD. Duodenal and antral pressure response to duodenal and then PA balloon distension with saline was recorded. These tests were repeated after separate anesthetization of DD and PA. RESULTS: Two and 4 mL of 1(st) DD balloon distension produced no pressure changes in DD or PA (10.7 +/- 1.2 vs 9.8 +/- 1.2, 11.2 +/- 1.2 vs 11.3 +/- 1.2 on H(2)O respectively, P > 0.05). Six mL distension effected 1(st) DD pressure rise (30.6 +/- 3.4 cm H(2)O, P < 0.01) and PA pressure decrease (6.2 +/- 1.4 cm H(2)O, P < 0.05); no response in 2(nd), 3(rd) and 4(th) DD. There was no difference between 6, 8, and 10 mL distensions. Ten mL PA distension produced no PA or 1(st) DD pressure changes (P > 0.05). Twenty mL distension increased PA pressure (92.4 +/- 10.7 cm H(2)O, P < 0.01) and decreased 1(st) DD pressure (1.6 +/- 0.3 cm H(2)O, P < 0.01); 30, 40, and 50 mL distension produced the same effect as the 20 mL distension (P > 0.05). PA or DD distension after separate anesthetization produced no significant pressure changes in PA or DD. CONCLUSION: Large volume DD distension produced DD pressure rise denoting DD contraction and PA pressure decline denoting PA relaxation. PA relaxation upon DD contraction is postulated to be mediated through a reflex which we call duodeno-antral reflex. Meanwhile, PA distension effected DD relaxation which we suggest to be reflex and termed antro-duodenal reflex. It is suggested that these 2 reflexes, could act as investigative tools in diagnosis of gastroduodenal motility disorders.

Electrophysiologic activity of the tunica albuginea and corpora cavernosa: possible role of tunica albuginea in the erectile mechanism.

INTRODUCTION: It is claimed that the tunica albuginea (TA) shares in the erectile mechanism by compressing the emissary veins passing through it. However, the TA does not contain smooth muscle fibers. AIM: We investigated the hypothesis that TA lacks a contractile activity on the emissary veins passing through it. METHODS: Fourteen healthy male volunteers (mean age 35.2 +/- 4.3 years) were studied. The electromyographic (EMG) activity of the TA and corpora cavernosa (CC) was individually recorded in the flaccid and erectile phases by EMG needle electrodes. Recording was performed in the upper, middle, and lower third of the TA and CC on one and then on the contralateral side. MAIN OUTCOME MEASURES: The TA lacks a contractile activity on the emissary veins passing through it. RESULTS: The EMG of the CC in the flaccid phase recorded regular slow waves and random action potentials. The wave variables in the erectile phase exhibited a significant decrease (P < 0.01) compared with the variables in the flaccid phase of the same subject. The TA EMG showed no electric waves in the flaccid or erectile phases. These recordings were similar from the upper-, middle-, and lower-third of the penis, and were reproducible from the contralateral CC. CONCLUSIONS: Electric waves were recorded from the CC in the flaccid phase; wave variables decreased at erection. In contrast, the TA showed no electric waves in the flaccid or erectile phases. It appears that the TA acts as a CC covering sheet which expands passively at erection, and shares in compressing the subtunical venular plexus between it and the tumescent CC.

The response of the corporal tissue and cavernosus muscles to urethral stimulation: an effect of penile buffeting of the vaginal introitus.

We investigated the hypothesis that urethral stimulation in humans induces sexual response in the form of activation of the corporal tissue and cavernosus muscles through a reflex mechanism. Electromyographic activity of corpora cavernosa (CC), corpus spongiosum (CS), bulbocavernosus (BCM), and ischiocavernosus (ICM) muscles was recorded in 43 healthy volunteers (24 men, 19 women; age, 37.7 +/- 8.2 years) during urethral stimulation. The tests were repeated after individual anesthetization of urethra, CC, CS, BCM, and ICM. During stimulation of the distal urethra, slow wave variables of CC and CS decreased while motor unit action potentials of BCM and ICM increased. Urethral stimulation after individual anesthetization of urethra, CC, CS, BCM, and ICM did not effect significant changes in these structures, but saline administration did. Diminished electromyographic activity of CC and CS with increased activity of BCM and ICM during distal urethral stimulation presumably denotes sinusoidal muscle relaxation of CC and CS and cavernosus muscles' contraction. Sinusoidal muscle relaxation and contraction of cavernosus muscles upon distal urethral stimulation are suggested to be mediated through a reflex that we call the "urethro-corporocavernosal reflex." Sinusoidal and cavernosus muscles' response during coitus appears to effect a degree of tumescence for both male and female partners.