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PubMed2000

Central noradrenergic control of penile erection.

Penile erection is completely dependent on commands from the central nervous system. Spinal centers controlling penile erection are located in the thoracolumbar and lumbosacral spinal cord. These centers are activated by information from the periphery and supraspinal nuclei so as to elicit penile erection in a variety of physiological contexts. A small number of nuclei including the locus coeruleus located in the pons sends noradrenergic fibers to the forebrain and spinal cord, including those areas controlling penile erection. Recent morphological techniques such as in situ hybridization and autoradiography using radioligand binding permit investigation of the brain and spinal pathways utilizing alpha adrenoceptor subtypes. Furthermore, pharmacological experiments suggest a modulatory role for noradrenaline in the control of penile erection either in the brain or in the spinal cord. The most robust evidence is that central inhibition of alpha-2 adrenoceptors facilitates sexual function. Taken together, the data propose new directions in the physiological exploration of penile erection and the therapeutic approach of erectile dysfunction.

Animals↗

PubMed2000

Central noradrenergic control of penile erection.

Journal Article↗

PubMed2004

Thalamus and penile erection.

Penile erection is a complex neurovascular event. The neuronal system involved is often divided into a spinal (generator) and supraspinal (controller) network. Little is known about the supraspinal control. The recent finding of changes in penile erection following deep brain stimulation of the thalamus in two patients has raised the question as to what extent the thalamus is involved in erectile function. The thalamus has generally been regarded as a group of relay nuclei that served as a 'gate' for sexual information from the spinal cord towards higher centres. Recent evidence, however, suggests a more integrated regulatory function. Our review of the literature from 1960 until 2003 revealed 13 reports describing original data (preclinical and clinical). Various thalamic regions, varying from the midline thalamus to the posterior thalamus, have been reported to be activated during erection. The majority of the reports, however, showed that mainly the mediodorsal (MD) nucleus and the centromedian-parafascicular nucleus (Cm-Pf complex) are involved in penile erection. MD is the second largest nuclear aggregation located within the medial part of the thalamus. Anatomically, the MD is closely related to the Cm-Pf complex. The Cm-Pf complex is one of the most important relay stations in which the anterolateral spinothalamic pathway is further processed. This pathway is thought to transmit peripheral sexual sensations. On the whole, the present data on the role of the thalamus in erection are far from complete and future experiments are required to delineate its involvement.

Animals↗

PubMed2000

Central neural regulation of penile erection.

Penile erection is caused by a change of the activity of efferent autonomic pathways to the erectile tissues and of somatic pathways to the perineal striated muscles. The spinal cord contains the cell bodies of autonomic and somatic motoneurons that innervate the peripheral targets. The sympathetic outflow is mainly antierectile, the sacral parasympathetic outflow is proerectile, and the pudendal outflow, through contraction of the perineal striated muscles, enhances an erection already present. The shift from flaccidity to erection suggests relations among these neuronal populations in response to a variety of informations. Spinal neurons controlling erection are activated by information from peripheral and supraspinal origin. Both peripheral and supraspinal information is capable of eliciting erection, or modulating or inhibiting an erection already present. One can hypothesize a spinal network consisting of primary afferents from the genitals, spinal interneurons and sympathetic, parasympathetic and somatic nuclei. This system is capable of integrating information from the periphery and eliciting reflexive erections. The same spinal network, eventually including different populations of spinal interneurons, would be the recipient of supraspinal information. Premotor neurons that project directly onto spinal sympathetic, parasympathetic or somatic motoneurons, are present in the medulla, pons and diencephalon. Several of these premotor neurons may in turn be activated by sensory information from the genitals. Aminergic and peptidergic descending pathways in the vicinity of spinal neurons, exert complex effects on the spinal network that control penile erection. This is caused by the potential interaction of a great variety of receptors and receptor subtypes present in the spinal cord. Brainstem and hypothalamic nuclei (among the latter, the paraventricular nucleus and the medial preoptic area) may not necessarily reach spinal neurons directly. However they are prone to regulate penile erection in more integrated and coordinated responses of the body, such as those occurring during sexual behavior. Finally, the central and spinal role of regulatory peptides (oxytocin, melanocortins, endorphins) has only recently been elucidated.

Animals↗

PubMed2001

The pathophysiological role of prostaglandins in penile erection.

Penile erection is a complex haemodynamic event and relaxation of the vascular smooth muscle of the penis is fundamental to this process. This is primarily mediated by nitric oxide (NO) produced from non-adrenergic non-cholinergic (NANC) nerves and the endothelium surrounding the corporal sinusoids. However, corporal tissue has been shown to produce a number of other vasoactive factors, including prostaglandins (PGs), which appear to not only have diverse physiological effects, but are also able to modulate the effects of other neurotransmitters, including NO.

Collagen↗

PubMed1996

[Physiology of penile erection].

Penile smooth muscle tone (arterial and trabecular) regulates the hemodynamic phenomena of erection. Nitric oxide is perhaps the most important mediator of penile smooth muscle relaxation and, consequently, of erection. Detumescence of the erect penis following contraction of the smooth muscles is mediated by the adrenergic nerves, which release noradrenalin that acts on alpha 1 adrenergic receptors. Other substances such as endothelin and prostanoids appear to be implicated in maintaining penile relaxation.

Humans↗

PubMed1987

[The physiology of penile erection. I. Hemodynamics of penile erection].

Arterial and venous flow and pressure studies of the corpora cavernosa were performed to elucidate the hemodynamics of canine penile erection. Being able to induce erection by electrical stimulation we were able to study the functionally relevant parameters at different stages of penile erection. From our results we conclude that penile erection can be subdivided in 5 phases: (1) latent-, (2) tumescence-, (3) erection-, (4) rigidity- and (5) detumescence phase. Furthermore, a differentiation of these subdivisions is made by observing at the mechanism of the 5 different stages: phase 1 to 4 is an active phenomenon, the detumescence phase is passive only.

Animals↗

PubMed1987

[The physiology of penile erection. II. Neurophysiology of penile erection].

Selective cavernous and pudendal nerve stimulation enabled us to study the neurophysiologic-/neurovascular mechanisms of penile erection in 6 monkeys. Corporeal pressure recordings during different neurostimulation patterns demonstrated that tumescence and erection are controlled by the autonomic nervous system (Nn. cavernosi) and has to be understood as the vascular phase of erection. However, rigidity is related to the muscle tone of the striated bulbospongiosus and ischiocavernosus muscles which are innervated by somatomotoric fibers of the pudendal nerve. This mechanism is defined as the muscular phase of penile erection.

Animals↗

PubMed2002

Akt-dependent phosphorylation of endothelial nitric-oxide synthase mediates penile erection.

In the penis, nitric oxide (NO) can be formed by both neuronal NO synthase and endothelial NOS (eNOS). eNOS is activated by viscous drag/shear stress in blood vessels to produce NO continuously, a process mediated by the phosphatidylinositol 3-kinase (PI3kinase)/Akt pathway. Here we show that PI3-kinase/Akt physiologically mediates erection. Both electrical stimulation of the cavernous nerve and direct intracavernosal injection of the vasorelaxant drug papaverine cause rapid increases in phosphorylated (activated) Akt and eNOS. Phosphorylation is diminished by wortmannin and LY294002, inhibitors of PI3-kinase, the upstream activator of Akt. The two drugs also reduce erection. Penile erection elicited by papaverine is reduced profoundly in mice with targeted deletion of eNOS. Our findings support a model in which rapid, brief activation of neuronal NOS initiates the erectile process, whereas PI3-kinase/Akt-dependent phosphorylation and activation of eNOS leads to sustained NO production and maximal erection.

Androstadienes↗

PubMed2000

Intraoperative penile erection.

OBJECTIVE: Penile erection following epidural anesthesia is an infrequent occurrence of unclear etioogy. It is very troublesome to perform the procedure during penile erection and attempting it leads to various complications. Three such cases are reported herein. The literature on the pathophysiology and management of intraoperative penile erection is discussed. METHODS: Eighteen hundred patients who received epidural anesthesia for various transurethral procedures like cystoscopy, ureterorenoscopy, transurethral resection of prostate and bladder tumors form the clinical material. RESULTS: Out of 1800 cases, we have encountered penile erection only in three cases. Two cases were managed with local application of cold saline and cold sponging followed by terbutaline. The third case could be managed with local application of cold saline and cold sponging of scrotum and penis. Afterwards the procedure could be performed safely. CONCLUSION: The pathophysiology and management of intraoperative penile erection is poorly understood. With the onset of erection during an operative procedure, the anesthesiologist must quickly initiate the therapy, as duration of erection is the critical factor in the detumescence of the penis.

Adult↗

PubMed2001

EP 91073 prevents EP 80661-induced penile erection: new evidence for the existence of specific EP peptide receptors mediating penile erection.

The effect of EP 91073, EP 51389, EP 70555 and EP 51216, peptide analogues of the growth hormone releasing peptide hexarelin, on penile erection induced by EP 80661 or EP 60761 injected into the paraventricular nucleus of the hypothalamus, was studied in male rats. Of the above peptides only EP 91073 (0.2-1 microg) was found capable of reducing penile erection induced by EP 80661 or EP 60761, when given into the paraventricular nucleus. Despite its ability to prevent EP peptide-induced penile erection, EP 91073 (1 microg) was unable to prevent penile erection induced by the dopamine receptor agonist apomorphine (50 ng), oxytocin (30 ng) and N-methyl-D-aspartic acid (50 ng), when given into the paraventricular nucleus 10 min prior to the above substances. The EP 91073-induced prevention of penile erection occurred with a reduction in the increase in nitric oxide production that occurs in the paraventricular nucleus concomitant to penile erection induced by EP 80661 and EP 60761, as measured by intracerebral vertical microdialysis. The present results are in line with the hypothesis that EP 80661 and EP 60761 induce penile erection by activating specific receptors in the paraventricular nucleus, located possibly in oxytocinergic neurons mediating penile erection, and show that EP 91073 acts as an antagonist of these EP peptide receptors mediating penile erection.

Animals↗

PubMed1989

Erectile dysfunction in hypertensive men: sleep-related erections, penile blood flow and musculovascular events.

To explore how hypertension affects penile erection, we studied erectile hemodynamics during nocturnal penile tumescence in 3 groups of middle-aged men: hypertensive patients with and without erectile dysfunction, and normotensive controls without erectile problems. The hypertensive patients were not taking antihypertensive medication. Evaluations included standard monitoring of penile circumference change as well as noninvasive monitoring of penile segmental pulsatile blood flow and activity in the bulbocavernosus-ischiocavernosus muscles. Variables differed in how they discriminated among groups. Median amplitude of penile blood flow during rapid eye movement sleep differed significantly among all 3 study groups: controls had the highest amplitudes, patients without erectile problems had lower values and patients with erectile complaints had the lowest values. By contrast, standard measures of nocturnal penile tumescence (that is based on penile circumference change during sleep) only distinguished the patients with erectile problems from the 2 other groups. Density of musculovascular event clusters during rapid eye movement sleep (nearly simultaneous muscle activity burst, blood flow burst and circumference pulsation) distinguished the 2 groups of hypertensive men from controls. The sensitivity of the blood flow measure to changes in the hypertensive men without erectile complaints may indicate that the measure can reveal subclinical signs of developing vasculogenic erectile dysfunction.

Hemodynamics↗

PubMed1988

Fundamentals and hemodynamics of penile erection.

Human penile erection is a complex phenomenon mediated through the coordinated interaction among the nervous, vascular, and musculosystems. For social and ethical reasons, the mechanism and hemodynamics of this essential human function remained speculative and controversial for many years. In the past decade, however, advances in technology, together with a marked increase in clinical and research activity, have resolved some of the controversy and have provided a better understanding of erectile physiology. In this essay, we will review traditional concepts, as well as the new and exciting findings from many different research centers, concerning the physiologic mechanisms of penile erection that involves the arterial, venous, and nervous systems.

Arteries↗

PubMed1994

Dorsal nerve block for management of intraoperative penile erection.

Intraoperative penile erection during general anesthesia can delay or prevent the completion of cystoscopic or penile surgical procedures. The dorsal penile nerve block is offered as a treatment for intraoperative erection. Advantages of this technique include less potential for cardiovascular complications and improved postoperative analgesia.

Adult↗

PubMed2003

Penile neuronal nitric oxide synthase and its regulatory proteins are present in hypothalamic and spinal cord regions involved in the control of penile erection.

Control of penile erection requires the coordination of the hypothalamus and the L6-S1 region of the spinal cord. Erection requires the activation of neuronal nitric oxide synthase (nNOS), which is tightly regulated. Because variants of nNOS (penile nNOS: PnNOS) and the N-methyl-D-aspartate receptor (truncated NMDAR subunit 1: NMDAR1-T) as well as protein inhibitor of NOS (PIN) have all been located in the pelvic ganglia and penile nerves, this work aims to determine whether these proteins are also present in the hypothalamus. It was found that PnNOS, the brain-type nNOS, and PIN, were expressed in the hypothalamus. In contrast, NMDAR1-T was expressed only in the penis, whereas the brain-type NMDAR1 was present in the brain and sacral spinal cord and not in the penis. PnNOS was found in the media preoptic area, posterior magnocellular, and the parvocellular regions of the paraventricular nucleus, supraoptic nucleus, septohypothalamic nucleus, medial septum, cortex, and in some of the nNOS staining neurons throughout the brain. It was absent in the organum vasculosum of the lamina terminalis. PIN staining was present in neurons of the medial preoptic area, paraventricular nucleus, medial septum, and cortex, but not in the supraoptic nucleus, septohypothalamic nucleus, or organum vasculosum of the lamina terminalis. Colocalization between PnNOS and PIN was found in the medial preoptic area, medial septum, and cortex, and less in the paraventricular nucleus. PnNOS and oxytocin were colocalized in the paraventricular nucleus and supraoptic nucleus. In hypothalamic extracts, recombinant PIN-GST protein bound to PnNOS in the extracts and partially inhibited NOS activity. These results indicate that both nNOS variants, and their respective regulatory proteins are present and colocalize in the hypothalamic and spinal cord regions involved in penile erection.

Animals↗

PubMed2001

Absence of penile erections during paradoxical sleep. Peculiar penile events during wakefulness and slow wave sleep in the armadillo.

The electroencephalogram (EEG) together with electromyogram (EMG) of the ischiocavernosus, bulbocavernosus and levator penis muscles were chronically monitored across behavioral states of the armadillo Chaetophractus villosus. This animal has a very long penis, which exhibits remarkable phenomena during wakefulness (W), slow wave sleep (SWS) and paradoxical sleep (PS). During W it remains retracted within a skin receptacle. During SWS penile protrusion can be observed together with very complex movements. Protrusion is a non erectile event during which the penis remains out of its receptacle but without rigidity. Penile erections are observed only during SWS. Contrasting with other mammals, no erections occur during PS. During this phase the penile muscles share the atonia of the body musculature characteristic of that phase. Some reflections on mechanisms of those penile events are presented.

Animals↗

PubMed1990

Intracavernosal metaraminol for treatment of intraoperative penile erection.

Four patients developed penile erection when regional anaesthesia was induced with spinal block. In another patient, penile erection developed during fentanyl-induced general anaesthesia. Injection of metaraminol into corpus cavernosum successfully achieved detumescence in all these patients. The dose of metaraminol ranged from 10 to 25 micrograms, much less than that required for the treatment of vasodilator-induced priapism. Intracavernosal injection of metaraminol is a simple, effective and safe method for immediate relief of intraoperative penile erection. It is most useful when urogenital operation would be delayed by penile tumescence.

Adult↗

PubMed2006

Penile erection during transurethral surgery.

Intraoperative penile erection during endoscopic surgery, although an infrequent occurrence, is a troublesome complication and a challenge to the urologist. It is difficult to perform the procedure during penile erection, because various complications may occur. The etiology is unclear, and a number of pharmacological remedies have been discussed in the literature. Herein, we describe the treatment and outcomes for 3 patients with intraoperative penile erection and provide a brief review of the associated literature. Intraoperative penile erection is a rare event during transurethral procedures, with a frequency of approximately 0.1% in our institution. To our knowledge, no generally accepted protocols for the prevention or treatment of this phenomenon have been reported in the literature. We recommend intracorporeal injection of 250 microg of phenylephrine: detumescence occurred rapidly in all patients after a single injection. The mode of administration is simple, and no complications have been reported.

Adult↗