Quantifying the advantages and acceptability of linking dialysis machines to an electronic medical record

AIM

To establish and quantify the time saved by redirecting nursing workload from recording and entering haemodynamic data during chronic dialysis sessions by linking dialysis machines directly to the electronic medical record.

METHODS

We developed a bespoke interface from the HL7 feed from the dialysis machines (largely Fresenius 5008) to our EMR system (Cerner). We quantified the time nurses spent with the patient, computer, dialysis machine and sorting our patient related issues by observation using independent observers in a time and motion study. We performed these observations before and after implementation of the computer interface. We established patient and nursing acceptance by survey. We established adequacy of observations by counting the number of patients who received the minimum number of observations recorded in the system before and after implementation.

RESULTS

Implementation of a dialysis machine direct EMR interface reduced the time the nurses spent with the computer significantly by ∼9 % (around 28 min, p < 0.05) per dialysis shift, and this was accompanied by a similar increase in time spent sorting out patient-related issues. The interface was well accepted by staff and patients. An immediate benefit was a ∼60 % improvement in the adequacy of recording vital signs in our dialysis patients. Then simply by showing these results to the nursing staff there was further improvement.

CONCLUSIONS

In these days of machine interconnectivity there is really no good reason why dialysis nurses should be used to transfer data between machines. It is far better to utilise their skills in helping patients with their medical issues. We have shown that such a link improves efficiency, patient and staff satisfaction and dialysis governance.

Efficacy of cyclo-oxygenase-2 inhibition by etoricoxib and naproxen on the axial manifestations of ankylosing spondylitis in the presence of peripheral arthritis

OBJECTIVE

The combined efficacy of selective and non-selective cyclo-oxygenase-2 (COX-2) inhibition on the axial manifestations of ankylosing spondylitis (AS) in the presence or absence of chronic peripheral arthritis was evaluated.

METHODS

In a post hoc subgroup analysis of a 6 week, randomised, double blind, placebo controlled trial, 387 patients with active axial AS were randomised to receive etoricoxib 90 mg or 120 mg once a day, naproxen 500 mg twice daily, or placebo. Randomisation was stratified by the presence or absence of chronic peripheral arthritis. The primary outcome measure was the time weighted average change from baseline of spine pain intensity. Efficacy data from the three groups receiving active treatment (the NSAID/COX-2 inhibitor group) were combined to improve precision. An analysis of covariance model was used to evaluate the effect of peripheral disease on treatment response.

RESULTS

93 patients were allocated to receive placebo and 294 to active treatment (naproxen or etoricoxib). The combined NSAID/COX-2 inhibitor group had a significant treatment response compared with the placebo group for all efficacy measures, both in patients with and without peripheral arthritis. A significantly greater difference in mean patient assessment of spine pain was found between active and placebo treatments in patients without compared with those with peripheral arthritis (p = 0.005; -32.5 mm v -17.0 mm, respectively). Similar differences, although not statistically significant, were seen for other end points.

CONCLUSION

NSAIDs and COX-2 inhibitors have a clinically relevant symptomatic effect on axial AS irrespective of the presence of peripheral arthritis. In this exploratory analysis spinal improvement appeared to be greater in patients without peripheral disease.

1,4-Benzodiazepine peripheral cholecystokinin (CCK-A) receptor agonists

A series of 1,4-benzodiazepines, N-1-substituted with an N-isopropyl-N-phenylacetamide moiety, was synthesized and screened for CCK-A agonist activity. In vitro agonist activity on isolated guinea pig gallbladder along with in vivo induction of satiety following intraperitoneal administration in a rat feeding assay was demonstrated.

Mixed effects logistic regression models for longitudinal ordinal functional response data with multiple-cause drop-out from the longitudinal study of aging

In the context of analyzing ordinal functional limitation responses from the Longitudinal Study of Aging, we investigate the association between current functional limitation and previous year's limitation and its modification by physical activity and multiple causes of drop-out. We accommodate the longitudinal nature of the multiple causes of informative drop-out (death and unknown loss-to-follow-up) with a mixed effects logistic model. Under the proposed model with a random intercept and slope, the ordinal functional outcome and multiple discrete time survival profiles share a common random effect structure. This shared parameter selection model assumes that the multiple causes of drop-out are conditionally independent of the functional limitation outcome given the underlying random effect representing an individual's trajectory of general health status across time. Although it is not possible to fully assess the adequacy of this assumption, we assess the robustness of the approach by varying the assumptions underlying the proposed model, such as the random effects distribution and the drop-out component. It appears that between-subject differences in initial functional limitation are strongly associated with future functional limitation and that this association is stronger for those who do not have physical activity regardless of the random effects and informative drop-out specifications. In contrast, the association between current functional limitation and previous trajectory of functional status within an individual is weaker and more sensitive to changes in the random effects and drop-out assumptions.

Aerosolization of P2Y(2)-receptor agonists enhances mucociliary clearance in sheep

The purpose of this study was to determine whether aerosolized INS316 (UTP) stimulates lung mucociliary clearance (MCC) in sheep and, if so, to compare its effects with INS365, a novel P2Y(2)-receptor agonist. In the first series of studies, we used a previously described roentgenographic technique to measure tracheal mucus velocity (TMV), an index of MCC, before and for 4 h after aerosolization of INS316 (10(-1) M and 10(-2) M) and INS365 (10(-1) M and 10(-2) M), or normal saline in a randomized crossover fashion (n = 6). In a second series of studies, we compared the ability of these agents to enhance total lung clearance. For these tests, the clearance of inhaled technetium-labeled human serum albumin was measured serially over a 2-h period after aerosolization of 10(-1) M concentration of each agent (n = 7). Aerosolization of both P2Y(2)-receptor agonists induced significant dose-related increases in TMV (P < 0.05) compared with saline. The greatest increase in TMV was observed between 15 and 30 min after drug treatment. The highest dose (10(-1) M) of INS316 produced a greater overall stimulation of TMV than did INS365 (10(-1) M). Both compounds, compared with saline, induced a significant increase in MCC (P < 0.05) within 20 min of treatment. This enhancement in MCC began to plateau at 60 min. Although the response to INS316 started earlier, there was no significant difference between the clearance curves for the two compounds. We conclude that inhaled P2Y(2)-receptor agonists can increase lung MCC in sheep and that for P2Y(2)-receptor stimulation TMV accurately reflects changes in whole lung MCC.

The relationship of biochemical markers of bone turnover to bone density changes in postmenopausal women: results from the Postmenopausal Estrogen/Progestin Interventions (PEPI) trial

We assessed the associations of eight bone turnover markers (BTMs) with baseline and 1-year percentage changes in lumbar spine and hip bone mineral density (BMD) of 293 postmenopausal women undergoing treatment with hormone replacement therapy (HRT) or placebo using squared correlation coefficients (R2). In 239 women assigned to treatment with estrogen alone or with with estrogen plus progestins (active treatment), mean percentage changes for all markers decreased significantly and remained below baseline values through 3 years of study, whereas mean percentage changes for 54 women assigned to the placebo group showed no significant change from baseline in any marker. At baseline, age and body mass index (BMI) together accounted for 16% and 25% of the variance in spine and hip BMD, respectively. The telopeptide resorption marker, cross-linked N-telopeptide of type I collagen (NTX), alone accounted for 12% and 8% of variance, respectively. Another telopeptide, carboxy-terminal telopeptide of type I collagen (Crosslaps), accounted for 8% and 7% of variance, respectively. A bone-specific alkaline phosphatase (BALP-2) accounted for 8% of variance at the spine and 5% at the hip. No other marker accounted for more than 5% of total variance at either site; adding either baseline NTX, Crosslaps, or BAP-2 to regressions containing age and BMI increased R2 values at the spine and hip to about 22% and 28%, respectively. In the placebo group, baseline spine BMD accounted for 4% of the variance in 1-year spine BMD percentage change, whereas baseline values for age and BMI accounted for 1% and 0% of the variance, respectively; none of the three accounted for more than 0% of hip BMD percentage change; Crosslaps and NTX contributed 5% and 4% to the variance in 1-year spine BMD percentage change, but other markers accounted for < 2% of variance at the spine. At the hip, another BALP (BALP-1) accounted for 4% of variance, but no other baseline marker except NTX accounted for more than 1% of variance. In the active treatment group, baseline values for age, BMI, and spine BMD together accounted for 13% of the percentage change in spine BMD and for 4% of the BMD change at the hip. No individual or pair of baseline markers significantly enhanced these R2 values, but addition of 1-year percentage changes in some individual markers did significantly increase it. The largest R2 value was obtained by adding the percentage change in BALP-2, which increased the R2 in spine BMD percentage change to 20% and that at the hip to 8%. Adding baseline and change variables for all eight markers to the regression increased R2 to 28% at the spine and 12% at the hip. Restricting the set of analyses to individuals who suppressed marker activity beyond the precision error for the measurement did not improve R2s for the regressions. When baseline marker values were stratified into quartiles, only NTX and osteocalcin showed significant relationships between quartile and change in spine BMD, and these did not reach significance at the hip. When the 1-year change in markers was stratified into quartiles, significant relationships with percentage change in spine BMD were observed only for BALP phosphatases. We conclude that BTMs are not a surrogate for BMD to identify women with low bone mass and that they offer little useful information for predicting BMD changes for individual untreated or HRT-treated postmenopausal women.

Validation of the PASE in older adults with knee pain and physical disability

PURPOSE

To examine the validity of the Physical Activity Scale for the Elderly (PASE) among individuals with disability.

METHODS

A sample of 471 participants (mean age = 71.36) in an epidemiological study of chronic knee pain completed the PASE and self-report measures of knee pain, perceived physical function, satisfaction with physical function, and importance of physical function. A 6-min walk test and an isokinetic assessment of knee strength were also administered.

RESULTS

PASE scores were significantly correlated in expected directions with performance on the 6-min walk, knee strength, frequency of knee pain during transfer, and perceived difficulty with physical functioning. Gender and age were identified as significant moderators of PASE scores and the scale's construct validity was supported by testing a conceptually driven hypothesis regarding patterns of physical activity.

CONCLUSIONS

These results support the PASE's validity for the assessment of physical activity among older adults with pain and disability.

Functional status, assistance, and the risk of a community-based move

This study examined the effects of declining functional status and the availability of assistance on community-based residential mobility. Wolinsky and colleagues (1993), using data from the 1984, 1986, and 1988 waves of the Longitudinal Study on Aging, reported other transitions that result from increased health demand, namely those of nursing home placement and death. Using their functional health scales and recently available statistical techniques, we performed a two-stage analysis within a health behavior conceptual framework. We conclude that older adults who report several cognitive limitations in the absence of assistance in the home are more likely to make residential changes. Additionally, we determined that the independent effects of cognitive and lower body deterioration trigger, in this case, community-based moves even when adjusting for the effect of baseline levels of functional health and other factors in the model. Our analysis extends the earlier findings of Wolinsky and colleagues to encompass residential change as an ecological outcome of health decline in old age.

Chemical composition of seeds and oil of Xylopia aethiopica grown in Nigeria

The chemical composition and mineral constituents of Xylopia aethiopica, which is valued as a spice in Nigeria, were determined along with the physicochemical characteristics of the seed oil. The seeds had the following chemical compositions moisture (8.43 g/100 g), ash (5.89 g/100 g), crude lipid (9.58 g/100 g), crude protein (12.45 g/100 g) crude fiber (8.66 g/100 g) and carbohydrate (63.65 g/100 g). Calcium and potassium were the major minerals in the seed. The extracted lipid was examined for fatty acid composition. Linoleic (45.1 g/100 g) and oleic (26.5 g/100 g) acids were the predominant unsaturated fatty acids, while palmitic acid (18.0 g/100 g) was the major saturated acid. The iodine value of 97 g/100 g indicates that the seed oil is a non-drying type.

The Kidney Outcomes Prediction and Evaluation (KOPE) study: a prospective cohort investigation of patients undergoing hemodialysis. Study design and baseline characteristics

PURPOSE

The purpose of the Kidney Outcomes Prediction and Evaluation (KOPE) study, was to more fully characterize the end-stage renal disease (ESRD) population with respect to social, psychological, and clinical characteristics, and to prospectively study the biomedical, social, and psychological factors that influence a range of ESRD outcomes in a large observational study of black and white patients on hemodialysis. This paper focuses on the KOPE study design as well as characteristics of patients at baseline.

METHODS

KOPE was a prospective cohort investigation of patients treated at four dialysis centers in Forsyth County, North Carolina. Participants were interviewed at the dialysis centers, semi-annually over a 3 1/2 year period. Prevalent cases who were being treated with hemodialysis at the initiation of the study were enrolled into KOPE. Incident cases were subsequently enrolled as they presented to the participating units for hemodialysis. A total of 304 prevalent and 162 incident cases were enrolled into the study. The baseline health and sociodemographic characteristics of KOPE participants reported in this paper were obtained from medical records and Southeast Kidney Council data. Laboratory values taken within a 30-day interval around the baseline interview are also reported.

RESULTS

KOPE participants differ from national statistics on race, age, and gender. Differences between KOPE participants and patients living in the region, but who did not participate in the study, can be explained by our recruitment criteria.

CONCLUSIONS

KOPE will enable the characterization of the ESRD population, identification of factors related to poor outcomes, and identification of opportunities for interventions to prevent death and morbidity.

The timing of change: patterns in transitions in functional status among elderly persons

Data from the Longitudinal Study on Aging (LSOA) were analyzed to describe the heterogeneity of functional status transitions over 2-years (single-state model), and to explore whether changes in status in the previous two to four year period enhance the prediction of a subsequent transition (two-state model). Multivariate logistic regression with a robust estimate of variance was used to analyze a 7-category nominal response of: functional status (4 levels), institutionalization, death, and missing. Weighted percentages for functional status transitions and stability (unchanged status) showed that unchanged or improved functioning were at least as common as death or worsened functional status. Initial disability level, morbidities, and self-rated health were the strongest predictors of disability status after 2-years. The two-state model revealed that a previous transition (positive or negative) increases the risk for a subsequent transition, independent of initial disability level. The predictive and explanatory quality of the two-state model is substantially improved over single-state models, particularly from its ability to identify subgroups of individuals with marked functional status instability.

Can we measure prior postmenopausal estrogen/progestin use? The Postmenopausal Estrogen/Progestin Interventions Trial. The PEPI Investigators

The objective of this study was to assess: 1) the accuracy of a single self-report question about postmenopausal estrogen use; and 2) the performance and repeated measures agreement of a standardized hormone use interview. Women (n = 863) in the Postmenopausal Estrogen/Progestin Interventions Trial (PEPI) completed a self-report baseline questionnaire (BQ) at enrollment and a History of Hormone Use interview (HHU) at the 3-month follow-up visit (HHU3mos). A subsample of 101 women completed a second HHU interview 3 years later (HHU3yrs). As determined by the HHU3mos, 479 (56%) of women had ever used postmenopausal estrogen and 261 (30%) had ever used postmenopausal progestin. The mean number of years since last estrogen or progestin use was 2.2 and 1.3 years, respectively. Overall, there was 95% agreement between self-reported estrogen use on the BQ and the HHU3mos (kappa = 0.91). Using the HHU3mos as the criterion standard, the BQ misclassified 2.3% of women as false positives and 6.3% as false negatives. The average duration of estrogen use in the false-negative classifications was 1.9 years (range: 1-9 years). On the HHU3mos, 39.7% of participants could not recall at least one of the specific details of estrogen use (preparation, dose, route, or starting or stopping year); similar patterns of recall were found for progestin use. Factors associated with discordant reporting of ever-use of ERT (BQ vs. HHU3mos) or incomplete reporting of estrogen/progestin use on the HHU3mos were: route of administration, recency of hormone use, duration of hormone use, and race. Age, years since menopause, education, income, and hysterectomy status were not related to discordant and/or incomplete reporting. Agreement between the HHU3mos and HHU3yrs for ever-use of estrogen was 85.2% (kappa = 0.71). In sum, a single self-report question was adequate to ascertain ever-use of postmenopausal estrogen. When a structured interview form was used, details of postmenopausal estrogen and progestin use were not well remembered. Some features of hormone use and participant characteristics were associated with completeness of recalled hormone use, which suggests the potential for differential misclassification.

Unique preclinical characteristics of GG745, a potent dual inhibitor of 5AR

Selective inhibition of type 2 5alpha-reductase has been shown to be efficacious in the treatment of benign prostatic hyperplasia. Pharmacokinetic and pharmacodynamic results are reported of treatment with a potent inhibitor of both 5alpha-reductase isozymes, GG745, in rats, dogs and men. In the rat, GG745 has a similar effect on DHT-driven prostatic growth as finasteride, another dual 5alpha-reductase inhibitor in this species. However, GG745 appears to be more potent in the rat, a result that likely reflects the greater inherent potency and terminal half-life of GG745 (14 hr) compared with that of finasteride (1 hr). These pharmacokinetic differences are also maintained in the dog (65 and 4 hr for GG745 and finasteride, respectively). From these results, the literature, and in vitro studies, we estimated doses of GG745 likely to prove efficacious in reducing DHT levels in man. These estimated values were predictive of single-dose effects of GG745 in man. Results from single-dose evaluations in man indicate that GG745 has a terminal half-life of approximately 240 hr, and single doses of >10 mg decreased DHT levels significantly more than did single 5-mg doses of finasteride. These data support the hypothesis that a molecule (GG745) that effectively inhibits both 5alpha-reductases will lower serum DHT levels significantly more than a molecule that inhibits only a single 5alpha-reductase isozyme (e.g., finasteride, a selective inhibitor of the type 2 enzyme in man).

Optimization of 3-(1H-indazol-3-ylmethyl)-1,5-benzodiazepines as potent, orally active CCK-A agonists

We previously described a series of 3-(1H-indazol-3-ylmethyl)-1,5-benzodiazepine CCK-A agonists exemplified by compound 1 (GW 5823), which is the first reported binding selective CCK-A full agonist demonstrating oral efficacy in a rat feeding model. In this report we describe analogs of compound 1 designed to explore changes to the C3 and N1 pharmacophores and their effect on agonist activity and receptor selectivity. Agonist efficacy in this series was affected by stereoelectronic factors within the C3 moiety. Binding affinity for the CCK-A vs CCK-B receptor showed little dependence on the structure of the C3 moiety but was affected by the nature of the second substituent at C3. Structure-activity relationships at the N1-anilidoacetamide "trigger" moiety within the C3 indazole series were also investigated. Both agonist efficacy and binding affinity within this series were modulated by variation of substituents on the N1-anilidoacetamide moiety. Evaluation of several analogs in an vivo mouse gallbladder emptying assay revealed compound 1 to be the most potent and efficacious of all the analogs tested. The pharmacokinetic and pharmacodynamic profile of 1 in rats is also discussed.

Benefits of linkage to the National Death Index in the Longitudinal Study of Aging

To reduce the potential bias resulting from differential loss to follow-up in the Longitudinal Study of Aging (LSOA), information obtained from household contact methods was supplemented with information from the National Death Index (NDI). This article examines the degree of agreement in the vital status data from two sources (reinterview contacts and the NDI system) and evaluates the potential gains of using the NDI data as a supplement to define participants' vital status. Results reveal that NDI information, used to supplement reinterview information, can substantially reduce bias due to the differential loss of participants to follow-up. Reliance on reinterview information alone was less likely to capture those deaths occurring in study participants who at the initial contact lived alone, were below the poverty index, were interviewed without use of a proxy, did not supply a phone number, and did not own a home.

Effect of postmenopausal hormone therapy on body weight and waist and hip girths. Postmenopausal Estrogen-Progestin Interventions Study Investigators

Reports from cross-sectional comparisons, nonrandomized prospective studies, and relatively small clinical trials indicate that postmenopausal hormone therapy may slightly decrease the amount of weight typically gained by women during the decade following menopause. Despite this, widespread belief remains that hormone therapy may cause weight gain. We use data from the Postmenopausal Estrogen/Progestin Interventions trial to characterize the impact of postmenopausal hormone therapy on weight and fat distribution and to examine the consistency of this impact among subgroups of women defined by lifestyle, clinical, and demographic factors. The Postmenopausal Estrogen/Progestin Interventions trial was a 3-yr, placebo-controlled, randomized clinical trial of 875 women assessing the effects on cardiovascular risk factors of four hormone regimens: oral conjugated equine estrogen (CEE) therapy (0.625 mg daily alone), CEE in combination with medroxyprogesterone acetate (2.5 mg daily), CEE in combination with medroxyprogesterone acetate (10 mg daily on days 1-12), and CEE in combination with micronized progesterone (200 mg daily on days 1-12). Women randomly assigned to CEE with or without a progestational agent averaged 1.0 kg less weight gain at the end of 3 yr (P = 0.006) than those assigned to placebo. Assignment to CEE was also associated with averages of 1.2 cm less increase in waist girth (P = 0.01) and 0.3 cm less increase in hip (P = 0.07) girth. In regression models that included weight change as a covariate, none of these differences reached statistical significance. There were no significant differences in weight or girth changes among any of the four active hormone regimens. After accounting for the effects of assignment to active hormone therapy and baseline weight, older age (P 0.008) and higher physical activity level at baseline (P = 0.002) were also independently predictive of less weight gain. The impact of hormone therapy on weight gain was similar among subgroups, except for those defined by baseline smoking status (P = 0.04) and physical activity level at home (P = 0.02). Factors that were independently associated with smaller increases in girths were: for waist, greater overall activity (P = 0.005) and Hispanic ethnicity (P = 0.02); and for hip, work activity (P = 0.003) and greater alcohol consumption (P = 0.03). None of these factors significantly affected the observed overall relationships between estrogen and changes in girth.

Comparative pharmacokinetics and pharmacodynamics of remifentanil, its principle metabolite (GR90291) and alfentanil in dogs

Remifentanil is an esterase-metabolized opioid developed for use in anesthesia. The principal metabolite of remifentanil, GR90291, is considered to be less potent. This study determined the relative potency of GR90291 and alfentanil, compared with remifentanil, in anesthetized dogs. Male dogs received thiamylal sodium, and anesthesia was maintained using isoflurane and N2O in oxygen. Each dog received a 5-min infusion of 0.5 microg/kg/min remifentanil, 500 microg/kg/min GR90291 and 1.6 mg/kg/min alfentanil in random order, separated by 1 week. Serial blood samples were collected during and after the infusion. The electroencephalogram was evaluated using aperiodic analysis. The pharmacokinetics and pharmacodynamics of remifentanil, GR90291 and alfentanil were determined using nonlinear least-squares regression analysis. Remifentanil was rapidly eliminated, with a terminal half-life of 6 min, compared with 19 min for GR90291 and alfentanil. Using the estimated concentration that elicits 50% of the maximum response (EC50) for delta EEG activity and spectral edge95, remifentanil was 4213 to 4637 times more potent than GR90291 and 7.7 to 8.5 times more potent than alfentanil. The blood-brain equilibration half-life was 2.3 to 5.2 min for remifentanil, 0.39 to 0.41 min for GR90291 and 3.1 to 3.7 min for alfentanil.

Discovery of 1,5-benzodiazepines with peripheral cholecystokinin (CCK-A) receptor agonist activity (II): Optimization of the C3 amino substituent

Analogs of the previously reported 1,5-benzodiazepine peripheral cholecystokinin (CCK-A) receptor agonist 1 were prepared which explore substitution and/or replacement of the C-3 phenyl urea moiety. Agonist efficacy on the isolated guinea pig gallbladder (GPGB) was retained with a variety of substituted ureas and amide analogs. Three compounds were identified which were orally active in the mouse gallbladder emptying assay (MGBE). The 2-indolamide (52) and N-(carboxymethyl)-2-indolamide (54) derivatives had improved affinity for the human CCK-A receptor but reduced agonist efficacy on the GPGB. Neither indolamide was orally active in a rat feeding assay. In contrast, the (3-carboxyphenyl)urea derivative (29, GW7854) had moderately increased affinity for the human CCK-B receptor but was a potent full agonist on the GPGB and was orally active in both the MGBE and rat feeding assays. GW7854 was a full agonist (EC50 = 60 nM) for calcium mobilization on CHO K1 cells expressing hCCK-A receptors and a potent antagonist of CCK-8 (pA2 = 9.1) on CHO K1 cells expressing hCCK-B receptors. GW7854 is a potent mixed CCK-A agonist/CCK-B antagonist which is orally active in two in vivo models of CCK-A-mediated agonist activity.

3-[2-(N-phenylacetamide)]-1,5-benzodiazepines: orally active, binding selective CCK-A agonists

A series of modifications were made to the C-3 substituent of the 1,5-benzodiazepine CCK-A agonist 1. Replacement of the inner urea NH and addition of a methyl group to generate a C-3 quaternary carbon resulted in acetamide 6, which showed CCK-A receptor binding selectivity and sub-micromolar agonist activity in vitro. Benzodiazepine 6 was active in an in vivo mouse gallbladder emptying assay and represents a novel orally active, binding selective CCK-A agonist.

Some techniques for the analysis of work sampling data

Work sampling is an observational technique that produces counts representing the number of times that an individual has been observed performing each of several tasks. These data are collected using either systematic or random times of observation, and typically exhibit correlation between repeated observations on the same individual, with the degree of correlation being a function of the amount of time elapsed between measurements. Using several recently developed statistical techniques, we illustrate how it is possible to carry out analyses of these nominal outcomes that account for the correlation between repeated outcomes. We use description of a work sampling study to motivate the techniques and we compare empirically results from analyses based on several different underlying assumptions.

Discovery of 1,5-benzodiazepines with peripheral cholecystokinin (CCK-A) receptor agonist activity. 1. Optimization of the agonist "trigger"

Directed screening of compounds selected from the Glaxo registry file for contractile activity on the isolated guinea pig gallbladder (GPGB) identified a series of 1,5-benzodiazepines with peripheral cholecystokinin (CCK) receptor agonist activity. Agonist efficacy within this series was modulated by variation of substituents on the N1-anilinoacetamide moiety. Remarkably, a single methyl group confers agonist activity, with an N-isopropyl substituent providing optimal efficacy. Hydrophilic substituents on the anilino nitrogen abolish agonist activity or produce antagonists of CCK. In contrast, hydrophilic electron-donating groups at the para-position of the anilino ring enhance or maintain in vitro and in vivo agonist activity. Despite decreased affinity for the human CCK-A receptor, relative to CCK-8, some of these compounds are equipotent to CCK as anorectic agents in rats following intraperitoneal administration.

Modification of receptor selectivity and functional activity in cholecystokinin peptoid ligands

Hybrid analogs of the cholecystokinin A (CCK-A) receptor selective tetrapeptide agonist Boc-Trp-Lys(Tac)-Asp-MePhe-NH2 (1,A-71623) and the CCK-B receptor selective antagonists PD-135118 (2) and CI-988 (3) were prepared. Incorporation of the Lys(Tac) side chain into 2 produced a moderately potent antagonist of CCK-8 in the isolated guinea pig gallbladder (GPGB). Incorporation of the Lys(Tac) side chain into 3 produced the novel agonist analog 7 (EC50 = 28 nM in the GPGB) with excellent affinity for both human CCK-A (IC50 = 12 nM) and CCK-B (IC50 = 17 nM) receptors. Analog 7 was a full agonist (EC50 = 3.5 nM) for calcium mobilization on CHO-K1 cells expressing hCCK-A receptors but a partial agonist on CHO-K1 cells expressing hCCK-B receptors, eliciting a weak agonist response (EC50 = 2800 nM) and antagonizing CCK-8-induced calcium mobilization (KB = 20 nM). Despite this unusual in vitro profile, analog 7 was a potent anorectic agent in rats (ED50 = 30 nmol/kg) following intraperitoneal administration.

Etiology of iliotibial band friction syndrome in distance runners

The objectives of our study were: 1) to examine differences between a noninjured cohort of runners (N = 70) and runners afflicted with iliotibial band friction syndrome (ITBFS) (N = 56) according to selected anthropometric, biomechanical, muscular strength, and training measures; 2) to explore multivariate relationships among these measures in both the well and injured groups; and 3) to develop specific hypotheses concerning risk factors for injury that will later be tested in a prospective observational study. High speed videography (200 fps), a force platform (500 Hz), and a Cybex II+ isokinetic dynamometer were used to assess rearfoot motion, ground reaction forces, and knee muscular strength and endurance, respectively. A linear discriminant function analysis of the training data revealed weekly mileage, training pace, number of months using current training protocol, % time spent swimming, and % time spent running on a track to be significant (P < 0.10). Height was a significant anthropometric discriminator, while seven isokinetic strength and endurance measures were found to discriminate significantly between the groups. Calcaneal to vertical touchdown angle, and maximum supination velocity were significant rearfoot movement discriminators. Maximum braking force was the only significant kinetic discriminator. A combined discriminant analysis using those variables found to be significant in the previous analyses revealed weekly mileage, and maximum normalized braking force to be the best discriminators (model P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Predicting inpatient costs with admitting clinical data

Hospital cost-containment programs should themselves be cost-effective, targeting high-cost physicians (which requires adjusting for case mix) and patients (which requires early identification). In this study, clinical data available within 24 hours of admission from an electronic medical record system were used to develop statistical models to predict hospital costs. In this retrospective analysis of clinical data and diagnosis-related groups (DRGs), study subjects were 2,355 patients admitted for at least 1 day to the medicine service at an urban teaching hospital with sophisticated electronic medical records. Of these 2,355 patients, 1,663 (71%) had one of the 41 most common DRGs. Predictive models were derived on a random subset of two thirds of the patients and were validated on the remaining third. The following patient data were obtained: admission and prior diagnostic test results, diagnoses, vital signs; demographic data; prior inpatient and outpatient visits; tests and treatments ordered within 24 hours of admission (discretionary data); DRGs; and total inpatient costs (estimated from charges). Diagnosis-related groups explained 24% of the variance in total costs in the derivation patient set and 16% in the validation set. When only nondiscretionary data were used, the models retained only clinical laboratory results and prior diagnoses, explaining 20% of the derivation set variance in total costs and 16% in the validation set. Adding DRGs increased the variance explained in the derivation set to 34%, but decreased to 24% in the validation set. Adding discretionary data substantially increased the explained variance in the derivation and validation patient sets. The models' median predicted costs underestimated true costs by 10% to 13%, with the lowest error in the models using all types of variables. Clinical data gathered during routine clinical care can be used to adjust for case mix and identify high-cost patients early in their hospital stays, when they could be targeted by cost-containment interventions.

A pharmacodynamic model to investigate the structure-activity profile of a series of novel opioid analgesics

A simple mathematical model of analgesia in the rat is developed and utilized to determine quantitative structure-activity relationships for a series of novel 4-anilidopiperidine opioids. The compounds tested (selected alkyl carboxyethyl esters attached at the one position of the piperidine ring) were designed for rapid inactivation by blood and tissue esterases. Model parameters included potency and rate constants for loss of pharmacodynamic effect by hydrolysis dependent and independent processes. A significant correlation is observed between duration of pharmacological effect in vivo and the rate constant for hydrolysis in human blood (r = 0.89). In vivo potency shows a moderate correlation with log P2 (r = -0.77). The validity of the model is shown by comparing model-based parameters which characterize potency and duration of effect in vivo with graphically derived parameters. Significant correlations are observed between model and graphically based estimates of potency (r = 0.75) and between model and graphically based estimates of duration of effect (r = 0.70). This model has potential application in studies of other classes of compounds in which hydrolytic cleavage limits duration of pharmacologic effect.

Effects of remifentanil, a new short-acting opioid, on cerebral blood flow, brain electrical activity, and intracranial pressure in dogs anesthetized with isoflurane and nitrous oxide

BACKGROUND

A new short-acting opioid, remifentanil, is metabolized by esterase activity in blood and tissue. It is important to know whether remifentanil may decrease the time to recovery of opioid-induced cardiovascular and cerebral effects compared to that of other short-acting agents such as alfentanil.

METHODS

Baseline measures were made during 1% end-tidal isoflurane and 50% N2O in oxygen in dogs. Approximately equipotent low- and high-dose remifentanil (0.5 and 1.0 micrograms.kg-1.min-1) or alfentanil (1.6 and 3.2 micrograms.kg-1.min-1) were infused for 30 min each (total infusion time 60 min) followed by a 30-min recovery period. Blood pressure, heart rate, and intracranial pressure were recorded continuously. Electroencephalogram measurements were made using aperiodic analysis, and regional cerebral blood flow using radioactive microspheres.

RESULTS

Both remifentanil and alfentanil decreased blood pressure and heart rate 25-30%. Cortex, hippocampus, and caudate blood flow decreased 40-50% during opioid infusion, but flow changes in lower brain regions were modest or absent. The electroencephalogram showed a shift from low-amplitude, high-frequency activity during baseline to high-amplitude, low-frequency activity during opioid infusion. During a 30-min recovery period, heart rate, electroencephalogram, and regional cerebral blood flow recovered to baseline levels in remifentanil--but not in alfentanil--treated dogs. Blood pressure and intracranial pressure decreased during opioid infusion and increased above baseline levels during the recovery period in remifentanil-treated dogs.

CONCLUSIONS

These results show that the cardiovascular and cerebral effects of remifentanil and alfentanil are similar but that recovery of these parameters occurs sooner following remifentanil.

Hemodynamic effects of GI 87084B, an ultra-short acting mu-opioid analgesic, in anesthetized dogs

Hemodynamic effects of GI 87084B, a novel ultra-short acting mu-opioid agonist, were studied in anesthetized dogs. In these studies, GI 87084B (0.3-20 nmol/kg/min i.v.) produced dose-dependent decreases in heart rate, arterial blood pressure, +dP/dt and cardiac output. Alfentanil produced similar effects but was less potent. After termination of the infusions (397 nmol/kg cumulative dose), the hemodynamic effects of GI 87084B dissipated over 30 to 40 min. The effects of alfentanil, however, persisted throughout the 60-min recovery period. Infusion of GI 87084B at lower dose rates (0.001-0.3 nmol/kg/min) in barbiturate-anesthetized dogs showed a threshold dose of 0.1 to 0.3 nmol/kg/min for effects on hemodynamic variables. After infusing 0.3 nmol/kg/min of GI 87084B for 10 min, hemodynamic variables recovered rapidly (10-20 min). Boli of GI 87084B (0.3-100 nmol/kg i.v.) produced dose-dependent decreases in the same hemodynamic variables. The duration of these effects increased from 5 to 20 min at 3 nmol/kg to 15 to 45 min at 100 nmol/kg. Naloxone (0.063 mg/kg/hr) decreased the magnitude and duration of the effects of GI 87084B, suggesting that these effects are mediated through opioid receptors. In summary, GI 87084B produced hemodynamic effects consistent with mu-opioid agonism when administered by infusion or bolus, but these effects were brief in duration compared to other opioids.

Opioid receptor activity of GI 87084B, a novel ultra-short acting analgesic, in isolated tissues

GI 87084B (3-[4-methoxycarbonyl-4-[(1-oxopropyl) phenylamino]1-piperidine]propanoic acid, methyl ester, hydrochloride) was found to be a potent opioid agonist in the guinea pig ileum (EC50 = 2.4 +/- 0.6 nM), the rat vas deferens (EC50 = 387 +/- 44 nM) and the mouse vas deferens (EC50 = 39.5 +/- 7.4 nM). In the guinea pig ileum, GI 87084B, was roughly equivalent in potency to fentanyl (EC50 = 1.8 +/- 0.4 nM). GI 87084B was more potent in this tissue than alfentanil (EC50 = 20.1 +/- 1.2 nM) and less potent than sufentanil (EC50 = 0.3 +/- 0.09 nM). Schild analyses of antagonism of GI 87084B by naloxone yielded pKB values of 8.2 and slopes indistinguishable from unity in the guinea pig ileum and the mouse vas deferens. Insurmountable antagonism of GI 87084B by naloxone was observed in the rat vas deferens. However, an empirical measure of antagonist potency could be made: apparent pA2 = 8.1. The agonist dissociation constant (KA) for GI 87084B (220 +/- 90 nM) was determined by receptor alkylation with beta-chlornaltrexamine in the guinea pig ileum. Calculation of receptor occupancy suggested poor receptor-effector coupling and limited receptor reserve in the rat vas deferens, which could explain the insurmountable antagonism seen with higher concentrations of naloxone. These data suggest that GI 87084B acted through the mu class of opioid receptors to inhibit contraction induced by field stimulation in these tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Design, synthesis, and pharmacological evaluation of ultrashort- to long-acting opioid analgetics

In an effort to discover a potent ultrashort-acting mu opioid analgetic that is capable of metabolizing to an inactive species independent of hepatic function, several classes of 4-anilidopiperidine analgetics were synthesized and evaluated. One series of compounds displayed potent mu opioid agonist activity with a high degree of analgesic efficacy and an ultrashort to long duration of action. These analgetics, 4-(methoxycarbonyl)-4-[(1-oxopropyl)phenylamino]-1-piperidinepropanoi c acid alkyl esters, were evaluated in vitro in the guinea pig ileum for mu opioid activity, in vivo in the rat tail withdrawal assay for analgesic efficacy and duration of action, and in vitro in human whole blood for their ability to be metabolized in blood. Compounds in this series were all shown to be potent mu agonists in vitro, but depending upon the alkyl ester substitution the potency and duration of action in vivo varied substantially. The discrepancies between the in vitro and in vivo activities and variations in duration of action are probably due to different rates of ester hydrolysis by blood esterase(s). The SAR with respect to analgesic activity and duration of action as a function of the various esters synthesized is discussed. It was also demonstrated that the duration of action for the ultrashort-acting analgetic, 8, does not change upon prolonged infusion or administration of multiple bolus injections.

A new method for estimation of agonist dissociation constants (KA): directly fitting the postinactivation concentration-response curve to a nested hyperbolic equation

The common method for estimating agonist dissociation constants (KA) is the method proposed separately by Furchgott and Mackay. Concentrations of the given agonist producing the same response before ([A]) and after ([A']) irreversible inactivation of a fraction of the receptors (1-q) are described by the equation: 1/[A] = 1/(q*[A']) + (1-q)/(q*KA) and plotted on axes of 1/[A] vs. 1/[A']. The double reciprocal method suffers from the disadvantage that undue weight may be placed on values generated from the smallest observed responses. Our new method of estimating KA and q uses hyperbolic functions to directly fit both concentration-response curves. The control curve is fit to the logistic equation: response = (M* [A]n)/(kn + [A]n); where M is the maximal tissue response, n is the apparent kinetic order of the response at low [A] and k is [A] required for a half-maximal response. The postinactivation concentration-response curve is simultaneously fit to the following equation: response' = M/(((k/(q*KA*[A']))*(KA + [A']* (1-q)))n + 1). This new method was shown to determine KA and q more accurately and precisely than other methods when applied to an artificial data set. In experiments with the rat anococcygeus muscle, the nested hyperbolic method gave estimates of KA with less variance and less range than the double reciprocal method. The nested hyperbolic method was shown to be a valid method of estimating KA and q that has advantages over the other methods.

Analysis of putative alpha-1s adrenoceptor agonism by Sgd 101/75 in the rat anococcygeus muscle

Sgd 101/75 [2-(2-methylindazol-4-imino)-imidazolidine hydrochloride] is an alpha 1 adrenoceptor agonist that shows a greater sensitivity to receptor alkylation with phenoxybenzamine (POB) than norepinephrine (NE) (present study). J. Coates, D.G. Weetman and their co-workers have concluded that Sgd 101/75 is selective for a subtype of alpha-1 receptors, i.e., alpha-1s. The present studies have shown that Sgd 101/75 was a full agonist in the rat anococcygeus muscle and acts at alpha-1 adrenoceptors, as determined by Schild analysis of prazosin antagonism (pKB = 9.24 +/- 0.21, slope = 0.87 +/- 0.13). Alkylation experiments showed that the contractile effects of Sgd 101/75 were more sensitive to POB than the effects of NE. These experiments also allowed the determination of KA values for these agonists (Sgd 101/75 KA = 1.5 +/- 0.6 X 10(-5) M, NE KA = 2.6 +/- 1.0 X 10(-6) M). At 3 X 10(-8) M POB (10 min), the contractile effect of Sgd 101/75 was eliminated, whereas the concentration-effect curve for NE was shifted approximately one log unit to the right with a 20% decrease in maximal response. After similar POB treatment, incubation with Sgd 101/75 (60 min, 3 X 10(-6) to 3 X 10(-4) M) shifted the NE curve to the right in a concentration-dependent manner. Schild regression of these data yielded a pKB = 5.22 +/- 0.09 and slope = 0.87 +/- 0.08. This pKB (-log KB) showed that Sgd 101/75 was competing for the same receptor after POB treatment and before POB treatment (mean of -log KA = 4.92 +/- 0.12).(ABSTRACT TRUNCATED AT 250 WORDS)

Ionic mechanism of dopaminergic and muscarinic auto- and heteroreceptor activation in superfused striatal slices: role of extracellular chloride

The Cl dependency of agonist-induced ionic mechanisms involved in the receptor-mediated modulation of electrically stimulated release of dopamine (DA) and acetylcholine (ACh) was examined in superfused rabbit striatal slices prelabeled with [3H] DA (3,4-[8-3H]dihydroxyphenylethylamine) and [14C]choline ([ methyl-14C]choline Cl). Cl- was substituted in the superfusion medium to varying degrees with the impermeant anions isethionate, methanesulfonate or gluconate. The sodium concentration was held constant. Apomorphine (30 nM), a DA receptor agonist, inhibited the stimulation-evoked (1 Hz, 2 min) release of both DA and ACh in Krebs-Ringer-bicarbonate medium (KRB; 125.4 mM Cl-). The inhibitory effects of the agonist were not altered significantly in media containing 66.4 mM Cl-. In 7.4 mM Cl- medium (isethionate replacement), apomorphine-induced inhibition of DA release was reduced (40% inhibition vs. 67% inhibition in KRB). Similarly, apomorphine inhibition of ACh release was lowered from 38% in KRB to 25% in 7.4 mM Cl-. The muscarinic receptor agonist carbachol (10 microM) inhibited the stimulation-evoked release of ACh while enhancing the evoked release of DA in normal Cl- (125.4 mM) medium. Inhibition of ACh release was not altered in 66.4 mM Cl- media but was increased in 7.4 mM Cl- (63% inhibition in low Cl- vs. 50% in KRB). The enhancing effects of carbachol on stimulated DA release were potentiated in 66.4 mM Cl- (88% enhancement vs. 57% in KRB), whereas no change in the agonist effect was observed in the lower Cl- medium (7.4 mM Cl-).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute cardiovascular and pulmonary effects of intravenous and aerosolized amiloride in the dog

Active Na+ absorption by the epithelia that line the airways can drive volume from the airway surface. Exposure of the lumen-facing surface of airway epithelia to amiloride inhibits Na+ transport. Consequently, aerosolized amiloride may help hydrate the desiccated surface liquid that characterizes lung diseases such as cystic fibrosis. We studied the acute cardiovascular and pulmonary effects of amiloride in anesthetized dogs. Intravenous amiloride reduced blood pressure and increased ventilation frequency and airways resistance of the dog. The effects were dose-related (ED50 = 1.3 X 10(-6) mol/kg), resembled those of injected histamine, and were antagonized by methapyrilene. These results were compatible with the release of endogenous histamine by amiloride, but the graded dose-effect relationship for amiloride differed from the quantal relationship induced by the prototypical releaser, 48/80. Aerosolization of a Ringer's solution that was nearly saturated with amiloride deposited, in upper airway surface liquid, drug concentrations which in previous studies, were sufficient to inhibit Na+ transport by canine airways (ED50 approximately 10(-6) M). Cardiovascular function, airways resistance, and indices of pulmonary tissue water, gas exchange, and perfusion were not affected. Since circulating amiloride after aerosolization was estimated to fall below the concentration that induced vasodepression and correct circled bronchoconstriction after intravenous injection, we conclude that the potency of aerosolized amiloride to induce acute effects in tissues other than airway epithelia is no greater than that of intravenous drug.

Naloxazone treatment in the guinea pig ileum in vitro reveals second functional opioid receptor site

Guinea pig ilea were incubated in vitro with naloxazone, an irreversible opioid receptor antagonist, in an attempt to determine a dissociation constant (KA) value for the opioid agonist, BW 942C, by the method of partial receptor alkylation. However, concentrations of naloxazone up to 3 X 10(-4) M (120 min incubation-60 min washout) did not depress the maximal response or the slope of the concentration-response curve for BW 942C and, therefore, did not allow calculation of KA value. To analyze the residual activity of BW 942C, tissues were incubated with naloxone for 60 min after naloxazone treatment. Schild analysis of naloxone antagonism after 3 X 10(-6) M naloxazone produced a pKB of 8.0 +/- 0.06 and a slope of 0.88 +/- 0.03, suggesting simple competitive antagonism at a single site. In the absence of naloxazone treatment, naloxone 10(-8) to 10(-5) M antagonized the effects of BW 942C yielding a pKB value and slope of 8.34 +/- 0.08 and 1.0 +/- 0.04, respectively. Schild analysis of naloxone antagonism after 10(-4) M naloxazone yielded a pA2 of 6.23 +/- 0.20 and a slope of 0.55 +/- 0.08. These values were not consistent with simple competitive antagonism at a single receptor site. Modeled curves showed that the data for naloxone antagonism after 10(-4) M naloxazone were consistent with action at two receptor sites with naloxone pKB values of approximately 8.3 (experimentally determined) and approximately 6.0. An alternative explanation of altered affinity for BW 942C and naloxone at a single site produced by naloxazone treatment cannot be excluded.

Pharmacologic characterization and functional role of muscarinic autoreceptors in the rabbit striatum

The objectives of the present studies were 1) to pharmacologically characterize the muscarinic autoreceptors in the striatum and 2) to examine their role in the regulation of physiologic acetylcholine (ACh) release. Schild plots were generated for atropine and pirenzepine against oxotremorine-induced inhibition of [3H]ACh release. Atropine, a nonselective antagonist, yielded a pA2 of 8.92. The pA2 for pirenzepine, a purported M1-selective antagonist, was 7.14. Both Schild plots had slopes not significantly different from one. Four agonists [oxotremorine, carbachol (CARB), McN-A-343 and pilocarpine] were tested for their effectiveness in inhibiting [3H]ACh release. McN-A-343 and pilocarpine have been reported to be selective for M1 receptors. Oxotremorine and carbachol were effective and potent inhibitors of [3H] ACh release, whereas McN-A-343 and pilocarpine were weak. Although the existence of muscarinic receptor subtypes remains an open question, these data are consistent with the "low" pirenzepine affinity (M2) subtype. Chronic treatments (14 days) with several agents were carried out (in vivo) to assess the role of muscarinic autoreceptors in the regulation of physiologic ACh release. Scatchard analyses of binding studies with [3H]quinuclidinyl benzilate were also performed to assess changes in the muscarinic receptor population in the striatum. Chronic treatment with scopolamine caused a 100% increase in the Bmax for [3H]quinuclidinyl benzilate binding but had no effect on the sensitivity of [3H]ACh release to inhibition by CARB. Fourteen-day treatment with physostigmine (3 mg/kg) produced a decrease in the sensitivity of [3H]ACh release to CARB plus a 42% decrease in Bmax and a 48% decrease in Kd for [3H]quinuclidinyl benzilate binding. Chronic haloperidol treatment caused an increase in the sensitivity of [3H]ACh release to CARB accompanied by a 46% increase in Bmax for 3H quinuclidinyl benzilate binding. These data suggest that muscarinic autoreceptors in the striatum do not regulate physiologic ACh release in the presence of intact acetylcholinesterase and that the interaction of dopaminergic and cholinergic neurons in the striatum may not be simple trans-synaptic inhibition.

Frequency-dependent muscarinic receptor modulation of acetylcholine and dopamine release from rabbit striatum

The effects of muscarinic receptor activation on the electrically evoked release of [3H]dopamine (DA) and [14C]acetylcholine (ACh) or [3H]ACh were investigated in rabbit striatal slices. Release was measured in the presence of 10 microM hemicholinium and 1 microM sulpiride to block choline uptake and prevent the effects of released DA on DA receptors modulating release. Stimulation (120 pulses, 20 mA, 2 msec) at 0.3, 3 and 10 Hz produced (3H or 14C) ACh release that sharply declined with increasing stimulation frequency. A flat frequency-release curve was obtained for DA. Oxotremorine (OXO), a direct muscarinic agonist (1-100 microM), produced a concentration-dependent inhibition of ACh release, inversely related to stimulation frequency, at a fixed number of pulses (120). When the number of pulses was modified to produce similar amounts of ACh release (20 pulses at 0.1 Hz, 39 pulses at 0.3 Hz, 120 pulses at 3 Hz and 350 pulses at 10 Hz), much greater inhibition of ACh release by OXO (0.3 and 3 microM) was obtained with lower frequencies and lower number of pulses. Physostigmine, an acetylcholinesterase inhibitor, decreased ACh release with an inverse relationship to stimulation frequency. Atropine (1 microM), a selective muscarinic antagonist, enhanced the release of ACh more at 10 Hz than at 0.3 and 3 Hz and completely antagonized the effects of OXO (10 microM) and physostigmine (1 microM) at all three stimulation frequencies. OXO (3 and 10 microM) enhanced DA release at 3 Hz. Physostigmine (1 microM) and atropine (1 microM) had no effect on DA release.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the sensitivity to apomorphine of dopamine receptors modulating dopamine and acetylcholine release after chronic treatment with bromocriptine or haloperidol

The release of dopamine (DA) and of acetylcholine (ACh) was monitored from rabbit striatal slices labeled with [3H]DA and [14C]choline. Chronic treatment with haloperidol (1 mg/kg b. wt. for 28 days, sacrifice 96 hr after last injection) increased the potency of in vitro apomorphine in inhibiting the release of DA and ACh evoked by electrical stimulation when compared to vehicle-treated rabbits. Potentiation of apomorphine effects was greater on DA than on ACh release. The effects of in vitro haloperidol on DA and ACh release and in antagonizing the inhibitory effects of apomorphine were not modified by chronic treatment with haloperidol. Bromocriptine (1.5 mg/kg b.wt. for 7 days, sacrifice 72 hr after last injection) did not affect the evoked release of DA and of ACh, or the sensitivity to apomorphine. However, 15 mg/kg b.wt. of bromocriptine for 7 days and sacrifice 72 hr after last injection, produced a 60 to 70% reduction in the evoked release of DA and ACh, and markedly antagonized the inhibition of DA and ACh release produced by apomorphine. These results indicate that the DA receptors which modulate the release of DA and of ACh play an important physiological role inasmuch as they develop adaptational changes after prolonged receptor activation or inhibition by DA agonists and antagonists, respectively. These adaptational changes affect the potency of DA agonists on release modulatory receptors without modifying that of DA antagonists. The possibility that bromocriptine has a residual agonistic effect on striatal DA receptors 3 days after the last injection cannot be ruled out.