Transcutaneous electrical nerve stimulation decreases lower esophageal sphincter pressure in patients with achalasia

Transcranial magnetic stimulation versus transcutaneous neuromuscular electrical stimulation in post stroke dysphagia: A clinical randomized controlled trial

OBJECTIVES

To evaluate the efficacy of high-frequency repeated transcranial magnetic stimulation (rTMS) applied contralesionally versus transcutaneous neuromuscular electrical stimulation (TNES) in acute post-stroke dysphagic patients.

MATERIALS AND METHODS

A randomized, parallel, comparative, controlled trial was conducted on patients with acute ischemic stroke who were admitted to our department. Fifteen patients received rTMS, 15 patients received TNES, and 15 patients were recruited as a control group. Between the second and tenth days after a stroke, patients were enrolled. The study and follow-up periods were completed by all patients.

RESULTS

Among the screened patients, 45 (31.47%) right-handed patients were diagnosed with post-stroke dysphagia with a mean age of 60.53 ± 8.23 years. Immediately after intervention both rTMS and TNES groups significantly improve the swallowing disturbance questionnaire (SDQ) and penetration aspiration scale (PAS), compared to the control (p < 0.001 and p = 0.027), respectively. rTMS was more effective than TNES in reducing SDQ and PAS (p < 0.05). rTMS and TNES improved the Yale Pharyngeal Residue Severity Rating Scale (YPRSRS) significantly (p = 0.002); however, their efficacy was comparable (p > 0.05). A significant (p < 0.001) strong negative correlation was observed between the grade of weakness and all scores.

CONCLUSION

Our findings showed that high-frequency rTMS and TNES effectively improved the clinical condition of acute post-stroke dysphagic patients in terms of swallowing disturbance assessed by SDQ, pharyngeal residue assessed by YPRSRS, and the severity of penetration and aspiration events evaluated by PAS, compared to the controls. The outcomes of high-frequency rTMS were more favorable than those of TNES in terms of SDQ and PAS.

Updated Systematic Review of Achalasia, with a Focus on POEM Therapy

AIM

To systematically review clinical presentation, diagnosis, and therapy of achalasia, focusing on recent developments in high-resolution esophageal manometry (HREM) for diagnosis and peroral endoscopic myotomy (POEM) for therapy.

METHODS

Systematic review of achalasia using computerized literature search via PubMed and Ovid of articles published since 2005 with keywords ("achalasia") AND ("high resolution" or "HREM" or "peroral endoscopic myotomy" or "POEM"). Two authors independently performed literature searches and incorporated articles into this review by consensus according to prospectively determined criteria.

RESULTS

Achalasia is an uncommon esophageal motility disorder, usually manifested by dysphagia to solids and liquids, and sometimes manifested by chest pain, regurgitation, and weight loss. Symptoms often suggest more common disorders, such as gastroesophageal reflux disease (GERD), thus often delaying diagnosis. Achalasia is a predominantly idiopathic chronic disease. Diagnosis is typically suggested by barium swallow showing esophageal dilation; absent distal esophageal peristalsis; smoothly tapered narrowing ("bird's beak") at esophagogastric junction; and delayed passage of contrast into stomach. Diagnostic findings at high-resolution esophageal manometry (HREM) include: distal esophageal aperistalsis and integrated relaxation pressure (trough LES pressure during 4 s) > 15 mmHg. Achalasia is classified by HREM into: type 1 classic; type 2 compartmentalized high pressure in esophageal body, and type 3 spastic. This classification impacts therapeutic decisions. Esophagogastroduodenoscopy is required before therapy to assess esophagus and esophagogastric junction and to exclude distal esophageal malignancy. POEM is a revolutionizing achalasia therapy. POEM creates a myotomy via interventional endoscopy. Numerous studies demonstrate that POEM produces comparable, if not superior, results compared to standard laparoscopic Heller myotomy (LHM), as determined by LES pressure, dysphagia frequency, Eckardt score, hospital length of stay, therapy durability, and incidence of GERD. Other therapies, including botulinum toxin injection and pneumatic dilation, have moderately less efficacy and much less durability than POEM.

CONCLUSION

This comprehensive review suggests that POEM is equivalent or perhaps superior to LHM for achalasia in terms of cost efficiency, hospital length of stay, and relief of dysphagia, with comparable side effects. The data are, however, not conclusive due to sparse long-term follow-up and lack of randomized comparative clinical trials. POEM therapy is currently limited by a shortage of trained endoscopists.

Changes in Esophageal Motility after Acupuncture

BACKGROUND

Chinese medicine is widely used in the East with good results for the treatment of many diseases. Acupuncture has been increasingly used and recognized as a complementary medical treatment. Some studies on gastrointestinal motility are available; however, acupuncture effect on esophageal motility is still elusive due to the lack of studies with adequate methodology. This study aims to evaluate acupuncture effect on esophageal motility.

METHODS

We studied 16 (50% females, mean age 26 years) volunteers. No individual underwent acupuncture sessions previously. All individuals underwent high-resolution manometry. The test was performed in three phases: basal measurements, 20 min after acupuncture stimulation of the gastrointestinal point (ST36), or 20 min after acupuncture stimulation of a sham point (5 cm medial to ST36) (crossover). ST36 or sham points were alternated in order based on randomization. Lower esophageal sphincter (LES) resting and residual pressure, distal latency (DL) ,and distal contractility integral (DCI) were recorded. All tests were reviewed by two experienced investigators blinded to the acupuncture point.

RESULTS

LES resting pressure was significantly reduced after acupuncture (p = 0.015, Wilcoxon signed-rank test). DL was significantly increased after acupuncture (either Sham or ST36) as compared to basal measurement.

CONCLUSION

Our results showed that acupuncture on the digestive point decreases LES basal pressure. Acupuncture may be an alternative treatment to spastic disorders of the LES.

Neuromodulation for constipation: sacral and transcutaneous stimulation

Constipation is a frequently occurring digestive ailment that is usually treated conservatively. Neuromodulation is altering function of an organ by altering neural activity. This paper reviews methods of neuromodulation used to treat constipation. This includes direct stimulation of sacral nerves and stimulation across the skin. Direct stimulation of sacral nerves is the most well developed method and is presented in detail. It is generally accepted that the mechanism of action is modulation rather than stimulation so it is called sacral neuromodulation (SNM). SNM involves percutaneous placement of an electrode in the third sacral foramen and implanting a stimulating device under the skin in the buttocks. SNM is founded on the physiological principle that activity in one neural pathway modulates pre-existing activity in another through synaptic interaction. The mechanism of action in constipation may be neuromodulation of the extrinsic neural control of the large bowel or modulation of reflexes inhibiting large bowel function. Limited evidence is available to assess the outcome of SNM in constipation. Results in the medium term seem promising for selected patients with idiopathic slow and normal transit constipation not responding to optimal conservative treatment. Adverse events include electrode migration and infection. The availability of a testing phase provides a predictor of treatment outcome. In addition, transcutaneous stimulation using sticky pad electrodes over the lumbosacral region or acupuncture points has been reported to improve constipation symptoms. In general, the level of evidence is low and further studies are needed.

Neuromodulation of thoracic intraspinal visceroreceptive transmission by electrical stimulation of spinal dorsal column and somatic afferents in rats

Clinical studies have shown that neuromodulation therapies, such as spinal cord stimulation (SCS) and transcutaneous electrical nerve stimulation (TENS), reduce symptoms of chronic neuropathic and visceral pain. The neural mechanisms underlying SCS and TENS therapy are poorly understood. The present study was designed to compare the effects of SCS and TENS on spinal neuronal responses to noxious stimuli applied to the heart and esophagus. Direct stimulation of an intercostal nerve (ICNS) was used to simulate the effects of TENS. Extracellular potentials of left thoracic (T3) spinal neurons were recorded in pentobarbital anesthetized, paralyzed, and ventilated male rats. SCS (50 Hz, 0.2 ms, 3-5 minutes) at a clinical relevant intensity (90% of motor threshold) was applied on the C1-C2 or C8-T1 ipsilateral spinal segments. Intercostal nerve stimulation (ICNS) at T3 spinal level was performed using the same parameters as SCS. Intrapericardial injection of bradykinin (IB, 10 microg/mL, 0.2 mL, 1 minute) was used as the noxious cardiac stimulus. Noxious thoracic esophageal distension (ED, 0.4 mL, 20 seconds) was produced by water inflation of a latex balloon. C1-C2 SCS suppressed excitatory responses of 16/22 T3 spinal neurons to IB and 25/30 neurons to ED. C8-T1 SCS suppressed excitatory responses of 10/15 spinal neurons to IB and 17/23 neurons to ED. ICNS suppressed excitatory responses of 9/12 spinal neurons to IB and 17/22 neurons to ED. These data showed that SCS and ICNS modulated excitatory responses of T3 spinal neurons to noxious stimulation of the heart and esophagus.

PERSPECTIVE

Neuromodulation of noxious cardiac and esophageal inputs onto thoracic spinal neurons by spinal cord and intercostal nerves stimulation observed in the present study may help account for therapeutic effects on thoracic visceral pain by activating the spinal dorsal column or somatic afferents.

Effects and mechanisms of electroacupuncture at PC6 on frequency of transient lower esophageal sphincter relaxation in cats

AIM: To investigate the effects of electroacupuncture (EA) at neiguan (PC6) on gastric distention-induced transient lower esophageal sphincter relaxations (TLESRs) and discuss the mechanisms of this treatment.

METHODS: ProtocolI: Twelve healthy cats underwent gastric distention for 60 min on the first day. Electrical acupoint stimulation was applied at the neiguan or a sham point on the hip in randomized order before gastric distention, on the third day and fifth day. Those cats that underwent EA at neiguan on the fifth day were named “Neiguan Group” and the cats that underwent EA at a sham acupoint on the fifth day were named “Sham Group” (control group). During the experiment the frequency of TLESRs and lower esophageal sphincter (LES) pressure were observed by a perfused sleeve assembly. Plasma levels of gastrin (GAS) and motilin (MTL) were determined by radioimmunoassay. Nitrite/nitrate concentration in plasma and tissues were measured by Griess reagent. The nuclei in the brain stem were observed by immunohistochemistry method of c-Fos and NADPH-d dyeing. Protocol II: Thirty six healthy cats were divided into 6 groups randomly. We gave saline (2 mL iv. control group), phaclofen (5 mg/kg iv. GABA-B antagonist), cholecystokinin octapeptide (CCK-8) (1 μg/kg per hour iv.), L-Arginine (200 mg/kg iv.), naloxone (2.5 μmol/kg iv.) and tacrine (5.6 mg/kg ip. cholinesterase inhibitor) respectively before EA at Neiguan and gastric distention. And the frequencies of TLESRs in experimental groups were compared with the control group.

RESULTS: ProtocolI: Not only the frequency of gastric distention-induced TLESR in 60 min but also the rate of common cavity during TLESRs were significantly decreased by EA at neiguan compared to that of sham acupoint stimulation. C-Fos immunoreactivity and NOS reactivity in the solitarius (NTS) and dorsal motor nucleus of the vagus (DMV) were significantly decreased by EA at neiguan compared to that of the sham group. However, the positive nuclei of C-Fos and NOS in reticular formation of the medulla (RFM) were increased by EA at neiguan. Protocol II: The inhibited effect of EA at neiguan on TLESR’s frequency was completely restored by pretreatment with CCK (23.5/h vs 4.5/h, P < 0.05), L-arginine (17.5/h vs 4.5/h, P < 0.05) and naloxone(12/h vs 4.5/h, P < 0.05). On the contrary, phaclofen (6/h vs 4.5/h, P > 0.05) and tacrine (9.5/h vs 4.5/h, P > 0.05) did not influence it.

CONCLUSION: Electric acupoint stimulation at Neiguan significantly inhibits the frequency of TLESR and the rate of common cavity during TLESR in cats. This effect appears to act on the brain stem, and may be mediated through nitric oxide (NO), CCK-A receptor and mu-opioid receptors. But the GABAB receptor and acetylcholine may not be involved in it.

Acupuncture for functional gastrointestinal disorders

Functional gastrointestinal (GI) symptoms are common in the general population. Especially, motor dysfunction of the GI tract and visceral hypersensitivity are important. Acupuncture has been used to treat GI symptoms in China for thousands of years. It is conceivable that acupuncture may be effective in patients with functional GI disorders because it has been shown to alter acid secretion, GI motility, and visceral pain. Acupuncture at the lower limbs (ST-36) causes muscle contractions via the somatoparasympathetic pathway, while at the upper abdomen (CV-12) it causes muscle relaxation via the somatosympathetic pathway. In some patients with gastroesophageal reflux disease (GERD) and functional dyspepsia (FD), peristalsis and gastric motility are impaired. The stimulatory effects of acupuncture at ST-36 on GI motility may be beneficial to patients with GERD or FD, as well as to those with constipation-predominant irritable bowel syndrome (IBS), who show delayed colonic transit. In contrast, the inhibitory effects of acupuncture at CV-12 on GI motility may be beneficial to patients with diarrhea-predominant IBS, because enhanced colonic motility and accelerated colonic transit are reported in such patients. Acupuncture at CV-12 may inhibit gastric acid secretion via the somatosympathetic pathway. Thus, acupuncture may be beneficial to GERD patients. The antiemetic effects of acupuncture at PC-6 (wrist) may be beneficial to patients with FD, whereas the antinociceptive effects of acupuncture at PC-6 and ST-36 may be beneficial to patients with visceral hypersensitivity. In the future, it is expected that acupuncture will be used in the treatment of patients with functional GI disorders.

Inhibition of transient lower esophageal sphincter relaxations by electrical acupoint stimulation

Acupuncture has been shown to modulate visceral sensation and function. Traditionally, stimulation at the Neiguan (pericardial meridian) has been used to treat upper gastrointestinal symptoms. Some of the effects of acupuncture may be mediated through release of endogenous opioids and are reversed by naloxone. Gastric distension is the major trigger for transient lower esophageal sphincter (LES) relaxations (TLESRs). The aim of this study was to investigate the effect of electric stimulation at the Neiguan and naloxone on the TLESRs. In 14 healthy volunteers, electrical acupoint stimulation was applied at the Neiguan and a sham point on the hip in randomized order on the same day. In 12 healthy volunteers, the effects of naloxone (80 microg/kg iv bolus injection) and saline on electrical acupoint stimulation were compared on separate days at least 1 wk apart. Esophageal motility was measured during distension of the proximal stomach with 500 ml of air using a barostat balloon. Electric acupoint stimulation at the Neiguan decreased the rate of TLESRs by approximately 40% from a median of 6/h to 3.5/h (P < 0.02). Acupoint stimulation had no effect on basal LES pressure, the residual LES pressure during TLESRs, the duration of TLESRs, or gastrointestinal symptoms of fullness, bloating, discomfort, or nausea. The effect of acupoint stimulation was not inhibited by naloxone. Electric acupoint stimulation at the Neiguan significantly inhibits the frequency of TLESRs in response to gastric distention in healthy subjects. This effect does not appear to be mediated through mu-opioid receptors.

Review article: therapeutic roles of acupuncture in functional gastrointestinal disorders

Acupuncture has been practiced empirically in China for several millennia, and is being increasingly accepted by practitioners and patients worldwide. Functional gastrointestinal disorders are common in clinical gastroenterology. The prevalence of one or more functional gastrointestinal disorders is estimated to be as high as 70% in general population using Rome diagnostic criteria. Since functional gastrointestinal disorders are diagnosed based on symptoms and the exact aetiologies for most of functional gastrointestinal disorders are not completely known, it is not unusual that the treatment for these disorders is unsatisfactory and alternative therapies are attractive to both patients and practitioners. During the latest decades, a considerable number of studies have been performed on acupuncture for the treatment of functional gastrointestinal disorders and underlying mechanisms. In this article, we reviewed available data in the literature on the applications and mechanisms of acupuncture for the treatment of functional gastrointestinal disorders, including functional oesophageal disorders, nausea and vomiting, functional dyspepsia, irritable bowel syndrome, constipation, etc. A summary is provided based on the quality and quantity of published studies regarding the efficacy of acupuncture in treating these various disorders. In addition, the methodology of acupuncture is also introduced.

Anorectal motility in patients with achalasia of the esophagus: recognition of an esophago-rectal syndrome

BACKGROUND

During my study of constipation, I encountered patients who had achalasia of the esophagus (AE) as well. The possibility of an existing relationship between the 2 conditions was studied.

METHOD

Investigations to study the anorectal motility in 9 AE patients included: the intestinal transit time, anorectal manometry, rectoanal inhibitory reflex, defecography and electromyography (EMG) of external anal sphincter and levator ani muscle. Anorectal biopsy was done. The study comprised 8 healthy volunteers as controls.

RESULTS

6/9 AE patients had constipation presenting as strainodynia (excessive prolonged straining at stool). Rectocele was present in 4 of them. The 6 constipated patients showed significantly high rectal neck pressure (p < 0.05), absent rectoanal inhibitory reflex and aganglionosis in the anorectal biopsy. The EMG revealed diminished activity in 4 of the 6 constipated patients. The remaining 3 patients with AE had normal anorectal function. Heller's myotomy with Nissen's fundoplication improved the dysphagia, but not the constipation which was, however, relieved after performance of anorectal myectomy.

CONCLUSION

The high incidence of constipation with AE postulates a relationship between the 2 conditions. Both have the same pathologic lesion which is aganglionosis. This study is preliminary and requires further studies on a larger number of patients.

The effect of transcutaneous nerve stimulation on intraductal biliary pressure in post-cholecystectomy patients with T-drainage

OBJECTIVE

To evaluate the effects of transcutaneous electrical nerve stimulation (TENS) on intraductal biliary pressure (IDP) in basal conditions and after intravenous morphine and oral meal stimulation.

DESIGN AND METHODS

Fifteen patients (5 male, 10 female) aged 31-83 years (mean 61.5 +/- 13.7 years) with prior cholecystectomy and residual in situ T-tube were examined. Final radiographs excluded any organic abnormalities. The study consisted of three sessions. On the first day (session 1), after the initial manometric intraductal pressure was measured for 15 min, TENS (using a PRO-TENS pocket stimulator) was applied for 15 min. Measurement was continued for 15 min after termination of TENS. The measurement was performed using a water-perfused manometry system (Synectics Medical, Stockholm, Sweden) by a triple-channel manometric catheter inserted into the common bile duct through a T-drain. On the following day (session 2), the protocol was similar except that, after basal IDP measurement, morphine hydrochloride 0.08 mg/kg was injected intravenously 10 min before TENS. On the third day (session 3), after basal measurements were taken, patients were given a standard test meal and the IDP was recorded continuously for 45 min. To estimate the effects of the stimuli applied, absolute intraductal pressure changes were analysed.

RESULTS

In session 1, TENS reduced basal IDP in all patients by a mean of 3.95 +/- 1.6 mmHg. In 13 patients, 15 min after cessation of TENS a further decrease in IDP was observed. In two patients, termination of TENS was followed by a rebound increase in IDP; however, it did not reach the initial value (mean total decrease 5.05 +/- 2.25 mmHg). In session 2, administration of morphine produced an evident increase in IDP in all subjects by 6.9 +/- 2.7 mmHg. TENS decreased IDP in 13 patients. In two patients, TENS initially failed to lower elevated pressure, but it appeared several minutes after the end of stimulation. In 13 patients, the final IDP values were lower than the baseline pressures. In session 3, after administration of a test meal, IDP decreased within 30-40 min by a mean of 4.89 +/- 1.29 mmHg.

CONCLUSIONS

TENS decreased basal as well as elevated IDP in the majority of the T-drain patients studied. The effect of TENS persisted after its termination. Elevated IDP is believed to be responsible for pain in patients with sphincter of Oddi dysfunction (SOD). Therefore, we think that TENS can be used effectively and safely as an optional therapeutic method in the treatment of biliary dyskinesia.

Current concepts on pathophysiology, diagnosis and treatment of diffuse oesophageal spasm

Diffuse oesophageal spasm is a functional oesophageal motility disorder of unknown aetiology, which appears to be due to a disturbance of the normal pharmacological timing of propulsive contraction occurring in the oesophageal body after swallowing. The lack of pathophysiological understanding may be due to the fact that there is more than one pathophysiological pathway causing symptoms of diffuse oesophageal spasm. Barium studies, oesophageal scintigraphy and fiberoptic examination can be helpful in finding the correct diagnosis, but manometry is still the gold standard of diagnostic procedures. Similar to other spastic oesophageal motility disorders, pharmacological treatment of diffuse oesophageal spasm includes nitrates, calcium antagonists, anticholinergics and antidepressants with varying beneficial effects. Botulinum toxin, which provides sufficient treatment as measured by symptom score and manometric patterns in patients with achalasia, was recently evaluated for the treatment of diffuse oesophageal spasm in small patient selections with promising results.

Esophageal pharmacology and treatment of primary motility disorders

Swallowing is a complex mechanism based on the coordinated collaboration of tongue, pharynx and esophagus. Disturbances of this interplay or disorders of one or several of these components lead to dysphagia, non-cardiac chest pain or regurgitation. The major primary esophageal motility disorders--achalasia, diffuse esophageal spasm, hypercontractile esophagus ('nutcracker esophagus') and non-specific motility disorder--are of unknown etiology. Other esophageal diseases, such as cervical diverticula or gastroesophageal reflux disease, might also be caused by a primary esophageal motility disorder. Medical treatment of esophageal disorders with esophageal hyper- or dysmotility requires agents that reduce esophageal contractile force (anticholinergic agents, nitrates, calcium antagonists). Despite the beneficial effect of the various drugs on esophageal motility parameters, the clinical benefit of medical treatment of esophageal motility disorders is rather disappointing. Calcium channel antagonist, alone or in combination with anticholinergics or nitrates, can be used as a medical trial, especially in mild achalasia. However, medical therapy is clearly inferior to pneumatic balloon dilation therapy. Recently, botulinum toxin injection was suggested as a therapeutic option in achalasia patients with good results on lower esophageal sphincter pressure (LESP) and symptom scores that were similar to the results achieved by pneumatic balloon dilation. Hypercontractile esophagus shows a good manometric response to calcium channel antagonists, but only little clinical effect in terms of improvement of symptoms. Diffuse esophageal spasm is a relatively rare disease and few clinical studies are available. The use of calcium channel antagonists can be beneficial, at least in some patients with diffuse esophageal spasm. From clinical and epidemiological studies, there is some evidence of a 'psychological' component in the pathogenesis or perception of esophageal symptoms. There is some clinical benefit from centrally acting drugs such as benzodiazepines or antidepressants. With the exception of botulinum toxin for achalasia, medical therapy of primary esophageal motility disorders is rather limited and the clinical results are poor. Further understanding of esophageal pathophysiology as well as development of new receptor-selective drugs might increase our chances of a successful treatment of primary esophageal motility disorders.

Pathophysiology and endoscopic/balloon treatment of esophageal motility disorders

Diagnostic and therapeutic dilemmas associated with esophageal dysmotility syndromes continue to confront physicians managing these patient populations. Although modern manometric systems have allowed us to better define normal parameters of esophageal motility, with the exception of primary achalasia, the clinical relevance of many aberrant motor patterns remains unclear. The novel use of botulinum toxin in idiopathic achalasia stems from increased understanding of the pathogenesis of the disease. Similarly, as our knowledge of the pathophysiology of other esophageal motor disorders grows, in conjunction with improved diagnostic capabilities, more effective management strategies may be used in the future.

Medical treatment of esophageal motility disorders

Swallowing is a complex mechanism that is based on the coordinated interplay of tongue, pharynx, and esophagus. Disturbances of this interplay or disorders of one or several of these components lead to dysphagia, non-cardiac chest pain, or regurgitation. The major esophageal motility disorders include achalasia, diffuse esophageal spasm, hypercontractile esophagus ("nutcracker esophagus"), and hypocontractile esophagus ("scleroderma esophagus"). Other esophageal diseases such as hypopharyngeal (Zenker's) diverticula or gastroesophageal reflux disease also may be sequelae of primary esophageal motility disorder. Finally, a substantial group of patients referred for evaluation of possible esophageal motor disorders have milder degrees of dysmotility--referred to as nonspecific esophageal motor disorder--that are of unclear clinical significance. Medical treatment of esophageal motility disorders involves the uses of agents that either reduce (anti-cholinergic agents, nitrates, calcium antagonists) or enhance (prokinetic agents) esophageal contractility. Despite the beneficial effect of the various drugs on esophageal motility parameters, the clinical benefit of medical treatment is often disappointing. From clinical and epidemiological studies there is some evidence for a "psychological" component in the pathogenesis or perception of esophageal symptoms. Further understanding of esophageal pathophysiology, as well as development of new receptor selective drugs, might increase our chances of successful treatment of esophageal motility disorders.

The effect of vasoactive intestinal polypeptide on the lower esophageal sphincter in achalasia

Vasoactive intestinal polypeptide (VIP) is one of the main neurotransmitters implicated in the relaxation of the lower esophageal sphincter (LES). The effect of exogenous VIP on LES motor activity was determined by esophageal manometry. LES pressure (LESP) and LES relaxation were compared in four healthy volunteers and in six patients with achalasia. The effects of intravenous doses of 1.5, 3, and 5 pmol.kg-1.min-1 of VIP were compared with placebo. Neither placebo nor 3 and 5 pmol.kg-1.min-1 of VIP produced any effect on esophageal motility in healthy volunteers. In achalasia the three doses of VIP caused a dose-dependent decrease in LESP with a significant improvement in LES relaxation. A dose of 5 pmol.kg-1.min-1 produced a maximal decrease of 51% in LESP. A beta-adrenergic agonist, isoproterenol, caused a decrease in LESP both in healthy volunteers and in patients with achalasia without improving LES relaxation. In summary, intravenous VIP improved LES relaxation and caused a decrease in LESP in patients with achalasia without affecting LESP in healthy volunteers, indicating that the LES muscle in achalasia is supersensitive to VIP. The current study suggests that a selective damage in the noncholinergic nonadrenergic innervation of the esophagus is in part responsible for the motor alteration seen in these patients. The findings and the inability of isoproterenol to improve LES relaxation despite decreasing LESP support a role in VIP as a indicator of LES relaxation.