By W. Phil. United States Naval Academy. 2019.
New York: Elsevier buy super levitra 80 mg with mastercard, 1999:711–714 purchase super levitra 80 mg without a prescription, with permis- means that eating a meal is not produced by a ballistic con- sion of the publisher buy super levitra 80mg. That meaning comes from experiments in the chronic decerebrate rat. Because the cau- dal brainstem contains the cpg and all of the projections of the afferent nerves mediating peripheral feedback effects, the decerebrate rat responds to direct controls (18,19). In contrast, none of the indirect controls that have been tested affect eating in the chronic decerebrate rat. Because indirect controls require the forebrain to be connected to the caudal brainstem in order to control eating, the reciprocal connec- tions between forebrain and hindbrain are necessary for the modulation of the direct controls by the indirect controls. This theory asserts that indirect controls have no direct ac- tion on the cpg during a meal in the absence of direct con- FIGURE 115. Flow diagram of the direct controls of meal size trols activated by ingested food. Specifying the peptidergic stimulated by ingested food acting on preabsorptive receptors of and aminergic connections that mediate an indirect con- the gastrointestinal tract. The efferent output of the central networks for the con- the neural control of eating converge. Because some The identification of the importance of the positive and of the direct controls are stimulated by ingested food in every meal, indirect controls of meal size exert their effects by modulat- negative feedbacks from the periphery in the direct controls ing direct controls. Feeding: tates the investigation of human eating disorders in three control of eating. The peripheral, preabsorptive sites of action are accessi- ble to controlled stimulation in the conscious human before, during, and after test meals. An increase or a decrease in meal size can be explained persion over large areas provides for the effect of stimulus by changes in feedback potency (Table 115. Identifying which combination of changes in feedback The second point is that all of the afferent fibers from the underlies the change in meal size focuses the search for mouth, stomach, and small intestine project to the caudal neurobiological mechanism because the feedbacks have brainstem. The direct preabsorptive stimulation by the stimuli of ingested food and its digestive products that provide feed- back control during a meal is a criterion for distinguishing these feedback controls from all other controls. CHANGES IN POTENCY OF AFFERENT back controls are direct controls of meal size (Fig. This is not an arbitrary classification because it is based Afferent Feedback on a biological criterion of site of action. The classification Change of Meal Size Positive Negative Increase Increase Decrease Increase Increase No change a Increase Increase Smaller increase TABLE 115. INDIRECT CONTROLS OF MEAL SIZE Increase No change Decrease Decrease Decrease Increase Categories Examples Decrease Decrease No change Rhythmic Diurnal, estrogen Decrease Decrease Smaller decrease Metabolic Changes in leptin, insulin, and fatty acids Decrease No change Increase Thermal Environmental and fever a Some changes of afferent feedbacks responsible for increased or Conditioned Preferences, aversions, and satiations decreased meal size. Identification of the mechanisms of a specific Cognitive Social and, in humans, cultural and esthetic change(s) in potency of feedbacks is an experimental problem. The controls of eating: a shift from aThe list of categories is neither mutually exclusive nor exhaustive; nutritional homeostasis to behavioral neuroscience. Nutrition this is particularly true for conditioned, cognitive, and ecological. Chapter 115: The Behavioral Neuroscience of Eating 1669 TABLE 115. MOLECULAR MECHANISMS OF DIRECT CONTROLS OF MEAL SIZE Direct controls Peripheral Central Orosensory Gustatory and olfactory transducers Dopaminea Opioidsa Gastric CCKa at CCK vagal mechanoreceptors, Amino acids from gastric vagal A other mechanoreceptors, and afferent terminals in NTS bombesin-like peptides Serotonina Small intestinal CCKaat CCK receptors on vagal Amino acids from duodenal and A mechanoreceptors and hepatic vagal afferent terminals chemoreceptors; glucagon,a in NTS amylin, enterostatin, apolipoprotein Serotonina IV, and insulin released by nutrient or digestive stimuli through contact with mucosal receptors or by the release of incretins NTS, nucleus tractus solitarius. The physiologic sta- tus of the other molecules is uncertain. The controls of eating: brain meanings of food stimuli. New York: Elsevier, 2000:173–186, with permission of the publisher. The combination of decreased central serotonergic pro- An example of the use of this theory of the control of cessing with decreased peripheral negative feedback could meal size is the recent work concerning the pathophysiology be particularly disruptive of satiation because the satiating of the abnormally large meals that characterize patients with potency of CCK in rats is synergistic with gastric distension bulimia nervosa. Since the 1970s there has been evidence and is reduced by decreased central serotonergic function, that these patients do not feel as full as normal after the particularly at 5-HT2C receptors (6). This has been confirmed more precisely in In addition to decreased negative feedback, bulimia pa- recent work that showed that bulimics require more food tients also have an abnormal cognitive indirect control. This suggests a defect in the They eat much larger meals when they are instructed to satiating process (21), specifically a defect in the potency of binge compared to when they are instructed not to binge negative feedback. The decreased negative feed- back could involve peripheral mechanisms or central modu- Numerous regions of the brain can be implicated in eating lation. Two peripheral abnormalities have been found: an by a variety of techniques in animals and humans. This enlarged stomach capacity (23) and a decreased release of reflects the fundamental biological importance of eating to CCK (24). The decreased release of CCK was ameliorated individual life and reproduction, and the functional require- when binge eating stopped in one experiment (25), but ments of a foraging omnivore. From this viewpoint, it is further experiments are required to evaluate this phenom- not surprising that learning and memory are important pro- enon. Three important types of There may also be a defect in the central processing of learning have been identified using Pavlovian procedures the decreased peripheral negative feedback information and theory: conditioned preference, conditioned aversion owing to abnormal function of the central serotonin system. If central serotonin function is decreased in bulimia pa- Conditioned preferences are formed by flavor–flavor as- tients, they should be more vulnerable than controls to a sociations or flavor–postingestive associations (28). Once further decrease in serotonin function produced by seroto- formed, the preferences increase the size of meals. This prediction has been confirmed: Acute the postingestive unconditioned stimulus is omitted, the tryptophan depletion that probably decreased central sero- conditioned preference persists for months, but its effect on 1670 Neuropsychopharmacology: The Fifth Generation of Progress intake extinguishes rapidly. The acquisition of a condi- UCS to form a conditioned satiation (41). Nothing is tioned flavor–postingestive preference requires dopamine known about the mechanisms that mediate this type of acting at D1 receptors, perhaps in the nucleus accumbens learning. It is interesting that the way to extinguish conditioned Conditioned aversions and avoidance are formed by asso- satiation in the rat is to prevent the accumulation of ingested ciations between orosensory stimuli (especially gustatory) food in the stomach and small intestine by draining the and aversive postingestive stimuli. Nausea is commonly re- gastric contents out through a chronic gastric fistula. This ported in humans who have conditioned aversions. It involves back from the stomach and small intestine. After three to a serotonergic mechanism because a 5-HT3 antagonist abol- five consecutive sham-meals, conditioned satiation is extin- ishes it (30). The same 5-HT mechanism is observed in guished and meal size is maximal.
Explore the acceptability of predictive risk stratification and communication of risk scores to patients and practitioners order generic super levitra from india. This issue may be freely reproduced for the purposes of private research and study and extracts (or indeed purchase super levitra 80 mg mastercard, the full report) may be included in professional journals xxv provided that suitable acknowledgement is made and the reproduction is not associated with any form of advertising order 80mg super levitra with visa. Applications for commercial reproduction should be addressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK. SCIENTIFIC SUMMARY Trial and study registration The trial is registered as ISRCTN55538212 and the study is registered as PROSPERO CRD42015016874. Funding Funding for this study was provided by the Health Services and Delivery Research programme of the National Institute for Health Research. A recent Health Foundation and Nuffield Trust report estimates that up to one in five emergency admissions are avoidable,10 especially where they relate to ambulatory care-sensitive conditions – conditions amenable to community prevention. Recent analysis in England suggests that better management of ambulatory care could achieve yearly savings of > £1. In England and Wales, > 16 million people have a long-term (or chronic) condition – and their care accounts for 70% of expenditure on health and social care. They shared key features of early identification and response to patient needs, joined-up care, and holistic support centred on the person rather than on specific conditions. Both models championed risk profiling as a means of identifying patients at risk (case finding) who may benefit from proactive management. The English model included systematic risk profiling as one of three primary drivers for the model, alongside integrated locality teams and systematised support for patients to manage themselves. This proactive targeting of services at people at defined risk has retained prominence in UK Government policy ever since, notably within efforts to introduce integrated care. The approach is based on proactive targeting and support for those at risk, with the aim of preventing health deterioration and emergency admissions to hospital. To be cost-effective, however, preventative interventions must use case-finding techniques that target those 3 15 18, , at risk. This issue may be freely reproduced for the purposes of private research and study and extracts (or indeed, the full report) may be included in professional journals 1 provided that suitable acknowledgement is made and the reproduction is not associated with any form of advertising. Applications for commercial reproduction should be addressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK. INTRODUCTION Identifying those at risk A number of approaches to identifying patients at risk have been explored. One approach is to ask clinicians to select at-risk patients based on their knowledge and experience, but a study by Allaudeen et al. An alternative is to use a criteria-based approach, whereby individuals meeting certain conditions are selected for intervention. For example, in the UK Evercare pilots, in nine English primary care trusts (PCTs), patients aged ≥ 65 years with two or more emergency admissions in the previous year were eligible for case management by community matrons. The intervention did not show an effect, however, with the accuracy of the approach to identifying patients at risk criticised. The resulting clinical prediction models are intended to help clinicians make better decisions by providing more objective 2324, estimates of probability as a supplement to other clinical information. Building on the successful implementation of risk models predicting diabetes mellitus (e. QDiabetes®) and cardiovascular disease (Framingham Risk Score25), emergency admission risk prediction (EARP) models have been widely developed – Table 1 provides examples. In calculating individualised risk for a given population, the models use data from up to three sources: self-reported data from patients; routinely collected administrative data; and data from the clinical record or other primary data source. Those models that performed best (in terms of predictive accuracy, as measured by c-statistics of > 0. These better-performing models all used routinely collected clinical patient data rather than self-reported patient data, and it is recognised that models reliant on self-reported (questionnaire) data are limited by response rates, recall issues and respondent burden. A 2015 NHS England paper on the Next Steps for Risk Stratification in the NHS recognised the need for robust evidence, and a pressing need for further research and evaluation, using high-quality study designs. The review confirms that the most common intervention used in emergency admission avoidance are various forms of case management. Although definitions of case management vary, Hutt et al. Case management often covers a range of activities, but it is recognised that these can vary widely between programmes. A 2013 review found good evidence that many common aspects of case management are effective, including continuity of care with a general practitioner (GP), structured discharge planning and advanced care planning (as cited in Lewis15). However, a recent systematic review by Stokes et al. The results of the subgroup of four remaining studies using routine data generated risk models to predict emergency admission were favourable, although none was from the UK. Avoiding Unplanned Admissions: Proactive Case Finding and Patient Review for Vulnerable People enhanced service committed funds of £480M over 3 years (2014–17). Such initiatives have prompted further development of risk tools and widespread take-up in the UK. It is estimated that over 7500 English GP practices have participated in the enhanced service initiative, which generally relies on predictive risk scores to identify patients for selection for case management – over 95% of all practices (NHS Digital, 2015, personal communication). Wales also introduced a variation to the general practice contract in 2013/14, encouraging the use of EARP tools to support hospital avoidance. Practices were encouraged to participate in this work, but it was not mandatory. This issue may be freely reproduced for the purposes of private research and study and extracts (or indeed, the full report) may be included in professional journals 3 provided that suitable acknowledgement is made and the reproduction is not associated with any form of advertising. Applications for commercial reproduction should be addressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK. INTRODUCTION BOX 1 Quality and productivity indicators within QOF guidance for the General Medical Services 2013/14 contract for Wales31 QP100W The practice produces a list of 5% of patients in the practice who are predicted to be at significant risk of unscheduled admission to secondary care or community-based alternatives (10 points). QP101W The practice identifies a minimum of 10% (with a maximum of 0. The active management plan must identify the lead clinician or care co-ordinator and an appropriate review date. The practice will be responsible for ensuring that an appropriate system is in place for monitoring and review of the patients identified (10 points). QP102W The practice has at least four meetings during the year to review the delivery of care for the patients identified in QP16. These meetings should be open to all relevant professionals engaged in the delivery of care to this group. The meetings should be used to review the clarity of care plans and the effectiveness of service delivery. Patient and carer feedback should play a key role in informing this assessment.
Seventeen different subunits of the nicotinic the central nervous system (Table 1 order 80 mg super levitra with amex. ACh receptor (nAChR) (2) and five different subtypes of The function of ACh has been best studied at the neuro- the muscarinic receptor (3) have been cloned to date buy 80 mg super levitra visa, and muscular junction buy super levitra 80 mg otc, where signaling occurs through the mus- a majority of those are known to be expressed in the brain. In the embryo, the nAChR at the Although the anatomic locations of cholinergic cell bodies neuromuscular junction is a pentamer made up of two , and their projections have been known for some time (Fig. In mice in which the sub- the functional role of the cholinergic system in the brain. KNOCKOUT OF MUSCARINIC- AND Cholinergic neurotransmission within the sympathetic NICOTINIC-RECEPTOR SUBUNITS ganglia occurs through several receptor subtypes. In the pe- ripheral nervous system, the issue of which ACh-receptor A particularly useful tool in identifying the role of individual subtypes are involved in cholinergic neurotransmission has molecules in the physiologic and behavioral functions of the been addressed both by knocking out muscarinic and nico- cholinergic system are transgenic animals that lack specific tinic subunits and by treating sympathetic neurons from subunits or subtypes of muscarinic receptors or nAChRs. Antisense proteins that have been identified through molecular clon- experiments have indicated that the 3 nAChR subunit ing (see refs. Mice plays a primary role in nicotinic transmission in sympathetic ganglia and that the 7 subunit also contributes to the ob- served currents (18,19). Picciotto and Meenakshi Alreja: Department of Psychiatry, electrophysiologic and immunoprecipitation studies of Yale University School of Medicine, New Haven, Connecticut. David Jentsch: Department of Neuroscience, University of Pittsburgh, nAChR subunits from ganglionic neurons (20). In studies of knockout mice, disruptions of two nico- tinic-receptor subunits expressed in sympathetic ganglia, 7 (9) and 2 (11), do not grossly alter ganglionic function. In contrast, if the 2 and the 4 nAChR-subunit mutations are combined (13), or if the 3 nAChR subunit is knocked out (6), mutant mice die perinatally of severe autonomic FIGURE 1. The principal source of cholinergic input to the cortex and failure. These experiments suggest that a nicotinic choliner- hippocampus is the basal forebrain complex, whereas the pedun- gic receptor composed of the 3/ 4or 2 subunit, or both, culopontine and laterodorsal tegmental areas innervate brain is responsible for mediating direct neurotransmission by stem and midbrain targets preferentially. Cholinergic interneu- rons are found in the olfactory tubercle, striatum, nucleus accum- ACh between ganglionic neurons. BFC, basal forebrain complex;VTA, Muscarinic function has also been studied in the auto- ventral tegmental area;IPN, interpeduncular nucleus;PPT, pe- nomic ganglia with knockout technology. Mutation of the dunculopontine tegmental nucleus;LDT, laterodorsal tegmental nucleus. M1 muscarinic receptor is sufficient to abolish the M cur- rent, a muscarine-mediated potassium current, in the sym- pathetic ganglia, but M1 mutation does not significantly perturb ganglionic function (14). KNOCKOUTS OF MUSCARINIC AND NICOTINIC SUBUNITS Subunit Knockout Knockout Phenotype References Muscarinic receptors M1 Viable Disruption of M current and (14,21) muscarinic seizures M2 Viable Disruption of muscarinic (15,21) receptor-dependent movement and temperature control and antinociception M4 Viable Enhancement of D1 (16,21) receptor-mediated locomotor stimulation Nicotinic subunits α3 High mortality Impaired growth, megalocystis (6) rate before (inflamed urinary bladder) and and after mydriasis (widely dilated ocular weaning pupils) α4 Viable Reduced antinociception (7) α5 Viable Not yet reported (8) α7 Viable Largely normal; lack MLA-sensitive (9,22) nicotine response in hippocampal interneurons; may have slightly decreased anxiety response α9 Viable Involved in cochlear efferent (10) innervation development and function β2 Viable Lack nicotine-induced increases in (7,11,24,31,32) passive avoidance, reinforcement, antinociception; show increased neurodegeneration during aging β3 Viable Altered locomotor activity (12) β4 Viable Viable, but lethal when combined (13) with β2 subunit knockout MLA, methyl-lyaconitine, a β7 antagonist. Chapter 1: Acetylcholine 5 the M2 muscarinic-receptor subtype do not show carba- lacking individual nAChR subunits should allow a finer chol-induced bradycardia, confirming that the effect of ACh definition of these receptor classes. In addition, knockout animals have receptor function has been the idea that nicotine exerts been very useful in determining which subtypes of musca- many of its functions in brain through the regulation of rinic receptors are responsible for the effects of ACh on neurotransmitter release, at least partly through terminal modulation of calcium channels in sympathetic neurons and preterminal nAChRs (25,26). A slow, voltage-independent modulation is mediated somes (nerve terminals) isolated from mice lacking the 2 by M1 receptors, whereas a fast, voltage-dependent modula- subunit of the nAChR have shown that presynaptic regula- tion is mediated through M2, and neither is affected in M4 tion of GABA release by nicotine is mediated through 2 knockout mice. This The function of ACh in the brain has also been examined is also likely to be the case for other neurotransmitters be- in electrophysiologic experiments with mice lacking cholin- cause the efflux of rubidium, a radioactive tracer that serves ergic-receptor subtypes. For example, a rapidly desensitizing as a marker of neurotransmitter vesicle fusion, is mediated nicotinic current in the hippocampus is mediated through through 2 subunit-containing receptors in most brain an 7-containing receptor (9). More recently, dopamine release from striatal appear grossly normal in behavioral experiments (22), but synaptosomes has been shown to be disrupted in 2-subunit future experiments should determine whether these currents knockout mice, while ACh release in the interpeduncular contribute to nicotine-induced improvements in cognitive nucleus is preserved (29). This suggests that a distinct function or to nicotine-induced seizure activity. Antisense nAChR subtype, most likely containing the 4 subunit, experiments have also demonstrated that the 5 nAChR mediates nicotine-elicited ACh release in the interpeduncu- subunit can alter the electrophysiologic properties of lar nucleus. Systems-level function and behavioral effects of ACh Mice lacking the 2 subunit have been used to characterize have also been examined in knockout mice. Muscarinic ago- four classes of nAChR in the brain by means of pharmaco- nist-induced seizures are dependent on the presence of the logic and electrophysiologic techniques (24) and to extend M1 receptor because M1 knockout mice are resistant to the existing pharmacologic characterization of nicotinic-re- pilocarpine-induced seizure activity (14). Future experiments using mice though the M1 receptor has been implicated in the modula- wild type β2 +/- β2 -/- FIGURE 1. Nicotinic ligand binding in brain slices from wild-type and 2-subunit knockout mice. Mice lacking individual subunits of the nicotinic acetylcholine receptor (nAChR) can be used to distinguish between subclasses of receptors. For example, although 2-subunit knockout mice lack the highest-affinity subclass of nicotine binding sites, the frog toxin epibatidine, shown here, still reveals 4 subunit-containing nAChRs in the medial habenula (remaining binding shown in panel at top, far right). Binding of epibatidine in brain slices through thalamus (top) or striatum (bottom) is shown in wild-type heterozygous ( 2 / ) and homozygous ( 2 / ) 2-subunit knockout mice. Stimulation of teg- channels is unchanged in the hippocampus of M1 knockout mental brainstem cholinergic neurons can evoke cortical mice (30). In contrast, the pharmacologic effects of musca- ACh release and EEG desynchrony, and these effects are rinic agonists on movement, temperature control, and anti- blocked by reversibly decreasing the activity of the basal nociception appear to be mediated through the M2 receptor forebrain (35). Moreover, application of cholinergic ago- because these responses are absent in M2 knockout mice nists to the basal forebrain produces behavioral activation (15). M4 receptors are also involved in locomotion; these and EEG desynchrony (33). Although the brainstem cholin- knockout animals exhibit increased basal locomotor activity ergic projections to the thalamus undoubtedly also contrib- and a potentiated locomotor response to D1-selective dopa- ute to EEG regulation (36), these findings suggest that cho- minergic agonists (16). In behavioral experiments, the 2 projections largely formed connections with noncholinergic nicotinic subunit mediates the ability of nicotine to improve neurons within the basal forebrain (37). This finding is avoidance learning and may also be involved in the circuitry critical because it could explain why stimulation of the hori- underlying this form of associative learning in wild-type zontal diagonal band, preoptic area, and substantia innomi- mice (11). In addition, this subunit appears to be necessary nata, but not of the septal nucleus and nucleus basalis, pro- for the mouse to experience the reinforcing properties of duces sleep in the cat (33). The ratio of cholinergic to nicotine because animals without the 2 subunit will not noncholinergic neurons in the horizontal diagonal band, self-administer nicotine (31). Extensions of these experi- preoptic area, and substantia innominata is significantly ments to mice lacking other subunits of the nicotinic recep- lower than in the septum and nucleus basalis. This observa- tor should allow identification of the receptor subtypes that tion has led to the hypothesis that activation of primarily are activated by smoking in humans and result in tobacco noncholinergic neurons is responsible for producing sleep addiction. An interesting effect of ACh on neuronal survival after basal forebrain stimulation (33). These noncholinergic was demonstrated in mice lacking the 2 nAChR subunit neurons are believed to be GABAergic and achieve their (32). Mice that lack this cholinergic-receptor subtype show effects through inhibition of cholinergic basal forebrain progressive neuronal loss with age in cortical and hippocam- neurons and neurons within the brainstem reticular forma- pal brain areas, which appears to lead to age-related impair- tion. In contrast, stimulation of the nucleus basalis or septal ments in spatial learning. These experiments demonstrate nucleus produces behavioral activation and cortical ACh that the effects of ACh on cognition, antinociception, loco- release, and this is consistent with the notion that basal motion, and overall neuronal activity are differentially me- forebrain cholinergic neurons are involved in behavioral diated through the various subtypes of muscarinic and nico- arousal (activation), whereas noncholinergic basal forebrain tinic receptors, and that the various roles of ACh may be neurons are involved in regulating the sleep state. These separated pharmacologically, suggesting new targets for ra- two effects are related (sleep vs. ROLE FOR CHOLINERGIC NEURONS IN AROUSAL AND SLEEP ROLE FOR CHOLINERGIC NEURONS IN MOTIVATION AND REWARD Traditionally, the basal forebrain complex, the primary source of cholinergic innervation to the telencephalon (Fig.
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