By Q. Norris. East Texas Baptist University.
These large specialized cardiac muscle cells contain very few myofibrils and function as part of a specialized conduction system that coordinates the contraction of the heart desyrel 100mg free shipping anxiety girl. With high magnification note the relative proportion of blue stained collagen order desyrel 100 mg anxiety service dog, pink smooth muscle, and unstained elastic tissue. Slide 56 External ear (Elastic stain) Look in the loose connective tissue near the elastic cartilage in this section and you will see a muscular artery and its companion vein. The internal elastic lamina of this small artery is very prominent because of the elastic fiber stain; in some places the external elastic lamina may be seen. Note the striking refractile internal elastic lamina and the pink staining smooth muscle (25 40 layers) of the tunica media (note that the smooth muscle nuclei are twisted into a corkscrew characteristics of contraction). The external elastic lamina (between the media and adventitia) is less pronounced. The connective tissue comprising the adventitia is oriented mostly longitudinally and most of the collagen bundles here (stained blue) are thus cut in cross section. Remember that in blood vessels the components of the adventitia are arranged longitudinally, those of the media are circular, and those of the intima are longitudinal. Venules, with an equally thin wall but a wider diameter, are found in the same area. These will be a bit lower in the dermis (the connective tissue immediately under the epithelium). Slide 23 Mesentery spread (flat mount, H and E) (C&M 150-156 for ultrastructure) This is not a section, but a piece of mesentery mounted under a coverslip. Observe the large, lymph vessel and smaller blood vessels running alongside it and extending into other parts of the mesentery. The lymph vessel contains valves that consist of a pair of pockets arranged on opposite walls. Arterioles have a smaller lumen, endothelium and a smooth muscle media; venules have a wider lumen and a thin endothelial lining. By adjusting the fine focus of your microscope, you can follow the smooth muscle nuclei as they encircle the arteriole. Trace small branches from the arteriole to see them become capillaries, and, if possible, follow them back to a venule. Capillaries are distinguished by a lumen size as small as a single red blood cell. In addition observe several medium-sized thin-walled veins, which are collapsed and hence have an irregular lumen. This is a cross section of a large vein which has been opened up and laid flat before sectioning. Observe the bundles of smooth muscle cells (red) and collagen (blue), which make up the thick adventitia. Calcium channels support slow propagation and help control action potential duration E. Calcium channels as targets of “calcium blockers” and sympathetic neurotransmitter In the last lecture we saw that the action potentials in different regions of the heart show considerable diversity. Unlike spikes in skeletal muscle, cardiac modifying action potentials not only trigger contractions but also have contraction considerable influence on contractility In this lecture, we will deal with the ionic basis for cardiac action potentials. Not surprisingly in view of these different functions, the underlying ionic mechanisms in various parts of the heart are somewhat different. The upstroke of the cardiac action potential closely resembles the spike in other excitable tissues. In ventricular and atrial muscle and in Purkinje fibers (where rapid conduction is critical) the ionic basis is quite similar to nerve. The rapidly rising phase is generated by an increase in Na conductance (gNa) as in the squid giant axon. If most of the external Na ions are replaced by choline (or NaCl replaced by dextrose) the following changes are observed: 1. The action potential is briefer (the plateau configuration is much less pronounced).
Traditional drugs are usual- ly easy to handle and can be administered to patients conve- niently in various forms such as tablets buy generic desyrel 100mg online anxiety when trying to sleep, juices or suppositories order 100 mg desyrel mastercard anxiety journal prompts. It is true that many traditional drugs were originally derived from natural products. For example, healers used an extract of the leaves or bark of certain willow species to treat rheumatism, fever and pain hundreds of years before the Bayer chemist Felix Hoffmann reacted the salicylate in the extract with acetic acid in 1897 to form acetylsalicylic acid, a compound that is gentler on the stomach. The methods have been tried and tested for decades, and the drugs can be manufactured anywhere to the same standard and in any desired amount. Ster- ile conditions, which pose a considerable technical challenge, are rarely necessary. On the other hand, preventing the organic solvents used in many traditional production processes from damaging the environment remains a daunting task. Unstable structure Biopharmaceuticals require a far more elaborate of proteins production process. Most drugs manufactured by biotechnological methods are proteins, and pro- teins are highly sensitive to changes in their milieu. Their struc- ture depends on diverse, often weak, interactions between their amino-acid building blocks. These interactions are optimally coordinated only within a very narrow range of ambient condi- tions that correspond precisely to those in which the organism from which the protein is derived best thrives. Because of this, even relatively small changes in the temperature, salt content or pH of the ambient solution can damage the structure. This, in turn, can neutralise the function of the protein, since this de- pends on the precise natural shape of the molecule. Most of these mole- cules act as vital chemical Detecting signals: interferon gamma and its receptor messengers in the body. The target cells that receive and translate the signals bear special receptors on their surface into which the cor- responding chemical mes- senger precisely fits. If the three-dimensional shape of The signal protein interferon gamma (blue) is recognised by a the chemical messenger is specific receptor (left and right) located on the surface of its even slightly altered, the target cells. Interferon gamma as a biopharmaceutical is used to treat certain forms of immunodeficiency. The situation is similar for another group of therapeutic proteins, the antibodies. Their function is to recognise foreign structures, for which purpose they have a special recognition region whose shape pre- cisely matches that of the target molecule. Changing just one of the several hundred amino acids that make up the recognition region can render the antibody inactive. It is possible to produce antibodies to target any desired foreign or endogenous sub- stance. Modern biotechnology makes use of the technique to block metabolic pathways in the body involved in disease pro- cesses. Like other therapeutic proteins, antibodies must there- fore assume the correct molecular arrangement to be effective. Biopharmaceuticals: This structural sensitivity also causes problems biological instead of because proteins do not always automatically as- chemical production sume the required structure during the produc- tion process. Long chains of amino acids in solu- tion spontaneously form so-called secondary structures, arranging themselves into helical or sheetlike structures, for ex- ample. However, this process rarely results in the correct overall shape (tertiary structure) – especially in the case of large pro- teins where the final structure depends on the interactions of several, often different, amino acid chains. During natural biosynthesis of proteins in the body’s cells, a se- ries of enzymes ensure that such ‘protein folding’ proceeds cor- rectly. The enzymes prevent unsuitable structures from being Drugs from the fermenter 29 Diverse and changeable: the structure of proteins primary structure } A chain of up to twenty different amino acids (primary struc- ture – the variable regions are indicated by the squares of dif- ferent colours) arranges itself into three-dimensional struc- secondary tures. The position of these secondary structures in rela- tion to one another determines the shape of the protein, i. Often, a number of proteins form func- tional complexes with quaternary structures; only when arranged in this way can they perform their intended func- tions. When purifying proteins, it is extremely difficult to retain such protein complexes in their original form. These strictly controlled processes make protein production a highly complex process that has so far proved impossible to replicate by chemical means.
I want you to prevent the potential crash of your health because of persistent stress purchase 100mg desyrel free shipping anxiety symptoms arm pain, and if you’re already experiencing the symptoms of adrenal anarchy generic desyrel 100 mg otc anxiety symptoms in children, the good news is that I came back to normal and you can too. Mind the Gap: You’re Not Crazy Even If Your Doctor Ignores Your Symptoms Low cortisol is an issue that you won’t hear about from a mainstream medical doctor unless you are flat on your back, in adrenal crisis, with blood pressure so low that you can’t send oxygen to your brain. I love mainstream, or allopathic, medicine—I’m board certified in it, and many of my closest friends are mainstream physicians. Low-grade symptoms such as fatigue, anxiety, and stress plague most of my clients, yet they were not well addressed in my own allopathic medical training, so it’s not surprising that women with these issues have trouble finding solutions in mainstream medicine. Hypocortisolism, Explained Hypocortisolism, or low cortisol, occurs when your adrenal glands are unable to make a normal amount of the main stress hormone, cortisol. Second only to hypercortisolism, or high cortisol, hypocortisolism is the next most common hormonal imbalance I find in my patients. Eventually, it waves the white flag of surrender, exhausted; that’s when you have low cortisol. In addition to cortisol, the adrenals release other hormones and neurotransmitters, including the following: • Pregnenolone is made from cholesterol and serves to reduce your anxiety. It’s considered the “mother” hormone because all other sex steroids—such as estrogens, progesterone, cortisol, testosterone, and aldosterone—are made from it. The Science of Low Cortisol Warning: If you are an overachiever and want more information, this section is for you, but please know this is a trait that puts you at greater risk for adrenal dysregulation. If all this talk is actually wigging you out a bit, feel free to skip this section, and go directly to “Part B: The Gottfried Protocol for Low Cortisol” (page 116). Causes of Low Cortisol The following conditions are causes of low cortisol, all of which are documented in mainstream medicine. This occurs when the adrenal glands fail to make enough cortisol, typically caused by the body’s own immune system attacking the adrenal glands and ultimately destroying them. Kennedy was the most famous person to have Addison’s, although his handlers concealed his diagnosis from the public. This can occur when the pituitary, the boss of the adrenals, is wiped out, usually suppressed by an outside source of cortisol, such as the medication Prednisone, or even hydrocortisone, a hormone that some antiaging physicians prescribe. This condition is when the pituitary does not make normal amounts of some or all of its hormones— including the hormones that control the ovaries, thyroid, and adrenals —as a result of head injury, brain surgery, radiation, stroke, or a problem called Sheehan’s syndrome, which is when a woman bleeds severely with childbirth (an obstetrician’s worst, cortisol-raising nightmare). Symptoms of Sheehan’s syndrome include fatigue, inability to breast- feed, lack of menstrual periods, and low blood pressure. I describe this condition in chapter 9, but I want to remind you of the interdependent relationship of the adrenal glands with the thyroid. Both low and high cortisol can exacerbate the symptoms of an underactive thyroid, or hypothyroidism, which include fatigue, weight gain, and mood problems. I find low cortisol in some people who experienced a traumatic event early in their lives. However, for reasons not yet understood, not everyone with severe trauma develops low cortisol. As I’ve described, low cortisol follows periods of unremitting stress, when you’ve entered the exhaustion phase of adrenal function. From Adrenal Health to Adrenal Dysregulation Adrenal health is the key difference between my approach to wellness and that of the traditional medical establishment, which holds that the adrenals are unimportant unless they completely fail, or are extremely overactive (that is, you have Cushing’s Disease). I regard stress resilience and adrenal wellness as the foundation of health and vitality, and I believe that it is largely unrecognized and under-addressed in conventional medicine. Time and again I have seen that the healthiest, most vibrant individuals cope successfully with stress and have found ways to keep their adrenals in top form. Those are the ideal hormonal specimens who experience the smart function of their glucocorticoids. That is, they experience an external stressor—a true physical threat—such as a car accident or robbery, and stress hormones such as cortisol help them focus and problem solve, and shunt blood to their legs and away from nonessential activities such as getting pregnant and digestion. They adapt to the stressor, recover swiftly, and then blood and energy can be directed once again to digesting lunch, reproduction, growth, and repair. Their cavewoman tendencies to constantly scan the environment for threats are contained and mostly dismissed.
Providing your patient with a physical activity prescription is the next key step you can take in helping your patients become more active safe 100mg desyrel anxiety box. Your encouragement and guidance may be the greatest influence on this decision as patient behavior can be positively influenced by physician intervention purchase 100 mg desyrel otc anxiety obsessive thoughts. The steps provided below will give you guidance in assessing your patients and their needs in becoming more active. At this point, you’ve already determined their current physical activity level (the Physical Activity Vital Sign). Next, you will determine if your patient is healthy enough for independent physical activity. Finally, you will be provided with an introduction to the Exercise Stages of Change model to help determine which strategies will best help your patient become physically active. Step 1 - Safety Screening Before engaging a patient in a conversation about a physical activity regimen, it is necessary to determine if they are healthy enough to exercise independently. However, it may be necessary to utilize more advanced screening tools such as the American College of Sports Medicine Risk Stratification (see Appendices D & E) or a treadmill stress test to determine whether your patient should be cleared to exercise independently or whether they need to exercise under the supervision of a clinical exercise professional. Individuals attempting to change their behaviors often go through a series of stages. Some patients may only be ready for encouragement, some will be prepared to take steps towards being more physically active, while others will be ready to receive a physical activity prescription and referral to certified exercise professionals. Therefore, prior to prescribing physical activity to your patients, it is important to determine their “Stage of Change”. Most commonly, there are 5 stages of change: precontemplation, contemplation, preparation, action, and maintenance phases. By determining the stage of change that they are in, you can then take the most appropriate action based and individualize your physical activity promotion strategy. The Exercise Stages of Change questionnaire (found in Appendix F) consists of 5 questions and can be completed in a matter of minutes when your patient first checks in at your office. The following table provides a brief outline of each of the five stages of change and recommended steps for patients in each stage. Stage of Change Action Step Promote being more physically active by discussing its health benefits, Precontemplation emphasizing the pros of changing their behavior, and helping work (Patient has no intention to be physically through the cons of being more physically active. Independent Supervision Necessary Write prescription; refer to Refer to clinical exercise exercise professional. Contemplation (Patient is thinking about becoming Continue to emphasize the pros and reducing the cons of being more physically active) physically active. Preparation Write prescription; refer to non- Refer to clinical exercise (Patient is active and making small clinical exercise professionals. The simplest prescription that you can provide your patient with is to participate in 150 minutes of moderate intensity physical activity each week as suggested in the 2008 5 Physical Activity Guidelines for Americans. Studies have shown that simply providing a written prescription is an effective means of motivating patients to be more physically active, sometimes by as 6 much as one hour per week. The Exercise Prescription Health Series consists of 45 customized exercise prescriptions specifically developed for individuals with a variety of health conditions such as diabetes, cardiovascular disease, osteoarthritis, and lower back pain. Your patients can then implement these prescriptions individually or take them to a certified exercise professional who can guide them in filling their customized exercise prescription. The 2008 Physical Activity Guidelines recommend a minimum of 150 minutes of moderate, or 75 minutes of vigorous, physical activity a week (for example, 30 minutes per day, five days a week) and muscle- strengthening activities on two or more days a week. Moderate physical activity means working hard enough to raise your heart rate and break a sweat, yet still being able to carry on a conversation. Your guidance in linking them to community resources and, more specifically to exercise professionals, is a key strategy. In fact, several studies have suggested that efforts made by healthcare systems to increase the physical activity habits of their patients are best accomplished by transforming their “patients” into “participants”. This is best done by providing your patients with information on local resources and support systems. When prescribing physical activity, it is necessary not just to counsel your patients, but to provide them with information on how and where they can ‘fill’ their prescription. The referral to an exercise professional can be an extremely useful tool for you as a healthcare provider. A qualified exercise professional can help your patient safely start and maintain an effective exercise program. They will understand the “fitness goals” you and your patient have discussed and work with them to create a plan of action to achieve them.
And yet we strike fire with it generic 100mg desyrel amex anxiety symptoms tingling, without understanding or comprehending this miracle of the inexhaustible caloric hidden in the cold steel cheap 100 mg desyrel visa anxiety symptoms 3 days, or the possibility of calling it out with a frictional stroke. Again, it would be just as silly as if we should refuse to learn to write, because we cannot comprehend how one man can communicate his thought to another through pen, ink, and paper - and yet we communicate our thoughts to a friend in a letter without either being able or desirous of comprehending this psychico-physical miracle! Why, then, should we hesitate to conquer and heal the bitterest foes of the life of our fellowman, the Chronic diseases, in the stated way, which, punctually followed, is the best possible method, because we do not see how these cures are effected? Another antipsoric remedy which may be ever so useful, but is prescribed too early and before the cessation of the action of the present remedy, or a new dose of the same remedy which is still usefully acting, can in no case replace the good effect which has been lost through the interruption of the complete action of the preceding remedy, which was acting usefully, and which can hardly be again replaced. It is a fundamental rule in the treatment of chronic diseases: To let the action of the remedy, selected in a mode homoeopathically appropriate to the case of disease which has been carefully investigated as to its symptoms, come to an undisturbed conclusion, so long as it visibly advances the care and the while improvement still perceptibly progresses. This method forbids any new prescription, any interruption by another medicine and forbids as well the immediate repetition of the same remedy. Nor can there be anything more desirable for the physician than to see the improvement of the patient proceed to its completion unhindered and perceptibly. There are not a few cases, where the practiced careful Homoeopath sees a single dose of his remedy, selected so as to be perfectly homoeopathic, even in a very severe chronic disease, continue uninterruptedly to diminish the ailment for several weeks, yea, months, up to recovery; a thing which could not have been expected better in any other way, and could not have been effected by treating with several doses or with several medicines. To make the possibility of this process in some way intelligible, we may assume, what is not very unlikely, that an antipsoric remedy selected most accurately according to homoeopathic principles, even in the smallest dose of a high or the highest potency can manifest so long- continued a curative force, and at last cure, probably, only by means of a certain infection with a very similar medicinal disease which overpowers the original disease, by the process of nature itself, according to which (Organon, ¤ 5, Fifth Edition,) two diseases which are different, indeed, in their kind but very similar in their manifestations and effects, as also in the ailments and symptoms caused by it, when they meet together in the organism, the stronger disease (which is always the one caused by the medicine, ¤33, ibid. In this case every new medicine and also a new dose of the same medicine, would interrupt the work of improvement and cause new ailments, an interference which often cannot be repaired for a long time. Yet when a sudden great and striking improvement of a tedious great ailment follows immediately on the first dose of a medicine, there justly arises much suspicion that the remedy has only acted palliatively, and therefore must never be given again, even after the intervention of several others remedies. Nevertheless there are cases which make an exception to the rule, but which not every beginner should risk finding out. We may declare it once, that the practice of late, which has even been recommended in public journals of giving the patient several doses of the same medicine to take with him, so that he may take them himself at certain intervals, without considering whether this repetition may affect him injuriously, seems to show a negligent empiricism, and to be unworthy of a homoeopathic physician, who should not allow a new dose of a medicine to be taken or given without convincing himself in every case beforehand as to its usefulness. This is rare in chronic diseases, but in acute diseases and in chronic diseases that rise into an acute state it is frequently the case. It is only then, as a practiced observer may recognize - when the peculiar symptoms of the disease to be treated, after fourteen, ten, seven, and even fewer days, visibly cease to diminish, so that the improvement manifestly has come to a stop, without any disturbance of the mind and without the appearance of any new troublesome symptoms, so that the former medicine would still be perfectly homoeopathically suitable, only then, if say, is it useful, and probably necessary to give a dose of the same medicine of a similarly small amount, but most safely in a different degree of dynamic potency. To adduce an example: a freshly arisen eruption of itch belongs to those diseases which might soonest permit the repetition of the dose (sulphur), and which does permit it the more frequently, the sooner after the infection the itch is received for treatment, as it then approaches the nature of an acute disorder, and demands its remedies in more frequent doses than when it has been standing on the skin for some time. But this repetition should be permitted only when the preceding dose has largely exhausted its action (after six, eight or ten days), and the dose should be just as small as the preceding one, and be given in a different potency. Nevertheless it is in such a case often serviceable, in answer to a slight change of symptoms, to interpose between the doses of pure sulphur, a small dose of Hepar sulphuris calcareum. This also should be given in various potencies, if several doses should be needed from time to time. Often also, according to circumstances, a dose of Nux voinica (x) or one of mercury (x)** may be used between. A dose of medicine may also have been suddenly counteracted and annihilated by a grave error in the regimen of the patient, when perhaps a dose of the former serviceable medicine might again be given with the modification mentioned above. Thereby the remedy seeing to take a deeper hold on the organism and hasten the restoration in patients who are vigorous and not too sensitive. Indeed it is hardly ever needed in chronic diseases, as we have a goodly supply of antipsoric remedies at our disposal, so that as soon as one well selected remedy has completed its action, and a change of symptoms, i. Nevertheless in very tedious and complex cases, which are mostly such as have been mismanaged by allopathic treatment, it is nearly always necessary to give again from time to time during the treatment, a dose of Sulphur or of Hepar (according to the symptoms), even to the patients who have been before dosed with large allopathic doses of Sulphur and with sulphur-baths; but then only after a previous dose of Mercury (x). Where, as is usually the case in chronic diseases, various antipsoric remedies are necessary, the more frequent sudden change of them is a sign that the physician has selected neither the one nor the other in an appropriately homoeopathic manner, and had not properly investigated the leading symptoms of the case before prescribing a new remedy. This is a frequent fault into which the homoeopathic physician falls in urgent cases of chronic diseases, but oftener still in acute diseases from overhaste, especially when the patient is a person very dear to his heart. Then the patient naturally falls into such an irritated state that, as we say, no medicine acts, or shows its effect,* yea, so that the power of response in the patient is in danger of flaring up and expiring at the least further dose of medicine. In such a case no further benefit can be had through medicine, but there may be in use a calming mesmeric stroke made from the crown of the head (on which both the extended hands should rest for about a minute) slowly down over the body, passing over the throat, shoulders, arms, hands, knees and legs down over the feet and toes. A dose of homoeopathic medicine may also be moderated and softened by allowing the patient to smell a small pellet moistened with the selected remedy in a high potency, and placed in a vial the mouth of which is held to the nostril of the patient, who draws in only a momentary little whiff of it. By such an inhalation the powers of any potentized medicine may be communicated to the patient in any degree of strength. One or more such medicated pellets, and even those of a larger size may be in the smelling-bottle, and by allowing the patient to take longer or stronger whiffs, the dose may be increased a hundred fold as compared with the smallest first mentioned.
The diversity library was then constructed by attaching many different substituents to this central moiety discount desyrel 100mg with visa anxiety depression. For example purchase 100 mg desyrel amex anxiety symptoms vs adhd symptoms, dioxapiperazines are cyclic dipeptides and thus are relatively trivial to prepare. Other monomers were selected because they had a good track record for being drug-like molecules. In preparing these various libraries, extensive use is made of solid phase synthetic methods. When performing a large number of synthe- ses, it is preferable to perform the synthetic steps on a solid bead rather than complet- ing the entire synthesis in the solution phase. The solid-phase technique makes byproduct removal and final compound purification easier. The organic chemistry literature con- tains a wealth of different types of solid-phase supports and novel linkers for attaching the synthetic substrate to the bead. If a 200,000 compound library is available, the biological evaluation assay must be rapid and reliable. If the assay were capable of test- ing five compounds per day, it would take 110 years to evaluate the entire library. The ability to inhibit an enzyme is a good example of a potentially useful assay for high throughput screening. A variety of high throughput assays have been developed and perfected over the past 10–20 years. Microplate activity assays (assay is in solution in a well; the result of the assay, such as enzyme inhibition, is linked to some observable, such as color change, to enable identification of bioactivity) 2. Affinity selection assays (compound library is applied to a protein target receptor; all compounds that do not bind are removed; compounds that do bind are then identified) Of these, microplate assays are probably the most widely used. Screening combinator- ial libraries in 96- or even 384-well microplates is time and cost efficient. Using modern robotic techniques, it is possible to perform more than 100,000 bioassays per week in a microplate system (permitting the above-described 200,000 compound library to be screened in two weeks, rather than over a century). In addition to selecting an appropriate assay, it is also necessary to have a pooling strategy. It is more efficient to test many compounds per well on the microplate, rather than one. If one could test 100 compounds per well, then the standard 96-well plate would enable almost 10,000 compounds to be evaluated in one experiment. The synthetic strategy employed during the combinatorial syntheses can be used to assist in determining these pooling strategies. In random incorporation syntheses,a single bead could contain millions of different molecular species. In mix and split syn- theses (also called pool and divide syntheses or one bead–one compound syntheses) only one compound is attached to any given solid-phase synthetic bead. The evolution of methods for combinatorial syntheses and high throughput screening will be necessary to address the explosion of druggable targets soon to be identified by the genomics and proteomics revolutions. Current drug design strategies are struggling with fewer than 500 druggable receptor proteins. Endeavoring to identify lead compounds for an additional 3500 targets will overwhelm present-day drug design technologies. Genomics and pro- teomics represent a possible pathway to enhanced future drug discovery. On June 26, 2000–the dawning of the present century–a historic milestone in genomic science was attained when researchers involved with the Human Genome Project jointly announced that they had sequenced 97–99% of the human genome–the all-encompassing collection of human genes. The human genome consists of 23 pairs of chromosomes with three billion base pair codes for approximately 24,000–30,000 functional genes (original estimates of 100,000–120,000 genes seem to have been incorrectly high). Despite the size of this flood, its flow has not filled the drug discovery pipeline with winning candidates. Determining gene structure and function through genomics definitely does illuminate the path for deciphering human biochemistry and for linking specific genes to specific diseases. Although genomics did deliver phenomenal masses of raw information, the genomics technologies have so far failed to deliver the more than 10,000 anticipated druggable targets predicted by the early hyperbole of the genomics era.
In addition to the triptans order desyrel 100 mg otc anxiety symptoms scale, the ergot alkaloids are also effective against migraine buy desyrel 100mg on-line anxiety symptoms grinding teeth. The efficacy of ergot derivatives in migraine is so specific that it almost con- stitutes a diagnostic test. Traditionally, ergotamine, when given during the aura, is par- ticularly effective. The interactions of ergots with serotonin receptors is complex, since these agents can be agonists, antagonists, or partial agonists at one or more of the various serotonin receptors. The most important among them is the N —H (tele-) tautomer,t which also appears to be the active form of the agonist on both receptors. Tautomerism does not appear to be important in H1receptor binding (in the intes- tine); however, it does seem to be important to gastric H2–receptor activity. Histamine may play the role of a proton-transfer agent, in a fashion similar to the charge-relay role of the imidazole ring in serine esterases. The percentage of the monocation tautomers is greatly influenced by substituents in position 4, which alter the electron density on the Nπ atom, an important consideration in modifying the receptor-binding properties of histamine. Histamine metabolism differs from that of classical neurotransmitters because hista- mine is so widely distributed in the body. The highest concentrations in human tissues are found in the lung, stomach, and skin (upto 33 µg/g tissue). Histamine metabolic path- ways are simple; histamine is produced from histidine in just one step (see figure 4. The principal production takes place in the mast cells of the peritoneal cavity and con- nective tissues. Histamine is released from mast cells in antigen–antibody reactions, as in anaphylaxis and allergy, which are the most widely known physiological reactions to histamine. Other agents present in mast cells, such as serotonin, acetylcholine, bradykinin (a nonapeptide), and a “slow-reacting substance” or leukotriene (see chapter 8) also contribute. In the stomach, where histamine induces acid secretion, its release seems to be regulated by the peptide hormone pentagastrin. The H1 receptor is found in the smooth muscle of the intestines, bronchi, and blood vessels and is blocked by the “classical” antihistamines. The H2 receptor, present in gastric parietal cells, in guinea pig atria, and in the uterus, does not react to H1 blockers but only to specific H2 antagonists. H2 receptors also appear to be involved in the immunoregulatory system and may be present in T lymphocytes, basophil cells, and mast cells. H3 receptors are found predominantly in brain but are also localized in stomach, lung, and cardiac tissue. H1 receptors are widely distributed, especially in the cerebellum, thalamus, and hippocampus, and are located on neurons, astrocytes, and blood vessels. Bottom: 4-substituted histamine derivatives act as proton-transfer agents in their tele-tautomeric form. H1 receptors are not very specific and are occupied by antidepressants and neuroleptics as well. The H1 receptors are easily solubilized and have been purified on lectin affinity columns, indicating their glycoprotein nature. H2 receptors are localized to the cortex and striatum and are found in neurons, glial cells (astrocytes), and blood vessels. Thus the role of the central histamine receptor may not be information transmission, but sensitization of brain areas to excitatory signals from “waking amines. H3 receptors have been described and seem to be localized in cortex and substantia nigra; these seem to be presynaptic autoreceptors, controlling histamine release and synthesis. They are activated by histamine concentrations that are two orders of magnitude lower than those necessary for triggering postsynaptic receptors. Their blockade may potentially lead to increased blood flow and metabolism combined with a central arousal, whereas their stimulation (or inhibition of central H2 receptors) could have a sedative effect. Histamine-mediated hypothermia, emesis, and hypertension have been shown to exist, and the well-known sedative effects of H1 antihistamines are centrally mediated. Large alkyl groups on C-4 decrease activity and lead to partial agonists, whereas side-chain N-substitution enhances the antagonistic properties of the molecule. It is a selective H2 agonist, having between 19% and 70% H2 activity, with no effect on the H1 receptor. The circulatory effects are manifested as arteriolar dilation and increased capillary permeability, causing plasma loss.