-
The Urologic Clinics of North America Nov 2021The science of penile erection, including recent advances in its molecular physiology and neuroanatomic pathways, is described. The pathophysiology of erectile... (Review)
Review
The science of penile erection, including recent advances in its molecular physiology and neuroanatomic pathways, is described. The pathophysiology of erectile dysfunction is presented, acknowledging associated disease states, and accordingly follows a practical classification scheme: vasculogenic, neurogenic, endocrine, and psychogenic.
Topics: Erectile Dysfunction; Humans; Male; Penile Erection
PubMed: 34602172
DOI: 10.1016/j.ucl.2021.06.009 -
International Journal of Impotence... Dec 2004Penile erection is a complex neurovascular event. The neuronal system involved is often divided into a spinal (generator) and supraspinal (controller) network. Little is... (Review)
Review
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.
Topics: Animals; Electric Stimulation; Humans; Male; Penile Erection; Thalamus
PubMed: 15085172
DOI: 10.1038/sj.ijir.3901233 -
Pharmacological Reviews Sep 2001Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, but also by visual, olfactory, and imaginary stimuli. The reflex involves... (Review)
Review
Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, but also by visual, olfactory, and imaginary stimuli. The reflex involves both autonomic and somatic efferents and is modulated by supraspinal influences. Several central transmitters involved in the erectile control have been identified. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropic/alpha-melanocyte-stimulating hormone, seem to have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. Peripherally, the balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa and determines the functional state of the penis. Noradrenaline contracts both corpus cavernosum and penile vessels via stimulation of alpha(1)-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and corpus cavernosum. The role of other mediators released from nerves or endothelium has not been definitely established. Erectile dysfunction (ED) may be due to inability of penile smooth muscles to relax. This inability can have multiple causes. However, patients with ED respond well to the pharmacological treatments that are currently available. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including prostaglandin E(1), NO donors, phosphodiesterase inhibitors, and alpha-adrenoceptor antagonists. Dopamine receptors in central nervous centers participating in the initiation of erection have been targeted for the treatment of ED. Apomorphine, administered sublingually, is the first of such drugs.
Topics: Animals; Erectile Dysfunction; Humans; Male; Muscle, Smooth; Penile Erection; Rats; Risk Factors
PubMed: 11546836
DOI: No ID Found -
Neuromodulation : Journal of the... Dec 2023This study aimed at determining whether stimulation of sacral spinal roots can induce penile erection in cats.
OBJECTIVE
This study aimed at determining whether stimulation of sacral spinal roots can induce penile erection in cats.
MATERIALS AND METHODS
In anesthetized cats, a 20-gauge catheter was inserted into the corpus cavernosum to measure the penile pressure. Stimulus pulses (5-80 Hz, 0.2 ms) were applied through bipolar hook electrodes to sacral ventral roots alone or to combined ventral and dorsal roots of a single S1-S3 segment to induce penile pressure increases and penile erection.
RESULTS
Stimulation of the S1 or S2 ventral root at 30 to 40 Hz induced observable penile erection with rigidity and the largest increase (169 ± 11 cmHO) in penile pressure. Continuous stimulation (10 minutes) of afferent and efferent axons by simultaneous stimulation of the S1 or S2 dorsal and ventral roots at 30 Hz also produced a large increase (190 ± 8 cmHO) in penile pressure that was sustainable during the entire stimulation period. After a complete spinal cord transection at the T9-T10 level, simultaneous stimulation of the S1 or S2 dorsal and ventral roots induced large (186 ± 9 cmHO) and sustainable increases in penile pressure.
CONCLUSION
This study indicates the possibility to develop a novel neuromodulation device to restore penile erection after spinal cord injury using a minimally invasive surgical approach to insert a lead electrode through the sacral foramen to stimulate a sacral spinal root.
Topics: Male; Cats; Animals; Penile Erection; Spinal Nerve Roots; Spinal Cord Injuries; Electric Stimulation
PubMed: 35941016
DOI: 10.1016/j.neurom.2022.06.003 -
Fertility and Sterility Jan 2020This literature review presents two unusual and mystifying disorders of penile erection: painful nocturnal erections, alternatively termed sleep-related painful...
This literature review presents two unusual and mystifying disorders of penile erection: painful nocturnal erections, alternatively termed sleep-related painful erections, and idiopathic stuttering priapism, a variant of recurrent ischemic priapism in which no cause is discernible. The disorders are closely related although they are distinct clinically and pathologically. The main subject areas of discussion are recognition, clinical evaluation and management although current concepts surrounding their causes and mechanisms are also addressed. It is acknowledged that despite the perceived rarities of these disorders they are impactful in terms of their disease profiles and consequences. Future advances in their management will require continued development of evidence-based treatments.
Topics: Humans; Male; Penile Erection; Priapism; REM Sleep Parasomnias; Rare Diseases
PubMed: 32033724
DOI: 10.1016/j.fertnstert.2019.11.013 -
The Urologic Clinics of North America Nov 1995Filling of the sinusoidal spaces with blood due to smooth muscle relaxation results from parasympathetic neural pathway activation and probably simultaneous inhibition... (Review)
Review
Filling of the sinusoidal spaces with blood due to smooth muscle relaxation results from parasympathetic neural pathway activation and probably simultaneous inhibition of sympathetic outflow. The final common pathway for proerectile fibers is represented by the cavernous nerves and fibers controlling detumescence and flaccidity originating in the sympathetic chain. The hypogastric nerve could represent an accessory proerectile pathway unmasked by a sacral spinal cord lesion. Nitric oxide, which can be colocalized with VIP and acetylcholine, is the main proerectile neurotransmitter and noradrenaline is considered to be the major antierectile agent. Reflexive erection elicited by recruitment of penile afferents involves both autonomic and somatic efferents. This reflex is mediated at the spinal cord level and modulated by supraspinal influences. Serotonergic pathways originating in the raphe nuclei may mediate inhibitory control on reflexive erections. The hypothalamic medial preoptic area is an important integrating center and dopamine may regulate penile erection at this level. Neuroendocrine regulation may vary depending on the context in which erection occurs, for example, coitus, in response to extrinsic or psychogenic stimuli, and rapid eye movement sleep.
Topics: Animals; Brain; Humans; Male; Neurotransmitter Agents; Penile Erection; Penis; Peripheral Nervous System; Spinal Cord
PubMed: 7483126
DOI: No ID Found -
International Journal of Impotence... May 1998Recent work on the central nervous system control of penile erection is reviewed. Penile erection is completely dependent on commands from the central nervous system.... (Review)
Review
Recent work on the central nervous system control of penile erection is reviewed. Penile erection is completely dependent on commands from the central nervous system. Clinical experience and experimental studies clearly demonstrate that systems within the spinal cord are fully capable of generating penile erection. Spinal erectile centers may be activated by genital afferents or by descending commands from higher CNS sites. An important inhibitory pathway from the nucleus paragigantocellularis has been demonstrated. The inhibition of spinal sexual responses is mediated by the neurotransmitter serotonin. The medial preoptic region has been demonstrated to be crucially involved in sexual behavior. It is likely that it participates in the integration of hormonal and sensory cues necessary for sexual behavior. The medial amygdala and paraventricular nucleus of the hypothalamus have also been shown to play key roles. Future CNS research may lead to new therapeutic approaches as well as the avoidance of untoward sexual side effects from centrally acting drugs.
Topics: Brain; Humans; Male; Penile Erection; Penis; Sexual Behavior; Spinal Cord
PubMed: 9669218
DOI: No ID Found -
Pharmacological Reviews Dec 2011Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual,... (Review)
Review
Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.
Topics: Alprostadil; Erectile Dysfunction; Humans; Male; Nervous System Physiological Phenomena; Neurotransmitter Agents; Penile Erection; Phosphodiesterase Inhibitors
PubMed: 21880989
DOI: 10.1124/pr.111.004515 -
Progress in Neurobiology 1995erection is regulated by several neurotransmitters and neuropeptides at penile tissue and central nervous system levels. At penile level, the key event is the relaxation... (Review)
Review
erection is regulated by several neurotransmitters and neuropeptides at penile tissue and central nervous system levels. At penile level, the key event is the relaxation of corpora cavernosa smooth muscles. Here, three kinds of neural autonomic control have been characterized in detail. one adrenergic stimulatory, that under normal conditions maintains the corpora cavernosa contracted (that is a flaccid penis), a second cholinergic inhibitory that is believed to cooperate with a third, nonadrenergic-noncholinergic control also inhibitory, possibly mediated by nitric oxide (NO), to reduce the adrenergic tone favouring the relaxation of corpora cavernosa, as during a sexual stimulus. However, the complex interactions between these neurotransmitters that determine the final condition of the corpora cavernosa, e.g. the presence or the absence of penile erection, are still a matter of controversy. This is further complicated by the presence of several neuropeptides in nervous penile vascular and smooth muscle tissues such as vasoactive intestinal polypeptide, peptide histidine- isoleucine, peptide histidine-methionine, neuropeptide Y and endothelins,that often exert very potent (relaxant or contractant) effects in penile tissues. Also at the central level, several neurotransmitters and neuropeptides that influence penile erection have been identified. Among neurotransmitters, the most studied are dopamine (DA), serotonin (SHT), acetylcholine (ACh), glutamic acid and NO. DA, ACh. glutamic acid and NO seem to have a facilitatory role, while 5HT may be either facilitatory or inhibitory, depending on the receptor subtype involved. Among neuropeptides, the best known are oxytocin, adrenocorticotropin (ACTH)-cc-melanocyte stimulating hormone (r-MSH)-related peptides and opioid peptides. Interestingly DA, glutamic acid and NO seem to facilitate while opioid peptides inhibit penile erection by increasing and decreasing, respectively, central oxytocinergic transmission by acting in the paraventricular nucleus of the hypothalamus. ACTH-MSH peptides also facilitate penile erection, although with a mechanism(s) different from those recalled above. Despite some recent progress, more has still to be done to clarify the role played by neurotransmitters and neuropeptides at peripheral and central levels in the control of this primary sexual function.
Topics: Humans; Male; Nervous System Physiological Phenomena; Neuropeptides; Neurotransmitter Agents; Penile Erection; Penis
PubMed: 26445737
DOI: No ID Found -
The American Journal of Cardiology Jul 2000Erection is initiated through the parasympathetic nervous system, activation of which overrides the sympathetic tone that maintains the penis in a nonerectile (flaccid)... (Review)
Review
Erection is initiated through the parasympathetic nervous system, activation of which overrides the sympathetic tone that maintains the penis in a nonerectile (flaccid) state. This state is maintained mainly through the release of norepinephrine from penile adrenergic nerves. Norepinephrine contracts the vasculature and cavernosal smooth muscle. Arousal/erection is associated with a decrease of norepinephrine release in the penis, with a release of nitric oxide, and with a reduction in penile smooth muscle tone. It is also associated with minor cardiovascular changes. Heart rate increases by 4-8 beats per minute, on average, and the rate-pressure product and oxygen consumption increase by approximately 25%. There may be no changes in systemic venous norepinephrine concentrations; systemic venous epinephrine concentrations increase by about 60%. Drugs initiating or enhancing erection act by inhibiting norepinephrine-induced contraction (e.g., phentolamine) or by enhancing or directly inducing relaxation of the corpora cavernosa and the penile vasculature (e.g., sildenafil). Despite potentially negative hemodynamic actions when given parenterally, oral phentolamine-in doses required for enhancing erection-appears to produce few cardiovascular adverse effects. The hemodynamic effects of sildenafil are small, even in patients with coronary artery disease. However, the effects of the drug on human myocardium have not been conclusively established, and should be further investigated. As judged by available information, the cardiac risk associated with erection, with or without enhancement of drugs currently used for treatment of erectile dysfunction, is low.
Topics: Adrenergic alpha-Antagonists; Animals; Coronary Disease; Erectile Dysfunction; Heart; Humans; Male; Norepinephrine; Penile Erection; Phentolamine; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones
PubMed: 10899273
DOI: 10.1016/s0002-9149(00)00887-0