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By W. Norris. Barber-Scotia College.

Once dissociation has oc- The construction of a quantal dose–response curve curred purchase 25mg indocin mastercard, drug action is terminated. The frequencies of association and dis- will not respond to a given dose, a comparison of indi- sociation are a function of the affinity between the drug viduals within a population shows that members of that and the receptor, the density of receptors, and the con- population are not identical in their ability to respond centration of drug in the biophase. This variability can be expressed as response is generally considered to be a function of the a type of dose–response curve, sometimes termed a concentration of the drug–receptor complexes formed at quantal dose–response curve, in which the dose (plotted any moment in time. Such a dose– DOSE–RESPONSE RELATIONSHIP response curve for the anticonvulsant phenobarbital is To understand drug–receptor interactions, it is neces- illustrated in Figure 2. Since the degree of ef- a particular dose of phenobarbital of 2, 3, 5, 7, or 10 fect produced by a drug is generally a function of the mg/kg body weight. The percentage of animals in each amount administered, we can express this relationship group protected against convulsions was plotted against in terms of a dose–response curve. Relationship between the dose of phenobarbital and the protection of groups of rats against convulsions. The therapeutic index for mulative plot of the normal frequency distribution phenobarbital used as an anticonvulsant is approxi- curve. For example, although the ther- dose, one obtains the sigmoid-shaped curve of Figure apeutic index of the cardiac glycosides is only about 2 2. The sigmoid shape is a characteristic of most for the treatment and control of cardiac failure, these dose–response curves when the dose is plotted on a geo- drugs are important for many cases of cardiac failure. The identification of a low Therapeutic Index margin of safety, however, dictates particular caution in Effective Dose its use; the appropriate dose for each individual must be The quantal dose–response curve represents esti- determined separately. In addition to this of drug safety would include a comparison of the lowest information, it also would be useful to have some way to dose that produces toxicity (e. A curve similar to that already discussed can be therapeutic index is a very rough measure of safety and constructed by plotting percent of animals killed by generally represents only the starting point in determin- phenobarbital against dose (Fig. Since the Usually, undesirable side effects occur in doses lower degree of safety associated with drug administration de- than the lethal doses. For example, phenobarbital in- pends on an adequate separation between doses produc- duces drowsiness and an associated temporary neuro- ing a therapeutic effect (e.

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Research has challenged conventional models of automatic and obligatory word recognition cheap indocin 25 mg overnight delivery, by demonstrating reduced SIE when individuals are given suggestions to see the presented words as meaningless characters of a foreign 107 language. Such effects are not due to simple eye defocusing, and research is slowly identifying the specific brain regions involved in hypnotic inhibition of the Stroop 108 effect. The use of hypnosis in memory research has aided in the examination of the 109,110 constructive and reconstructive nature of memories and the nature, structure and 111 function of autobiographical memories. Researchers have also investigated conditions such as conversion hysteria by generating symptoms in healthy subjects using hypnosis. In a single-case PET scan study in which a hypnotized subject was given suggestions for 112 left-leg paralysis, the resultant hypnotic paralysis activated similar brain areas to those 113 found in a similar study of conversion hysteria (leg paralysis). Though not conclusive, there is some indication that conversion disorder patients are more responsive to hypnotic 114 suggestions and research has shown hypnosis to be an effective treatment for various 115 motor-type conversion disorders. With integration of brain mapping techniques, hypnosis is a tool that can readily assist in characterizing discrete cognitive components in neurophysiological terms. Two qualifiers must be made, however: first, identifying brain areas associated with certain tasks or mental phenomena (such as visual hallucinations) does not disqualify that particular brain area from active involvement in other (non-hallucination) tasks; and second, isolating individual components associated with a given task does not provide a complete model of the neurophysiological processes involved with that task—identified brain areas are almost certainly part of a more distributed network of activation. The next step will be to identify the temporal relationship of activation in these distributed components. HYPNOSIS AS A DIAGNOSTIC TOOL Considerable controversy surrounds provocation methods as a tool for differentiating epileptic and non-epileptic seizures. Non-epileptic seizures are reported in 10–23% of patients referred to epilepsy centers. While long-term video-EEG monitoring can commonly be used to detect distinguishing EEG changes accompanying clinical seizures, the expense, duration and accessibility of such techniques often makes it unfeasible. However, the necessary use of deception in such techniques presents certain ethical (and perhaps legal) dilemmas in terms of informed 116,117 consent. In light of this, it has been suggested that hypnotically provoked pseudoseizures can be elicited without the need for deception, and preliminary reports Hypnosis 215 118–120 have shown it to be an effective technique.