Psychogenic vomiting: the relation between patterns of vomiting and psychiatric diagnoses

Chronic Unexplained Vomiting: A Case Report on Psychogenic Vomiting

Psychogenic vomiting is defined as recurrent vomiting without any known discernible organic reasons, or functional vomiting occurring from psychological stress. The overall clinical presentation of psychogenic vomiting suggests a wide range of disability levels, such as stress disorders, mood changes, depression, sexual problems, personality disorders, learned responses, conversion disorders, and illness problems. Non-pharmacological treatment modalities are important as medication for psychogenic vomiting such as individual and group psychotherapy, supportive and behavioral therapy, and family and marital therapy. In this case report, a 25-year-old male with schizophrenia on medication presented to an outpatient clinic with the primary complaint of recurrent vomiting. After ruling out pathologic and physiologic causes of vomiting. It was classified as psychogenic vomiting.

Psychogenic vomiting: A case series

Psychogenic vomiting is a syndrome in of recurrent vomiting without any organic pathology. It must be differentiated from cyclical vomiting syndrome, functional vomiting, and chronic idiopathic nausea. It occurs as a result of an emotional or psychic disturbance. This condition is highly disabling, increasingly recognized, and under-researched. In India, the number of patients reporting to the psychiatric outpatient department with eating disorders is comparatively very less. We describe how two patients with diagnostic dilemmas who were treated successfully after psychiatric intervention.

Fifty-eight-year-old female with abdominal migraine: A rare cause of episodic gastrointestinal disturbance in adults

Abdominal migraine (AM) is a predominantly pediatric condition characterized by erratic episodes of abdominal pain, nausea, and vomiting with spontaneous periodic relief. It should be considered as a differential diagnosis in symptomatic adults.

Psychological intervention in cyclic vomiting syndrome in adolescents: A case series

Objective: Cyclic vomiting syndrome (CVS) is difficult to diagnose, thus there is often a delay in diagnosis or a misdiagnosis. In the absence of an adequate understanding of the pathophysiology of the syndrome, it is under-recognised and treatment is difficult. The present case series aimed to assess and manage three adolescents with CVS.Method: The Children's Apperception Test was administered on the three Asian adolescents who were referred for the management of CVS to the Department of Clinical Psychology at a tertiary care hospital in New Delhi, India. A treatment module was developed to treat CVS in these adolescents.Results: A strong link was found between the psychological stressors and their physical manifestations in the episodes of vomiting. Therapeutic management with a focus on behavioural modification, adaptive coping skills, and a healthy therapeutic relationship was found to be efficacious in gradually remitting this condition.Conclusions: Thus, the focus of treatment in cases of CVS should be to understand the psychological underpinning and help the adolescents to incorporate healthy coping strategies.

Charles Darwin's (1809-1882) illness - the role of post-traumatic stress disorder

During most of his adult life, in counterpoint to his fame in describing the theory of evolution, Charles Darwin was chronically ill. He consulted many doctors with only limited and temporary success. His symptoms were many and varied. His doctors favoured dyspepsia or suppressed gout as the diagnosis. The Water Cure was only effective initially. Many diagnoses have been proposed by physicians since then. Perhaps he suffered from post-traumatic stress disorder (PTSD), not instead of but as well as other physical problems. His symptoms match with criteria for PTSD. Traumatic episodes from his life are considered in this paper: his mother's painful, sudden death from an acute abdominal event when he was eight; his reaction to seeing operations without anaesthetic; the deaths of three of his children, including his beloved daughter, Annie, aged ten; and being overwhelmed by his chronic, unrelenting symptoms. Trauma had not been conceptualised as a diagnosis in Darwin's time. Rather, hysteria and, in war, irritable heart were names given to what is now called PTSD.

Role of the abdominal vagus and hindbrain in inhalational anesthesia-induced vomiting

The incidence of postoperative nausea and vomiting (PONV) can be as high as 80% in patients with risk factors (e.g., females, history of motion sickness). PONV delays postoperative recovery and costs several hundred million dollars annually. Cell-based assays show that halogenated ethers (e.g., isoflurane) activate 5-HT₃ receptors, which are found on gastrointestinal vagal afferents and in the hindbrain - key pathways for producing nausea and vomiting. This project evaluated the role of the vagus and activation of the hindbrain in isoflurane-induced emesis in musk shrews, a small animal model with a vomiting reflex, which is lacking in rats and mice. Sham-operated and abdominal vagotomized shrews were exposed to 1 to 3% isoflurane to determine effects on emesis; vagotomy was confirmed by lack of vagal transport of the neuronal tracer Fluoro-Gold. In an additional study, shrews were exposed to isoflurane and hindbrain c-Fos was measured at 90min after exposure using immunohistochemistry. There were no statistically significant effects of vagotomy on isoflurane-induced emesis compared to sham-operated controls. Isoflurane exposure produced a significant increase in c-Fos-positive cells in the nucleus of the solitary tract and vestibular nuclei but not in the area postrema or dorsal motor nucleus. These results indicate that the abdominal vagus plays no role in isoflurane-induced emesis and suggest that isoflurane activates emesis by action on the hindbrain, as shown by c-Fos labeling. Ultimately, knowledge of the mechanisms of inhalational anesthesia-induced PONV could lead to more targeted therapies to control PONV.

Chronic nausea and vomiting: insights into underlying mechanisms

Chronic nausea and vomiting are common and debilitating symptoms in adults. There are some fundamental problems that make our understanding of mechanisms difficult, diagnostic definitions of patient-cohorts being central. As there is no unifying mechanism with a direct link to chronic nausea or vomiting, it is most likely that several mechanisms interact, e.g., pylorus function and its relation to gastric emptying, or gastric sensory and motor function. In this mini-review, we highlight the roles and evidence for brain-gut interactions as well as gastrointestinal neurophysiologic, motor, sensory, and hormonal factors involved in the pathophysiology of chronic nausea and vomiting. There are factors not mentioned in the text, mostly as they are not well characterized in the setting of chronic symptoms or only in animal models.

Advantageous Use of Hypnosis in a Case of Psychogenic Vomiting

This case study describes in detail the role of hypnosis in treatment of a case of psychogenic vomiting. The patient, a 60-yearold woman, had been suffering for 9 months from episodes of vomiting which resulted in weight loss, dehydration, and hypokalemia. She was a conscientious woman with high standards of behavior, which did not allow an expression of the extreme hostility she felt toward her daughter-in-law. Hypnotherapeutic sessions reduced her anxiety, restored her sleep, improved mood, and helped deepen rapport, all of which created the ideal setting for Gestalt's empty chair technique. Integrating hypnosis greatly enhanced the quality of the empty chair dialogue, which by bringing about a shift in the patient's emotions from hostility to sympathy, facilitated recovery.

'Idiopathic' intestinal failure--the importance of identifying and treating primary psychopathology

BACKGROUND

Gastrointestinal neuromuscular disorders (GINMD) are an important cause of intestinal failure (IF). We present six cases of IF in whom a diagnosis of GINMD was initially suspected, but in whom psychopathology was discovered to be the primary etiology.

METHODS

(i) Six consecutive cases referred to our unit with IF, initially presumed to be due to GINMD, were selected. Informed consent was obtained from all patients. Case notes were reviewed for salient clinical information. (ii) A literature search was performed to ascertain the epidemiology of psychopathology in IF and the current evidence for the management of severe functional GI disorders with a multidisciplinary psychiatric approach.

KEY RESULTS

(i)All six cases required multidisciplinary psychiatric management in a specialized psychiatric unit that included the use of antidepressants, antipsychotics, mood stabilizers, and Electroconvulsive therapy in addition to nutritional support via enteral or parenteral routes. (ii) The evidence base for the treatment of severe FGIDs is sparse.

CONCLUSIONS & INFERENCES

There is a need for additional reporting of such cases and further research. Our experience would suggest that a delay in the involvement of a specialist liaison psychiatrist has the potential to be life threatening in such cases. This may be more likely with greater severity, where the apparent predominance of 'physical' symptoms generates reluctance in both patient and physician to consider a psychiatric etiology and also appears to occur due to a lengthier investigative process than existed previously. We therefore propose that the provision of a specialist psychiatric assessment for all patients presenting with IF is indicated at the point of initial clinical contact, based upon the substantial clinical benefit it has the potential to confer upon a significant minority. This process need not delay investigation, which can continue as indicated in parallel, but can be life-saving.

Psychiatric Co-morbidity and Efficacy of Mirtazapine Treatment in Young Subjects With Chronic or Cyclic Vomiting Syndromes: A Case Series

The aim of this case report was to evaluate the psychiatric co-morbidity and efficacy of mirtazapine treatment in young subjects with chronic or cyclic vomiting syndromes. This is a case series of 8 young subjects (age range of 6-16 years, 11.12 ± 3.52 years) who were referred or consulted to child psychiatry department. They were referred or consulted by pediatric gastroenterology or surgery departments for the presence of non-remitting and medically unexplained vomiting. They were investigated for co-morbid psychiatric disorders using a structured psychiatric interview. An open trial of mirtazapine was conducted for the treatment and/or prevention of vomiting. Primary outcome measure was Clinical Global Impression-Improvement scale. Subjects were diagnosed with chronic (n = 5) or cyclic (n = 3) vomiting syndromes. Duration of vomiting ranged from 6 months to 10 years (3.5 ± 3.2 years). All subjects received multiple psychiatric diagnoses with anxiety disorders being the most frequent. Maximum mirtazapine dosage was 7.5-30 mg/day (16.00 ± 6.16 mg/day). Three subjects showed complete remission and 5 subjects showed much to very much improvement in vomiting. Most frequent side effects were increased appetite, weight gain and sedation. Young subjects with chronic or cyclic vomiting may frequently suffer anxiety and/or depressive symptoms or disorders. Mirtazapine could be an effective treatment option for the treatment of vomiting and co-morbid anxiety or depressive disorders in these subjects. More systematic research are needed on this topic.

Characteristics of patients with chronic unexplained nausea and vomiting and normal gastric emptying

BACKGROUND & AIMS

Chronic nausea and vomiting with normal gastric emptying is a poorly understood syndrome; we analyzed its characteristics.

METHODS

We collected and analyzed data from 425 patients with chronic nausea and vomiting, enrolled at 6 centers by the Gastroparesis Clinical Research Consortium in the National Institute of Diabetes and Digestive and Kidney Diseases Gastroparesis Registry.

RESULTS

Among the patients, 319 (75%) had delayed emptying, defined by the results of a standardized, low-fat meal, and 106 had normal gastric emptying. Patients with or without delayed emptying did not differ in age, sex, or race, although those with normal gastric emptying were less likely to be diabetic. Symptom severity indexes were similar between groups for nausea, retching, vomiting, stomach fullness, inability to complete a meal, feeling excessively full after meals, loss of appetite, bloating, and visibly larger stomach. There were no differences in health care utilization, quality of life indexes, depression, or trait anxiety scores. However, state anxiety scores were slightly higher among patients with delayed gastric emptying. Total gastroparesis cardinal symptom index scores were not correlated with gastric retention after 2 or 4 hours in either group. Patients with the syndrome were not adequately captured by the stand-alone criteria for the Rome III diagnoses of chronic idiopathic nausea and functional vomiting. With rare exceptions, the diagnosis remained stable after a 48-week follow-up period.

CONCLUSIONS

Patients with nausea and vomiting with normal gastric emptying represent a significant medical problem and are, for the most part, indistinguishable from those with gastroparesis. This syndrome is not categorized in the medical literature--it might be a separate clinical entity.

Escitalopram for psychogenic nausea and vomiting: a report of two cases

Psychogenic nausea and vomiting is defined as vomiting without any obvious organic pathology or vomiting with a psychological etiology. The treatment for such a condition is a challenge in clinical practice. The first patient was a 46-year-old married factory worker who was repeatedly hospitalized for recurring bouts of nausea and vomiting. After consultation, she was diagnosed with major depressive disorder. The frequency of nausea and vomiting decreased after treatment with daily doses of 10-20 mg escitalopram. The second patient was a 37-year-old married teacher who had bouts of nausea and vomiting and was also hospitalized repeatedly. She was diagnosed with mixed anxiety-depressive disorder. After treatment with 10 mg/day escitalopram, her episodes of nausea and vomiting decreased. Escitalopram may be an effective treatment for psychogenic nausea and vomiting associated with depression.

Pathophysiological and psychosocial study in patients with functional vomiting

Background/Aims

To explore clinical patterns, predisposing factors, psychosocial aspects and the possible pathogenesis in Functional Vomiting (FV) patients.

Methods

Ten healthy subjects and 19 FV patients participated in this study. Gastrointestinal symptoms and psychological state were evaluated by questionnaires, including Zung self-rating anxiety and depression scale and Eysenck personality questionnaire. Cutaneous electrogastrography, perfusion nutrition load test and intragastric pressure were performed in patients. Perfusion nutrition load test and intragastric pressure were also performed in healthy subjects.

Results

FV involved young female predominantly (4 male, 15 female; age 25.8 ± 8.4 years). Postprandial vomiting soon after meal without self-induced maneuver was the most common pattern of FV. Prevalence for overlaps between FV and functional dyspepsia was high (84.2%). Emotional changes and stress contributed to the development of FV. Prevalence of abnormal psychological status and personality in patients with FV was high (83.3% and 47.1%). Patients with FV had significant postprandial gastric dysrhythmia, impaired gastric accommodation and enhanced gastric sensitivity. There were significant correlations between clinical presentations, gastric function and psychological states.

Conclusions

Patients with FV had abnormal psychological status, gastric dysmotility and hypersensitivity, which indicated that both of peripheral and central abnormalities could contribute to the pathogenesis of FV.

Hyperirritable stomach as a cause of nausea and vomiting: clinical and radiographic findings

OBJECTIVE

The purpose of our study was to characterize the clinical and radiographic features of the hyperirritable stomach and to determine if it is associated with extraintestinal causes of nausea and vomiting in the absence of gastric outlet obstruction, gastroparesis, or intestinal obstruction or ileus.

CONCLUSION

The hyperirritable stomach was characterized on barium studies in 15 patients by rapid emesis of ingested barium, a collapsed stomach with little or no retained debris or fluid, and normal emptying of residual barium into nondilated duodenum and proximal jejunum. Fourteen (93%) of these 15 patients had extraintestinal causes of nausea and vomiting, and 13 (93%) of 14 with clinical follow-up had marked improvement or resolution of symptoms after treatment. Radiologists therefore should evaluate the stomach and duodenum even after rapid emesis of ingested barium in patients with nausea and vomiting to differentiate a hyperirritable stomach from mechanical or functional gastrointestinal obstruction.

Functional gastroduodenal disorders

A numerically important group of patients with functional gastrointestinal disorders have chronic symptoms that can be attributed to the gastroduodenal region. Based on the consensus opinion of an international panel of clinical investigators who reviewed the available evidence, a classification of the functional gastroduodenal disorders is proposed. Four categories of functional gastroduodenal disorders are distinguished. The first category, functional dyspepsia, groups patients with symptoms thought to originate from the gastroduodenal region, specifically epigastric pain or burning, postprandial fullness, or early satiation. Based on recent evidence and clinical experience, a subgroup classification is proposed for postprandial distress syndrome (early satiation or postprandial fullness) and epigastric pain syndrome (pain or burning in the epigastrium). The second category, belching disorders, comprises aerophagia (troublesome repetitive belching with observed excessive air swallowing) and unspecified belching (no evidence of excessive air swallowing). The third category, nausea and vomiting disorders, comprises chronic idiopathic nausea (frequent bothersome nausea without vomiting), functional vomiting (recurrent vomiting in the absence of self-induced vomiting, or underlying eating disorders, metabolic disorders, drug intake, or psychiatric or central nervous system disorders), and cyclic vomiting syndrome (stereotypical episodes of vomiting with vomiting-free intervals). The rumination syndrome is a fourth category of functional gastroduodenal disorder characterized by effortless regurgitation of recently ingested food into the mouth followed by rechewing and reswallowing or expulsion. The proposed classification requires further research and careful validation but the criteria should be of value for clinical practice; for epidemiological, pathophysiological, and clinical management studies; and for drug development.

Chronic nausea and vomiting: new insights and approach to treatment

Chronic vomiting of unclear etiology has been given a number of names over time. For many years, it was known as "psychogenic" vomiting because a psychiatric etiology was considered the most likely cause. More recently, the concepts of cyclic vomiting syndrome (CVS) and functional vomiting (FV) have been proposed to better explain this perplexing phenomenon. CVS is a dramatic clinical syndrome characterized by intense episodes of vomiting lasting over a period of days but alternating with periods of intense quiescence. FV, as defined by the Rome II diagnostic criteria, is vomiting of at least 3 months, which need not be consecutive, in the preceding year with at least three separate vomiting episodes in a week. It is found in the absence of obvious metabolic, structural, or psychiatric disorders which could explain the vomiting (Table 1). It will be the purpose of this article to review the history of chronic vomiting from a nomenclature perspective. Methodologic limitations of early studies will be described as well as more contemporary reviews that used updated methodologic approaches to describe this perplexing problem.

A Somatoform Variant of Obsessive-Compulsive Disorder: A Case Report of OCD Presenting With Persistent Vomiting

Acute nausea and vomiting are often self-limited or easily treated. Persistent vomiting, however, poses diagnostic and therapeutic challenges for the primary care physician. In addition to gastrointestinal, neurologic, and endocrine disorders, the differential diagnosis includes psychiatric illnesses, such as eating and factitious disorders. We present the case of a 52-year-old woman referred to the Tulane University Internal Medicine/Psychiatry clinic with persistent daily vomiting for 8 years despite repeated medical evaluations. The vomiting was of sufficient severity to require intensive care unit admission for hematemesis. A dually trained internal medicine-psychiatry house officer obtained further history and identified that the woman experienced an intrusive thought that urged her to vomit after each meal. Resisting the urge resulted in intolerable anxiety that was relieved only by vomiting. Obsessive-compulsive disorder (OCD) was diagnosed according to DSM-IV criteria. Initiation of escitalopram with titration to clinical response resulted in full symptom resolution and meaningful quality of life improvement. Pertinent literature was reviewed using 2 methods: (1) an English-language MEDLINE search (1966-February 2004) using the search terms vomiting and (chronicor psychogenicor psychiatric), and obsessive-compulsive disorder and (primary care or treatment); and (2) a direct search of reference lists of pertinent journal articles. A review of psychiatric etiologies of vomiting and primary care aspects of OCD is presented. Primary care clinicians are strongly encouraged to consider psychiatric etiologies, including OCD, when common symptoms persist or present in atypical ways. Such disorders can be debilitating but also responsive to treatment.

Intractable vomiting in diabetic patients

Intractable nausea and vomiting have been described in individuals without any underlying physical etiology explaining these complaints. Physical or emotional abuse has been described in individuals suffering from these symptoms and associated with somatoform disorders manifesting primarily as gastrointestinal complaints. We present five patients with long-standing Type 1 diabetes who suffered from intractable vomiting. Personality disorders, profound depression and emotional abuse dramatically influenced the course of these patients' illness. In most of the patients, physical symptoms remarkably improved after identification and removal of the triggering factors. Therefore, psychogenic vomiting must be considered among the differential diagnoses of intractable nausea and vomiting, especially in individuals with chronic illnesses. A careful search for a physical etiology and medical treatment that does not cause relief of symptoms should suggest that there is almost certainly a psychological issue at the root of the problem.

Heterogeneity of diagnoses presenting as cyclic vomiting

OBJECTIVE

To establish the diagnostic profile in children who present with cyclic vomiting.

METHODS

We studied 225 children < 18 years of age who presented to our pediatric gastroenterology service from 1986 to 1997 with at least three discrete episodes of vomiting between which they were well. To determine the diagnoses in those presenting with a pattern of cyclic vomiting, the results of diagnostic testing and responses to various treatments were obtained from a combination of chart review and structured telephone interviews.

RESULTS

The largest diagnostic category included idiopathic cyclic vomiting syndrome (88%). Extraintestinal disorders (7%) and gastrointestinal disorders (5%) constituting the probable cause of vomiting were established in those having complete cessation of episodes after therapy. In 12%, serious surgical disorders of the gastrointestinal (malrotation), renal (acute hydronephrosis), and central nervous systems (neoplasm) were found. In 2%, serious endocrine (Addison's disease) and metabolic disorders (disorder of fatty acid oxidation) were found. Among those with idiopathic cyclic vomiting syndrome, 41% had associated disorders (gastroesophageal reflux and chronic sinusitis) that could contribute to the vomiting, but, based on a partial response to therapy, were not deemed to be the main cause. Altogether 49% had an identified disorder that probably caused or could contribute to the vomiting.

CONCLUSIONS

The cyclic pattern of vomiting is a symptom complex that can be induced by heterogeneous disorders that either cause or contribute to the vomiting. Once the cyclic vomiting pattern is identified, systematic diagnostic testing is warranted to look for these underlying disorders.

Psychogenic vomiting complicated by marijuana abuse and spontaneous pneumomediastinum

OBJECTIVE

This case illustrates an unusual physical sequel of psychogenic vomiting.

CLINICAL PICTURE

A 22-year-old man with a picture of psychogenic vomiting and marijuana use developed the complications of a pneumomediastinum and subcutaneous emphysema.

TREATMENT

Therapy included gradual exposure to anxiety provoking stimuli, psychotropics to reduce vomiting and psychotherapeutic exploration of family relationships.

OUTCOME

The patient's vomiting and physical state resolved without complication. Follow-up at 12 months revealed continued improvement with occasional less severe vomiting.

CONCLUSIONS

Psychogenic vomiting as a manifestation of anxiety can result in serious physical and psychological sequelae. This patient's desperate attempts to control such vomiting complicated the picture. Successful short term intervention included the use of several treatment modalities.

Psychosocial aspects of functional gastrointestinal disorders

Increased numbers of psychiatric diagnoses and increased levels of psychological distress are seen in the majority of medical clinic patients with gastrointestinal motility disorders. In IBS, psychological symptoms are believed to be comorbid conditions, which do not cause the motility disorder but which do influence the patient's decision to consult a physician. In functional dyspepsia, psychological symptoms are present in many patients, but their role is not known; the available data suggest that psychological symptoms do not predict which patients will consult a physician. Among constipated patients, anxiety is believed to contribute to the development and course of pelvic floor dyssynergia by increasing pelvic floor muscle tension. Constipated patients without physiologic abnormalities to explain their constipation appear to have more psychological symptoms than those with delayed colonic transit, but there is significant psychological distress even in patients with slow transit constipation. Psychological symptoms do not seem to predict which constipated patients will consult a physician. There is an increased incidence of psychiatric diagnoses in patients with esophageal motility disorders as well, but the role that these psychological symptoms play in the course of the disorder is not known. Patients with the most common gastrointestinal motility disorders, IBS and dyspepsia, report experiencing more stressful life events, and IBS patients appear to show a greater increase in gastrointestinal symptoms when exposed to stressors. Laboratory studies document that acute psychological stressors do alter gastric, small bowel, and colonic motility, and patients with IBS appear to show a greater change in colonic and ileal motility with stress than healthy controls. Greater reactivity has not been demonstrated for the esophagus or stomach, however, and it has not been demonstrated for other gastrointestinal motility disorders. A characteristic of many patients who consult gastroenterologists for IBS and other motility disorders is a tendency to report multiple somatic complaints (including many nongastrointestinal complaints) and to overuse medical resources. This pattern of behavior is referred to as somatization or abnormal illness behavior. One source of abnormal illness behavior is childhood social learning, which occurs (1) when parents provide gifts or special privileges to a child who reports somatic symptoms or (2) when parents model abnormal illness behaviors themselves.

The use of contingency management in the treatment of a geriatric nursing home patient with psychogenic vomiting

A substantial percentage of nursing home residents evidence psychosocial and behavioral problems. However, surprisingly little is known about how effectively to treat geriatric patients with behavioral problems. The present study reports the behavioral treatment of a patient with psychogenic vomiting. The patient was successfully treated by changing the contingencies of her illness behavior and of behavior associated with rehabilitation goals. This indicates the importance of nursing home staff attending to the operants of illness behavior. Specifically, independent behavior should be rewarded by praise and attention and illness behavior should be ignored in terms of attention.

Brain areas essential or non-essential for emesis

This study was undertaken to better delineate those brain regions that are either essential or non-essential for vomiting. Fictive vomiting, identified by a characteristic pattern of respiratory nerve discharge, was induced by a combination of emetic drugs and electrical stimulation of abdominal vagal afferents in decerebrate, paralyzed cats. Regions non-essential for coordinating vomiting included the entire cerebellum, structures rostral to the medullary retrofacial nucleus, and spinal cord. Fictive coughing was also elicited following cerebellar removal but was not studied after other procedures. The respiratory-related components of fictive vomiting were abolished by large lesions or kainic acid injections in the lateral medulla at the level of the retrofacial nucleus, where respiratory pre-motor and motor neurons are known to exist. Electrical stimulation of this region of the brainstem failed to evoke vomiting. The results of the present study are consistent with our previous electrical stimulation [Brain Res., 270 (1983) 154-158] and c-fos [J. Neurosci., 14 (1994) 871-888] studies and the hypothesis that emesis is coordinated not by a unique, well-defined 'vomiting center' but rather by a distributed control system located in the medulla between the levels of the obex and the retrofacial nucleus.

The connectivity of the area postrema in the ferret

The area postrema (AP) is the chemosensitive trigger zone for the emetic reflex. We have investigated the connectivity of the AP and adjacent solitary complex (SC) to identify possible sites of the motor emetic center. The AP and SC were infused with HRP or WGA-HRP in 30 ferrets that were perfused transcardially after 24-72 h. A block from the pons to upper cervical spinal cord, and one with hypothalamus and basal forebrain, was cut at 50 microns, reacted, and mounted. Data support the conclusion, at variance with those from other preparations, that in ferrets the AP has reciprocal connections only with the SC, which serves as a relay in both ascending and descending pathways between AP and higher levels of the neuraxis. Connectivity of the SC with brain stem and forebrain structures including the rostral ventrolateral medulla, parabrachial nuclei, paraventricular nucleus, and amygdala was demonstrated. At least in ferrets, our results suggest that the motor emetic center must be located within the SC. While this may not apply to all species, it is also possible that some reports of AP projections elsewhere were results of label within the SC. Alternatively, the somewhat different pattern of emesis in the ferret as compared to the dog (greater role for vagal inputs in response to radiation and cytotoxic drugs, lesser role for humoral inputs) may reflect differences in AP connectivity.