Differential Roles of GABAA Receptor Subtypes in Benzodiazepine-Induced Enhancement of Brain-Stimulation Reward

Benzodiazepines such as diazepam are widely prescribed as anxiolytics and sleep aids. Continued use of benzodiazepines, however, can lead to addiction in vulnerable individuals. Here, we investigate the neural mechanisms of the behavioral effects of benzodiazepines using the intracranial self-stimulation (ICSS) test, a procedure with which the reward-enhancing effects of these drugs can be measured. Benzodiazepines bind nonselectively to several different GABA_A receptor subtypes. To elucidate the α subunit(s) responsible for the reward-enhancing effects of benzodiazepines, we examined mice carrying a histidine-to-arginine point mutation in the α1, α2, or α3 subunit, which renders the targeted subunit nonresponsive to diazepam, other benzodiazepines and zolpidem. In wild-type and α1-point-mutated mice, diazepam caused a dose-dependent reduction in ICSS thresholds (reflecting a reward-enhancing effect) that is comparable to the reduction observed following cocaine administration. This effect was abolished in α2- and α3-point-mutant mice, suggesting that these subunits are necessary for the reward-enhancing action of diazepam. α2 Subunits appear to be particularly important, since diazepam increased ICSS thresholds (reflecting an aversive-like effect) in α2-point-mutant animals. Zolpidem, an α1-preferring benzodiazepine-site agonist, had no reward-enhancing effects in any genotype. Our findings implicate α2 and α3 subunit containing GABA_A receptors as key mediators of the reward-related effects of benzodiazepines. This finding has important implications for the development of new medications that retain the therapeutic effects of benzodiazepines but lack abuse liability.     

Qualitätsentwicklung im Gesundheitswesen: Sind wir schon so weit,wie wir wollten?

Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz -     

Monitor units are not predictive of neutron dose for high-energy IMRT

ABSTRACT: BACKGROUND: Due to the substantial increase in beam-on time of high energy intensity-modulated radiotherapy (>10 MV) techniques to deliver the same target dose compared to conventional treatment techniques, an increased dose of scatter radiation, including neutrons, is delivered to the patient. As a consequence, an increase in second malignancies may be expected in the future with the application of intensity-modulated radiotherapy. It is commonly assumed that the neutron dose equivalent scales with the number of monitor units. METHODS: Measurements of neutron dose equivalent were performed for an open and an intensity-modulated field at four positions: inside and outside of the treatment field at 0.2 cm and 15 cm depth, respectively. RESULTS: It was shown that the neutron dose equivalent, which a patient receives during an intensity-modulated radiotherapy treatment, does not scale with the ratio of applied monitor units relative to an open field irradiation. Outside the treatment volume at larger depth 35% less neutron dose equivalent is delivered than expected. CONCLUSIONS: The predicted increase of second cancer induction rates from intensity-modulated treatment techniques can be overestimated when the neutron dose is simply scaled with monitor units.     

Exercise Capacity and Quality of Life in Patients with Schizophrenia

The aim of this study was to resolve the relationship between physical capacity (PC) and quality of life (Qol) in schizophrenic patients and healthy controls. 31 patients (PG: 18 male, 13 female) and a control group (CG) of 50 healthy subjects (15 male, 35 female) were involved. PC was assessed as peak oxygen uptake [VO₂peak, (ml (min kg_KG)^?1)] and power output expressed as watts per kilogram (W kg^?1). Qol was assessed using the SF-36 questionnaire. Patients with schizophrenia showed reduced VO₂peak (male: PG 29 ± 5 vs. CG 44 ± 10; female: PG 21 ± 4 vs. CG 30 ± 8) and power output (male: PG 2.04 ± 0.47 vs. CG 3.43 ± 0.70; female PG 1.40 ± 0.28 vs. CG 2.43 ± 0.52). Scales of the SF-36 questionnaire were lower in the PG. While in the CG correlations were found between PC and several subscales of Qol, this was not the case in the PG. The restricted PC seen in the PG showed no relation to their subjectively assessed worsened Qol, which would indicate that schizophrenic patients evaluate limitations arising from this differently than healthy control subjects.     

Combination reperfusion therapy with eptifibatide and reduced-dose tenecteplase for ST-elevation myocardial infarction: results of the integrilin and tenecteplase in acute myocardial infarction (INTEGRITI) Phase II Angiographic Trial

OBJECTIVES: The goal of this study was to evaluate combinations of eptifibatide with reduced-dose tenecteplase (TNK) in ST-elevation myocardial infarction (STEMI). BACKGROUND: Glycoprotein IIb/IIIa inhibitors enhance thrombolysis. The role of combination therapy in clinical practice remains to be established. METHODS: Patients (n = 438) with STEMI <6 h were enrolled. In dose-finding, 189 patients were randomized to different combinations of double-bolus eptifibatide and reduced-dose TNK. In dose-confirmation, 249 patients were randomized 1:1 to eptifibatide 180 microg/kg bolus, 2 microg/kg/min infusion, and 180 microg/kg bolus 10 min later (180/2/180) plus half-dose TNK (0.27 mg/kg) or standard-dose (0.53 mg/kg) TNK monotherapy. All patients received aspirin and unfractionated heparin (60 U/kg bolus; infusion 7 U/kg/h [combination], 12 U/kg/h [monotherapy]). The primary end point was Thrombolysis In Myocardial Infarction (TIMI) grade 3 epicardial flow at 60 min. RESULTS: In dose-finding, TIMI grade 3 flow rates were similar across groups (64% to 68%). Arterial patency was highest for eptifibatide 180/2/180 plus half-dose TNK (96%, p = 0.02 vs. eptifibatide 180/2/90 plus half-dose TNK). In dose-confirmation, this combination, compared with TNK monotherapy, tended to achieve more TIMI 3 flow (59% vs. 49%, p = 0.15), arterial patency (85% vs. 77%, p = 0.17), and ST-segment resolution (median 71% vs. 61%, p = 0.08) but was associated with more major hemorrhage (7.6% vs. 2.5%, p = 0.14) and transfusions (13.4% vs. 4.2%, p = 0.02). Intracranial hemorrhage occurred in 1.0%, 0.6%, and 1.7% of patients treated with any combination, eptifibatide 180/2/180 and half-dose TNK, and TNK monotherapy, respectively. CONCLUSIONS: Double-bolus eptifibatide (180/2/180) plus half-dose TNK tended to improve angiographic flow and ST-segment resolution compared with TNK monotherapy but was associated with more transfusions and non-cerebral bleeding. Further study is needed before this combination can be recommended for general use.     

Brain natriuretic peptide predicts right heart failure in patients with acute pulmonary embolism

Background

Plasma levels of brain natriuretic peptide (BNP) are increased in patients with left heart failure. In patients with severe pulmonary embolism (PE), primary right ventricular (RV) dysfunction is frequent. Little is known about BNP secretion in acute RV failure.

Methods

We prospectively studied 50 consecutive patients with confirmed PE (age range, 57 ± 19 years; 36 men). PE was confirmed with pulmonary angiography, spiral computed tomography, or echocardiography and subsidiary analyses. On admission, echocardiography and BNP measurements were performed in all patients.

Results

Patients without RV dysfunction had significantly lower BNP levels than patients with RV dysfunction (55 ± 69 pg/mL vs 340 ± 362 pg/mL, P <.001). There was a significant correlation between RV end-diastolic diameter and BNP (r = 0.43, P <.05). BNP discriminated patients with or without RV dysfunction (area under the receiver operating characteristic curve, 0.78; 95% CI, 0.64-0.92). A BNP >90 pg/mL was associated with a risk ratio of 28.4 (95% CI, 3.22-251.12) for the diagnosis of RV dysfunction. All patients without LV systolic dysfunction who had syncope necessitating cardiopulmonary resuscitation had normal BNP levels. Patients with RV dysfunction had significantly more in-hospital complications (cardiogenic shock, inotropic therapy, mechanical ventilation). However, BNP levels were not predictive of mortality or in-hospital complications.

Conclusions

BNP levels are frequently increased in patients with PE who have RV dysfunction, whereas patients without RV dysfunction show reference range BNP levels in the absence of left ventricular dysfunction. In acute PE, BNP elevation is highly predictive of RV dysfunction, but not of in-hospital complications and mortality.