Intentional paediatric poisoning presentations to emergency departments during the COVID-19 pandemic

OBJECTIVE

To characterise paediatric poisoning presentations to EDs and determine if the advent of the COVID-19 pandemic was associated with increased intentional paediatric poisoning presentations.

METHODS

We performed a retrospective analysis of paediatric poisoning presentations to three EDs (two regional and one metropolitan). Simple and multiple logistic regression analysis were performed to determine the association between COVID-19 and intentional poisoning events. In addition, we calculated the frequency with which patients reported various psychosocial risk factors as being an implicating factor in engaging in an intentional poisoning event.

RESULTS

A total of 860 poisoning events met inclusion criteria during the study period (January 2018-October 2021), with 501 being intentional, and 359 unintentional. There was an increased proportion of intentional poisoning presentations during the COVID-19 pandemic (261 intentional and 218 unintentional in the pre-COVID-19 period vs 241 intentional and 140 unintentional during the COVID-19 period). In addition, we found a statistically significant association between intentional poisoning presentations and an initial COVID-19 lockdown (adjusted odds ratio 26.32, P < 0.05). 'The COVID-19 lockdown' or 'COVID-19' was reported to be implicating factor for psychological stress in patients who presented with intentional poisonings during the COVID-19 pandemic.

CONCLUSIONS

Intentional paediatric poisoning presentations increased during the COVID-19 pandemic in our study population. These results may support an emerging body of evidence that the psychological strain of COVID-19 disproportionately impacts adolescent females.

Utility of non-contrast head computed tomography in poisoned patients

OBJECTIVE

To investigate the utility of non-contrast head computed tomography (CT) in poisoned patients.

METHODS

A retrospective cohort study of patients referred to a toxicology unit between August 2010 and December 2017. Our database yielded patients who underwent head CT at presentation to the ED. Pre-specified information was compiled from the medical records.

RESULTS

There were 6261 presentations of which 1142 underwent head CT (17%). Median age was 41 years, and 437 (38%) were female. There were 492 (43%) recreational ingestions and 466 (41%) deliberate self-poisonings. The commonest agents were sedatives 376 (33%) and opioids 282 (24%); 334 (29%) cases were intubated. Signs of head injury were found in 153 cases (13%) and focal neurological signs in 68 (6%). No acute pathology was reported in 884 head CTs (77%), chronic changes in 193 (17%) and incidental findings in 26 (2%). Acute pathology was found in 39 (4%) patients: 15 with hypoxic-ischaemic injury, three infarctions, nine with intra-cranial haemorrhage, 11 facial bone fractures and one retro-bulbar haematoma. No patient required an immediate surgical intervention, and only one patient had a change to clinical treatment. Acute head CT pathology was associated with at least one of the following clinical features: need for intubation, signs of head injury, seizure, headache, and unexpected neurological signs.

CONCLUSION

Non-contrast head CT is a low-yield investigation in patients presenting with poisoning. Consideration should be given as to whether the clinical presentation is consistent with the expected toxidrome and whether the patient would benefit from head CT.

Innovative Approaches to Improve Public Health Practice in the Eastern Mediterranean Region: Findings From the Sixth Eastern Mediterranean Public Health Network Regional Conference

Public health professionals in the Eastern Mediterranean region (EMR) have limited access to continuing education, including workshops and conferences in public health. Held under the theme Innovative Approaches: Adapting to the Current EMR Context, the Eastern Mediterranean Public Health Network (EMPHNET) organized and conducted the Sixth EMPHNET Regional Conference from March 26 to 29, 2018. This paper summarizes the key activities including workshops, roundtable discussions, oral and poster presentations, keynote speeches, and side meetings. Before the opening, 5 preconference workshops were held: “Field Epidemiology Training Program (FETP) Accreditation,” “Innovative Public Health Surveillance,” “Human and Animal Brucellosis,” “Rapid Response Teams,” and “Polio Transition and Routine Immunization.” The conference hosted 6 roundtable discussions: “Consolidation of the FETP Network,” “One Health to Achieve Global Health Security,” “Polio Eradication Efforts and Transition Planning for Measles Elimination,” “Mobile Data Collection and Other Innovative Tools to Enhance Decision Making,” “Confronting Candida auris: An Emerging Multidrug-resistant Global Pathogen,” and “Functioning and Sustainable Country Public Health Emergency Response Operation Framework.” One of the conference’s key objectives was to provide a space for FETP residents, graduates, and public health professionals to showcase achievements. A total of 421 abstracts were submitted and after professional review, 34.9% (147/421) were accepted (111 for oral presentations and 36 for poster presentations) and published by Iproceeding. The conference met the primary objectives of showcasing the public health accomplishments and contributions of the EMR, encouraging the exchange of ideas and coordination among stakeholders, and engaging cross-sectoral workforce in producing recommendations for approaching regional and global health concerns. Moreover, the conference presented a unique opportunity for FETPs and other public health professionals from the Mediterranean region to present their significant scientific work and also facilitated networking among professionals. EMPHNET strives to continue to present similar exchange opportunities for public health professionals in the region.

Training experience in drug and alcohol liaison work

We describe our training experience as members of a drug and alcohol liaison service within a major general teaching hospital. This type of liaison work offers valuable experience in the joint management of patients with well established substance misuse problems and also provides the opportunity for early recognition and preventative interventions.

Psychiatry and the media: from pitfalls to possibilities

In war, truth is said to be the first casualty. Something similar may be said for psychiatry. The ability of the media to distort public understanding of mental illness is well described (Wahl, 1995; Philo et al, 1994). Psychiatric disorders, their treatments and those who provide them are all subject to overwhelmingly negative portrayals in the print and broadcast media (Hyler et al, 1991). Dehumanisation, inaccuracy and sensationalism seem to be the media's stock-in-trade. Media professionals make no apology for this, citing the provision of impartial, emotionally-neutral accounts as one of their least pressing concerns (Salter & Byrne, 2000). They also reject the notion that they are responsible for the perpetuation of harmful stereotypes, claiming instead that they merely mirror the values and beliefs of our society (Bolton, 2000). This distorting mirror is of great relevance to psychiatry. It is probably no exaggeration to state that the celebrated cases of Christopher Clunis and Ben Silcock have done more to change the practice of community psychiatry than any College President or Secretary of State over the past 5 decades.

Forensic psychiatry and general psychiatry: re-examining the relationship

Something is going wrong with forensic psychiatry, as a concept and as a service. Beds in medium secure units are logjammed, and relations with general adult services increasingly fraught with disputes over resources and responsibilities. Despite a remarkable investment in buildings, and the 300% growth of the forensic specialty (Goldberg, 2006), offending behaviour by individuals with mental illness shows no sign of decline, either in terms of prison numbers (at record high levels in the UK) or the countless demands for risk assessment (Duggan, 1997; Moon, 2000).

Mental Health Act reform

Psychiatrists have been complaining about mental health legislation for over a century (Smith, 1891), usually in terms of the delays engendered, paperwork and bureaucracy, and the impositions on clinical practice. As a result they have gained more powers, and perhaps much-needed status within the medical profession, to the concern of some commentators (e.g. Fennell, 1996). Thus, the ‘triumph of legalism’ (Jones, 1993) of the Lunacy Act 1890 was modified by the Mental Treatment Act 1930, whereby outpatients and voluntary patients were encouraged and ‘asylums' became ‘mental hospitals'. Then came the radical change of the Mental Health Act (MHA) 1959, making compulsory detention an essentially medical decision and removing the routine of the courts, but retaining a theme of requiring ‘treatment in hospital’. The Mental Health Act 1983, however, was a touch anti-medical, since it strengthened the role of the approved social worker (ASW) and enhanced the importance of a patient's consent to treatment. “The primacy of the medical model and the paramountcy of the psychiatrist are certainly subject to greater limitations and external review”, was the opinion of William Bingley, then Mind's Legal Director, now Chief Executive of the Mental Health Act Commission – reviewing the Act in its early days (Bingley, 1985).

Serious Incident Inquiries: a survival kit for psychiatrists

Since 1999, a formal external inquiry into every homicide committed by a person with a mental disorder has been mandatory in the UK (Department of Health, 1994). Common opinion among psychiatrists is that Serious Incident Inquiries are unhelpful as they all reach similar conclusions, add nothing to our current knowledge and do more harm than good in terms of adverse publicity for mental health services (Buchanan, 1999). Despite this, there is presently little sign of a change in public policy. Psychiatrists continue to face the fact that the next incident could be ‘the one that's coming here’. Although the many flaws of the inquiry process have been well described (Szmukler, 2000), few have interpreted this knowledge in a way that is of practical help to a psychiatrist facing an inquiry.

Vaccination and established microbiological testing is essential in managing cholera and Ebola infection

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Frailty and mortality in kidney transplant recipients

We have previously described strong associations between frailty, a measure of physiologic reserve initially described and validated in geriatrics, and early hospital readmission as well as delayed graft function. The goal of this study was to estimate its association with postkidney transplantation (post-KT) mortality. Frailty was prospectively measured in 537 KT recipients at the time of transplantation between November 2008 and August 2013. Cox proportional hazards models were adjusted for confounders using a novel approach to substantially improve model efficiency and generalizability in single-center studies. We precisely estimated the confounder coefficients using the large sample size of the Scientific Registry of Transplantation Recipients (n = 37 858) and introduced these into the single-center model, which then estimated the adjusted frailty coefficient. At 5 years, the survivals were 91.5%, 86.0% and 77.5% for nonfrail, intermediately frail and frail KT recipients, respectively. Frailty was independently associated with a 2.17-fold (95% CI: 1.01-4.65, p = 0.047) higher risk of death. In conclusion, regardless of age, frailty is a strong, independent risk factor for post-KT mortality, even after carefully adjusting for many confounders using a novel, efficient statistical approach.

Limbic Encephalitis and Refractory Status Epilepticus in the ICU: Classification, Diagnosis and Treatment

Limbic encephalitis is a rare auto-immune condition that usually presents subacutely with vague symptoms such as headache, confusion and memory loss.1 If not diagnosed early the sequelae can be severe, including refractory status epilepticus. The majority of cases are associated with underlying neoplasia. We present a case of voltage-gated potassium channel limbic encephalitis and its subsequent management during a long ICU admission. We discuss the classification, diagnosis and treatment of limbic encephalitis, review the use of sodium thiopental to achieve burst suppression in refractory status epilepticus, and the use of continuous EEG monitoring in the ICU.

Achieving compliance with the International Health Regulations by overseas territories of the United Kingdom of Great Britain and Northern Ireland

The 2005 International Health Regulations (IHR) came into force for all Member States of the World Health Organization (WHO) in June 2007 and the deadline for achieving compliance was June 2012. The purpose of the IHR is to prevent, protect against, control – and provide a public health response to – international spread of disease. The territory of the United Kingdom of Great Britain and Northern Ireland and that of several other Member States, such as China, Denmark, France, the Netherlands and the United States of America, include overseas territories, which cover a total population of approximately 15 million people. Member States have a responsibility to ensure that all parts of their territory comply with the IHR. Since WHO has not provided specific guidance on compliance in the special circumstances of the overseas territories of Member States, compliance by these territories is an issue for self-assessment by Member States themselves. To date, no reports have been published on the assessment of IHR compliance in countries with overseas territories. We describe a gap analysis done in the United Kingdom to assess IHR compliance of its overseas territories. The findings and conclusions are broadly applicable to other countries with overseas territories which may have yet to assess their compliance with the IHR. Such assessments are needed to ensure compliance across all parts of a Member States’ territory and to increase global health security.

Establishing an enteric bacteria reference laboratory in Sierra Leone

In 2012, Sierra Leone experienced its worst cholera outbreak in over 15 years affecting 12 of the country’s 13 districts. With limited diagnostic capability, particularly in bacterial culture, the cholera outbreak was initially confirmed by microbiological testing of clinical specimens outside of Sierra Leone. During 2012 – 2013, in direct response to the lack of diagnostic microbiology facilities, and to assist in investigating and monitoring the cholera outbreak, diagnostic and reference services were established in Sierra Leone at the Central Public Health Reference Laboratory focusing specifically on isolating and identifying Vibrio cholerae and other enteric bacterial pathogens. Sierra Leone is now capable of confirming cholera cases by reference laboratory testing.

Perceptions of community- and family-level injection drug user (IDU)- and HIV-related stigma, disclosure decisions and experiences with layered stigma among HIV-positive IDUs in Vietnam

This paper explores how perceived stigma and layered stigma related to injection drug use and being HIV-positive influence the decision to disclose one's HIV status to family and community and experiences with stigma following disclosure among a population of HIV-positive male injection drug users (IDUs) in Thai Nguyen, Vietnam. In qualitative interviews conducted between 2007 and 2008, 25 HIV-positive male IDUs described layered stigma in their community but an absence of layered stigma within their families. These findings suggest the importance of community-level HIV prevention interventions that counter stigma and support families caring for HIV-positive relatives.

Bench-to-bedside review: the value of cardiac biomarkers in the intensive care patient

The use of cardiac biomarkers in the intensive care setting is gaining increasing popularity. There are several reasons for this increase: there is now the facility for point-of-care biomarker measurement providing a rapid diagnosis; biomarkers can be used as prognostic tools; biomarkers can be used to guide therapy; and, compared with other methods such as echocardiography, the assays are easier and much more affordable. Two important characteristics of the ideal biomarker are disease specificity and a linear relationship between the serum concentration and disease severity. These characteristics are not present, however, in the majority of biomarkers for cardiac dysfunction currently available. Those clinically useful cardiac biomarkers, which naturally received the most attention, such as troponins and B-type natriuretic peptide, are not as specific as was originally thought. In the intensive care setting, it is important for the user to understand the degree of specificity of these biomarkers and that the interpretation of the results should always be guided by other clinical information. The present review summarizes the available biomarkers for different cardiac conditions. Potential biomarkers under evaluation are also briefly discussed.

Pharmacological properties of the enhanced-affinity glucocorticoid fluticasone furoate in vitro and in an in vivo model of respiratory inflammatory disease

Fluticasone furoate (FF) is a novel enhanced-affinity glucocorticoid that has been developed as topical therapy for allergic rhinitis. The pharmacological properties of FF have been investigated using a number of in vitro experimental systems. FF demonstrated very potent glucocorticoid activity in several key pathways downstream of the glucocorticoid receptor (GR) as follows: the transrepression nuclear factor-kappaB (NF-kappaB) pathway, the transactivation glucocorticoid response element pathway, and inhibition of the proinflammatory cytokine tumor necrosis factor-alpha. Furthermore, FF showed the greatest potency compared with other glucocorticoids for preserving epithelial integrity and reducing epithelial permeability in response to protease- and mechanical-induced cell damage. FF showed a 30- to >330,000-fold selectivity for GR-mediated inhibition of NF-kappaB vs. the other steroid hormone receptors, substantially better than a number of other clinically used glucocorticoids. In studies examining the respiratory tissue binding properties of glucocorticoids, FF had the largest cellular accumulation and slowest rate of efflux compared with other clinically used glucocorticoids, consistent with greater tissue retention. The in vivo anti-inflammatory activity of FF was assessed in the Brown Norway rat ovalbumin-induced lung eosinophilial model of allergic lung inflammation. At a dose of only 30 microg, FF achieved almost total inhibition of eosinophil influx in the lung, an inhibition that was greater than that seen with the same dose of fluticasone propionate. In conclusion, the potent and selective pharmacological profile of FF described here could deliver an effective, safe, and sustained topical treatment of respiratory inflammatory diseases such as allergic rhinitis and asthma.

Design and synthesis of new nonsteroidal glucocorticoid modulators through application of an "agreement docking" method

Structurally related glucocorticoid receptor (GR) binders were docked into the GR active site to select the binding mode closest to the true docking mode. This process, termed an "agreement docking method", led to the design of tetrahydronaphthalene 9. The method was validated by the syntheses of 9 and related analogues, which are potent binders of GR. 15a is a partial agonist while 9e and 15a are micromolar antagonists in a mouse mammary tumor virus transactivation assay.

Quantifying the hurdle concept by modelling the bacterial growth/no growth interface

The hurdle concept described eloquently over many years by Professor Leistner and his colleagues draws attention to the interaction of factors that affect microbial behaviour in foods. Under some circumstances these effects are additive. Under others the implication is that synergistic interactions lead to a combined effect of greater magnitude than the sum of constraints applied individually. Predictive modelling studies on the combined effects of temperature and water activity and temperature and pH suggest that the effect of these combinations on growth rate is independent. Where the effect of the two factors is interactive rather than independent is at the point where growth ceases--the growth/no growth interface. An interesting and consistent observation is that a very sharp cut off occurs between conditions permitting growth and those preventing growth, allowing those combinations of factors to be defined precisely and modelled. Growth/no growth interface models quantify the effects of various hurdles on the probability of growth and define combinations at which the growth rate is zero or the lag time infinite. Increasing the stringency of one or more hurdles at the interface by only a small amount will significantly decrease the probability of an organism growing. Understanding physiological processes occurring near the growth/no growth interface and changes induced by moving from one side of the interface to the other may well provide insights that can be exploited in a new generation of food preservation techniques with minimal impact on product quality.

Do not resuscitate (DNR): analysis of the DNR act

Due to advances in technology, physicians and patients are being faced with the issue of do not resuscitate (DNR). DNR is an order that determines whether or not cardiopulmonary resuscitation (CPR) should be administered to a critically ill person. Within the state of Oklahoma, the Oklahoma DNR act was created in order to establish regulations regarding the decision-making of when to use CPR. This Act gives rise to legal and ethical problems, which have been taken into consideration by the Oklahoma Association for Healthcare Ethics (OAHE). The following article focuses on DNR with examples of case histories and possible recommendations for improvement to the current law. Furthermore, this article sets out to show why the decision of whether or not to resuscitate should be made by the patient or their family.

Final report of Intergroup Trial 0122 (ECOG PE-289, RTOG 90-12): Phase II trial of neoadjuvant chemotherapy plus concurrent chemotherapy and high-dose radiation for squamous cell carcinoma of the esophagus

PURPOSE

To determine the outcome of neoadjuvant chemotherapy followed by concurrent chemotherapy plus high-dose radiation therapy in patients with local/regional squamous cell carcinoma of the esophagus.

METHODS AND MATERIALS

Forty-five patients with clinical Stage T1-4N0-1M0 squamous cell carcinoma were entered on a prospective single-arm study, of which 38 were eligible. Patients received 3 monthly cycles of 5-FU (1000 mg/m2/24 h x 5 days) and cisplatin (100 mg/m2 day 1; neoadjuvant segment) followed by 2 additional monthly cycles of 5-FU (1000 mg/m2/24 h x 5 days) and cisplatin (75 mg/m2 day 1) plus concurrent 6480 cGy (combined modality segment). The median follow-up in surviving patients was 59 months.

RESULTS

For the 38 eligible patients, the primary tumor response rate was 47% complete, 8% partial, and 3% stable disease. The first site of clinical failure was 39% local/regional and 24% distant. For the total patient group, there were 6 deaths during treatment, of which 9% (4/45) were treatment related. The median survival was 20 months. Actuarial survival at 3 years was 30%, and at 5 years, 20%.

CONCLUSION

This intensive neoadjuvant approach does not appear to offer a benefit compared with conventional doses and techniques of combined modality therapy. However, high dose radiation (6480 cGy) appears to be tolerable, and is being tested further in Intergroup Trial INT 0123.

N-Phenylamidines as selective inhibitors of human neuronal nitric oxide synthase: structure-activity studies and demonstration of in vivo activity

Selective inhibition of the neuronal isoform of nitric oxide synthase (NOS) compared to the endothelial and inducible isoforms may be required for treatment of neurological disorders caused by excessive production of nitric oxide. Recently, we described N-(3-(aminomethyl)benzyl)acetamidine (13) as a slow, tight-binding inhibitor, highly selective for human inducible nitric oxide synthase (iNOS). Removal of a single methylene bridge between the amidine nitrogen and phenyl ring to give N-(3-(aminomethyl)phenyl)acetamidine (14) dramatically altered the selectivity to give a neuronal selective nitric oxide synthase (nNOS) inhibitor. Part of this large shift in selectivity was due to 14 being a rapidly reversible inhibitor of iNOS in contrast to the essentially irreversible inhibition of iNOS observed with 13. Structure-activity studies revealed that a basic amine functionality tethered to an aromatic ring and a sterically compact amidine are key pharmacophores for this class of NOS inhibitors. Maximal nNOS inhibition potency was achieved with N-(3-(aminomethyl)phenyl)-2-furanylamidine (77) (Ki-nNOS = 0.006 microM; Ki-eNOS = 0.35 microM; Ki-iNOS = 0.16 microM). Finally, alpha-fluoro-N-(3-(aminomethyl)phenyl)acetamidine (74) (Ki-nNOS = 0. 011 microM; Ki-eNOS = 1.1 microM; Ki-iNOS = 0.48 microM) had excellent brain penetration and inhibited nNOS in a rat brain slice assay as well as in the rat brain (cerebellum) in vivo. Thus, N-phenylamidines should be useful in validating the role of nNOS in neurological disorders.

Sucralfate for radiation mucositis: results of a double-blind randomized trial

PURPOSE

To determine if addition of the ulcer-coating polysaccharide sucralfate could improve symptomatic relief of radiation mucositis over a popular combination of antacid, diphenhydramine, and viscous lidocaine alone.

METHODS AND MATERIALS

A double-blind study was conducted in which nurses and pharmacists coded patient groups and distributed medication in a manner blinded to both the patients and physicians. Eligible patients receiving radiation to the head and neck and/or chest sites that included the esophagus were randomized to a standard combination of antacid, diphenhydramine, and viscous lidocaine vs. the same solution plus sucralfate. Eligible patients were those receiving >40 Gy at 1.8 Gy/fraction, one fraction/day, five fractions/week. Participating patients were stratified between chest, small field head and neck, and large field head and neck. The patients subjective evaluation of throat soreness and relief with medication was elicited as well as physician observations and smears for Candidiasis screening. Medication was prescribed when the patient became symptomatic and concomitant use of other locally effective nonstudy agents was not allowed. The ability to eat various consistency of foods was graded 0-5, with 5 indicating no compromise of ability to ingest a food compared to baseline. Statistical analysis included mean + SD for food and soreness scores, paired t-test, and two-way analyses of variance to evaluate effects of site and treatment group on the changes in scores.

RESULTS

Over 2 years, 111 patients were entered. Because some withdrew and others did not require medication, results are presented for evaluable patients in each category. Mild adverse effects from the medication solution (usually mouth discomfort) were reported by <10% of patients in each treatment group among 106 patients evaluable for toxicity. There was a comparable incidence of mild-moderate mucositis for the two treatment groups. Severe mucositis was noted in two patients of the standard medication group and none among patients receiving sucralfate. The groups were comparable for indicators including degree of soreness, dietary changes, and objective measures or mucosal irritation or infection. For the head and neck patients there was a significant worsening in soreness and in the ability to eat in both treatment groups, whereas patients treated to the chest had less nutritional change. Multivariate analysis including control for confounding factors did not detect treatment effects for any of the response measures. No patient had occult fungal infection detected by oral pathology evaluation of routine mucosal scrapings.

CONCLUSIONS

A trend (that was not statistically significant) of less severe radiation mucositis was noted for patients receiving sucralfate in addition to the combination of viscous lidocaine, diphenhydramine, and antacid for nonulcerative radiation mucositis.

Quantitative microbiology: a basis for food safety

Because microorganisms are easily dispersed, display physiologic diversity, and tolerate extreme conditions, they are ubiquitous and may contaminate and grow in many food products. The behavior of microbial populations in foods (growth, survival, or death) is determined by the properties of the food (e.g., water activity and pH) and the storage conditions (e.g., temperature, relative humidity, and atmosphere). The effect of these properties can be predicted by mathematical models derived from quantitative studies on microbial populations. Temperature abuse is a major factor contributing to foodborne disease; monitoring temperature history during food processing, distribution, and storage is a simple, effective means to reduce the incidence of food poisoning. Interpretation of temperature profiles by computer programs based on predictive models allows informed decisions on the shelf life and safety of foods. In- or on-package temperature indicators require further development to accurately predict microbial behavior. We suggest a basis for a "universal" temperature indicator. This article emphasizes the need to combine kinetic and probability approaches to modeling and suggests a method to define the bacterial growth/no growth interface. Advances in controlling foodborne pathogens depend on understanding the pathogens' physiologic responses to growth constraints, including constraints conferring increased survival capacity.

Determination of the flux control coefficient of nitric oxide synthase for nitric oxide synthesis in discrete brain regions in vivo

The flux control coefficient of nitric oxide synthase (NOS), for the in vivo synthesis of the key biological mediator nitric oxide (NO), was determined in four rat brain regions with varying NOS activities (cerebral cortex, hippocampus, amygdala and cerebellum) using metabolic control theory. Flux control coefficients were calculated from the ratio of the initial slopes of the fractional effect of the NOS inhibitor N omega-nitro-L-arginine (L-NA) on NO pathway flux and NOS activity. Under conditions of normal behaviour in the rat, NOS had a flux control coefficient not significantly different from one in all regions examined. These data demonstrate that the large majority of flux control for the synthesis of NO in the brain resides in NOS itself and not in the transport of its amino acid precursor, L-arginine, across the blood-brain or neuronal cell membranes. This paper describes the first example in which the control of metabolic flux has been quantified in a mammalian system in vivo and demonstrates the power of metabolic control theory to elucidate the distribution of control within a metabolic pathway in vivo.

The nitric oxide-cyclic GMP pathway is required for nociceptive signalling at specific loci within the somatosensory pathway

The involvement of nitric oxide in nociceptive processing was examined at the main loci of synaptic transmission within the rat somatosensory pathway from the caudal sural cutaneous nerve. Intrathecal (lumbar 1-3) administration of the nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester (30 micrograms), inhibited nitric oxide synthase in this region of the spinal cord by greater than 80% but had no significant effect on nitric oxide synthase in parietal cerebral cortex, thalamus or medulla/pons. In a rat model of peripheral neuropathy (one to two week ligation of the caudal sural cutaneous nerve), intrathecal administration of the same dose of N omega-nitro-L-arginine methyl ester prevented the hyperalgesic response to thermal stimuli. Administration of 30 micrograms N omega-nitro-L-arginine methyl ester into the lateral ventricle had no effect on nitric oxide synthase in the lumbar 1-3 region of the spinal cord but gave substantial inhibition in higher areas of the somatosensory pathway (parietal cerebral cortex, thalamus and medulla/pons). Nitric oxide synthase in the parietal cerebral cortex (but not thalamus) was inhibited to a greater extent in the hemisphere ipsilateral to the site of administration. Administration of 30 micrograms N omega-nitro-L-arginine methyl ester into the lateral ventricle decreased thermal hyperalgesia, but only when N omega-nitro-L-arginine methyl ester was administered contralateral to the ligated caudal sural cutaneous nerve and therefore ipsilateral to the cortical nociceptive processing from this nerve. Intrathecal and intracerebroventricular administration of the selective inhibitor of nitric oxide-sensitive guanylyl cyclase, 1-H-[1,2,4]oxadiazalo[4,3-a]quinoxalin-1-one, also decreased the hyperalgesic response to thermal stimuli. These data demonstrate that, in a model of neuropathic pain, nitric oxide is involved in nociceptive processing at spinal and cerebrocortical synaptic loci of the somatosensory pathway and that its actions appear to be mediated through guanylyl cyclase.