Developing quality indicators for general practice care for vulnerable elders; transfer from US to The Netherlands

BACKGROUND

Measurement of the quality of healthcare is a first step for quality improvement. To measure quality of healthcare, a set of quality indicators is needed. We describe the adaptation of a set of systematically developed US quality indicators for healthcare for vulnerable elders in The Netherlands. We also compare the US and the Dutch set to see if quality indicators can be transferred between countries, as has been done in two studies in the UK, with mixed results.

METHOD

108 US quality indicators on GP care for vulnerable elders, covering eight conditions, were assessed by a panel of nine clinical experts in The Netherlands. A modified version of the RAND/UCLA appropriateness method was used. The panel members received US literature reviews, extended with more recent and Dutch literature, summarising the evidence for each quality indicator.

RESULTS

72 indicators (67% of US set) were (nearly) identical in the Dutch and US sets. For some conditions, this percentage was much lower. For undernutrition, only half of the US indicators were included in the Dutch set. For depression, many indicators were discarded or changed in a significant way, with the result that only five of the original 17 indicators (29%) are the same in the Dutch and the US set.

CONCLUSIONS

Quality indicators can be transferred between countries, but with caution, because in two of the three studies on transferring indicators between the US and Europe, 33-44% of the indicators were discarded. For some conditions in the current study, this percentage is much higher. For undernutrition, there is hardly any evidence, and differences between the indicator sets can be attributed to differences in expert opinion between the countries. For depression, it seems that different evidence is considered important in the US and in The Netherlands, of which the Dutch body of knowledge is not known in the US.

Guideline adherence rates and interprofessional variation in a vignette study of depression

OBJECTIVE

To assess the appropriateness of and variation in intention-to-treat decisions in the management of depression in the Netherlands.

DESIGN

Mailed survey with 22 paper cases (vignettes) based on a population study.

SETTING

A random sample from four professional groups in the Dutch mental healthcare system.

SUBJECTS

264 general practitioners, psychiatrists, psychotherapists, and clinical psychologists.

MAIN OUTCOME MEASURES

Each vignette contained information on a number of patient characteristics taken from three national depression guidelines. The distribution of patient characteristics was based on data from a population study. Respondents were asked to choose the best treatment option and the best treatment setting. For each vignette we examined which of the selected treatments was appropriate according to the recommendations of the three published Dutch clinical guidelines and a panel of experts.

RESULTS

31% of all intention-to-treat decisions were not consistent with the guidelines. Overall, less severe depression, alcohol abuse, psychotic features, and lack of social resources were related to more inappropriate judgements. There was considerable variation between the professional groups: psychiatrists made more appropriate choices than the other professions although they had the highest rate of overtreatment.

CONCLUSIONS

There is sufficient variation in the intentions to treat depression to give it priority in quality assessment and guideline development. Efforts to achieve appropriate care should focus on treatment indications, referral patterns, and overtreatment.

N-methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (MBDB): its properties and possible risks

Abstract MBDB (N -methyl-1-(1,3-benzodioxol-5-yl)-2-aminobutane) is the alpha-ethyl homologue of MDMA (3,4-methylenedioxy-N-methylamphetamine). MBDB is metabolized and excreted similarly to MDMA: presumably, the majority of oral MBDB is excreted in urine unmetabolized.The main metabolic routes in man are thought to be O-dealkylation and subsequent methylation, sulphation and glucuronidation of the newly formed hydroxy groups. The major acute neuropharmacological effects of MBDB in the rat are an increase in serotonin release in the brain and an inhibition of serotonin and noradrenaline re-uptake. These effects compare well with those of MDMA, although the latter is more potent. MBDB may also slightly increase dopamine release and inhibit dopamine re-uptake, but to a lesser extent than MDMA. This is important, as dopamine release has been implicated in the reinforcing qualities of substances such as cocaine and amphetamine. The neuroendocrine effects of MBDB resemble those of MDMA. Both substances increase plasma ACTH, corticosterone, prolactin and renin. The neurophysiological effects of MBDB are characterized by a decrease in electrical activity throughout the brain, most notably in the alpha 2 and delta frequency bands. In contrast, hallucinogens increase the activity in the alpha 1 band, especially in the corpus striatum. In drug discrimination tests in the rat, MBDB, like MDMA, can be distinguished clearly from both stimulants and hallucinogens.The class of substances to which MBDB belongs may be named entactogens. MBDB dose-dependently increases locomotor activity and decreases exploratory behaviour in the rat and causes distress vocalization and wing extension in the newly hatched chicken. The rewarding properties of MBDB appear to be smaller than those of MDMA, as suggested by a 2.5 times weaker potency in the conditioned place preference test in rats. The main subjective effects of MBDB in man are a pleasant state of introspection, with greatly facilitated interpersonal communication and a pronounced sense of empathy and compassion between subjects. In this respect, MBDB again resembles MDMA. However, there are also differences. MBDB has a slower and more gentle onset of action than MDMA, produces less euphoria and has less stimulant properties. The few toxicological data available suggest that MBDB may cause serotonergic deficits in the brain, although the potency of MBDB to cause this neurotoxic effect is smaller than that of MDMA. Severe acute reactions in man as have been reported for MDMA have not been published for MBDB. The dependence potential of MBDB appears to be small, probably even smaller than that of MDMA. MBDB has been available at least since 1994 but its position on the synthetic drugs market is marginal. Subjective reports indicate that MBDB is less popular among users than MDMA. The reason may be that MBDB produces less euphoria than MDMA. Another possible explanation is that MBDB largely lacks the stimulant properties of MDMA.We calculated a margin of safety with a method similar to one used in the risk assessment of pharmaceuticals. The results suggest that MBDB is three times less likely to cause serotonergic brain deficits than MDMA. However, it should be noted that for both substances the margin of safety is less than one, indicating that the risk of neurotoxicity is not negligible. In animals, serotonergic brain deficits after exposure to MDMA have been linked to the degeneration of serotonergic nerve terminals.

Effect of physician specialty on treatment recommendation to patients with coronary artery disease

OBJECTIVE

To assess the influence of physician specialty and the way in which patient data are presented in the treatment recommended for patients with coronary artery disease.

METHODS

In a prospective study, 3,628 patients with significant coronary artery disease who had been referred to 1 of 10 heart centers in the Netherlands as possible candidates for either percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass graft surgery (CABG) were recruited. Within each center, the recommended treatment is determined by a team consisting of cardiologists only, cardiovascular surgeons only, or cardiologists and cardiovascular surgeons (i.e., composite teams). The main outcome measures are the proportions of patients for whom PTCA, CABG, or noninvasive (medical) therapy was recommended.

RESULTS

Composite teams made 71% of recommendations, surgeon-only teams, 12%, and cardiologist-only teams, 17%. Cardiologist-only teams primarily recommended patients to PTCA, surgeon-only teams to CABG, while combined teams made more evenly distributed recommendations (p < .001). Although the patients discussed by the three types of teams were clinically different, the recommendation patterns remained significant after adjusting for these differences (p < .001). For patients with recent myocardial infarction, direct presentation of the case to the team by the referring cardiologist reduced the likelihood that CABG would be recommended.

CONCLUSIONS

The treatment recommended to patients with coronary artery disease is affected by the composition of the team providing the recommendation. These findings have important implications for clinical decision making for patients with cardiovascular disease.

Waiting for coronary revascularization: a comparison between New York State, The Netherlands and Sweden

OBJECTIVE

To compare waiting times for percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass graft (CABG) surgery in New York State, the Netherlands and Sweden and to determine whether queuing adversely affects patients' health.

METHODS

We reviewed the medical records of 4487 chronic stable angina patients who underwent PTCA or CABG in one of 15 New York State hospitals (n = 1021) or were referred for PTCA or CABG to one of ten hospitals in the Netherlands (n = 1980) or to one of seven hospitals in Sweden (n = 1486). We measured the median waiting time between coronary angiography and PTCA or CABG.

RESULTS

The median waiting time for PTCA in New York was 13 days compared with 35 and 42 days, respectively, in the Netherlands and Sweden (P < 0.001). For CABG, New York patients waited 17 days, while Dutch and Swedish patients waited 72 and 59 days, respectively (P < 0.001). The Swedish and Dutch waiting list mortality rate was 0.8% for CABG candidates and 0.15% for PTCA candidates.

CONCLUSIONS

There were large variations in waiting time for coronary revascularization among these three sites. Patients waiting for CABG were at greatest risk of experiencing an adverse event. In both the Netherlands and Sweden, the capacity to perform coronary revascularization has been expanded since this study began. Further international cooperation may identify other areas where quality of care can be improved.

Setting standards for effectiveness: a comparison of expert panels and decision analysis

OBJECTIVE

To compare criteria for coronary revascularization developed by the expert panel process and by decision analysis.

METHOD

We reviewed the medical records of 3080 chronic stable angina patients who either underwent coronary artery bypass graft surgery (CABG) or percutaneous transluminal coronary angioplasty (PTCA) and determined the agreement between appropriateness ratings made by two expert physician panels, one from the United States and the second from The Netherlands. We also evaluated the agreement between these panels' appropriateness ratings and a decision analytic model's effectiveness categories.

RESULTS

There was poor agreement between U.S. and Dutch panel appropriateness ratings for PTCA (kappa = 0.03) and slight agreement for bypass surgery (kappa = 0.18). Dutch ratings had substantial agreement with the decision analytic models effectiveness categories for both PTCA and CABG (kappa = 0.83 and 0.79, respectively) whereas there was no systematic agreement between U.S. ratings and the decision analytic model for PTCA and poor agreement for CABG (kappa = 0.00 and 0.18, respectively).

CONCLUSIONS

Although the level of agreement between expert panels and decision analysis on when a procedure is appropriate or effective may vary by procedure and the strength of the scientific evidence, we found that Dutch physicians agree much more strongly with decision analysis than U.S. physicians.

Indications for coronary revascularisation: a Dutch perspective

OBJECTIVE

To assess the appropriateness of indications for coronary artery bypass graft (CABG) surgery and percutaneous transluminal coronary angioplasty (PTCA).

METHODS

A modified Delphi group judgement process with input from a panel of six interventional cardiologists and six cardiopulmonary surgeons. There was one clinician from each of the 12 tertiary referral heart centres in The Netherlands.

MAIN OUTCOME MEASURE

Ratings by panel members, on a 1 to 9 scale, of indications presented as a choice between two treatments (CABG v medical treatment, PTCA v medical treatment, and CABG v PTCA) for 1182 model cases. Each case represented a unique combination of clinical features in terms of symptoms, medical history, and results of tests. Ratings were analysed with respect to degree of agreement among panelists, degree of appropriateness of indications, and panel's preference for invasive or medical treatment.

RESULTS

The panel agreed on 58.6% and disagreed on 3.2% of the indications. The panel opted for invasive treatment in 48.2% and medical treatment in 22.8%, and had no clear preference for either method in 29.0% of the cases. When compared with medical treatment, CABG was more often rated appropriate than PTCA: 35.4% v 21.6% (P < 0.001). Panel scores depended on severity of anatomical disease. For instance, for 51.5% of the model cases with one-vessel disease not including the proximal left anterior descending artery, the panel preferred medical treatment to invasive treatment, while the latter was preferred in 18% of the cases. In cases with type C lesions, the panel frequently rated PTCA as inappropriate. Panel scores were also affected by nonclinical factors. Cardiologists and surgeons rated the procedure of their own specialty higher than the alternative invasive intervention.

CONCLUSIONS

The panel method yields logically consistent scores of the appropriateness of indications for carrying out medical procedures. It may be an aid in formulating clinical practice guidelines.

The appropriateness of intention to treat decisions for invasive therapy in coronary artery disease in The Netherlands

OBJECTIVE

To determine the appropriateness of intention to treat decisions concerning coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA) for patients with coronary artery disease in The Netherlands.

DESIGN

Prospective study of intention to treat decisions using a computerised expert system.

SETTING

"Presentation" sessions in 10 tertiary referral heart centres in 1992.

PATIENTS

3207 consecutive patients: 1618 CABG and 1589 PTCA candidates.

MAIN OUTCOME MEASURE

Percentage of invasive treatment decisions rated appropriate, uncertain, or inappropriate by the expert system.

RESULTS

PTCA decisions were common for patients with one-vessel disease and CABG decisions for patients with three-vessel and left main disease. PTCA decisions outnumbered CABG decisions in acute myocardial infarction. Of CABG decisions, 84% were rated appropriate, 12% uncertain, and 4% inappropriate. The proportions for PTCA decisions were 39% appropriate, 31% uncertain, and 29% inappropriate. Type C lesion was the main determinant of inappropriateness of PTCA decisions. If type C lesions were downgraded to type A/B lesions the rate of inappropriate PTCA decisions dropped to 6%.

CONCLUSIONS

Clinicians in tertiary referral centres in The Netherlands favoured CABG if vessel disease was extensive or involved the left main artery, and PTCA for patients with less extensive disease and with acute myocardial infarction. Few CABG decisions were inappropriate. The main determinant of inappropriateness of PTCA decisions was its intended use in patients with type C lesions.

Panellist consistency in the assessment of medical appropriateness

Where information about the appropriateness of a surgical procedure is lacking, expert panels have been used to establish guidelines for medical practitioners. Such a panel was convened to assess the appropriateness of percutaneous transluminal coronary angioplasty and coronary artery bypass graft surgery in the Netherlands. The panel, consisting of interventional cardiologists and cardiothoracic surgeons, used a modified Delphi process to rate 1126 clinical indications over two rounds. This article describes the degree of change in both agreement amongst members and in the appropriateness ratings over the two rounds, and examines the internal consistency of the ratings of individual panellists. Over the two rounds, agreement increased. Although most appropriateness ratings remained unchanged, there was significant movement from equivocal ratings to determinate ratings. While individual members showed some degree of inconsistency in their scoring, the panel as a whole scored very consistently. The observed changes in appropriateness were consistent with expectations, showing that the appropriateness method is used logically and consistently by panellists.

[Effect of physical activity in the elderly: a review of current literature and the possibility of economic evaluation]

The Netherlands government emphasizes the importance of preventive care for the elderly. From an economic and preventive point of view the potential of exercise programmes to reduce the use of health care services by the elderly deserves attention. We present an overview of the literature on the effects of physical activity on health and psychological well-being of the elderly and their use of health services. Our review covers the period 1988-1993 and also includes review articles. We found almost sixty relevant articles which about all satisfied our methodological criteria. In men, physical activity probably has a positive influence on the frequency of ischaemic heart disease. Exercise delays the onset of osteoporosis in women. The results for other diseases are ambiguous, despite the large amount of literature. Similarly, it is not clear yet whether physical activity can enhance well-being. Research on the effects of physical activity on the use of health services has hardly been done. We conclude that well-designed studies are needed to determine the cost-effectiveness of exercise programmes in the elderly.

[Assessment of indications using the RAND method: invasive therapy in coronary sclerosis as an example]

OBJECTIVE

To assess indications for performing medical procedures for their appropriateness, using a method designed by an American research institute, RAND.

DESIGN

Delphi investigation

SETTING

The Netherlands.

METHOD

The RAND method was applied in the 'Dutch inventory of invasive coronary atherosclerosis treatments' study which concerns treatment choices in coronary artery disease: coronary artery bypass grafting (CABG), percutaneous transluminal coronary angioplasty (PTCA) and conservative treatment. Essential in the RAND method is the construction of a comprehensive matrix of potential indications. Each indication entails a comparison of two or three treatment options. A panel of 12 experts rated each indication in a two-stage process. When the majority of the panelists agreed that treatment option X was strongly to be preferred over Y, it was considered appropriate to perform X and inappropriate to perform Y.

RESULTS

The experiences with the RAND method indicated that panelists judged critically and rated many indications for invasive treatment options as inappropriate or uncertain. The method was feasible, although not easy, and produced clinically valid results.

CONCLUSION

The RAND method is especially useful when medical literature does not supply sufficient grounds in rating the appropriateness of an indication for medical procedure. However, the verdict 'appropriate' is not eternal. Medical science keeps evolving.

Recent public policies in The Netherlands to control pharmaceutical pricing and reimbursement

In The Netherlands, the rate of consumption of medicine is low compared with that in other member states of the European Community. Nevertheless, expenditure on medicines is high in this country, because of a high price level. In the past decade, the cost of medicines has been growing more rapidly than the total expenditure on healthcare in The Netherlands. This prompted The Netherlands government to take action against the rise in the cost of medicines. Some policies were directed at the volume of consumption, but most focused on price. All had in common that they failed to produce lasting cost containment or did not stand up in court or to political debate. As a result, the measures proposed and implemented by the government have become increasingly harsh, departing from the Dutch tradition of harmonious policy-making carried out jointly by government and societal groups. The latest step has been the introduction (as of July 1, 1993) of a new version of a price reference system, which discourages the prescription of innovative but expensive drugs. It is too early to tell whether this policy will have a more enduring effect on cost than the previous measures.

The diffusion of organ transplantation in Western Europe

The moment of introduction of clinical organ transplantations varied in Western Europe from country to country. In retrospect, one can distinguish pioneering countries (most notably the U.K. and France), and countries that were early or late adopters of the new technologies. An early start did not necessarily lead to extensive diffusion of organ transplantations, as shown by the example of the U.K. In general, Western Europe is lagging behind the U.S.A. In diffusion of organ transplantation technologies. With few exceptions, the introduction and diffusion of organ transplantations in Western Europe have been largely autonomous developments, not regulated by government or third party payers and only slowed down by lack of organs, facilities or funds. The lack of organs has been reduced by the activities of organ procurement and exchange organisations, and perhaps by legislation promoting organ donation. Nevertheless, the growth of the number of patients waiting for an organ is in almost all countries outpacing the increase in availability of organs.

Health care technology assessment in The Netherlands

Our present-day health sectors are increasingly characterized by both rapid technological change and growing visibility of its considerable consequences in terms of the quality and costs of health care. Improved health care decision-making in such an environment requires adequate and timely information on the benefits, risks, and costs of health care technology. Whereas traditionally, technology assessment focused predominantly on evaluating efficacy and (short-term) safety in a more or less “controlled” environment, an interesting shift in emphasis is now occurring. There is a growing recognition that improved information is also needed on the health and economic outcomes of technology as used in everyday clinical practice, i.e., on its effectiveness, cost-effectiveness, and long-term safety in normal “uncontrolled” daily medical life. Moreover, because the treatment of particular clinical conditions (such as stable angina, gallstones, or prostatism) increasingly involves choices among alternative diagnostic and therapeutic options, these assessments should ideally provide effectiveness and cost-effectiveness information for all the various technological alternatives involved.

Euthanasia across the North Sea

The United Kingdom and The Netherlands are separated by a narrow stretch of sea but in terms of an understanding of euthanasia they seem to be light years apart. An attempt to bridge the information gap seems in order. The position paper on euthanasia published by the Royal Dutch Medical Association contains 16 typed pages.¹ In contrast, the report on euthanasia issued by a working party of the British Medical Association is 80 pages in small print.²

GABA-B receptor activation and conflict behaviour

Baclofen and oxazepam enhance extinction of conflict behaviour in the Geller-Seifter test while baclofen and diazepam release punished behaviour in Vogel's conflict test. In order to investigate the possibility that the effect of the selective GABA-B receptor agonist baclofen is mediated indirectly via the GABA-A/benzodiazepine receptor complex, the effect of pretreatment of rats with baclofen on [3H]-diazepam binding to washed and unwashed cortical and cerebellar membranes of rats has been studied. Baclofen pretreatment increased Bmax in washed cerebellar membranes when bicuculline was present in the incubation mixture. No effect was seen in cortical membranes. The present results render it unlikely that the effect of baclofen on extinction of conflict behaviour and punished drinking is mediated via the GABA-A/benzodiazepine receptor complex.

Vasopressin and ethanol preference. I. Effects of vasopressin and the fragment DGAVP on altered ethanol preference in Brattleboro diabetes insipidus rats

Preference for concentrations of ethanol between 2.2 and 10 percent versus tap water was studied in Brattleboro rats homozygous for diabetes insipidus (di/di), heterozygous (di/+) or normal (+/+). The di/di rats, totally lacking in vasopressin, had greatly reduced preference scores for all concentrations of ethanol. Their intake of ethanol (g/day) was higher than heterozygotes or normals, but only when 2.2 percent ethanol was offered as a choice. Administration of lysine vasopressin or the vasopressin fragment des-9-Glycinamide-[Arginine8] vasopressin (DGAVP) using osmotic minipumps enhanced ethanol preference scores, reduced ethanol (g/day) intake, and restored total daily fluid intake in di/di rats. When di/di and di/+ rats were first allowed to develop stable ethanol preference before treatment with DGAVP, the peptide had no effect on preference scores. Thus, no treatment was effective in dissociating polydipsia from reduced ethanol preference and increased ethanol intake. While these results cannot exclude a possible regulatory role for endogenous vasopressin in ethanol preference drinking, they more strongly suggest that reduced preference for ethanol and increased ethanol intake are epiphenomena secondary to a polydipsic state.

Vasopressin and ethanol preference. II. Altered preference in two strains of diabetes insipidus rats and nephrogenic diabetes insipidus mice

In the first paper of this series, the influence of a single gene (di) for vasopressin deficiency on ethanol intake in rats was demonstrated. We studied preference for concentrations of ethanol between 2.2 and 10 percent versus tap water in Brattleboro rats homozygous for diabetes insipidus (di/di), heterozygous (di/+) or normal (+/+). The di/di rats, totally lacking in vasopressin, had greatly reduced preference scores for all concentrations of ethanol. Their intake of ethanol (g/day) was higher than heterozygotes or normals, but only when 2.2 percent ethanol was offered as a choice. Treatment with vasopressin or related peptides restored ethanol drinking to normal but also corrected water balance. In the experiments reported here, Roman High Avoidance (RHA) rats of three genotypes (+/+, di/+, and di/di) were also tested for ethanol intake and preference with similar but not identical results. Thus, the effects of the di gene are independent of the genetic background on which it is placed to at least some extent. Chlorothiazide, a drug unrelated to vasopressin, also normalized ethanol drinking and corrected water balance in di/di rats. In nephrogenic diabetes insipidus mice, there was a strong negative correlation between severity of polydipsia and preference for ethanol. Thus, no paradigm tested was effective in dissociating polydipsia from reduced ethanol preference and increased ethanol intake. While these results cannot exclude a possible regulatory role for endogenous vasopressin in ethanol preference drinking, they more strongly suggest that reduced preference for ethanol and increased ethanol intake are epiphenomena secondary to a polydipsic state.

Antagonism of effects of vasopressin (AVP) on inhibitory avoidance by a vasopressin antagonist peptide [dPtyr(Me)AVP]

After training in two different passive avoidance tasks, the platform box of Ader and De Wied (1972) and the Jarvik box of Jarvik and Kopp (1967), rats injected with vasopressin immediately following the training trial showed a significant enhancement of retention 24 hours later. This vasopressin effect was reversed by high doses of the vasopressor antagonist, dPtyr(Me) AVP. These results support the hypothesis that the visceral afferent signals may be involved in the apparent memory-enhancing effects of AVP, but the high doses of antagonist required suggest that factors other than a simple reversal of the pressor effects of AVP may be important.

Spatial learning and the hippocampal corticosterone receptor system of old rats: effect of the ACTH4-9 analogue ORG 2766

Old (26 months) and young (6 months) male Wistar rats were treated chronically for 2 weeks with ORG 2766 or with vehicle, delivered via subcutaneously implanted minipumps (0.5 microgram peptide/0.5 microliter/h). Learning of a spatial task was not impaired in the old animals, except for one measure, i.e. the latency to find the goal box. In neither age group did ORG 2766 influence behavioral performance. The number of corticosterone receptor sites was decreased in the hippocampus of senescent rats, but restored to the level observed in young rats following ORG 2766 treatment. It is concluded that the number of hippocampal corticosterone receptor sites is a sensitive index of brain aging and effectiveness of ORG 2766.

Learning and memory in young and aged Fischer 344 rats

Changes in learning and memory processes that occur with senescence were investigated in male and female Fischer 344 rats, 3-26 mth of age. Age-related impairments were seen in retention of inhibitory avoidance learning, acquisition of a Y-maze discrimination task, and in a swim escape task with short intertrial training intervals. In contrast, old animals performed better than the young rats in an active avoidance task. No age differences were observed in either open field activity or in flinch or jump thresholds to footshock. These results indicate that impairments in learning and memory processes of aged rats are task-specific, and that memory deficits in old rats are best seen following one-time-only events or with weak training. The behavioral baselines described will help in the design of further research to correlate memory and neurobiological changes observed during the aging process in the rat.

Assessment of retention capacities in old rats

Young (3-6 month) and old (24-27 month) barrier reared Wistar rats were tested for their ability to retain an inhibitory (passive) avoidance, acquired immobility, and a conditioned taste aversion response as a function of time. Old rats exhibited accelerated forgetting of both the inhibitory avoidance and acquired immobility response in comparison to young rats. In contrast, old rats displayed good retention of the conditioned taste aversion response at all time intervals tested. It appears that the dynamic aspects of retention are altered in aged rats depending on the task, and in some instances may be expressed as accelerated forgetting.

Facilitation of hot-plate response learning by pre- and posttraining naltrexone administration

Retention performance for shock-motivated learning is generally enhanced by opiate antagonists. To test the hypothesis that opioid systems mediate learning and memory in nonshock-motivated tasks, the effects of naltrexone on hot-plate response learning were investigated. Naltrexone (0.1 or 1.0 mg/kg IP) 10 min before hot-plate exposure produced hyperalgesia, as measured by decreased latencies of naltrexone-injected mice to escape. Jump latencies, however, were not significantly decreased by naltrexone given 10 min before initial testing. Nevertheless, jump latencies of naltrexone-injected mice, but not saline-injected mice, decreased further on subsequent test trials 1 and 4 days later although treatment was discontinued, suggesting that the opiate antagonist also influenced learning or memory. Mice given naltrexone (0.3-10.0 mg/kg IP) immediately after their first hot-plate exposure also exhibited learning of the jump response, on a test trial 48 h later. The decreases in jump latencies on test trials were smaller after posttraining, than pretraining naltrexone administration. The results indicate that the effect of naltrexone on learning and memory can be at least partially separated from its hyperalgesic activity.

Enkephalin actions on avoidance conditioning may be related to adrenal medullary function

The present series of studies was undertaken to better characterize the mechanisms mediating enkephalin actions on avoidance conditioning. Both Leu-and Met-enkephalin administered i.p. in amounts of 1.0 or 10.0 micrograms/kg 5 min before training in an active avoidance task significantly impaired acquisition of the response. Adrenal medullectomy, which removes an endogenous store of enkephalin-like peptides, abolished the effect on avoidance conditioning of 10.0 micrograms/kg of exogenously administered Met- or Leu-enkephalin. Increasing the dose of Leu-enkephalin by 10- or 100-fold restored its behavioral activity in adrenal demedullated rats. However, increasing (10-100-fold) or decreasing (10-fold) the dose of Met-enkephalin did not restore its activity in adrenal demedullated animals. This finding suggests that the impairing actions of the two enkephalins are not produced in the same way, but it is consistent with the interpretation that the adrenal medulla may play a role in mediating the actions of Met- and Leu-enkephalin on active avoidance conditioning.

A mouse model of alcoholism

A model of alcoholism should demonstrate self-administration of alcohol by the animal and a withdrawal syndrome when the animal no longer has access to the drug. A mouse model is described that meets these criteria and enables the induction of "alcoholism" in a large number of animals within a short period of time. Mice were injected daily with pyrazole, an inhibitor of alcohol dehydrogenase. The animals self-administered ethanol by inhaling vapour containing a relatively constant concentration of ethanol. Self-administration was voluntary: the mice could move to a chamber without ethanol vapour. During the first six days of each experiment, the animals were prompted to select the ethanol chamber by darkening that chamber. Most mice continued to self-administer ethanol without any prompting for at least 3 days; thereafter, preference for ethanol waned. Self-administration led to measurable levels of ethanol in blood and to the development of withdrawal when infusion of vapour was stopped.

Tolerance to ethanol hypothermia in inbred mice: genotypic correlations with behavioral responses

Hypothermia was studied 5 min before, and 30 and 60 min after intraperitoneal administration of ethanol (3 g/kg) in 20 inbred strains of mice. Ethanol was given daily for 8 days, and temperatures were taken on Days 1, 3, 5, and 8. Tolerance was indexed by the reduction in hypothermia over days. There were large strain differences in baseline temperature, the hypothermic effect of ethanol, and in development of tolerance to hypothermia. Some strains of mice (DBA/1J, DBA/2N, MA/MyJ, and PL/J) did not develop tolerance to the hypothermic effect of ethanol. Initial sensitivity to the hypothermic effect of ethanol was significantly genetically correlated with tolerance development, indicating control of these responses by common genes. Ethanol-induced changes in activity and ataxia, as well as blood ethanol concentrations, were also assessed. Although there were significant strain differences in activity reduction, ataxia, blood-ethanol concentrations, and changes in these parameters during the course of chronic treatment, none of these variables could explain the genetic differences in hypothermic sensitivity and tolerance.

Memory consolidation in senescence: effects of CO2, amphetamine and morphine

Alterations in memory storage processes that occur in senescence were investigated by challenging young and old female "small Wistar" rats with posttraining administration of CO2, amphetamine or morphine, and measuring retention performance. Neither duration of CO2 immersion, nor the time of CO2 immersion after training had a differential amnestic effect with age on retention of a one-trial, shock-motivated inhibitory avoidance task. These results indicate that the times during which memory is susceptible to disruption for old and young rats are similar. Challenge with drugs, however, did reveal age-related alterations in memory storage processes. Amphetamine attenuated CO2-induced amnesia in young rats, but had no effect in old rats. This could not be attributed to a general decline in response to amphetamine in old rats because amphetamine increased open field activity of both young and old animals. Morphine also had a differential effect on memory with age: it caused amnesia in old rats trained in a one-trial hot plate escape task, while having no effect on retention performance of young rats. Thus, the modulatory influence of catecholamine and opioid systems on memory processes is probably altered in senescence.

Analysis of behavioural responses to an ACTH analog in CXB/By recombinant inbred mice

Male mice of the C57BL/6By and BALB/cBy inbred strains, their reciprocal F1 hybrids, and 7 recombinant inbred strains, were tested for open-field activity, a shock-motivated successive reversal position discrimination problem in a T-maze, and a toggle box exploration task. The test battery was repeated one month later. Finally, mice were tested for the acquisition and extinction of a taste aversion conditioned by ethanol injection. Mice of each strain were tested after injection with saline or one of 3 doses of an ACTH analogue. Highly significant genotypic differences were found for all measures, an expected result. The strain distribution pattern seen in the toggle box suggested single gene mediation of exploratory activity after habituation. One aspect of avoidance responding and extinction of conditioned taste aversion also yielded strain distribution pattern consistent with single gene control. Peptide treatment reduced internal field crossings in the open field. This effect was not strain dependent. Peptide treatment had no effect on T-maze learning, conditioned taste aversion, or toggle-box exploration.

A comparison of the ability of opioid peptides and opiates to affect active avoidance conditioning in rats

Enkephalins reduce acquisition of an active avoidance response when administered intraperitoneally shortly before training. The present study examined whether microgram or delta opiate receptors are involved in this enkephalin effect. This was done by comparing the efficacy of micro- and delta-receptor agonists; by attempting to block the enkephalin effect with micro- and delta-receptor antagonists; and by comparing the characteristics of the effects of Met-enkephalin and Leu-enkephalin. In addition, the efficacy of kappa-agonists in reducing acquisition was assessed. It was found that micro-agonists are inactive in this assay; several delta- and kappa-agonists are active. However, not all of the data are consistent with the adequacy of this receptor classification. The micro-receptor antagonist naloxone did not readily block the effect of Met- or Leu-enkephalin but neither did the micro/delta-antagonist, diprenorphine. An additional complexity is the emergence of differences in behavioral activity of Met- snd Leu-enkephalin.

Changes in rat brain norepinephrine levels and turnover after olfactory bulbectomy

After bilateral olfactory bulbectomy in rats a significant increase of norepinephrine (NE) level in the hypothalamus was found. However, no difference was observed between hypothalamic NE turnover of bulbectomized and sham operated animals in the amygdaloid cortex the NE level was not affected by bulbectomy. In this area, however, the NE turnover appeared to be decreased after bulbectomy. The latter finding may be related to the deficits in passive avoidance behaviour as found in bulbectomized rats.

Endorphins alter acquisition and consolidation of an inhibitory avoidance response in rats

Peripheral i.p. administration of 1.0 microgram/kg gamma-endorphin to rats, 30 min prior to training in a 1-trial inhibitory avoidance task, enhanced retention performance measured 72 h later. A much smaller dose of 0.1 microgram/kg beta-endorphin administered immediately following training produced a retention deficit. Both of these endorphin effects were time dependent, since gamma-endorphin given 90 min prior to, and beta-endorphin given 90 min after training produced no effect on retention performance. A wide dose range of either gamma-endorphin (0.1-10 micrograms/kg) administered after training or beta-endorphin (0.1-10 micrograms/kg) administered before training had no effect. These results suggest that the behavioral actions of beta-endorphin and smaller beta-lipotropin sequences such as gamma-endorphin, are distinct. We also found that 0.1-100 micrograms/kg of either alpha-endorphin or Met-enkephalin given before or after training was without effect on retention of the response.

Attenuation of amphetamine-induced enhancement of learning by adrenal demedullation

These experiments investigated the effect of immediate posttrial administration of peripherally acting DL-4-hydroxyamphetamine on retention of a one-trial inhibitory avoidance response in intact, adrenal medullectomized, sympathectomized, and medullectomized and sympathectomized rats. In intact rats, 0.82 mg/kg of DL-4-OH-amphetamine enhanced retention performance. In rats sympathectomized by peripheral 6-hydroxydopamine, 24 h prior to training, a lower dose of 4-OH-amphetamine (0.21 mg/kg) was most effective in enhancing retention. Adrenal demedullation abolished the memory enhancing effects of DL-4-OH-amphetamine and also D-amphetamine. These findings suggest that the memory enhancing effects of DL-4-OH-amphetamine and D-amphetamine involve adrenal medullary catecholamines.