Paravertebral Sympathetic Chain Research Articles

Dissection of the Sympathetic Nerves Around the Mesorectum at the Abdominopelvic Border.

Introduction Along the border between the abdominal cavity and pelvis are nervous structures that belong to the autonomous nervous system, which is delicate. These can be easily injured during regional surgical procedures such as the total mesorectal excision, where the preservation of the nervous structures should be one of the main objectives. In our study, we aimed to dissect all the sympathetic nerve formations listed at the abdominopelvic border and to present their formation, anatomical routes, and relations, as well as the surgical importance of their preservation. Method We performed anatomical dissections on eight 60- to 75-year-old cadavers (three male and five female) in the Dissection Laboratory of Carol Davila University of Medicine and Pharmacy, Bucharest, ROM. We sectioned each pelvis along the right pararectal line and exposed the hypogastric plexuses and their branches, following their pathways toward the pelvic viscera. Results We highlight the main nervous structures in the pelvis, namely the paravertebral sympathetic ganglion chain, which continues into the pelvis with the sacral ganglion chain, and the prevertebral component of the abdominal sympathetic system, represented by the superior hypogastric plexus and its continuation via the hypogastric nerves toward the inferior hypogastric plexuses. We followed the pathway of the superior hypogastric plexus from its origin down to its bifurcation into the two hypogastric nerves. We then followed the nerves into the pelvis and observed the formation of the inferior hypogastric plexuses, from which branches emerged toward the pelvic organs. Along the way, we point out anatomical landmarks that are crucial in an attempt to spare these nervous structures during regional surgical procedures. Conclusions While performing surgeries such as rectal resection with the excision of the mesorectum, radical hysterectomy, and radical prostatectomy, a thorough knowledge of the sympathetic nerve structures that pass from the abdominal cavity into the pelvis is required to spare pelvic innervation. In such a context, the dissection and anatomical assessment of regional sympathetic nerves can prove to be crucial in establishing operative protocols.

Chronic Diarrhea and Weight Loss in an 18-month-old Boy.

Chronic Diarrhea and Weight Loss in an 18-month-old Boy.

Thoracic ganglioneuroma with extension into the epidural space

A patient in their 30s presented with chronic right upper quadrant abdominal pain, nausea, bloating, and constipation. Her clinical exam was unremarkable, and computed tomography (CT) of the chest and abdomen which showed a large right-sided thoracic mass with extension into the thoracic spinal canal. A needle biopsy revealed a diagnosis of ganglioneuroma, the patient then underwent a combined approach for excision the tumor. Ganglioneuroma is a neuroblastic tumor of a neural crest origin, it originates from paravertebral sympathetic chain ganglia of the posterior mediastinum or retroperitoneum. They usually extend through neuroforamina to involve the epidural space and surgical excision can be curative.

Functional Cardiological Changes Resulting from Thoracoscopic Thoracic Sympathectomy: Systematic Review

Hyperhidrosis is a condition resulting from a systemic sympathetic hyperactivity. The gold standard treatment is the resection or surgical ablation of the paravertebral sympathetic chain: the endoscopic thoracoscopic sympathectomy (ETS). Non-cardiac thoracic surgeries carry a considerable incidence of pathological postoperative cardiac events, raising attention to possible worsen cardiac functional capacity after the resection of a pair of thoracic sympathetic ganglia. The aim of this study is to investigate literature evidences of postoperative cardiovascular functional changes on patients submitted to ETS as treatment for hyperidrosis. This is a systematic review of the literature. Clinical studies published between January 1999 and April 2019 were analyzed. The PICO strategy was used to construct the question of systematic reviews research. The process of selecting articles was organized according to PRISMA Diagram. The search in electronic databases resulted in seven articles, of which one was excluded for being out of scope of the research, leaving six articles. All studies showed a pattern of heart rate (HR) reduction after endoscopic thoracic sympathectomy. It was suggested a relation between the extension of the procedure and the presence of cardiac functional alterations. There was an improvement in myocardial physical conditioning and maintenance of functional capacity. To elucidate the real mechanisms involved in the maintenance of myocardial function, and even its improvement, it is necessary to develop further studies that directly evaluate them.

Isolation and Electrophysiology of Murine Sympathetic Postganglionic Neurons in the Thoracic Paravertebral Ganglia.

The thoracic paravertebral sympathetic chain postganglionic neurons (tSPNs) represent the predominant sympathetic control of vascular function in the trunk and upper extremities. tSPNs cluster to form ganglia linked by an interganglionic nerve and receive multisegmental convergent and divergent synaptic input from cholinergic sympathetic preganglionic neurons of the spinal cord (Blackman and Purves, 1969; Lichtman et al., 1980 ). Studies in the past have focused on cervical and lumbar chain ganglia in multiple species, but few have examined the thoracic chain ganglia, whose location and diminutive size make them less conducive to experimentation. Seminal studies on the integrative properties of preganglionic axonal projections onto tSPNs were performed in guinea pig (Blackman and Purves, 1969; Lichtman et al., 1980 ), but as mice have become the accepted mammalian genetic model organism, there is need to reproduce and expand on these studies in this smaller model. We describe an ex vivo approach that enables electrophysiological, calcium imaging, and optogenetic assessment of convergence, divergence, and studies on pre- to postganglionic synaptic transmission, as well as whole-cell recordings from individual tSPNs. Preganglionic axonal connections from intact ventral roots and interganglionic nerves across multiple segments can be stimulated to evoke compound action potential responses in individual thoracic ganglia as recorded with suction electrodes. Chemical block of synaptic transmission differentiates spiking of preganglionic axons from synaptically-recruited tSPNs. Further dissection, including removal of the sympathetic chain, enables whole-cell patch clamp recordings from individual tSPNs for characterization of cellular and synaptic properties.

CD40L reverse signaling suppresses prevertebral sympathetic axon growth and tissue innervation.

CD40‐activated CD40L reverse signaling is a major physiological regulator of the growth of neural processes in the developing nervous system. Previous work on superior cervical ganglion (SCG) neurons of the paravertebral sympathetic chain has shown that CD40L reverse signaling enhances NGF‐promoted axon growth and tissue innervation. Here we show that CD40L reverse signaling has the opposite function in prevertebral ganglion (PVG) sympathetic neurons. During a circumscribed perinatal window of development, PVG neurons cultured from Cd40 –/– mice had substantially larger, more exuberant axon arbors in the presence of NGF than PVG neurons cultured from wild‐type mice. Tissues that receive their sympathetic innervation from PVG neurons were markedly hyperinnervated in Cd40 –/– mice compared with wild‐type mice. The exuberant axonal growth phenotype of cultured CD40‐deficient perinatal PVG neurons was pared back to wild‐type levels by activating CD40L reverse signaling with a CD40‐Fc chimeric protein, but not by activating CD40 forward signaling with CD40L. The co‐expression of CD40 and CD40L in PVG neurons suggests that these proteins engage in an autocrine signaling loop in these neurons. Our work shows that CD40L reverse signaling is a physiological regulator of NGF‐promoted sympathetic axon growth and tissue innervation with opposite effects in paravertebral and prevertebral neurons.

Ganglion Impar Pulsed Radiofrequency for Intractable Coccydynia

Ganglion impar is the lowest paravertebral sympathetic chain, which is placed at the anterior aspect of sacrococcygeal disc used to be blocked in many chronic pain conditions originating from pelvic structures such as the coccyx.

Unilateral Brown Fat Suppression on FDG PET/CT-detecting Sympathetic Denervation.

We present here a case of primitive neuroectodermal tumor (PNET) who initially presented with involvement of the right 3rd rib and underwent neoadjuvant chemotherapy, rib excision, and adjuvant chemoradiotherapy and later underwent posterolateral thoracotomy, pleural nodule excision, and the right 11th rib metastatic lesion excision. Follow-up 18F-FDG PET/CT/computed tomography revealed unilateral brown fat suppression in the form of decreased metabolic uptake in the ipsilateral cervical, axillary, and paravertebral brown fat as compared to metabolically active contralateral brown fat, likely due to paravertebral sympathetic chain damage.

Differential Distribution of Renal Nerves in the Sympathetic Ganglia of the Rat.

The renal nerve plexus comprises efferent and afferent fibers. It controls urine production and bodily fluid homeostasis. Efferent fibers to the kidney include sympathetic nerve fibers from their main ganglia, the prevertebral suprarenal ganglia (SrG), and the paravertebral sympathetic chain ganglia (ChG). In the present study, we examined topological innervation from these ganglia to the renal parenchymal segments of the left kidney of the rat. Fluoro-Gold was injected into the rostral or caudal poles of the left kidney. Approximately 50% of the cells in the SrG of rats injected in the rostral pole were labeled, while 60% of the cells in the ChG T13 of rats injected in the caudal pole were labeled. In addition, we performed dual-probe retrograde tracing of the nerves using two kinds of fluorescent-conjugated cholera toxins (f-CTbs) injected into the rostral and caudal poles of the left kidney. The cells labeled with each f-CTb were distributed differently in the left SrG and the lower ChGs; no dual-labeled cells were found in these ganglia. Anterograde tracing with pCAGGS-tdTomato vector transfected into the left SrG showed that tdTomato-labeled nerve varicosities extended to the cortical arterioles and urinary tubules. Immunohistochemistry revealed that they were positive to tyrosine hydroxylase and synaptophysin, suggesting that they possessed sympathetic nerve endings. Our results show that renal efferent nerves in the SrG may control the rostral part of the kidney and innervate the multiple effectors in the cortex. Anat Rec, 300:2263-2272, 2017. © 2017 Wiley Periodicals, Inc.

Bioelectronic block of paravertebral sympathetic nerves mitigates post–myocardial infarction ventricular arrhythmias

Autonomic dysfunction contributes to induction of ventricular tachyarrhythmia (VT). To determine the efficacy of charge-balanced direct current (CBDC), applied to the T1-T2 segment of the paravertebral sympathetic chain, on VT inducibility post-myocardial infarction (MI). In a porcine model, CBDC was applied in acute animals (n = 7) to optimize stimulation parameters for sympathetic blockade and in chronic MI animals (n = 7) to evaluate the potential for VTs. Chronic MI was induced by microsphere embolization of the left anterior descending coronary artery. At termination, in anesthetized animals and following thoracotomy, an epicardial sock array was placed over both ventricles and a quadripolar carousel electrode positioned underlying the right T1-T2 paravertebral chain. In acute animals, the efficacy of CBDC carousel (CBDCC) block was assessed by evaluating cardiac function during T2 paravertebral ganglion stimulation with and without CBDCC. In chronic MI animals, VT inducibility was assessed by extrasystolic (S1-S2) stimulations at baseline and under >66% CBDCC blockade of T2-evoked sympathoexcitation. CBDCC demonstrated a current-dependent and reversible block without impacting basal cardiac function. VT was induced at baseline in all chronic MI animals. One animal died after baseline induction. Of the 6 remaining animals, only 1 was reinducible with simultaneous CBDCC application (P < .002 from baseline). The ventricular effective refractory period (VERP) was prolonged with CBDCC (323 ± 26 ms) compared to baseline (271 ± 32 ms) (P < .05). Axonal block of the T1-T2 paravertebral chain with CBDCC reduced VT in a chronic MI model. CBDCC prolonged VERP, without altering baseline cardiac function, resulting in improved electrical stability.

Review of Sympathetic Blocks: Anatomy, Sonoanatomy, Evidence, and Techniques.

The autonomic nervous system is composed of the sympathetic and parasympathetic nervous systems. The sympathetic nervous system is implicated in situations involving emergent action by the body and additionally plays a role in mediating pain states and pathologies in the body. Painful conditions thought to have a sympathetically mediated component may respond to blockade of the corresponding sympathetic fibers. The paravertebral sympathetic chain has been targeted for various painful conditions. Although initially injected using landmark-based techniques, fluoroscopy and more recently ultrasound imaging have allowed greater visualization and facilitated injections of these structures. In addition to treating painful conditions, sympathetic blockade has been used to improve perfusion, treat angina, and even suppress posttraumatic stress disorder symptoms. This review explores the anatomy, sonoanatomy, and evidence supporting these injections and focuses on ultrasound-guided/assisted technique for the performance of these blocks.

Ganglion Impar Phenol Injection in a Pediatric Patient with Refractory Cancer Pain

Dear Editor, Cancer pain is still a major issue despite the World Health Organization ladder. Up to 30% of the patients experience poor pain control, especially at late stages and during the last year of life [1]. While opioids are the gold standard for treatment of moderate to severe cancer pain, at least 10–15% may benefit from interventional procedures [2,3]. The main reason to advocate interventional pain management (IPM) is either a lack of efficacy of the opioids and the co-adjuvant therapy or intolerable side effects of such therapy. IPM includes neurolytic procedures (celiac plexus neurolysis, superior hypogastric neurolysis, and impar ganglion neurolysis), continuous epidural and intrathecal analgesia radiofrequency, and vertebral or bone cement augmentation [4]. Most of the IPM experience has been done on adult population, and the information in pediatric population is limited. Neurolytic injection on the impar ganglion is reported since 1990. This ganglion is a single retroperitoneal structure, marking the end of the paired paravertebral sympathetic chains. It is responsible for visceral-perineal pain that is sympathetically maintained [5]. There are no reports of neurolytic impar ganglion injection in …

Paraganglioma: Carotid Body Tumor

Extra-adrenal paragangliomas are neoplasms of the paraganglia located within the paravertebral sympathetic and parasympathetic chains. Thus paragangliomas may arise anywhere along these tracts and common sites of occurrence include abdomen, retroperitoneum, chest and mediastinum and various head and neck locations such as jugulotympanic membrane, orbit, nasopharynx, larynx, vagal body and carotid body. Recent literature suggests a molecular basis for the development of some paragangliomas, i.e. germline mutations. Six genes have been identified and are thought to contribute to the development of pheochromocytoma/paraganglioma. These include RET, VHL, NF1 and SDH subunits SDHB, SDHC, and SDHD. SDHD and SDHB mutations account for a significant percentage of head and neck paragangliomas. It is well know that paragangliomas may be hereditary and may be part of genetic syndromes such as Von Hippel-Lindau syndrome, neurofibromatosis type I (von Recklinghausen disease), MEN 2A and MEN 2B. When features of these more commonly known syndromes are not present, many familial cases, often associated with the above mentioned germline mutations, go unrecognized. In the head and neck region the normal paraganglia are associated with the parasympathetic nervous system and paragangliomas arising from these parasympathetic sites account for up to 70% of extra-adrenal paragangliomas. The most common site is the carotid body. Carotid body paragangliomas arise at the bifurcation of the internal and external carotid arteries and have classic radiographic

IN VIVO PATHWAY ANALYSIS FOR THE EFFECT OF HYPERTHYROIDISM ON EJACULATION IN PHARMACOLOGICALLY-INDUCED EJACULATION IN ANAESTHETISED MALE RATS

INTRODUCTION AND OBJECTIVE: The aim of the current study is to determine the possible effects of hyperthyroidism on ejaculatory pathways in p-Chloroamphethamine(PCA) induced ejaculation in anaesthetised male rats. METHODS: Sixty male Wistar rats (300-350gr) were used in this study. Subcutaneous injection of L-Thyroxine for 14 days was performed to induce hyperthyroidism in thirty rats. Thyroid hormone status were evaluated by serum TSH measurements in all rats. Under intraperitoneally(i.p.) urethane anaesthesia; euthyroid and hyperthyroid rats underwent bilateral hipogastric nerve(HNx,n=6 for both groups), bilateral pelvic nerve(PNx,n=6 for both groups), bilateral paravertebral sympathetic chain (PSCx,n=6 for both groups) transections, complete spinal transection at the T8-T9 level (n=6 for both groups ) and no peripheral transection (Nonx) was performed for 6 rats in each group. After performing seminal vesicle (SV) catheterization and bulbospongiosus (BS) muscle dissection for SV pressure measuring and BS electromyographic (EMG) recordings we induced ejaculation with i.p. administration of 5 mg/kg PCA. Ejaculatory responses were recorded before and 30 min after PCA administration. RESULTS: After PCA administration SV pressure tonic amplitude, SV phasic contraction(SVPC) frequency, SVPC maximal amplitude and BS EMG area under curve values were higher in hyperthyroid Nonx rats than euthyroid Nonx rats. The time interval between PCA administration and first ejaculation, the time interval between first SVPC and first BS contraction of hyperthyroid Nonx rats were significantly shorter than euthyroid Nonx rats. In hyperthyroid rats bilateral HNx and bilateral PSCx significantly reduced SV tonic pressure ampitude, SVPC frequency and SVPC maximal amplitude. There were no differences in SVPC frequency and SVPC maximal amplitude values for HNx and PSCx between euthyroid and hyperthyroid rats. These values were higher in hyperthyroid PNx rats than euthyroid PNx rats. There were no significant differences between all parameters of emission and expulsion phases of ejaculation for euthyroid and hyperthyroid spinally transected rats. CONCLUSIONS: In this study we confirmed the recent data that hyperthyroidism effects both the emission and expulsion phases of ejaculation. The effect of hyperthyroidism on emission phase is probably by sympathetic pathways. However the overall effect of hyperthyroidism on ejaculation may take place in the central nervous system above T8 level

A Two-Faced Young Woman

A 34-year-old woman, heavy smoker, noticed after horseback riding, flushing and sweating exclusively of the left side of her face (Figure 1A). Following this she developed progressive right shoulder pain radiating to the medial side of the forearm in addition to ipsilateral ptosis, miosis, and enophtalmos (Figure 1B). She was then referred to our department for investigations. Chest radiograph showed an ill-defined opacity of the right apex and computed tomography-scan (Figure 2) confirmed a 5 cm tumor of the superior sulcus invading the thoracic inlet, including the subclavian vessels, the stellate ganglion, and the lower nerve roots of the brachial plexus, best shown on T1-weighted sagittal magnetic resonance imaging. Bronchoscopy was normal and the diagnosis of adenocarcinoma was obtained by computed tomography guided transthoracic fine needle biopsy. Concurrent chemotherapy with cisplatin—vinorelbine (four courses) and radiation therapy (46 Grays), were performed. A partial response was obtained and the patient underwent an en bloc resection (right upper lobectomy), extended to the first two ribs and to the lower roots of the brachial plexus. Described separately by Tobias in 1931 and Henry Pancoast in 1932, these tumors arise in the superior sulcus of the apex. They are situated in the costovertebral gutter and may be responsible for the following symptoms: (i) shoulder pain radiating to the ulnar aspect of the forearm with decreased strength, atrophy of small muscles of the hand by invasion of C8 and T1 roots of the brachial plexus, (ii) Horner syndrome characterized by miosis, enophtalmos, ptosis, and anhidrosis ipsilateral to the tumor by invasion of the paravertebral sympathetic chain and the inferior cervical stellate ganglion, (iii) pain in the posterior upper ribs due to chest invasion. Intervertebral foraminal invasion, as well as medullar compression and paraplegia may occur.1 This report shows originality through the presence of hemifacial sweating and flushing with Horner syndrome, known as Harlequin sign and also ipsilateral anhidrosis which was the first symptom noticed by the patient, who then took a picture of this classic but seldom seen clinical sign. Service de *Pneumologie, †Radiologie, and ‡Chirurgie thoracique, Nouvel Hopital Civil, Hopitaux Universitaires, 67091 Strasbourg cedex, France. Disclosure: The authors declare no conflicts of interest. Address for correspondence: Elisabeth Quoix, MD, Service de Pneumologie, Hopitaux Universitaires, 1 place de l’hopital, 67091 Strasbourg cedex, France 67091. E-mail: elisabeth.quoix@chru-strasbourg.fr Copyright © 2009 by the International Association for the Study of Lung Cancer ISSN: 1556-0864/09/0402-0240 FIGURE 1. A, An assymetrical coloring of the face, right anidrosis. B, Horner syndrome characterized by mild ptosis, miosis, and enophtalmos of the right side of the face.

Mediolateral and rostrocaudal topographic organization of the sympathetic preganglionic cell pool in the spinal cord of Xenopus laevis

The sympathetic preganglionic cell pool in Xenopus laevis can be divided into four parts, i.e., the intercalated nucleus (IC) and the intermediolateral nucleus (IML) located respectively at the medial and the lateral borders of the lateral field, the lateral funiculus, and the ventral field within the thoracolumbar spinal segments. We compared the location of the preganglionic cells labeled following tracer application to the paravertebral sympathetic chain with those labeled following application to the celiac ganglion (CG), the adrenal gland (AG), and the splanchnic nerves (SNs) and found that their relative contribution differs depending on the sites. In tracer application to the paravertebral chain ganglia and the sympathetic trunk, 31.4-41.9% and 43.9-58.4% of labeled cells were detected respectively in the IC and in the IML, whereas application to the CG, AG, and on all the SNs, revealed that more than 84% of labeled cells were found in the IML and in the lateral funiculus with less than 8.6% in the IC. The contribution of the ventral field cells was less than 7.5% in all experiments. This type of topographic cytoarchitecture is a character shared with the mammalian preganglionic cell pool, but what distinguishes it from that of mammals is its systematic form throughout the entire longitudinal extent of the pool. In Xenopus, differences of mean soma areas and dendritic projections of labeled cells also suggest that the cell pools are distinguished not only by their location and axonal projections, but also by the morphology of their cells.

The nerve supply of the lumbar intervertebral disc

The anatomical studies, basic to our understanding of lumbar spine innervation through the sinu-vertebral nerves, are reviewed. Research in the 1980s suggested that pain sensation was conducted in part via the sympathetic system. These sensory pathways have now been clarified using sophisticated experimental and histochemical techniques confirming a dual pattern. One route enters the adjacent dorsal root segmentally, whereas the other supply is non-segmental ascending through the paravertebral sympathetic chain with re-entry through the thoracolumbar white rami communicantes. Sensory nerve endings in the degenerative lumbar disc penetrate deep into the disrupted nucleus pulposus, insensitive in the normal lumbar spine. Complex as well as free nerve endings would appear to contribute to pain transmission. The nature and mechanism of discogenic pain is still speculative but there is growing evidence to support a 'visceral pain' hypothesis, unique in the muscloskeletal system. This mechanism is open to 'peripheral sensitisation' and possibly 'central sensitisation' as a potential cause of chronic back pain.

Parkinson’s Disease

Parkinson’s Disease (PD) is generally considered a movement disorder characterized by loss of dopaminergic neurons in the central nervous system (CNS), most notably in the substantia nigra. The pathogenesis of the neuronal degeneration is not completely understood but is characterized by abnormal protein deposits forming characteristic neuronal inclusions, which are visible by light microscopy of autopsy samples, and termed Lewy bodies. α-Synuclein is one of the proteins found in these inclusions and has attracted interest because mutations of the gene encoding for this protein are found in familiar cases of PD. Most of the disability associated with PD is indeed the result of this CNS defect, and the treatment is aimed at increasing dopamine levels in the CNS, while avoiding as much as possible an increase in the periphery. Less widely recognized is the fact that orthostatic hypotension can occur in PD patients and can become symptomatic and disabling in a significant proportion of patients. The incidence of documented orthostatic hypotension in PD, in community-based studies, ranges from 10% to 40%. Orthostatic hypotension in PD is commonly attributed to the known adverse effects of dopaminergic drugs. However, over the last decade there is growing evidence that peripheral nerves, particularly autonomic neurons, are also involved in PD. Lewy body inclusions, containing α-synuclein, have been found in peripheral autonomic neurons in autopsy cases of otherwise classic PD.1 Microscopically, eosinophilic ubiquitin- and α-synuclein–positive Lewy Bodies and Lewy neurites are not only found in the substantia nigra and locus ceruleus but also are widespread in ganglions cells …

Role of Peripheral Innervation in P‐Chloroamphetamine—Induced Ejaculation in Anesthetized Rats

The occurrence of ejaculation, which consists of 2 distinct phases (emission and expulsion), requires a tight coordination of peripheral autonomic and somatic nerves. However, some aspects of the mechanism of ejaculation are not clearly defined. To clarify this issue, we used the p-chloroamphetamine (PCA)-induced ejaculation model in anesthetized rats and investigated the effects of selective peripheral nerves lesions on seminal vesicle and bulbospongiosus (BS) muscle activities as representing physiological markers of emission and expulsion phases, respectively. In intact rats, ejaculation induced with PCA (intraperitoneal 5 mg/kg) correlated with coordinated increases in seminal vesicle pressure (SVP) and BS electromyographic activity. PCA-induced ejaculation was still observed in rats with bilateral lesion of hypogastric nerves (HNx), lumbar paravertebral sympathetic chain (LSCx), or dorsal nerves of the penis (DNPx). Conversely, bilateral section of pelvic nerves (PNx) or L6-S1 dorsal roots (DRx) abolished PCA-induced ejaculation. The amplitude of SVP increases induced by PCA was reduced in PNx, HNx, and LSCx rats, whereas it was unchanged in DRx and DNPx rats. The time interval between SVP increases and BS muscle contractions induced by PCA was comparable in the different neural lesion groups. In conclusion, PCA initiates both emission and expulsion independently from each other. In this model, afferents conveyed by the pelvic nerves appear to be unnecessary for occurrence of BS muscle contractions but are essential for a complete ejaculatory response.

Melanotan-II: Investigation of the inducer and facilitator effects on penile erection in anaesthetized rat

The effects of melanotan-II, a non-specific agonist of melanocortin receptors, on erection and its possible sites of action were investigated in anesthetized rats. Delivered i.v. (0.1, 0.3 and 1mg/kg) or within the paraventricular nucleus of the hypothalamus (0.1 and 1μg), melanotan-II exerted a dose-dependent inducer activity on erection by eliciting erectile events and shortening latency of the first erectile event to occur. Erectile events were of higher amplitude in rats treated with melanotan-II i.t. (0.2μg) delivered at the L6–S1 level than in animals treated with the vehicle i.t. delivered. Erectile responses elicited by cavernous nerve stimulation were increased after i.v. melanotan-II (1mg/kg), thereby exerting facilitator effect on erection. In contrast, melanotan-II injected within the corpus cavernosum (1μg) did not display any facilitator activity. To investigate the neural pathways involved in the facilitator effect of melanotan-II, we performed acute spinalization (T8 level) and differential selective nerve transections. Neither spinalization nor bilateral transection of pelvic nerves or dorsal penile nerves impaired facilitator activity of i.v. melanotan-II (1mg/kg). Conversely, the facilitator effect of melanotan-II was abolished after acute removal of the lumbar paravertebral sympathetic chain. These results lead to the conclusion that central and peripheral melanocortin pathways are recruited by melanotan-II, depending on its route of delivery, to exert both inducer and facilitator activities on erection.