Putative calcium channel molecular weight determination by target size analysis

The molecular weight of the putative calcium channel in guinea-pig brain membranes, labelled with [3H]-nimodipine, has been determined in situ by target size analysis. Irradiation of guinea-pig brain membranes at 153-173 K with 10 MeV electrons reduced the density of [3H]-nimodipine binding sites without affecting the equilibrium dissociation constant. The decay of the calcium channel blocker binding site density as a function of radiation dose fits to a monoexponential function. Application of the target size theory gives a molecular weight of 185,000. [3H]-Flunitrazepam labelled benzodiazepine receptor target size was measured as an internal control. The molecular weight of the benzodiazepine receptors was 76,000, which is in good agreement with published results.

Photoaffinity-labelling of the glycine receptor of rat spinal cord

The irreversible incorporation upon ultraviolet illumination of the glycine receptor antagonist, [3H]strychnine, into synaptic membrane fractions of rat spinal cord has been investigated. The specificity of this photoaffinity-labelling reaction for the glycine receptor was demonstrated by the following results: (a) the Kd value (9.7 nM) of the glycine-displaceable irreversible incorporation of [3H]strychnine was similar to the previously reported Kd of [3H]strychnine binding to the glycine receptor; (b) pre-illumination of the membranes with unlabelled strychnine led to a corresponding reduction in the number, but not the affinity, of reversible glycine-displaceable [3H]strychnine binding sites; (c) the ultraviolet light-induced incorporation into the membranes of [3H]strychnine was inhibited by different glycine receptor agonists; other neurotransmitter substances had little or no effect. Also, [3H]strychnine alone was shown to be stable upon illumination with ultraviolet light; this suggests that photocrosslinking of [3H]strychnine may require energy transfer from specific groups of its high-affinity receptor binding site. Upon sodium dodecyl sulphate/polyacrylamide gel electrophoresis a single labelled polypeptide with a relative molecular mass of 48000 was revealed from spinal cord membranes photoaffinity-labelled with [3H]strychnine. Spinal cord membranes photoaffinity-labelled with the gamma-aminobutyric acid receptor ligand [3H]flunitrazepam, however, gave a single polypeptide with a relative molecular mass of 5- 0000. Treatment of membranes, labelled with [3H]strychnine, by endoglycosidase H did not alter the relative molecular mass of the 48000-Mr labelled polypeptide. Trypsin treatment, on the other hand, successively produced major fragments of relative molecular masses of 42000 and 37000. Also, even after extensive treatment with trypsin or chymotrypsin, greater than or equal to 90% of the radioactivity incorporated into the labelled membranes remained membrane-associated. It is concluded that the strychnine binding site of the glycine receptor is located on a protease-inaccessible, i.e. probably hydrophobic domain of the 48000-Mr subunit.

Production of a high affinity antiserum to benzodiazepines

Antibodies specific for benzodiazepines were raised in rabbits by immunization with a conjugate of a benzodiazepine derivative, Ro 7-1986/1, with bovine serum albumin. The presence of anti-Ro 7-1986/1 antibodies in the sera was demonstrated by a radioimmunoassay using the radioligand [3H]flunitrazepam ([3h]FNZ). The antibodies displayed a high-affinity for [3H]FNZ (KD = 0.073 +/- 0.003 nM) and and cross-reacted with a broad spectrum of benzodiazepine derivatives. Benzodiazepine levels in samples of sera and urine of benzodiazepine-treated humans were determined. Due to the high sensitivity of the assay only minute volumes (microliter quantities) of body fluids are employed and, therefore, no extraction of the drugs is required. Nitrazepam and diazepam levels as low as 20 picograms can be easily observed. Intoxicating levels of benzodiazepines can be detected by a single measurement in less than 10 min. This radioimmunoassay is advantageous for pharmacokinetic studies, toxicological examinations and forensic medicine due to its high sensitivity, wide-range specificity and technical simplicity.

Comparison of isoflurane and halothane when used to control intraoperative hypertension in patients undergoing coronary artery bypass surgery

The hemodynamic effects of isoflurane and halothane when used to control intraoperative hypertension were evaluated in 20 patients undergoing coronary artery bypass grafting. The patients were anesthetized with flunitrazepam, fentanyl, pancuronium, and N2O-O2. Control measurements were made after skin incision. When mean arterial pressure increased to 110 mm Hg due to sternal spread or surgical manipulation of the aorta, isoflurane or halothane were used to return arterial pressure to control levels. Using a non-rebreathing system, inspired isoflurane concentrations of 1.5-2.0 vol% or halothane concentrations of 1.0-1.5 vol% were necessary. Measurements were repeated during the hypertensive episode and after treatment with isoflurane or halothane while surgical stimulation continued. Both inhalation anesthetics decreased arterial pressure to baseline values within 5-10 min. The lowering of arterial pressure with halothane was not accompanied by significant decreases in the elevated systemic vascular resistance and pulmonary capillary wedge pressure. Cardiac index and stroke volume index decreased markedly when halothane was used (18% and 25%, respectively). In contrast, isoflurane significantly decreased systemic vascular resistance (42%). This reduction of left ventricular afterload was associated with an increase in cardiac index (22%) and a decrease in left ventricular filling pressure. Heart rate did not change significantly. These findings indicate that isoflurane is superior to halothane for controlling intraoperative hypertension during coronary artery bypass surgery.

[Hemodynamic analysis of 6 different anesthesia induction procedures in coronary surgery patients]

We investigated the cardiovascular effects of intravenous thiopentone (3.0 mg/kg), etomidate (0.3 mg/kg), althesin (0.07 ml/kg), ketamine (1.5 mg/kg), diazepam (0.15 mg/kg) and flunitrazepam (0.015 mg/kg) alone and after the addition of fentanyl (0.01 mg/kg) during induction of anaesthesia in 46 premedicated patients subjected to coronary artery bypass surgery. Thiopentone, etomidate or diazepam caused only small changes in the haemodynamic determinants of myocardial oxygen supply and demand (arterial pressure, heart rate, left and right ventricular filling pressure) in patients with coronary artery disease in whom global resting left ventricular function was normal. Althesin and flunitrazepam produced a significant fall in arterial pressure, cardiac index and stroke index; heart rate increased after the administration of althesin. Ketamine markedly elevated systemic and pulmonary pressure, heart rate, systemic and pulmonary vascular resistance, right and left ventricular filling pressure. The subsequent administration of fentanyl was associated with a further decrease in arterial pressure in the althesin and flunitrazepam group. The circulatory stimulating effects of ketamine were largely abolished by fentanyl. None of the induction procedures was associated with cardiovascular stimulation during laryngoscopy and tracheal intubation.

[The use of tramadol-HCl (Tramal) as adjuvant in regional anaesthesia. Clinical report (author's transl)]

The report deals with the clinical use and effects of tramadol-HCl (Tramal) as an adjuvant in regional anaesthesia. As distinguished from triflupromazine, diazepam, flunitrazepam, droperidol, piritramide and pentazocine this drug can be applied safely, reliably and without secondary effects in patients of all ages for sedation and analgesia without loss of cooperation (no sleep, no pain from body-positioning, no psychic distress) and for the prevention of centralisation in the unblocked region (no trembling- and freezing-reaction, no alteration of the blood-gas-analysis.

Radioreceptor assay for benzodiazepines in biological fluids using a new dry and stable receptor preparation

A method for determination of benzodiazepines in human blood, plasma, saliva and urine has been developed. The method is based upon the competition between 3H-flunitrazepam and biologically active benzodiazepines in biological fluids for brain specific receptors, prepared in a stable, dry form and easy to handle. The pharmacological specificity for benzodiazepines of the dry stable receptor preparation is closely similar to that of fresh membrane-bound rat brain receptors. The method is specific for biologically active benzodiazepines; it is relatively rapid, sensitive and reproducible, and can be performed at room temperature.

Benzodiazepine receptors on primary cultures of mouse astrocytes

Benzodiazepines bind to glial membranes on a single type of site, with a high affinity (KD = 5 x 10(-9) M) on about 100 fmol of sites per mg protein. The number of binding sites is increased when the membranes are treated with Triton X-100. Antiepileptic drugs such as clonazepam and phenobarbital and hypnotic drugs such as Ro-11-3128 and Ro-11-6896 are able in pharmacological concentrations to displace [3H]flunitrazepam from its glial binding sites.

[The effects of flunitrazepam and benzoctamine on the blood gases during translumbar aortography in spinal analgesia (author's transl)]

In thirty patients the influence of intravenous Flunitrazepam (0.4-0.8 mg) and Benzoctamine (10-20 mg) on blood gases during short acting diagnostic procedures in spinal anaesthesia in prone position was investigated. The changes of paO2 and PaCO2 were neglectible after Benzoctamin and a control group up to 10 minutes after injection. After Flunitrazepam there was a significant reduction of paO2 and rise of paCO2. The results are discussed.