Intracavernous Pressure Changes Research Articles

Effect of excitatory amino acid receptor agonists on penile erection after administration into the CA3 hippocampal region in the rat

Objectives To examine whether hippocampal injection of specific agonists for glutamate ionotropic (NMDA, AMPA) and metabotropic (ACPD) receptors modulates erectile response in adult male rats. The paraventricular nuclei of the hypothalamus and hippocampus are believed to play a role in the central regulation of erectile function. Methods Four groups of 5 male Sprague-Dawley rats each were anesthetized and placed in a stereotaxic apparatus after carotid artery catheterization for measurement of arterial pressure and insertion of a 25-gauge needle in the corpus cavernosum for measurement of intracavernous pressure (ICP). The rats underwent hippocampal injections of saline (1 μL), NMDA (10 nmol/L), AMPA (10 nmol/L), or ACPD (10 nmol/L) followed by perfusion with saline and 10% formalin solutions. Brain slices 24 μm thick were mounted and stained with cresyl violet to identify the drug injection sites. Results Hippocampal injection of glutamate receptor subtype agonists produced multiple episodes of ICP elevation. NMDA injection was associated with a greater maximal ICP increase, duration of action, and mean onset of action latency than AMPA injection. ACPD injection had no statistically significant impact on ICP or arterial pressure changes. Histologic evaluation confirmed the injected sites were the CA3 fields of the hippocampus. Conclusions Our results suggest hippocampal glutamate receptors may be involved in initiation of penile erection. Ionotropic receptors appear to play a significant role in these regulatory mechanisms. NMDA receptors appear to be more potent than AMPA receptors, which appear to mediate fast excitatory synaptic transmission.

Effects of icariin on intracavernosal pressure and systematic arterial blood pressure of rat

To realize the effect of icariin on erectile function of penis. After the cavernous nerve (CN) of rat was isolated unilaterally, the corpora cavernosa (CC) and right carotid artery were exposed. A 26G needle catheter was inserted into the right CC to monitor the intracavernous pressure (ICP), and another 26G needle catheter was inserted into the left CC for drug administration. Another catheter was placed into the carotid artery to monitor mean systematic arterial blood press (MBp). Icariin of different concentrations was administrated intracavernosally, and the ICP and MBp were recorded during electric stimulation on CN. Sildenafil and papaveine were used as controls. The effects of nitric oxide syntheses (NOS) inhibitor N(omega)-nitro-L-arginine (LNNA), and soluble guanylate cyclase inhibitor H-[1,2,4] oxadiazolo [4,3,-a] quinoxalin-1-one (ODQ) on icariin (10(-4)mol/L) induced ICP changes were investigated also. Icariin, sidenafil and papaverine increased the ICP in a dose-depended manner (P < 0.01). Icariin and sildenafil did not influence the MBp (P > 0.05), however, papaverine significant influenced MBp (P < 0.01). EC(50) of Icariin, sildenafil and papaveine on ICP/MBp were 2.23 micro mol/L, 0.24 micro mol/L and 9.73 micro mol/L respectively. ODQ and LNNA significantly decreased ICP induced by icariin (10(-4)mol/L). Icariin increases ICP without influence on MBp and such effect is inhibited by LNNA and ODQ significantly. Icariin regulates the activity of NO-cGMP signal pathway on CC to enhance erectile function by oral therapy.

Intraoperative electrical stimulation of cavernous nerves with monitoring of intracorporeal pressure to confirm nerve sparing during radical prostatectomy: Early clinical results.

We performed intraoperative cavernous nerve stimulation with an intracavernous pressure (ICP) monitoring system to confirm nerve sparing during radical pelvic surgery and assessed the results. Nineteen cases of radical prostatectomy and three of radical cystoprostatectomy were examined. Electrical stimulation of the site where the neurovascular bundle (NVB) was determined to run was performed and changes in ICP were measured before and after prostate removal. Of the 22 patients, bilateral NVBs were preserved in six patients while unilateral NVB was preserved in 16. Before dissection, all NVBs examined exhibited positive responses (ICP changes of>5 mmHg) to nerve stimulation. After removal of the prostate, positive responses were observed in 22 (79%) of 28 macroanatomically preserved NVBs. Of 16 sides on which the NVB was not preserved, there were positive responses in five (31%). In these patients, some nerve fibers were macroscopically observed lateral to the original site of NVB. Finally, bilateral or unilateral nerve sparing was confirmed electrophysiologically in 20 (91%) of the 22 patients. Intraoperative stimulation of the NVB while monitoring ICP changes is a simple and reliable method of accurately evaluating the preservation of cavernous nerves. This system may provide further insight into the mechanism of postoperative erectile dysfunction.

Effect of apomorphine on intracavernous pressure and blood pressure in conscious, spinalized rats.

Apomorphine, given subcutaneously (s.c.), induces erection and bladder overactivity in rats through stimulation of dopamine (D1- and D2-like) receptors in the central nervous system. In paraplegic patients, apomorphine was reported to cause bladder overactivity. This suggests that apomorphine may have a spinal site of action also for stimulation of erection. The present study was initiated to evaluate the effect of apomorphine on erectile function in spinalized rats. Apomorphine (100 microg/kg, s.c.) was given to awake, unrestrained male Sprague-Dawley rats (300 g) with or without spinal cord injury, made at the Th 8 level 2 weeks before the experiment. Intracavernous pressure changes from baseline were evaluated as time to first response to apomorphine (TFR; sec), number of phasic pressure changes in the first 30 min (PP30), duration (D; sec) of the phasic pressure changes, the amount of increase in tonic peak pressure (TPP; cmH2O), and burst peak pressure (BPP; cmH2O). Blood pressure (cmH2O) was recorded via an intra-arterial catheter. Apomorphine, 100 microg/kg, caused no significant differences in TFR (217.8 vs 271.2), PP30 (6.4 vs 6.5), D (38.9 vs 37.6.), TPP (51.0 vs 54.0) and BPP (128.9 vs 160.4) between normal (n=8) and spinalized rats (n=6). However, blood pressure decreased significantly more in spinalized than in normal animals (17.7 vs 43.3; P<0.05). The results suggest that both in normal rats, and in rats with spinal cord injury, apomorphine given s.c., can produce erection. This finding supports the use of apomorphine for treatment of erectile dysfunction in paraplegia patients. However, due consideration should be given to possible decreases in blood pressure.

A simple and reliable monitoring system to confirm the preservation of the cavernous nerves.

It is important to establish a procedure with which to confirm the preservation of the cavernous nerves during nerve-sparing radical surgery. For this purpose, we examined changes in intracavernous pressure (ICP) following electrical stimulation of the neurovascular bundle (NVB) with respect to the continuity of the cavernous nerves. Six cases of radical prostatectomy and eight cases of radical cystoprostatectomy were examined. In all cases, prior to prostate removal, electrical stimulation of the site where the NVB was determined to run was performed and the changes in ICP measured. In eight cases, ICP changes were also measured following prostate removal. Prior to prostate removal, ICP changes could be measured in all 28 sides of 14 cases. These changes were classified into two patterns: stimulation-related increases of convex waveform (t1) were observed in 24 sides (85.7%); and waveforms with reversed type (t2), which was thought to be an incomplete type t1, were observed in four sides (14.3%). There were no ICP changes following non-sparing or incomplete sparing of NVB macroanatomically. Of five sides where the NVB was supposedly completely preserved macroanatomically, ICP changes consisted of type t1 on three sides, t2 on one side and type t2 or no change on a single side. All measurements were obtained within 10 min. Neither electrical stimulation nor measurement of ICP caused any adverse effects. Intraoperative stimulation of the NVB while monitoring ICP changes provides a simple and reliable method of accurately evaluating the preservation of the cavernous nerves.

Differential ICP responses elicited by electrical stimulation of medial preoptic area.

Recent findings indicate a complex role for the medial preoptic area (MPOA) in modulating penile erection. To further investigate this important area we measured changes in intracavernous pressure (ICP) elicited by electrical stimulation of the MPOA and evaluated the contribution of the cavernous nerve to the ICP responses after bilateral transection of the cavernous nerve (CN). In all experiments electrical stimulation was performed unilaterally in anesthetized male rats. Two distinct patterns of ICP response were seen after electrical stimulation of the MPOA: 1) increases in ICP during electrical stimulation (pattern 1, n = 10 rats) and 2) increases in ICP after electrical stimulation was terminated (pattern 2, n = 10 rats). For pattern 1, increases in ICP during stimulation exhibited a stable plateau without contraction of striated penile muscles, and bilateral transection of the CN eliminated the ICP responses. For pattern 2, increases in ICP observed after stimulation were lower, more variable, and accompanied by significant amplitude variations ("peaks"), caused by contraction of striated penile muscles. Bilateral transection of the CN eliminated the pattern 2 ICP response but did not alter striated muscle contraction. Histological studies documented that pattern 1 and pattern 2 responses occurred via electrical stimulation of the anterior and posterior areas of the MPOA, respectively. Thus both responses appear to result from activation of the CN, but the pattern 2 response apparently involves contraction of the striated penile muscles as well.

Intracavernous pressure during erection in rats: an integrative approach based on telemetric recording.

To better understand the similarities and differences in the neural control of penile erection occurring in different contexts, we recorded intracavernous pressure (ICP) in conscious rats using a miniaturized telemetric device. ICP changes during reflexive, noncontact, and apomorphine-induced erections were characterized by a plateau increase surmounted by peaks. Plateaus were also elicited by cavernous nerve stimulation in anesthetized rats, suggesting that the cavernous nerve represents the final common proerectile autonomic pathway in these contexts and that it responds similarly to information originating in the periphery or in supraspinal nuclei. During reflexive, noncontact, and apomorphine-induced erections, activation of spinal autonomic nuclei, considered the spinal generators of erection, would take place first, representing a prerequisite for the occurrence of peaks. Suprasystolic peaks would result from the addition of pudendal motoneuron activity. In contrast, only peaks were recorded during copulation. In this context, the convergence of peripheral and supraspinal information apparently elicits the best temporal arrangement of autonomic and somatic outflows, reflecting a highly organized and integrated spinal activity.

Spinal Fos labeling and penile erection elicited by stimulation of dorsal nerve of the rat penis.

Penile afferents present in the dorsal nerve of the penis (DNP) convey sensory information from the penis to the spinal cord and represent the afferent limb of reflexive erections. Immunocytochemical staining of Fos was used to identify spinal neurons that receive excitatory inputs from the DNP in anesthetized rats. Intracavernous pressure (ICP) was recorded as an index of erection. Dissection as well as stimulation of the DNP elicited a comparable increase in Fos staining. Labeling was present in the dorsal horn, the dorsal gray commissure, and the sacral parasympathetic nucleus, supporting the hypothesis of direct or indirect afferent projection from the penis and penile sheath in these areas. No change in ICP was observed in these rats. Stimulation of the DNP elicited both increased Fos labeling and ICP after spinalization, demonstrating the presence of a supraspinal inhibitory control exerted on the polysynaptic intraspinal circuitry responsible for reflexive penile erection.

Could Standardized Cavernosometry be Helpful in Therapeutic Management of Veno-Occlusive Dysfunction?

Purpose Due to the lack of a gold standard for performing cavernosometry, we selected 30 patients with veno-occlusive dysfunction to evaluate the internal relationships of cavernosometric parameters and their reliability for therapeutic decisions. Materials and Methods Cavernosometry was performed after injection of 20 to 40 microgram of prostaglandin E1. Maintenance flow rates, intracavernous pressure decay following cessation of flow and intracavernous pressure changes after compression maneuvers were the main parameters considered. Results Cavernosometric results were standardized as grade 1--7 patients with maintenance flow rate less than 20 ml. per minute (mean 18 plus/minus 2.5) and intravernous pressure decay 27.5 plus/minus 15 percent, grade 2--11 with maintenance flow rates significantly lower (p less than 0.001) than grade 1 (mean 37 plus/minus 11 ml. per minute) and intracavernous pressure decay 33 plus/minus 20 percent, and grade 3--12 with only recorded induction flows greater than 70 ml. per minute and intracavernous pressure less than 50 mm. Hg. A strong statistical correlation (p less than 0.01) was noted between maintenance flow rate and percent of intracavernous pressure decays. Conclusions These parameters allowed us to choose different therapies, such as complex venous surgery, mixed pharmacotherapy or prosthetic implants. Good sexual function was restored in 85 percent of the cases. We can conclude that our model of standardized cavernosometry has made easier the therapeutic choices in patients who do not respond to intracavernous drugs.

Neural control of penile erection in the rat

The role of autonomic and somatic neural pathways involved in the control of penile erectile tissue was investigated in an in vivo rat model. Intracavernous pressure (ICP) changes were recorded during single or combined electrical stimulation of peripheral nerves in anesthetized rats. Stimulation of the pelvic and cavernous nerves elicited similar ICP increases. Ganglionic blockade abolished the response to pelvic nerve stimulation. Stimulation of the hypogastric nerve, the sensory or motor branches of the pudendal nerve, or the paravertebral sympathetic chain at L4-L5 by themselves did not produce any change in ICP. Stimulation of some of these nerves caused changes in ICP when combined with cavernous nerve stimulation. Stimulation of the paravertebral sympathetic chain reduced the ICP increase elicited by cavernous nerve stimulation. A decrease in ICP in response to cavernous nerve stimulation was also elicited by stimulation of the peripheral cut end of the sensory branch of the pudendal nerve or in paralyzed rats, the motor branch of the pudendal nerve. After sectioning the two branches of the pudendal nerve, stimulation of the sympathetic chain still reduced the ICP increase in response to cavernous nerve stimulation. Stimulation of the motor branch ofthe pudendal nerve during erection elicited by cavernous nerve stimulation was responsible for an additional ICP increase, which reached suprasystolic values. The present study confirms a proerectile role for parasympathetic pathways. Sympathetic fibers conveyed in both branches of the pudendal nerve exert an antierectile role in the rat. We idenfied an antierectile sympathetic outflow, originating in the caudal sympathetic chain, the anatomical arrangement of which remains unknown. In this model, penile erection appeared to be dependent on the recruitment of sacral parasympathetic outflow. Additional recruitment of efferent somatic fibers present in the motor branch of the pudendal nerve could participate in more rigid erection. This study provides new information about the organization of the pathways through which the rat penis is innervated, and would be of interest to investigators in the field of male sexual function.

Intracavernous pressure changes during reflexive penile erections in the rat

Reflexogenic penile erections have been previously described in the rat. However, exact involvement of the corpus cavernosum in reflex responses is indefinite. We report changes in intracavernous pressure (ICP) recorded in 10 awake rats by means of a telemetric device. The ICP changes and penile reflex esponses (lengthening of the penile body, glans erection, cup, and flip) were recorded during ex copula tests. Each type of penile response was characterized by a specific ICP variation. Mean maximal ICP increase during lengthening of the penile body was 58.6 mmHg, during glans erection 67.3 mmHg, during cups 99.1 mmHg, and 215.2 mmHg during flips. ICP increases to 35.1 mmHg immediately preceding each cluster of penile responses. This study provides quantitative data on the involvement of the corpus cavernosum during reflexive erections. Tumescence of the corpus cavernosum was present during glans erection and suprasystolic ICP peaks occurred during flips. ICP measurements during reflexive erections should bring new insights into the analysis of their physiological mediation.

Telemetric Monitoring of Intracavernous Pressure in Freely Moving Rats During Copulation

Changes in intracavernous pressure (ICP) were recorded in freely moving rats by means of a catheter implanted in the corpus cavernosum and connected to a pressure transducer located subcutaneously. Intracavernous pressure changes and copulatory events (mounts, intromissions and ejaculations) were recorded during several overnight testing sessions with 12 rats in the presence of receptive females. Video recordings of sexual behavior in the implanted and nonimplanted rats revealed that the ICP device did not impair copulatory behavior. Comparison between copulatory behavior and ICP changes revealed that ICP profiles could identify the number of intromissions and ejaculations as well as the timing of these events. The results showed that during mounts, intromissions and ejaculations, ICP increases were 36.9mm. Hg, 62mm. Hg and 106.3mm. Hg in 4 rats. The increases in ICP during mounts and intromissions appeared higher in sexually experienced as compared with sexually naive rats. These results demonstrate the reliability of the telemetric measurement of ICP in freely moving rats under natural physiological conditions. The model provides quantitative data for research on the neurophysiology of penile erection and evaluation of oral treatments for impotence.

Penile Detumescence: Characterization of Three Phases

In 22 dogs in which erection was induced by cavernous nerve stimulation, we analyzed the intracavernous pressure changes during detumescence without and with acute clamping of the aorta or electrostimulation of the lumbar sympathetic chains. Additionally, the degree of venous outflow obstruction was assessed by saline perfusion of the cavernous body during aortic occlusion.Detumescence had three distinct phases: an initial phase exhibiting a small pressure increase; a second phase showing a slow pressure decrease; and a third phase in which a fast decrease occurred. The first phase was abolished by aortic clamping, whereas the other phases were not significantly affected. Sympathetic stimulation abolished or prevented the second phase. Perfusion of the cavernous body during the second phase resulted in a pressure rise to off-scale values; however, when initiated during the terminal phase or in the nonstimulated penis, the pressure increase was slight.Our study indicates that the arterial flow rate influences the duration of the first phase of detumescence and that venous drainage is completely restored in the third phase. Furthermore, sympathetic stimulation causes an almost immediate full restoration of venous drainage, as cavernous perfusion initiated with an intracavernous pressure about twice as high as without sympathetic stimulation failed to increase pressure to off-scale values.

Reflex Contractions of the Ischiocavernosus Muscles Following Electrical and Pressure Stimulations

In a previous study, we have demonstrated that voluntary muscular contractions of the ischiocavernosus muscles (IC) correlate with changes in intracavernous pressure and, therefore, with penile rigidity. The purpose of our current research project was to verify whether reflex contractions of the IC muscles exist and under what conditions. Our results confirm that reflex contractions occur following electrical or pressure stimulations. Following electrical stimulation, the mean latency of the reflex contractions was 67.5 ms for the IC muscles and 34.9 ms for the bulbocavernosus muscles (BC). Following pressure stimulation, the pressure threshold necessary to elicit contractions of the IC muscles varied between 18.2mm. Hg and 34.8mm. Hg. We also observed that pressure variation (increase and decrease) rather than a relatively constant pressure is necessary to produce this reflex response. We interpret these results to suggest that pressure stimulations on the glans penis during coitus contribute to the erectile process and, specifically, to the increase in intracavernous pressure. These findings suggest the possibility of a physiotherapeutic management for patients with penile rigidity problems.

Relationship Between Perineal Muscle Contractions, Penile Tumescence, and Penile Rigidity During Nocturnal Erections

The mechanism of penile erection and erectile dysfunction is still unclear and widely debated. The role of the perineal muscles in the erectile process, especially in changes in intracavernous pressure, is increasingly being studied on the hypothesis that perineal muscular contractions are essential to full penile rigidity. In a previous investigation we studied the correlation between voluntary perineal muscle contractions and intracavernous pressure during artificially induced erections. The purpose of the current study was to examine whether under normal conditions of nocturnal erection a similar relationship exists between the electromyographic activities of perineal muscles and changes in penile rigidity. Nocturnal penile recordings were made of seven volunteers with psychogenic erectile dysfunctions. During nocturnal erections simultaneous computerized recordings were made of penile tumescence, penile rigidity, and electromyographic activities of perineal muscles. The peaks for the three variables were reached simultaneously. The results of this study suggest the existence of two different physiologic phases: a vascular phase and a muscular phase. Furthermore, in cases of dysfunctions, specific diagnostic assessment and therapeutic management will be required for both penile tumescence and penile rigidity.

Correlation Between Intracavernous Pressure and Contraction of the Ischiocavernosus Muscle in Man

An artificial erection was induced in nine patients consulting for erectile dysfunction. Changes in the intracavernous pressure (ICP) and in the integrated EMG of the ischiocavernosus muscle were recorded during voluntary muscular contractions. During such contractions elevations in ICP, varying between 100 and 525mm. Hg, were recorded. Changes in ICP were always in phase with changes in the integrated electromyogram (EMG) of the ischiocavernosus muscle, and correlations between the duration of changes showed an almost perfect linear relationship between both physiological events. Correlations between maximum changes in ICP and integrated EMG generally showed a positive relationship between both measures. Results are interpreted to suggest involvement of the ischiocavernosus muscle in the process of penile rigidity.