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In the 70s and 80s the Pharmacology department at the University of Massachusetts Medical School developed an innovative approach to the teaching of Pharmacology to medical students. The approach, a "conference-centred model" (CCM), was based on the use of small group teaching sessions guided by a structured set of conference questions. Lectures were eliminated if the material which would have been covered was essentially available already in a standard textbook. Thus the student passivity associated with the lecture was replaced by a much more active participation in small group exchanges. This article is a description of the experience.

One can often gain new insights into a topic when approaching it from a new angle. The paradigm example involves the insights into histology that can be gained from studying pathology. For example, a rare cell type in the pituitary suddenly becomes very easy to recognize once a whole field of them can be seen in a tumour. Similarly, one can gain insights by looking at species other than our own. In this article, Doug Waud, using the kidney in Vulcans, takes this latter theme one step further to provide useful insights into renal physiology and pharmacology.

Background: Experimental investigation of stroke, in particular the evaluation of therapeutic maneuvers, is difficult because even well-controlled experiments show considerable variability. Optimal use of resources requires efficient statistical analysis., Summary of Review: A body of experience in pharmacology that is directly applicable to stroke studies is reviewed. The general approach, though well known to pharmacologists, is less familiar to neurologists. This paper attempts to give a survey so that neurologists encountering studies using this general class of analysis will better be able to put the technique into context. The general nature of a quantal bioassay is described, the underlying conceptual models are discussed, and specific examples are given., Conclusions: The pharmacologist's approach to the analysis of quantal bioassays can easily be adapted to the quantification of results in studies of stroke.

The ability of gallamine, metocurine, pancuronium, tubocurarine and atropine to block the response to postganglionic stimulation of the vagus nerve were measured in isolated, spontaneously beating guineapig atria. From analysis of the results in conjunction with those of earlier assays of concentrations that block effects of preganglionic vagal stimulation, it was concluded that only tubocurarine possessed ganglionic blocking activity. From calculation of the extent of block of muscarinic receptors at drug concentrations which blocked the response to postganglionic vagal stimulation, it was concluded that gallamine and pancuronium have an antivagal action exerted most probably on the postganglionic nerve terminal, and that this action is the most likely explanation of the tachycardia seen clinically with these two drugs.

Gallamine, metocurine, pancuronium, and d-tubocurarine were compared when given alone and in combination with isolated guinea pig nerve-lumbrical preparations stimulated via the nerve. The experimental design was set up to control the effects of variation among preparations, order of administration, and time of administration (i.e., fresh vs. older preparation). The result was an assay able to measure potentiation with a coefficient of variation of 3%. A format for a graphic presentation to summarize such results is presented and discussed. Two combinations, gallamine plus d-tubocurarine and gallamine plus pancuronium, showed no sign of an interaction beyond that to be expected from a simple competitive interaction. Two others, metocurine plus pancuronium and gallamine plus metocurine, showed about a twofold greater potency when combined than would have been expected. The last two sets, pancuronium plus d-tubocurarine and metocurine plus d-tubocurarine, showed a slight degree of potentiation. These studies demonstrate that the deviation from simple additivity seen in vivo persists when examined in a system free from artifacts associated with uptake and distribution in the whole organism.

To examine the basis of tachycardia seen clinically with some neuromuscular blocking agents, the potencies of d-tubocurarine, dimethyltubocurarine, gallamine, and pancuronium in antagonizing the effects of vagal stimulation on the guinea pig atrial pacemaker were determined and expressed as an ED50 for vagal blockade. These ED50 values were compared with the respective potency values of these agents at the motor endplate. This comparison showed that in clinical doses, gallamine and pancuronium may reach levels that produce vagal blockade. Comparison with atropine indicated that the vagolytic action of the neuromuscular blocking agents was not attributable to receptor occlusion, but reflected instead an action on the vagus nerve itself.

Dose-response curves for blockade of the indirectly elicited twitch of isolated guineapig nerve-lumbrical muscle preparations were determined for tubocurarine and pancuronium in the presence of potassium 2,4 and 6 mmol litre-1 and calcium 1,2 and 3 mmol litre-1. Increases in concentration of either ion decreased the sensitivity of the preparation to both drugs. Over the physiological range of concentrations of potassium and calcium, 36% and 27% variation in dosage can be expected.

Spinal cord blood flow can be accurately and rapidly measured in rabbits by intravenous injection of [14C]iodoantipyrine, collection of sequential arterial samples, and abrupt termination of blood flow to the spinal cord by severing the aorta with a previously implanted ligature. The radioactive tracer concentrations in arterial and spinal cord samples can be rapidly measured in a scintillation counter. The spinal cord blood flow can then be calculated from these blood and tissue tracer concentrations. This method is suitable for use in anesthetized or unanesthetized small animals.

The apparent atracurium-receptor dissociation constant was assayed at the end-plate region of isolated guinea pig muscles. In a parallel series of experiments, the ED50 for producing neuromuscular block in the lumbrical muscle was also determined. The ratio of these two values was similar to the ratio found with classical competitive neuromuscular blocking agents like d-tubocurarine or pancuronium. We conclude that the commercial preparation of atracurium, though a mixture containing isomers of different configurations, behaves kinetically in a manner indistinguishable from what would be expected from a single substance.

The results of many biochemical, pharmacological and physiological experiments fit a rectangular hyperbola. Several methods for analysis of this curve have been developed but these techniques have not been readily available to researchers who are not interested in becoming mathematical statisticians. We have reviewed these analytical methods and concluded that, the Eadie-Hofstee technique is the best choice. We explain how to use this method and include sample calculations and calculator programs. We are especially interested in showing scientists who are not particularly mathematically inclined how to use these methods effectively and thus save a great deal of time and expense.

Isolated guinea pig nerve-lumbrical muscle preparations were exposed to halothane, methoxyflurane, isoflurane, enflurane, fluroxene, and diethyl ether. The temporal courses of the effects on indirectly and directly elicited twitch responses were determined over a range of concentrations for each agent. When the anesthetics were compared at concentrations equivalent in terms of minimum alveolar concentration (MAC), a spectrum was observed in which halothane, methoxyflurane and isoflurane depressed the indirect twitch response at 3.5--5 MAC and the direct twitch response at 8--10 MAC. Diethyl ether and fluroxene depressed the indirect twitch response at 2--3.5 MAC and the direct twitch response at 3--6 MAC. Enflurane depressed the indirect response at 1.5--2.5 MAC and the direct response at 6--8 MAC. When the anesthetics were compared at concentrations equivalent in terms of their abilities to depress end-plate depolarization, however, all anesthetics were equipotent. Depression of the indirect twitch response occurred only when anesthetic concentrations were great enough to depress depolarization by 50 per cent.

Statistical methods for analyzing enzyme kinetic or drug binding assays involving simple first-order kinetics have been reviewed. The Eadie-Hofstee format combines many attractive features. Specifically, this plot is as efficient as any of the alternatives, shows no tendency to produce grossly aberrant values, does not require explicit weighting, does not require an iterative fitting process, gives the parameters of interest and their errors of estimate directly, and is unbiased (after correction). A correction for the bias inherent in the Eadie-Hofstee format has been developed. A numerical example and computer program are given in appendices.

The actions of diethyl ether, enflurane, and isoflurane at the neuromuscular junction were examined in isolated guinea pig lumbrical muscles. These anesthetics depressed the ability of carbachol to depolarize the endplate region; this depression of depolarization did not show competitive kinetics. None of the anesthetics altered the affinity of the acetylcholine receptor for d-tubocurarine, i.e., the dissociation constant of d-tubocurarine was unchanged. Since diethyl ether, enflurane, and isoflurane produced no observable alteration of the receptor, the antagonism of the drug-induced depolarization of the neuromuscular junction appears to be exerted at a stage subsequent to reaction with the receptor. (Key words: Anesthetics, volatile, diethyl ethers; Anesthetics, volatile, euflurane; Anesthetics, volatile, isoflurane; Neuromuscular relaxants, d-tubocurarine; Neuromuscular junction.).

The effect of low potassium diets with and without deoxycorticosterone (DOCA), furosemide, chlorothiazide, or ethacrynic acid on sensitivity of isolated guinea pig lumbrical nerve-muscle preparations to d-tubocurarine was examined. The ED50 of d-tubocurarine was found to fall as the potassium level was lowered by dietary restriction. Addition of DOCA or furosemide was without effect while chlorothiazide reduced and ethacrynic acid enhanced the effect of diet alone. Acute restoration of potassium levels of 5.9 mM reversed considerably, but not completely, the effect of chronic depletion. Thus, a patient suffering from chronic potassium depletion would be expected to require a decreased dose of d-tubocurarine, and although acute replacement of potassium preoperatively would tend to return the dose requirement toward normal, such reversal might not be complete.

1. The influence of saturable drug uptake on the drug concentration near the receptor sites was shown theoretically to depend on the geometry of the preparation; increases in the volume/surface ratio (V/S) of the preparation decrease the sensitivity of the preparation to an agonist inactivated in the tissue. 2. The positive inotropic effect of (-)-noradrenaline was found to depend on the ratio V/S of the preparation; papillary muscles with larger V/S were less sensitive to the drug and showed steeper noradrenaline concentration-effect curves. 3. An algorithm for the statistical estimation of the parameters of the saturable uptake process was derived. It was applied to the positive inotropic noradrenaline effect in relation to muscle geometry. As an analysis of variance showed, the model explained a significant proportion of the shift of (-)-noradrenaline concentration-effect curves associated with variation in size of the preparation.

The effect of immobilization of a limb on subsequent sensitivity of the diaphragm to d-tubocurarine was examined in the guinea pig. A forelimb was immobilized in a plaster cast for 1 or 3 weeks. An isolated nerve-diaphragm preparation was then set up and the sensitivity to d-tubocurarine measured. Parallel assays on a nerve-lumbrical muscle preparation from the limb in the cast were also examined for comparison. The diaphragm from unimmobilized animals showed the normal decreased sensitivity relative to the lumbrical. After immobilization the sensitivity of the lumbrical decreased, whereas that of the diaphragm did not change. Thus in contrast to previously observed behavior in limb muscles, changes in d-tubocurarine sensitivity produced by immobilization do not involve the diaphragm.

The concentrations of d-tubocurarine and pancuronium producing 50% block of the indirectly elicited twitch were determined in isolated mouse nerve-diaphragm preparations at 37 and 25 C. The contralateral side was used as a control in a 2 x 2 factorial analysis of variance. Cooling shifted the dose-response curves for both drugs to the left, but only slightly (from 1.69 +/- 0.022 microM to 1.49 +/- 0.021 microM with d-tubocurarine and from 0.65 +/- 0.012 microM to 0.46 +/- 0.009 microM with pancuronium). The dose-response relationship was, however, so steep (Hill coefficient approximately 5 to 6) that a slight horizontal shift of the dose-response curve corresponds to a considerable decrease in the twitch response at a concentration midway between the curves. Thus, studies using only the concentration that produces partial block of twitch responses misleadingly suggest a large effect of temperature. Similarly, if in another system the curve were to shift to the right even only slightly, a temperature effect in the reverse direction might be reported. It is concluded that temperature appears to have little influence on cellular potency of neuromuscular blocking agents.

The influence of gallamine, metocurine, pancuronium, and tubocurarine on depolarization of a mammalian muscle end-plate region was examined to determine whether the antagonists given in combination exerted a degree of block consistent with the simple classical competitive model. Depolarization was produced by carbachol in isolated guinea pig lumbrical muscles and recorded by the moving fluid electrode technique. The dose-response values obtained were fitted to a regression embedded in a split plot factorial experimental design such as both to control and to measure effects of variation among preparations, order of administration, time, and level of block. Of the six possible pairings of the four drugs, four showed the simple additivity expected from a competitive mechanism, while two (pancuronium plus metocurine and metocurine plus gallamine) showed potentiation beyond additivity. In these latter two pairs the combination shifted the carbachol dose-response curve, respectively, 41 and 21% further than predicted from the classical model. The significance of this deviation in the light of alternative receptor models is discussed, and a model consistent with the observed results is outlined.

ORG NC45, a neuromuscular blocking agent not producing tachycardia, was examined first, to establish the kinetics of the anatagonism it produces, and second, to test the hypothesis that the tachycardia seen with pancuronium and gallamine reflects an action on vagal postganglionic nerve endings. The action of ORG NC45 was studied on end-plate depolarization and neuromuscular transmission in the guinea pig lumbrical muscle. Also, the effect of ORG NC45 on the response of the cardiac pacemaker to carbachol and on the response of the pacemaker to pre- and postganglionic vagal stimulation was examined in isolated guinea pig atria. ORG NC45 was a potent neuromuscular blocking agent (twice as potent as pancuronium) in this species and showed typical competitive kinetics with a dissociation constant of 0.0103 micro M. However, ORG NC45 affected the atrial system only at very high concentrations and did not affect release of transmitter from vagal nerve terminals. These results thus confirm the hypothesis that presence or absence of vagolytic action goes hand-in-hand with tachycardia or its absence clinically.

The effects of repeated doses of decamethonium or succinylcholine in muscles of the cat, dog, and rabbit have been examined. In particular, the relation of degree of neuromuscular block to intensity of the electrical change at the end-plate region has been found to be more consistent when the peak spatial gradient of depolarization is used as a measure of electrical effect than when the peak depolarization is used; the reason for this difference is discussed. A plot of twitch height against electrical change provides a convenient frame of reference for following the development of phase II block quantiatively. Examples presented show that the extent and kinetics of phase II block can vary considerably among species or among muscles in a given species.

The effect of immobilization on subsequent sensitivity of limb muscles to d-tubocurarine was examined in a guinea pig model. A foreleg was immobilized in a cast for 1-4 weeks. At the end of this period, isolated nerve-lumbrical muscle preparations were set up and sensitivity to d-tubocurarine assayed. Immobilization increased the ED50 of the drug not only in muscles from the limb in the cast but also those from contralateral forelimbs and from hindlimbs. The increase in ED50 was not accompanied by atrophy. In a parallel series of experiments measuring the effect of d-tubocurarine on depolarization by carbachol, the apparent d-tubocurarine-receptor dissociation constant was determined. Immobilization produced no change in this parameter. Because immobilization of one extremity produced sensitivity changes in others, the anesthesiologist must be careful not to assume that monitoring from any limb will yield normal values in a patient with partial immobility.

The ability of a series of barbiturates to depress the depolarizing action of carbachol at the end-plate of guinea-pig lumbrical muscle was studied. The compounds studied were: amorbarbital, aprobarbital, barbital, barbituric acid, butabarbital, butalbital, dimethylbutylethyl barbituric acid, hexobarbital, mephobarbitak, secobarbital, thiamylal, and thiopental. The depressant activity was sensitive to small changes in structure of the compounds strongly suggesting that a specific receptor site was involved in the interaction of the drug with the tissue. The observed relative potencies on the motor end-plate were compared with their anesthetic potencies assayed on tadpoles. The two potencies went hand-in-hand for all the compounds studied, including the convulsant member of the series.

1. The margin of safety for neuromuscular transmission in the tibialis and sartorius muscles of the cat has been determined by measuring the ratio by which end-plate depolarization produced by succinylcholine, decamethonium, octamethonium or iodocholine is antagonized, in the presence of neuromuscular block produced by tubocurarine, gallamine or DF-596. The estimate of the margin of safety was independent of the particular drugs chosen for the measurement.2. To produce threshold block to indirect stimulation once every 10 sec, a fractional occupancy by the antagonist of 0.76 +/- 0.05 (S.D.) was required; for nearly complete block, an occupancy of 0.917 +/- 0.16 (S.D.) was required. These figures correspond to factors of safety of 4.1 and 12 for the most sensitive and the most resistant groups of fibres respectively.3. The interaction between the agonists and the antagonists, when tested over a wide range of dosage, did not conform with the conditions of full competitive equilibrium. It was concluded that this arose, not because of some interfering non-competitive process, but because, during the relatively brief exposure to agonist, the equilibrium between the antagonist and the receptors is not significantly disturbed. An analysis of this condition of quasi-equilibrium is given. A correction downwards of the direct estimates of the margin of safety is required, but this proves to be small, about 8%, and may not be significant.4. The safety factor diminished when the motor nerve had been cut more than 5 hr; it is suggested that this represents an early sign of nerve degeneration.5. With dog sartorius muscle, results similar to those in the cat were obtained. But for deep block in the rabbit, the safety factor was only about 4.6. The existence of a substantial margin of safety influences considerably the interpretation of the time course of action of blocking drugs, and of comparisons between responses to nervous excitation and drug injection.