The importance of sodium pyruvate in assessing damage produced by hydrogen peroxide

OBJECTIVES: The external striated urethral sphincter (rhabdosphincter) is a tubular muscle sleeve that extends from the prostato-membranous urethra and perineal membrane to the bladder neck. The male rhabdosphincter neuroanatomy remains unclear, and a better understanding of its innervation may provide insight into potential modifications of radical pelvic surgery to improve urinary continence. METHODS: Fresh cadaveric dissections of 12 male hemipelves were undertaken to investigate the neuroanatomy of the urinary rhabdosphincter. RESULTS: Neuroanatomic courses of the nerve supply to the rhabdosphincter revealed that, in the perineum, the perineal nerve (a terminal branch of the pudendal nerve) provided branches directly to the bulbospongiosus muscle and the urinary rhabdosphincter. In the pelvis, the course of the pelvic nerve was as follows: (1) arising from the inferior hypogastric plexus, it had a weblike course beneath the muscle fascia of the levator ani muscle; (2) traveling posterolateral to the rectum, it gave many branches that perforated into the lateral rectum; and (3) at the level of the prostatic apex, still beneath the levator ani muscle fascia (superior fascia), it sent multiple direct branches to the inferolateral aspect of urinary rhabdosphincter. The pudendal nerve traversed the pelvis in the pudendal canal, and, before leaving the pelvis to enter the perineum, it gave an intrapelvic branch that courses with the pelvic nerve to innervate the rhabdosphincter. CONCLUSIONS: Our understanding of the neuroanatomy of what may be the continence nerves has been improved by fresh cadaveric dissection. The rhabdosphincter receives nerve fibers from the pelvic nerve and dual innervation from an intrapelvic branch and a perineal branch of the pudendal nerve. Better understanding of these anatomic findings may have potential surgical significance with respect to improvement in postoperative urinary continence.     

Electrophysiological technique for evaluating lesions of the conus medullaris and cauda equina

The authors describe the use of evoked electromyographic responses recorded in the anal sphincter induced by stimulation of the bladder wall and urethra in evaluating lesions of the conus medullaris and cauda equina in 110 patients. This reflex response took effect by way of the pelvic nerves and cauda equina to the sacral cord where the pudendal nerve nucleus was activated, resulting in a contraction of the external anal sphincter. Various lesions along this pathway have been shown to produce either increased latencies and depressed responses or complete loss of response depending on the extent of the lesion. The correlation of results of this technique with clinical, myelographic, and operative findings indicate it to be a useful clinical tool.     

Nitric oxide synthase in the heterogeneous population of intramural striated muscle fibres of the human membranous urethral sphincter

PURPOSE: Nitric oxide (NO) is known to relax urethral smooth muscle. The role of NO in the control of urethral striated muscle remains unknown. We have investigated the distribution of nitric oxide synthase (NOS) immunoreactivity and its possible relationship with subtypes of intramural striated muscle fibers in the human male membranous urethra. MATERIALS AND METHODS: Whole transverse cryostat sections from seven membranous urethrae were studied using NOS immunohistochemistry and NADPH diaphorase histochemistry. Striated fiber subtypes were demonstrated using immunohistochemistry for troponin T and histochemistry for myofibrillary adenosine triphosphatase (ATPase). Consecutive sections were used to assess the correlation between the distribution of NOS immunoreactivity and the type of striated fibers. RESULTS: NOS immunoreactivity and NADPH diaphorase activity were detected in the sarcolemma of 48.5% of the intramural striated muscle fibers. NOS immunoreactive nerve trunks and fine nerve fibers, a few of which appeared to end on muscle fibers, were present in the striated sphincter. Fast twitch fibers were detected by ATPase staining, and also exhibited positive immunoreactivity for troponin T, constituting 34.6% of the total number of striated fibers. Two populations of slow twitch fibers were identified; one with small diameter (mean: 15.7 microns) and another of larger diameter (mean: 21.7 microns) comparable to that of fast twitch fibers. 86% of the fast twitch fibers and 29% of slow twitch fibers (most of which had larger diameters) exhibited NOS immunoreactivity and NADPH diaphorase activity in the sarcolemma. CONCLUSIONS: The presence of nitrergic nerve fibers in the striated urethral sphincter suggests an involvement in the innervation of urethral striated muscle. Furthermore, the presence of NOS immunoreactivity in the sarcolemma may indicate a role for NO in the regulation of urethral striated muscle metabolism and contraction.     

Kinetic characterisation and solubilisation of gamma-hydroxybutyrate receptors from rat brain

The effects of single electrical shocks to myelinated A and unmyelinated C afferent fibers of perineal and limb somatic nerves on the reflex discharges in pelvic parasympathetic (L6/S1) efferent nerves to the bladder were examined in anesthetized central nervous system (CNS)-intact and acute spinal rats. When the bladder was empty, stimulation of perineal somatic inputs to the L6 and S1 segments from the perineo-femoral branch of a pudendal nerve produced excitatory A- and C-reflex discharge components in postganglionic parasympathetic efferent nerve branches on the bladder surface. When the bladder was expanded and pelvic efferent neurons were rhythmically active, additional inhibitory A- and C-reflex components could be seen. After acute spinal transection, the same stimuli elicited excitatory A- and C-reflex discharges of similar latency as those observed before the spinal transection, but were of larger amplitude and longer duration; resting activity in the pelvic nerve was low, and no evoked inhibitory reflex components could be observed. Electrical stimulation of afferents in the tibial nerve had no effect when the bladder pressure was low, but when the bladder was distended, early and late components of reflex inhibition and excitation of parasympathetic activity were visible in CNS-intact rats; these reflex responses were abolished following spinalization.     

The urethral resistance to rapid dilation: an analysis of the effect of autonomic receptor stimulation and blockade and of pudendal nerve blockade in healthy females

The urethral closure function is based upon permanently as well as adjunctively acting closure forces during rest and stress episodes, respectively. During urine ingression intra- and peri-urethral structures are suddenly stretched resulting in a pressure response which strengthens the closure function by sustaining the resistance to dilatation of the urethra. A method for measurement of the resistance to rapid urethral dilatation was used to evaluate the influence of noradrenaline, prazosin, terbutaline, propranolol, carbachol, and atropine, as well as bilateral pudendal nerve blockades in 40 healthy women. The drugs caused no significant change in the urethral resistance to dilatation, whereas the pudendal blockade produced a significant (p < 0.05) reduction at the bladder neck and in the high pressure zone. Although a quantitative assessment of their contribution cannot be obtained from this study, it may be concluded that the striated muscles innervated by the pudendal nerve are of major importance for the urethral resistance to dilatation.     

Decreased sensitivity in the membranous urethra after orthotopic ileal bladder substitute

PURPOSE: The effect of cystoprostatectomy with orthotopic substitution on membranous urethral sensation and subsequent urinary continence is unknown. We determined the sensory threshold for electrical stimulation of the membranous urethra and correlated it with continence, nerve sparing surgical technique and potency. MATERIALS AND METHODS: The sensory threshold was measured in a control group of 35 men before radical prostatectomy or cystoprostatectomy and in 47 men after cystoprostatectomy and ileal bladder substitution. RESULTS: The sensory threshold of the membranous urethra was 9+/-2 in the control group compared to 27+/-11 mA. in the postoperative group (p<0.001). Patients with daytime continence had a threshold of 24+/-9 compared to 39+/-10 mA. in incontinent patients (p<0.001). We were unable to show any correlation between the sensory threshold in patients with (25+/-10 mA.) and without (31+/-11 mA.) attempted nerve sparing surgery (p = 0.1) nor between potent (25+/-12 mA.) and impotent (27+/-11 mA.) patients (p = 0.4). CONCLUSIONS: Sensitivity in the membranous urethra decreased in patients after cystoprostatectomy and ileal bladder substitution. Urethral sensitivity in the sphincter area was better in continent than incontinent patients. Since we were unable to find any correlation between the sensory threshold and nerve sparing surgery or potency, it may be assumed that at least part of the sensory fibers to the membranous urethra pass through the pudendal nerve and/or the intrapelvic extrapudendal nerve fibers.     

Nervous regulation of the tone of the retractor penis muscle in the goat

The nervous control of the retractor penis muscle (rp) was investigated in the anaesthetized goat. Also, isolated field stimulated strips of the muscle were studied. The noradrenaline (NA) and acetylcholine (ACh) content of the rp was determined, and histochemistry for adrenergic and acetylcholinesterase (AChE) positive nerves was performed. The muscle exhibited spontaneous activity that persisted after section of all nerves. There was, however, also a tendency of the activity to follow the general vasomotor tone, which disappeared after section of the sympathetic chains. The excitatory adrenergic nerves which innervate the muscle come from the sympathetic chains and run along the pudendal, the hypogastric and the pelvic nerves. The rp has a dense network of adrenergic fibres and is very sensitive to excitatory adrenergic stimulation. It has a fairly large NA content, which is higher in old goats (5.95 +/- 0.42 micrograms g-1) than in young goats (2.87 +/- 0.78 micrograms g-1). Inhibitory non-adrenergic non-cholinergic (NANC) innervation reaches it via the pelvic and the hypogastric nerves. The maximum inhibitory response is reached at low frequencies (2-4 Hz). Cholinergic prejunctional inhibition of the excitatory response to sympathetic chain stimulation was effected by simultaneous stimulation of the hypogastric nerves. In vitro experiments confirmed the presence of endogenous cholinergic muscarinic suppression of the excitatory adrenergic neurotransmission. Significant amounts of ACh (0.81 +/- 0.18 micrograms g-1) are present in the muscle, and it contains strongly AChE positive nerve fibres and nerve cell bodies. It is concluded that the goat rp is innervated by sympathetic adrenergic excitatory nerves and parasympathetic NANC inhibitory nerves. It further has a direct sympathetic inhibitory NANC innervation, and an indirect inhibitory cholinergic innervation which at least in part is sympathetic.     

Functional significance of thoracic vagal branches in the chicken

One minute electrical stimulation was used to excite the right and left cervical vagi as well as specific points on, or branches of, the left thoracic vagus. Respiratory, heart rate and blood pressure responses were observed with the nerves intact and cut. Stimulation of either intact cervical vagus produced apnea, bradycardia and blood pressure depression. Stimulation of the cut ends after nerve section demonstrated that the heart rate and blood pressure effects were efferent and the respiratory change was afferent. No responses were observed due to stimulation of the vagus caudal to the lungs. Stimulation of cardiac branches reduced heart rate and blood pressure but did not produce significant respiratory effects. Middle and anterior pulmonary branches were found to contribute only to respiratory changes through afferent nerves. Sudden, sustained reduction of CO2 in the airways produced immediate, sustained apnea. The data suggest that CO2 sensitive thoracic receptors important in regulation of respiration are confined primarily to the lungs and that these receptors play no direct role in cardiovascular function.     

Salmonella penetration through eggshell associated with freshness of laid eggs and refrigeration

BACKGROUND: Significant associations between perineal descent and pudendal nerve latency have previously been described in fecally incontinent patients. This has led to the hypothesis that pelvic floor muscle and nerve injury initiated by childbirth might progress and cause fecal incontinence. PURPOSE: The study contained herein was undertaken to test whether changes in perineal position and pudendal nerve latency were associated in a population of healthy middle-aged women. METHODS: A cross-sectional study of 144 women were selected randomly from the Danish National Register; they had a mean age of 50 (range, 45-57) years and a mean parity of 2 (range, 0-6). Perineal position at rest and during simulated defecation and pudendal nerve terminal motor latency were measured. All examinations were performed by one of the authors (AMR) and without the knowledge of parity. RESULTS: The perineal position both at rest and during straining was significantly lowered, and the pudendal nerve terminal motor latency was significantly prolonged with increasing numbers of vaginal deliveries (data not shown). There was, however, no association between pudendal nerve terminal motor latency and perineal position at rest (correlation coefficient, r = -0.15, P = 0.1) or during simulated defecation (r = -0.08, P = 0.4). CONCLUSION: Small but significant effects of vaginal deliveries were detected in a random population of healthy perimenopausal women. However, because perineal descent and pudendal nerve latency were not associated, our findings do not support the hypothesis that damage induced by vaginal delivery to the pudendal nerves and pelvic floor will progress.     

Sympathetic efferent pathways projecting to the vas deferens

The abdominal and pelvic sympathetic nervous system controlling the vas deferens has elaborate mechanisms to preserve its function against various injuries. The main sympathetic signals to the vas deferens proceed the common pathway in mammalians, which consists of the lumbar splanchnic nerve, caudal mesenteric plexus, hypogastric nerve, pelvic plexus and its branches. On the way of this common pathway, some signals cross to the other side of the body at the level of the caudal mesenteric plexus and/or the pelvic plexus. The preganglionic axons passing through the hypogastric nerve very likely provide a bilateral innervation to postganglionic neurons in the pelvic plexuses, which also exhibit crossing to the bilateral vasa deferentia. The sympathetic nerves originating from the thoracic spinal cord are of minor importance in contraction of the vas deferens but possibly influence it by the hormonal system consisting of the major splanchnic nerve and the adrenal medulla. When the common pathway is interrupted, various compensatory mechanisms are generated: enhancement of the remaining sympathetic pathways or reorganization of synaptic connection in the pelvic plexus. Surgical reconstruction of the transected hypogastric nerve is possible and cross-innervation mechanism via the hypogastric nerve can also be preserved. Elevation of intraluminal pressure at the cauda epididymis/proximal vas deferens induced by nerve impulse pushes the spermatozoa out to the ampulla and distention of the wall of the ampulla triggers its contraction to emit the content into the urethra. After seminal emission, a portion of the seminal fluid remaining in the vas deferens moves in a retrograde direction to the cauda epididymis for the next emission. It remains to be seen whether similar mechanisms in animals are at work in humans.     

Neurovascular supply of the gracilis muscle: a study in the monkey and human

A comparison of the gross anatomy, extramuscular nerve branches, and intramuscular blood supply of the gracilis muscle showed similar patterns in both monkey and human. The number and pattern of distribution of the extramuscular terminal branches to the muscle were similar. The intramuscular neural pattern demonstrated with the Sihler's staining technique was also similar in both species. In vivo electrical stimulation studies in the monkey revealed that stimulating each extramuscular terminal nerve branch produced a distinct segmental contraction of the muscle. Independent contraction with force generation was observed when the monkey muscle was split into anterior and posterior segments and stimulated through each of the two subdivisions of the main nerve trunk to the muscle. Angiograms verified that circulation was preserved in these two segments.     

Pelvic and pudendal nerves influence the display of paced mating behavior in response to estrogen and progesterone in the female rat.

Two experiments examined whether the pudendal and pelvic autonomic nerves are important for pacing behavior shown by the female rat during mating. Ovariectomized female rats received bilateral transection of the pudendal (Pux), pelvic (Pex), or pudendal and pelvic (Pu?+?Pex) nerves, or were sham-operated. Lordotic behavior, precopulatory solicitations, postural adjustments, and pacing behavior were measured 14 days after nerve transection in Exp 1 after sequential treatment with estradiol benzoate (EB) and progesterone (P) and in Exp 2 on the day after 7 daily injections of EB. After combined EB and P treatment, disruption of pacing behavior occurred in Pex and Pu?+?Pex animals. After EB-only treatment, Pux animals as well as Pex and Pu?+?Pex animals showed decreased pacing behavior. Thus, afferent input via the pelvic nerve is important for the display of pacing behavior, and P may counteract the effects of autonomic nerve transection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preservation of putative continence nerves during radical retropubic prostatectomy leads to more rapid return of urinary continence

OBJECTIVES: Urinary incontinence is a significant complication of radical pelvic surgery. A better understanding of the neuroanatomy of the rhabdosphincter has led to the modification of the radical retropubic prostatectomy to optimize the recovery of postoperative urinary control. METHODS: Mock radical retropubic prostatectomy was performed on fresh cadavers to determine which surgical maneuvers could injure what may be the continence nerves. To assess the clinical significance of modifying the radical retropubic prostatectomy based on these anatomic studies, a contemporary series of 60 consecutive patients who underwent radical retropubic prostatectomy with continence nerve preservation was compared with a control group of 38 consecutive patients who had a standard anatomic radical retropubic prostatectomy. RESULTS: At the level of the prostatic apex, both the pelvic and pudendal nerves gave intrapelvic branches that bilaterally coursed to the external urinary sphincter to enter at the 5 and 7 o'clock positions. The mock radical prostatectomy revealed that the nerves to the external urinary sphincter were most prone to injury when a right angle clamp was used to develop a plane between the posterior rhabdosphincter and anterior rectum and if the urethral anastomotic sutures were placed at the 5 and 7 o'clock positions. In addition, blunt dissection of the tips of the seminal vesicles injured the inferior hypogastric plexus. Modifications to preserve the continence nerves were incorporated in the anatomic radical prostatectomy. Although overall continence rates were similar for the two groups (98.3% for continence nerve-preserving radical prostatectomy versus 92. 1% for standard prostatectomy), continence nerve preservation decreased the time to achieve continence. CONCLUSIONS: During radical retropubic prostatectomy, surgical maneuvers that avoid injury to the continence nerves resulted in the more rapid return of urinary control.     

Excitability changes of terminal arborizations of single Ia and Ib afferent fibers produced by muscle and cutaneous conditioning volleys

1. In cats anesthetized with sodium pentobarbital, recordings were made from dorsal root ganglion (DRG) cells having a peripheral process in the gastrocnemius-soleus (GS) nerve. The GS nerve was left in continuity with the muscle to allow identification of group Ia and Ib fibers by responses of the receptors to muscle stretch and contraction. The central processes of the DRG cells were activated antidromically by stimulation within the spinal cord so that changes in the excitability of the fibers could be examined following conditioning volleys in muscle and cutaneous nerves. 2. Recordings were made from 44 DRG cells. Of these, 15 were group Ia and 9 group Ib afferents of the GS nerve. 3. Of 15 Ia fibers, 12 were activated antidromically by stimulation in the motor nucleus, but no Ib fibers were discharged by such stimulation. Ib fibers could be antidromically activated by stimulation in the intermediate nucleus. 4. The central processes of the Ia DRG cells had slower conduction velocities than did the peripheral processes. 5. The thresholds to electrical stimulation of the peripheral processes of Ia and Ib fibers of the GS nerve showed considerable overlap. 6. All of the Ia DRG cells tested showed an increased excitability following conditioning volleys in the biceps-semitendinosus (BST) nerve. The increase in excitability was produced by the largest fibers of the BST nerve. 7. Stimulation of the sural (SU) or superficial peroneal (SP) cutaneous nerves also increased the excitability of some Ia fibers. However, other Ia fibers were unaffected, and in two cases the excitability was reduced. 8. The excitability of group Ib fibers was increased by conditioning volleys in the BST, SU, or SP nerves. 9. It is concluded that cutaneous volleys produce a mixture of primary afferent depolarization and primary afferent hyperpolarization in Ia fibers of anesthetized cats. Such converse actions probably cancel in excitability tests using population responses. 10. The excitability of single Ia fibers is not stationary in excitability presumably reflect slow alterations within the central nervous system, perhaps related to spontaneous alterations in the level of tonically maintained primary afferent depolarization.     

Polymerase chain reaction (PCR) and its possible applications in diagnosis of infection in ophthalmology

Fecal incontinence resulting from pudendal canal syndrome has been treated by pudendal canal decompression (PCD) with satisfactory results. Considering the possible difficulty in exposing the pudendal canal and nerve by the open method, laparoscopic PCD was practiced in 9 women aged between 37 and 52 years. They were complaining of fecal incontinence; urinary stress incontinence was an additional complaint in 4/9 women. Neurologic, manometric, and EMG studies confirmed the diagnosis of pudendal canal syndrome. For laparoscopic PCD a 1-cm incision lateral to the anal orifice was performed. A balloon dilator was introduced in the ischiorectal fossa (IRF) to create a working space, and CO2 was insufflated. Under the guidance of a laparoscope, the IRF was entered and the inferior rectal nerve identified and followed to the pudendal canal. The latter was split open, releasing the pudendal nerve into the IRF. Fecal control was achieved in 7/9 patients and urinary control in 2/4. Fecal and urinary control were associated with improvement in perianal sensation, rectal neck pressure, EMG of external anal sphincter and levator ani muscle as well as in pudendal nerve terminal motor latency. Two women showed no improvement. Failure is suggested to be due to an advanced pudendal neuropathy. In conclusion, laparoscopic PCD is a simple, easy, and safe procedure. It allows for better exposure of the contents of the IRF than the open procedure, thus avoiding injury of the pudendal nerve and its branches during the performance of the PCD.     

On the surgical treatment of refractory epilepsy in tuberous sclerosis complex

Using the pig as a model, it was shown that stimulation of the distal nerve ending of the pudendal nerve leads to the isolated stimulation of the external anal sphincter muscle. No difference in pressure response was noted after application of between 0.5 and 1.5 mA unilateral or bilateral stimulation. Major advantages observed using between 1.5 and 2.5 mA bilateral stimulation; with a stimulation between 2.0 and 2.5 mA the pressure response was twice as high compared to unilateral stimulation. Continuous stimulation of the striated anal sphincter muscle leads to fatigue, reaching 50% fatigue after a median time between 40-90 s. In cyclic stimulation (alternation every 15 s, duration 20 min) a fatigue reaction was also seen. The peak pressure decreased after 20 min for a median of 11%, the final pressure was lowered in 15% following a logarithmic curve pattern. The experimental application of variable impulse ranges also caused pressure differences. Increasing the impulse range from 200 to 450 microseconds (peak pressure) vs. 400 microseconds (final pressure) resulted in a statistically significant pressure increase. Therefore, it was proven that selective stimulation of the external anal sphincter muscle can lead to a transient pressure increase, which possibly improves fecal continence.     

Mechanisms of efferent neuronal control of the reflex nicitating membrane response in rabbit (Oryctolagus cuniculus)

Efferent mechanisms controlling the nicitating membrane (NM) reflex response to air puff in the albino rabbit were analyzed using stimulation, lesions, and recording techniques. In brief, stimulation of the sixth nerve (abducens) yields short-latency NM extension. Stimulation of the fourth and seventh nerves and the superior cervical ganglion has essentially no effect on the NM. Stimulation of the third nerve causes short-latency retraction of the NM. Lesions and recording data are consistent with this result - the sole efferent neuronal control of NM extension is the sixth cranial nerve and of NM retraction is the third cranial nerve. The NM extension response appears to be mediated by mechanical actions via retraction of the eyeball by the retractor bulbi muscle, and NM retraction appears to result from direct activation of muscle fibers in the NM by the third nerve. The superior cervical ganglion appears to play no role in reflex NM retraction in the rabbit, in contrast to its action in the cat.     

Re-intervention in the anal region

In 29 rats, responses evoked by pelvic and hypogastric nerve stimulation were recorded from postganglionic nerves to bladder and penis (clitoris). Responses to pelvic nerve stimulation had nonsynapsing and synapsing components. The nonsynapsing component was relatively large in main nerve to penis and small in lateral nerve to penis and nerves to bladder. Pelvic nerve fiber synapsing on pelvic ganglion neurons to bladder had a large subliminal fringe, while fibers synapsing on neurons supplying penis (clitoris) had a small subliminal fringe. Recruitment was greater in nerves to bladder and lateral nerve to penis (clitoris) compared to main nerve to penis (clitoris), indicating more synapsing fibers in the former nerves. Almost all hypogastric fibers to bladder were direct. A small subliminal fringe was demonstrated for hypogastric fibers synapsing on neurons supplying penis. No subliminal fringe was evident for the bladder. Pelvic and hypogastric nerve interaction on pelvic ganglion neurons could not be demonstrated with either single shock or tetanic trains of conditioning stimuli. With antidromic stimulation, conduction velocities of afferent fibers in pelvic nerve ranged from 0.15 m per sec to 2.9 m per sec. In hypogastric nerve they ranged from 0.35 m per sec to 2.8 m per sec.     

Identification of two Y-box binding proteins that interact with the promoters of columbid annexin I genes

The aim of this study was to investigate the role of noradrenergic descending nervous pathways in external anal sphincter motility. For this purpose, the effects of intravenously injected adrenoceptor antagonist and agonist on the tonic electrical activity of this sphincter were studied in anesthetized cats. The effects of stimulating the region of the locus coeruleus and the effects of intravenous, intracerebroventricular and intrathecal injection of the above drugs on the electromyographic responses of this muscle to pudendal nerve stimulation were also investigated. The tonic sphincteric activity and the reflex response triggered by electrically stimulating pudendal afferent nerve fibers were inhibited by alpha1-adrenoceptor antagonist nicergoline and enhanced by alpha1-adrenoceptor agonist phenylephrine. Stimulation of the locus coeruleus area either inhibited or enhanced the reflex responses. Intracerebroventricular and intrathecal injection of the alpha2-adrenoceptor agonists, morphine and leu-enkephalin decreased the amplitude of these reflex responses. All the effects of opioids were blocked by naloxone and by spinalization performed at the cervical and lumbar levels. The direct response elicited by stimulating the sphincteric motor axons was not affected either by these drugs or by the brainstem stimulation. These results suggests the existence of a pontine neuronal network controlling the motility of the external anal sphincter via noradrenergic and opioid neurons.