Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “IRT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1984

Serum immunoreactive trypsin, pancreatic polypeptide, and pancreatic isoamylase as diagnostic tests for chronic pancreatitis.

The efficiency of immunoreactive trypsin (IRT), pancreatic polypeptide (PP), and pancreatic isoamylase (PI) in the diagnosis of chronic pancreatitis was studied in 80 consecutive patients clinically suspected of having chronic pancreatitis. Twenty-five patients had chronic pancreatitis, and of these, 17 had pancreatic insufficiency. IRT, PP, and PI were of no value in the diagnosis of chronic pancreatitis without insufficiency. The three tests were of equal but limited value in diagnosing pancreatic insufficiency (nosographic sensitivities, 0.53 to 0.59, and predictive values of a negative test, 0.88 to 0.90). The combination of IRT, PP, and PI did not increase the diagnostic efficiency compared with each of the three tests alone. We conclude that IRT, PP, and PI are of similar but limited value as diagnostic tests for pancreatic insufficiency.

Adult↗
PubMed1995

[Reactive hyperemia after arterial occlusion: comparison of infrared telethermography and laser Doppler flowmetry].

Before, during and after arterial occlusion we measured Laser-Doppler Flux (LDF) and skin temperature using Infrared-Thermographie (IRT) in 40 healthy adults (20 female, 20 male). In the region of the hypothenar eminence of the left hand LDF and skin temperature showed significantly higher values in male compared with female subjects prior to occlusion (p < 0.01 resp. p < 0.05). After arterial occlusion for 120 seconds LDF showed a significant overshoot of 71.3% (+/- 39.5%) above baseline. During this phase of hyperemia skin temperature rose from 33.5 to 34.8 degrees C (p < 0.0001). This reaction was similar in men and in women. Changes in skin temperature were slower and more prolonged compared with the rapid changes of LDF. The absolute temperatures were significantly higher when we used IRT compared with temperatures measured by resistance thermometry. Both methods showed a close correlation (p < 0.0001, r = 0.891). Using the IRT technique a large number of skin temperatures can be measured simultaneously and temperature changes can be detected and visualized by colour thermograms. Postocclusive cutaneous hyperemia induces similar responses in LDF parameters and in skin temperatures. IRT therefore could be used as an additional tool for the assessment of physiological and pathological functions of the cutaneous microcirculation.

Adolescent↗
PubMed1994

Dopamine D2 receptor imaging with iodine-123-iodobenzamide SPECT in idiopathic rotational torticollis.

UNLABELLED: The cause of idiopathic rotational torticollis (IRT) is not completely understood to date. However, basal ganglia are believed to be involved in the pathophysiology of IRT. To elucidate this disorder further, the value of iodobenzamide (IBZM) SPECT was studied for the evaluation of striatal dopamine D2 receptors in these patients. METHODS: Striatal dopamine D2 receptor density was assessed in 10 patients with IRT using 123I-IBZM SPECT. The images were interpreted by a nuclear medicine physician initially to determine IBZM binding within the striatum and the cerebellum and, secondly, interstriatal IBZM binding. The results were correlated with the clinical parameters of the patients and compared with the results obtained from normal controls. RESULTS: No difference was found in average, specific striatal IBZM binding (basal ganglia/cerebellum ratio) between patients and controls. However, interstriatal analysis of IBZM binding revealed a significantly higher binding in the striatum contralateral to the direction of the torticollis (p = 0.026, by chi-square test). CONCLUSION: It was concluded that the striatal dopamine D2 receptor status is altered in patients with IRT.

Adult↗
PubMed1995

New index of combined systolic and diastolic myocardial performance: a simple and reproducible measure of cardiac function--a study in normals and dilated cardiomyopathy.

BACKGROUND: Because systolic and diastolic dysfunction frequently coexist, it is hypothesized that a combined measure of left ventricular chamber performance may be more reflective of overall cardiac dysfunction than systolic or diastolic measures alone. METHODS Study patients consisted of 170 subjects: 70 normals, 47 patients with severe dilated cardiomyopathy in NYHA class III-IV awaiting cardiac transplantation and 53 patients with idiopathic dilated cardiomyopathy of intermediate severity [NYHA class II, ejection fractions (EF) 30-50%]. EF, stroke volume and cardiac indexes were measured using conventional echo-Doppler methods. Pre-ejection period/ejection time (PEP/ET), isovolumetric relaxation time (IRT), isovolumetric contraction time/ET (ICT/ET) were also measured. A new derived index of myocardial performance: (ICT+IRT)/ET, was obtained by subtracting ET from the interval between cessation and onset of the mitral inflow velocity to give the sum of ICT and IRT. RESULTS The index was easily measured, reproducible, and had a narrow range in normals. The mean value of the index was significantly different between normal, intermediate and pre-transplant subjects (0.39 +/- 0.05, 0.59 +/- 0.10 and 1.06 +/- 0.24, respectively, p < 0.001 for all comparisons). The degree of inter-group overlap was smaller for the index compared to PEP/ET, ICT/ET and other parameters. Within functional groups, the value of the index did not appear to be related to heart rate, mean arterial pressure and the degree of mitral regurgitation. CONCLUSION (ICT+IRT)/ET is a conceptually new, simple and reproducible Doppler index of combined systolic and diastolic myocardial performance in patients with primary myocardial systolic dysfunction.

Adult↗
PubMed1998

Doppler echocardiographic assessment of left ventricular isovolemic relaxation flow.

BACKGROUND: It is not infrequent to observe a peculiar intraventricular relaxation flow (IRF) pattern during the isovolumic relaxation time (IRT), especially in patients (pts) with left ventricular hypertrophy (LVH). This is even more likely in pts with hypertrophic obstructive cardiomyopathy and in VVI-paced pts. Despite these observations, the prevalence and clinical relevance of this finding have not been evaluated thoroughly and systematically in a consecutive series of patients. METHODS: Ninety-two consecutive pts underwent a conventional Doppler echo study for the evaluation of systolic and diastolic function (fractional shortening, EF, E and A wave velocity, duration and ratio, and IRT). of these, 42 pts had LVH, 14 had mitral regurgitation (MR) with depressed EF, 8 had CAD with depressed EF and 28 were normal subjects. IF was searched for during the evaluation of IRT and its duration, velocity and integral were measured when noted. RESULTS: Fifty-six patients (61%) showed an IRF at Doppler examination. Of these, fifteen were normal subjects (53%) and 34 (81%, p = 0.03 vs normal) were hypertensive pts. Among pts with depressed EF, only two of 14 with MR and 5 of 8 with no MR showed an IRF (14 vs 62%; p = 0.032). When evaluating LV function, we observed that pts with an IRF had a larger atrial filling fraction, a longer isovolumic relaxation time and a higher ejection fraction with respect to pts with no IRF (respectively, 40 +/- 13% vs 30 +/- 13%, p = 0.005; 108 +/- 23 ms vs 77 +/- 22 ms, p = 0.0001; 70 +/- 14% vs 61 +/- 16%, p = 0.01). CONCLUSIONS: Our data confirm that IRF may be observed in healthy subjects and may be due to an asynchronous relaxation of the LV during IRT, in consideration of a higher prevalence of a greater atrial filling fraction in pts with IF as compared to those in whom this Doppler signal is absent. Moreover, IRF is more frequent in pts with LVH and is rare in pts with MR (predominantly due to a very short isovolumic relaxation time).

Adult↗
PubMed2000

The measurement and diagnostic utility of intrasubtest scatter in pediatric neuropsychology.

Intrasubtest scatter (ISS) is a measure of person's tendency toward inconsistency when responding to test items. It has been claimed that ISS may be suggestive of intellectual inefficiency, difficulty with recall of specific information, or fluctuating levels of arousal/attention. The research investigating these claims has been inconclusive, possibly because traditional indices of ISS may not adequately measure inconsistent responding. Item Response Theory (IRT) approaches to the detection of unusual response sequences appear to have a much firmer psychometric foundation but have been largely ignored in the neurodiagnostic literature. This study compares the utility of traditional and IRT-based indices of ISS in identifying children known to be experiencing information-processing difficulties. The WISC-R item responses of 100 children who have received cranial irradiation treatment for leukemia are compared with those of 100 healthy children. Results confirm the diagnostic utility of an IRT-based measure of unusual test behavior in this clinical group.

Adolescent↗
PubMed1992

New approaches to noninvasive assessment of pulmonary artery pressure.

Direct measurement of pulmonary artery pressure (PAP) was performed in 36 patients; right ventricular (RV) isovolumic relaxation time (IRT) and RV systolic output acceleration time (AcT) values were assessed by pulsed Doppler and 2-M echocardiography. There was a fairly good correlation between RV IRT and systolic PAP (r = 0.898; SEE = 7.8 mmHg) and a somewhat weaker one between RV AcT and systolic PAP (r = -0.880; SEE = 8.37 mmHg). Correlation coefficients were the highest between systolic PAP and the [formula: see text] (r = 0.972; SEE = 4.14), and also between mean PAP and the 10-RV AcT/100 predictor: y = 158x + 6.7 (r = 0.951; SEE = 3.48 mmHg). With +/- 5 mmHg deviations, systolic PAP measurements were accurate in 78% and those of mean PAP in 98% of the patients. The double-blind assessment of the reproducibility of the suggested noninvasive PAP measurement was performed in 18 subsequent patients; the interstudy variability of the measurement was 0.88 +/- 0.94 mmHg and 1.22 +/- 1.23 mmHg (p > 0.05), whereas interobserver variability was 1.90 +/- 1.70 mmHg and 1.67 +/- 1.63 mmHg, respectively (p > 0.05). Thus, a combined use of the most informative intervals of RV cycle--IRT and AcT--contributes to the accuracy of noninvasive PAP measurement.

Adolescent↗
PubMedDate not supplied

Immunoreactive trypsin level in fetoscopically-obtained cord sera of second trimester fetuses.

Immunoreactive trypsin (IRT) has been assayed in cord blood collection by fetoscopy from fetuses with estimated gestational ages of between 16-24 weeks. Eighty per cent of the specimens contained more than 5 ng/ml of IRT indicating pancreatic synthesis of trypsin by mid-term. A prenatal test for cystic fibrosis based on IRT estimation might be valid if the onset of pancreatic dysfunction associated with the disease also occurs at mid-trimester.

Cystic Fibrosis↗
PubMed2004

Test bias in a cognitive test: differential item functioning in the CASI.

Assessment of test bias is important to establish the construct validity of tests. Assessment of differential item functioning (DIF) is an important first step in this process. DIF is present when examinees from different groups have differing probabilities of success on an item, after controlling for overall ability level. Here, we present analysis of DIF in the Cognitive Assessment Screening Instrument (CASI) using data from a large cohort study of elderly adults. We developed an ordinal logistic regression modelling technique to assess test items for DIF. Estimates of cognitive ability were obtained in two ways based on responses to CASI items: using traditional CASI scoring according to the original test instructions as well as using item response theory (IRT) scoring. Several demographic characteristics were examined for potential DIF, including ethnicity and gender (entered into the model as dichotomous variables), and years of education and age (entered as continuous variables). We found that a disappointingly large number of items had DIF with respect to at least one of these demographic variables. More items were found to have DIF with traditional CASI scoring than with IRT scoring. This study demonstrates a powerful technique for the evaluation of DIF in psychometric tests. The finding that so many CASI items had DIF suggests that previous findings of differences between groups in cognitive functioning as measured by the CASI may be due to biased test items rather than true differences between groups. The finding that IRT scoring diminished the impact of DIF is discussed. Some preliminary suggestions for how to deal with items found to have DIF in cognitive tests are made. The advantages of the DIF detection techniques we developed are discussed in relation to other techniques for the evaluation of DIF.

Bias↗
PubMed2003

Fetal cardiac function assessed by Doppler myocardial performance index (Tei Index).

OBJECTIVES: The Tei Index (TI) is a useful, non-invasive, Doppler-derived myocardial performance tool which can be used to assess aspects of systolic and diastolic function. The aim of this study was to determine normal values of fetal left ventricular (LV) TI in second- and third- trimester fetuses and to compare these to other values reported in the literature. METHODS: Doppler waveforms of the LV outflow tracts were obtained in 74 second- and early third-trimester fetuses. The LV isovolumic contraction time (ICT), isovolumic relaxation time (IRT) and ejection time (ET) were measured and the TI calculated using the formula (ICT + IRT)/ET. The literature on LV myocardial function in the fetus was also reviewed. RESULTS: The normal TI in second- and early third-trimester fetuses (18-31 weeks' gestation) was 0.53 +/- 0.13. The ICT was 43 +/- 14 ms, the ET was 173 +/- 16 ms and the IRT was 48 +/- 13 ms. CONCLUSION: The TI can be easily obtained in the fetus without the need for precise anatomic imaging. The TI may be a useful tool to explore fetal myocardial function in different clinical situations.

Diastole↗
PubMed2005

A modified myocardial performance (Tei) index based on the use of valve clicks improves reproducibility of fetal left cardiac function assessment.

OBJECTIVE: To determine whether a modified myocardial performance index (Mod-MPI) involving assessment of the movements (clicks) of the mitral valve (MV) and aortic valve (AV), improves intra- and interobserver agreement as compared to the previously reported method for MPI estimation. METHODS: The Mod-MPI was recorded by two experienced operators in the left cardiac chambers of 25 normally grown fetuses using pulsed Doppler ultrasonography. The isovolumetric contraction time (ICT) was measured from the closure of the MV to the opening of the AV, the ejection time (ET) from the opening to the closure of the AV, and the isovolumetric relaxation time (IRT) from the closure of the AV to the opening of the MV. The Mod-MPI was calculated as (ICT + IRT)/ET. In addition, the MPI was estimated without using the valve clicks (F-MPI) as previously described. Intra- and interobserver agreement were then analyzed for both modalities. RESULTS: There was a significantly lower intra- and inter-observer variability in the estimation of all time periods with the Mod-MPI than with the F-MPI (ICT: intra-observer, 9.9% vs. 13.9%; interobserver 9.9% vs. 15.6%; IRT: intraobserver, 9.9% vs. 14.8%; interobserver 10.4% vs. 18.3%; and ET: intraobserver, 4.5% vs. 6.1%; interobserver 2.8% vs. 5.2%, respectively). Intraclass correlation coefficient (IntraCC) for the Mod-MPI was 0.8 (95% confidence interval (95% CI), 0.56-0.9) and for the F-MPI, the IntraCC was 0.62 (95% CI, 0.26-0.84); P = 0.01. Agreement between observers using the Mod-MPI showed a mean difference of 0.0 with 95% limits of agreement (LA) -0.09 (95% CI, -0.1 to -0.075) to 0.09 (95% CI, 0.075-0.1) and for the F-MPI the mean difference was -0.01 with 95% LA -0.26 (95% CI, -0.3 to -0.22) to 0.25 (95% CI, 0.21-0.29). CONCLUSION: Calculation of the Mod-MPI based on Doppler echoes of the MV and AV clicks is associated with a lower variation and better inter- and intraobserver agreement than the previously used method for fetal cardiac evaluation.

Aortic Valve↗
PubMedDate not supplied

Short- and long-term effects of nisoldipine on cardiac function and exercise tolerance in patients with hypertrophic cardiomyopathy.

UNLABELLED: Nisoldipine is a second generation dihydropyridine calcium antagonist having characteristics of strong coronary artery dilating effect and less negative inotropic action. The purpose of this study was to evaluate the effect of nisoldipine on the cardiac function (systolic and diastolic) and the exercise tolerance, in patients with hypertrophic cardiomyopathy (HCM). SUBJECTS: Twenty-three patients with HCM were studied. METHODS: We measured the following indices using M-mode and pulsed wave Doppler echocardiography before and after nisoldipine therapy; left ventricular fractional shortening (LVFS), isometric relaxation time (IRT), deceleration half-time (DHT) of early diastolic mitral (E) flow, late diastolic mitral (A) flow and A/E ratio. Symptom-limited treadmill exercise test was performed. Exercise tolerance (EX) time was measured. Nisoldipine of 10 mg/day was orally administered. Same tests were repeated on day 14 and after 6 months. RESULTS: 1) Short-term effects; LVFS did not change (55.9 +/- 5.9%-->57.0 +/- 7.4%, NS) after 2 weeks. However, LV diastolic function significantly improved (IRT; 92.1 +/- 7.7 ms-->85.2 +/- 11.6 ms, p < 0.05, DHT; 70.7 +/- 16.2 ms-->63.3 +/- 3.7 ms, p < 0.05). EX time increased (8.9 +/- 2.6 min-->10.0 +/- 3.3 min, p < 0.05), 2) Long-term effects; LV diastolic function had a tendency toward improvement, but is statistically not significant (IRT; 91.1 +/- 7.6-->83.8 +/- 11.6 ms, DHT; 73.1 +/- 23.4-->61.0 +/- 11.4 ms, A/E; 1.26 +/- 0.29-->1.11 +/- 0.36) after 6 months. EX time was significantly increased (9.4 +/- 1.7--> 10.1 +/- 1.7 min, p < 0.05). CONCLUSIONS: Nisoldipine improved LV diastolic dysfunction and exercise tolerance in patients with HCM. These effects were similar to the first generation calcium antagonists. LV diastolic dysfunction may be improved due to the reduction of intracellular calcium concentration and the relief of myocardial ischemia by strong coronary artery dilating effect. However, nisoldipine did not affect the LV systolic function because of its less negative inotropic effect.

Adult↗
PubMed1994

Cystic fibrosis screening in neonates--measurement of immunoreactive trypsin and direct genotype analysis for delta F508 mutation.

This study investigated the clinical usefulness of screening for cystic fibrosis (CF) in 19,992 newborns, over 39 months, in an Austrian population. Immunoreactive serum trypsin (IRT) determination was followed by sweat chloride analysis (sweat test) to establish diagnosis. In a retrospective analysis covering 6 months of the study period, individuals who were considered to be at risk after IRT estimation (n = 22) were analysed for delta F508 mutation, using a new method of DNA extraction from the initial dried blood specimens. A total of 119 infants (0.6%) had values greater than 750 ng trypsin/ml whole blood. In 88 babies sweat tests were performed, leading to the diagnosis of CF in 11 cases. One patient was not initially identified by screening but was later discovered due to his clinical status. Three infants were noted to carry the delta F508 mutation (1 homozygous, 2 heterozygous). Two of these babies already had CF. The second heterozygote was a carrier. A highly efficient three tier screening strategy is presented in which IRT estimation, determination of delta F508 status and sweat chloride testing could lead to a high sensitivity analysis of this population.

Cystic Fibrosis↗
PubMed1994

The effects of behavioral history on cocaine self-administration by rhesus monkeys.

The purpose of the present study was to examine whether a history of responding under schedules that generate either high or low response rates could modify previously established cocaine self-administration. Eight experimentally naive rhesus monkeys were trained to respond on one of two levers under a fixed-interval (FI) 5-min schedule of intravenous cocaine (0.03 mg/kg per injection) presentation. When responding was stable a cocaine dose-response curve (saline, 0.01-0.3 mg/kg per injection) was determined. Following completion of the dose-response curves, the monkeys were randomly assigned to one of two groups (n = 4/group) and trained to respond on the other lever under either a fixed-ratio (FR) 50 or inter-response times (IRT) > 30-s schedule of cocaine (0.03 mg/kg per injection) presentation. After 65 sessions responding was again maintained under the FI5-min schedule of 0.03 mg/kg per injection cocaine for 60 sessions, followed by redetermination of the cocaine dose-response curve. During the initial exposure to the FI schedule, the mean rate of responding was 4.02 (+/- 0.33) responses/min and the cocaine dose-response curve was characterized as an inverted-U shape function of dose, with peak responding at 0.03 mg/kg per injection. The FR50 schedule generated high rates (66.80 +/- 5.6 responses/min), while response rates under the IRT > 30-s schedule were low (2.62 +/- 0.2 responses/min). Following different behavioral histories, response rates under the FI5-min schedule were significantly higher for 60 sessions in FR-history monkeys compared to IRT-history subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

2,4-Dithiobiuret in rats: cognitive facilitation after acute injection precedes motor impairment after repeated daily injections.

2,4-Dithiobiuret (DTB) is a sulfonated derivative of urea that is used as a reducing agent in chemical manufacture. Its low acute toxicity to rodents belies a peripherally mediated, delayed-onset muscle weakness which develops during repeated daily exposure. In experiment 1, a standard dose regimen of DTB (0.5 mg/kg per day IP for 5 days) was used to induce motor dysfunction as a way to dissociate peripheral and central influences on a test of cognitive and motor function in rats. Sixteen male rats were trained to perform a Delayed Matching-to-Position/Visual Discrimination (DMTP/VD) task which permits quantification of working memory (matching accuracy), reference memory (discrimination accuracy), and motor function (choice response latency and nosepoke inter-response time, IRT). The first dose of DTB significantly increased matching accuracy; during the following week, DTB reduced matching accuracy, increased choice response latency and nosepoke IRT, and reduced trial completion. Discrimination accuracy remained unaffected. Experiment 2 explored the effects of single administrations of DTB on DMTP/VD. Sixteen other trained rats were divided into two groups with equal matching accuracy. One group received DTB (0.5,1.0, and 2.0 mg/kg, IP) in separate injections at least 1 week apart; the other group received vehicle at the same times. Matching accuracy increased significantly in the treated rats and not in the controls following each dose of DTB. The magnitude of this increase was dose dependent, and lasted from 1 to 8 weeks after each injection. Discrimination accuracy, response latency, nosepoke IRT and trial completion remained unaffected throughout the study. After DTB, matching accuracy was less easily disrupted by scopolamine (0.1-0.3 mg/kg, IP). However, DTB did not alter the rats' response to reducing the distance between the response levers, to reversal of the matching rule to a nonmatching rule, or to challenge with MK-801 (0.05-0.10 mg/kg, IP). These data indicate that acute DTB causes a long-lasting facilitation of working memory in rats in the absence of any of the indications of motor impairment which follow repeated, daily injections of the chemical.

Animals↗
PubMed1996

Effects of desipramine and fluvoxamine on timing behavior investigated with the fixed-interval peak procedure and the interval bisection task.

Acute treatment with antidepressant drugs is known to increase the mean interresponse time (IRT) in the IRT > 72-s schedule of reinforcement. In order to examine the possibility that this effect may reflect an action of the antidepressants on timing processes, we tested the effects of two antidepressants, desipramine and fluvoxamine, on behaviour maintained under two other timing schedules in rats. In the fixed-interval peak procedure (fixed-interval 30-s), acute treatment with desipramine (8 mg kg-1) reduced response rate, whereas acute treatment with fluvoxamine (8 mg kg-1) increased it. Neither drug significantly altered the time to attainment of peak response rate or the Weber fraction. In the interval bisection task (standard durations 2 s and 8 s), the bisection point was not significantly altered by acute treatment with either drug. Chronic treatment with desipramine (8 mg kg-1 b.d.) had no effect on any of the indices of timing under either schedule. Chronic treatment with fluvoxamine (8 mg kg-1 b.d.) reduced the time to attainment of peak response rate but had no effect on the Weber fraction under the fixed-interval peak procedure, and did not alter the bisection point or Weber fraction under the interval bisection procedure. The failure of desipramine and fluvoxamine to increase the time to peak response rate or the bisection point at doses that significantly altered operant response rate suggests that the effect of these drugs on IRT schedule performance is unlikely to reflect an interaction with timing processes.

Adrenergic Uptake Inhibitors↗
PubMed2005

The accuracy of a new infrared ear thermometer in patients undergoing cardiac surgery.

PURPOSE: To evaluate the equivalency of the prototype of a new infrared ear thermometer (IRT 4000) in comparison to the temperature measurements of a pulmonary artery catheter (PAC) and a continual contact probe on the tympanic membrane. METHODS: After approval by the local Ethics Committee, 26 (six female and 20 male) patients undergoing elective cardiac surgery were included in a single center open trial. During surgery, temperature measurements were recorded with the IRT 4000 in the left ear, and with a tympanic contact probe in the right ear, as well as with a PAC as reference. Measurements with the infrared ear thermometers and continual PAC values were recorded every six minutes. RESULTS: The average temperature measured with the IRT 4000 was 0.08 degrees C above the temperature of the PAC (95% confidence interval from -0.44-0.61 degrees C). CONCLUSION: Infrared ear thermometers 4000 temperature readings accurately reflect body core temperature and correlate well with the invasive PAC. Infrared ear thermometers may present a clinically useful alternative to the pulmonary artery thermometry for the measurement of core temperature in the perioperative setting or in the intensive care unit.

Aged↗
PubMed1997

Sensitization to amphetamine on the differential-reinforcement-of-low-rate 72-s schedule.

The purpose of the present study is to determine whether the effect of specific intermittent injections of amphetamine (AMPH) on a differential reinforcement schedule of low rate (DRL) would result in a sensitized response to subsequent AMPH injections. Two groups of rats were trained on a DRL 72-s schedule until they reached stable baseline performance. One group (SENS, n = 8) was treated intermittently (no more than twice a week) with 1.5 mg/kg amphetamine for 3.5 weeks. The other group (CONT, n = 8) received intermittent saline (SAL) 1 ml/kg for 3.5 weeks. Acute injections of 1.5 mg/kg AMPH in the SENS group, engendered an increase in response rate, a decrease in reinforcement rate and disruption of the inter-response time (IRT) distribution profile. Acute SAL injections in the CONT group had no effect. Rats pretreated with intermittent 1.5 mg/kg AMPH, when treated with a lower dose of AMPH (0.5 mg/kg), showed an increase in response rate, a decrease in reinforcement rate and disruption of the IRT distribution profile by decreasing peak area and shifting the peak location towards a shorter IRT duration. Therefore, in rats pretreated intermittently with 1.5 mg/kg AMPH (SENS group), the dose of 0.5 mg/kg AMPH elicited a similar change in DRL 72-s response pattern, as did the acute injection of 1.5 mg/kg AMPH. In contrast, in rats pretreated with SAL (CONT group), the low dose of AMPH had either no or small effects. Thus, pretreatment with 1.5 mg/kg AMPH increases the magnitude of the response to 0.5 mg/kg AMPH. These results indicate that rats performing on the DRL 72-s schedule exhibit sensitization to AMPH, after AMPH is given intermittently over a 3-week period.

Amphetamine↗