Predictive value of allergy tests for neuromuscular blocking agents: tackling an unmet need

BACKGROUND

Neuromuscular blocking agents (NMBAs) are a predominant cause of perioperative anaphylaxis in Europe. Diagnosis of NMBA allergy relies upon the careful review of the anaesthetic report complemented with skin tests. Additional diagnostic tests are quantification of specific IgE antibodies (sIgE) and basophil activation test (BAT). However, data on the predictive value of the skin tests, the BAT and the sIgE assays (drug-specific and substituted ammonium structures) are limited or not available, mainly because such exploration requires dangerous NMBA provocation tests.

METHODS

In this study, the predictive value of skin test, BAT and measurement of sIgE to substituted ammonium structures is gathered from a review of anaesthetic records of subsequent surgical procedures with NMBA administration and/or occurrence of perioperative incidents.

RESULTS

We investigated a series of 272 patients with perioperative anaphylaxis, of whom 100 had undergone second general anaesthesia. Negative skin test and negative BAT assisted the selection of alternative NMBA, which were well tolerated in all cases. Five patients with a positive sIgE to rocuronium but with negative skin testing and BAT safely received rocuronium during second anaesthesia. Twelve patients with sIgE reactivity to morphine, but negative skin test and BAT to benzylisoquinolines, tolerated administration of cisatracurium or atracurium. Alternatively, benzylisoquinoline allergy went undetected in the morphine solid-phase assay.

CONCLUSIONS

Skin test and BAT have an excellent negative predictive value in our series. The uneventful re-exposure of rocuronium in patients with an isolated positive sIgE result to rocuronium calls into question the predictive value of this assay and suggests sIgE serology to be less clinically predictive than the functional investigations relying upon activation of mast cells or basophils. The presence of a positive sIgE to substituted ammonium structures such as morphine does not preclude further use of benzylisoquinolines.

Flowcytometric diagnosis of atracurium-induced anaphylaxis

BACKGROUND

Allergy to atracurium is a rare condition with serious consequences of diagnostic error. However, correct diagnosis is not always straightforward. The aim of this study is to assess the utility of the basophil activation test (BAT) in atracurium sensitization and to investigate its role in identifying cross-reactivity between muscle relaxants.

METHODS

For validation, eight patients with perioperative anaphylaxis to atracurium and seven individuals experiencing perioperative anaphylaxis but not exposed to neuromuscular blocking agents (NMBA) were included. Furthermore, five other patient groups were included in the study, and all individuals exposed to different NMBA, either sensitized or not to the drug. Basophil activation with atracurium was analysed flow cytometrically.

RESULTS

ROC analyses between eight atracurium-sensitized patients and seven nonexposed controls allowed identification of 5% as the decision threshold for BAT positivity. For this cutoff, the BAT attained a sensitivity of 63%, specificity of 100%, positive predictive value of 100% and negative predictive value of 70%. Of the atracurium-exposed individuals with a negative atracurium skin test (ST), two individuals had a clear positive BAT. BAT atracurium was positive in one cisatracurium-sensitized patient and negative in all cisatracurium-exposed patients with a negative ST to cisatracurium. All rocuronium- and suxamethonium-sensitized patients displayed a negative BAT with atracurium.

CONCLUSIONS

The BAT proves to be a useful diagnostic for atracurium-induced anaphylaxis and may be complementary to STs. The technique enables quick and simultaneous testing of potentially crossreactive NMBA and the identification of safe alternatives for future surgery.

Component-resolved diagnosis of wasp (yellow jacket) venom allergy

BACKGROUND

Wasp venom allergy is a potentially life-threatening condition with serious consequences of diagnostic error.

OBJECTIVE

To assess whether component-resolved diagnosis, using non-glycosylated recombinant allergen components from yellow jacket can add to the diagnosis of wasp venom allergy.

METHODS

In total, 148 patients with a wasp (yellow jacket) allergy were included, 91 with unequivocal tests, 26 with double positivity of serum-specific IgE (sIgE) to both venoms, 21 with discrepant sIgE and skin test results and finally 10 having their diagnosis only confirmed by basophil activation test (negative sIgE and skin test results). Specific IgE to recombinant species-specific allergen components Ves v 1 and Ves v 5 from yellow jacket, Api m 1 from honeybee and Ves v 5 complemented wasp venom were tested by ImmunoCAP.

RESULTS

Overall, combined use of sIgE to rVes v 1 and rVes v 5 allowed correct diagnosis in 139 of the 148 patients (94%) and rApi m 1 was demonstrable in only one patient. Supplementing the traditional yellow jacket allergosorbent with rVes v 5 allowed to correctly diagnose wasp allergy in patients sensitized to Ves v 5 but demonstrating a negative sIgE to wasp venom.

CONCLUSION

Component-resolved diagnoses with the wasp-specific recombinant allergen components Ves v 1 and Ves v 5 is a reliable method to diagnose yellow jacket allergy and can help to take out the sting of difficult cases. However, as the number of patients with doubt after conventional tests is small, larger collaborative studies are needed to draw more definitive conclusions. Whether the rVes v 5 supplemented yellow jacket allergosorbent constitutes an asset in the diagnostic management of wasp venom allergy remains to be further established.

Sensitization to the mammalian oligosaccharide galactose-alpha-1,3-galactose (alpha-gal): experience in a Flemish case series

BACKGROUND

Recent observations have disclosed that the galactose-alpha (1,3)-galactose (alpha-gal) moiety of non-primate glycoproteins can constitute a target for meat allergy.

OBJECTIVE

To describe adults with allergic reactions to mammalian meat, dairy products and gelatin. To investigate whether patients could demonstrate sensitization to activated recombinant human coagulation factor VII ectapog alpha that is produced in baby hamster kidney cells.

METHODS

Ten adults with mammalian meat, dairy products and gelatin allergies were examined using quantification of specific IgE and/or skin prick test for red meat, milk, milk components, gelatin, cetuximab and eptacog alpha.

RESULTS

Most patients demonstrate quite typical clinical histories and serological profiles, with anti-alpha-gal titers varying from less than 1% to over 25% of total serum IgE. All patients demonstrate negative sIgE for gelatin, except the patient with a genuine gelatin allergy. All patients also demonstrated a negative sIgE to recombinant milk components casein, lactalbumin and lactoglobulin. Specific IgE to eptacog was positive in 5 out of the 9 patients sensitized to alpha-gal and none of the 10 control individuals.

CONCLUSION

This series confirms the importance of the alpha-gal carbohydrate moiety as a potential target for allergy to mammalian meat, dairy products and gelatin (oral, topical or parenteral) in a Flemish population of meat allergic adults. It also confirms in vitro tests to mammalian meat generally to be more reliable than mammalian meat skin tests, but that diagnosis can benefit from skin testing with cetuximab. Specific IgE to gelatin is far too insensitive to diagnose alphaa-gal related gelatin allergy. IgE binding studies indicate a potential risk of alpha-gal-containing human recombinant proteins produced in mammalians.

IgE-mediated allergy to pholcodine and cross-reactivity to neuromuscular blocking agents: Lessons from flow cytometry

BACKGROUND

Immunoglubulin E antibody-mediated allergic reactions to opioids are rare and difficult to document correctly.

OBJECTIVE

Assessment of the basophil activation test in the diagnosis of IgE-mediated allergy to the antitussive pholcodine and associated sensitizations to neuromuscular blocking agents (NMBA).

METHODS

Three patients with a suspected IgE-mediated allergy to pholcodine were investigated using skin tests, quantification of specific IgE, and flow cytometric activation of basophils.

RESULTS AND CONCLUSION

Flow cytometric activation of basophils, with simultaneous analysis of CD63 appearance and median histamine content per cell, is the only technique capable to correctly document pholcodine allergy. The negative predictive value of basophil activation tests might help to elucidate on the controversial putative cross-reactivity between pholcodine and NMBA.

Allergy to chlorhexidine: beware of the central venous catheter

The example reported here illustrates the frequent belief that "innocent" products such as central venous catheters do not produce allergic reactions. However, they might be impregnated with chlorhexidine and elicit serious life-threatening anaphylaxis in patients with allergy to this antiseptic agent.

The in vitro diagnosis of drug allergy: status and perspectives

Adverse drug reactions (ADR) can result from immune-mediated (drug allergy) and nonimmune-mediated mechanisms. In both types of reaction, conclusive diagnosis and appropriate management remain major problems in daily clinical practice. This review summarizes the potentials and shortcomings of the currently available in vitro tests in the diagnosis of immediate (mostly IgE mediated) and nonimmediate (mostly T-cell mediated) drug allergy, particularly quantification of specific IgE, flow-assisted analysis of in vitro activated lymphocytes and basophils and the enzyme-linked immunosorbent spot.

Allergy to rocuronium: from clinical suspicion to correct diagnosis

BACKGROUND

Allergy to rocuronium can be life-threatening. Correct diagnosis is a prerequisite because of serious consequences of diagnostic error.

OBJECTIVE

To assess skin testing, quantification of specific IgE (sIgE) and flow-assisted activation of basophils [basophil activation test (BAT)] in the diagnosis of rocuronium allergy.

METHODS

This study comprises 104 curarized patients with a history of profound hypotension and severe bronchospasm immediately after induction of anaesthesia. All patients had skin tests, quantification of sIgE and BAT to rocuronium, together with investigations for all relevant compounds administered during anaesthesia that could have evoked the reaction. Diagnosis of rocuronium allergy was considered definite when the patient demonstrated a positive outcome for at least two of the three aforementioned tests.

RESULTS

The positive predictive value for skin testing, BAT and sIgE was 98% (CI 95%: 92-99%), 97% (CI 95%: 88-100%) and 83% (CI 95%: 74-89%), respectively. The negative predictive value for skin testing, BAT and sIgE was 96% (CI 95%: 86-99%), 75% (CI 95%: 67-75%) and 72% (CI 95%: 58-83%), respectively. Cross-reactivity with vecuronium was documented in 69% of the patients.

CONCLUSION

Skin testing merits the status of primary diagnostic investigation to document rocuronium allergy and cannot be substituted by quantification of sIgE or BAT. SIgE can offer a diagnostic advantage in cases where skin tests yield negative results. However, additional tests (e.g. BAT) are of capital importance in patients with negative skin tests and positive sIgE results to help in interpreting the clinical significance of a positive sIgE result. Optimal assessment of cross-reactivity between rocuronium and vecuronium implies both skin testing and BAT.

Standard ENT clinical evaluation of the sleep-disordered breathing patient; a consensus report

Sleep disordered breathing (SDB) patients usually undergo an ENT clinical examination before any therapeutic decision. This clinical examination would be predictive about the occurrence of Obstructive Sleep Apnea Syndrome, cost effective, reproducible and would determine the sites of obstruction in the upper airways. To achieve this, ENT specialists from Belgium, representatives of academic hospitals in the country, have tried to establish an updated work-up in the clinical evaluation of the SDB patients. History, risk factors evaluation, excessive daytime sleepiness, static and dynamic evaluation of the upper airways (velopharynx aspect, tonsils grading, Mallampati score, Müller's maneuver, fiberoptic evaluation) have been standardized in a consensus report easily accessible to the vast majority of ENT specialists. This consensus must be understood as a clinical work-up to perform before the monitoring of breathing during sleep.

Surgical treatment of the sleep-disordered breathing patient; a consensus report

Sleep disordered breathing patients may undergo surgical treatment after history, clinical examination and polysomnographic study if they demonstrate upper airway obstruction. This article focus on the surgical treatment designed for these patients. Sino-nasal surgery, rhinopharyngeal procedure, velopharyngeal procedures (Uvulopalato-pharyngoplasty, Laser assisted uvulopalatoplasty, Radiofrequency tissue volume reduction) as well as base of the tongue procedures were discussed among a panel of Belgian ENT specialists offering their experience in this field. Algorithm on corrective surgery as well as guidelines for postoperative management are proposed in the management of sleep disordered breathing patients.

Structure of the human serotonin 5-HT4 receptor gene and cloning of a novel 5-HT4 splice variant

Several variants of the serotonin 5-HT4 receptor are known to be produced by alternative splicing. To survey the existence and usage of exons in humans, we cloned the human 5-HT4 gene. Based on sequence analysis seven C-terminal variants (a-g) and one internal splice variant (h) were found. We concentrated in this study on the functional characterization of the novel splice variant h, which leads to the insertion of 14 amino acids into the second extracellular loop of the receptor. The h variant was cloned as a splice combination with the C-terminal b variant; therefore, we call this receptor 5-HT4(hb). This novel receptor variant was expressed transiently in COS-7 cells, and its pharmacological profile was compared with those of the previously cloned 5-HT4(a) and 5-HT4(b) isoforms, with the latter being the primary reference for the h variant. In competition binding experiments using reference 5-HT4 ligands, no significant differences were detected. However, the broadly used 5-HT4 antagonist GR113808 discriminated functionally among the receptor variants investigated. As expected, it was an antagonist on the 5-HT4(a) and 5-HT4(b) variant but showed partial agonistic activity on the 5-HT4(hb) variant. These data emphasize the importance of variations introduced by splicing for receptor pharmacology and may help in the understanding of conflicting results seen with 5-HT4 ligands in different model systems.

The tachykinin NK1 receptor antagonist, RP67580, inhibits the bradykinin-induced rise in intracellular Ca2+ concentration in bovine pulmonary artery endothelial cells

The bradykinin-induced rise in intracellular Ca2+ concentration ([Ca2+]i) and the bradykinin receptor involved in this response were characterized in bovine pulmonary artery endothelial cells. It was found that bradykinin induces an intracellular biphasic Ca2+ response, consisting of a transient peak followed by an elevated plateau phase. Both bradykinin and the bradykinin B1 receptor agonist, des-Arg9-bradykinin, induced a concentration-dependent increase in [Ca2+]i, but the bradykinin-induced rise was much greater. Moreover, the bradykinin-induced [Ca2+]i rise could be inhibited by the bradykinin B2 receptor antagonists, D-Arg0[Hyp3, Thi(5,8), D-Phe7]bradykinin and Hoe 140 (D-Arg[Hyp3, Thi5, D-Tic7, Oic8]bradykinin), but not by the bradykinin B1 receptor antagonist, des-Arg9-[Leu8]bradykinin. From these results it can be concluded that a bradykinin B2 receptor is involved in this response. Furthermore, we found that the tachykinin NK1 receptor antagonist, RP67580 ([imino 1 (methoxy-2-phenyl)-2 ethyl]-2 diphenyl 7,7 perhydroisoindolone-4 (3aR, 7aR)), and its negative enantiomer, RP68651 (2-[1-imino 2-(2 methoxy phenyl) ethyl] 7,7 diphenyl 4-perhydroisoindolone (3aS-7aS)), could inhibit the bradykinin-induced [Ca2+]i response, although no functional tachykinin NK1 receptors were found. Binding studies evidenced no binding of RP67580 or RP68651 to the bradykinin receptor. We conclude that RP67580 inhibits the bradykinin-induced rise in [Ca2+]i via a bradykinin B2 receptor-independent mechanism.

Cloning and expression of a human serotonin 5-HT4 receptor cDNA

Using a combination of library screening and nested PCR based on a partial human serotonin 5-HT4 receptor sequence, we have cloned the complete coding region for a human 5-HT4 receptor. The sequence shows extensive similarity to the published porcine 5-HT4A and rat 5-HT4L receptor cDNA; however, in comparison with the latter, we find an open reading frame corresponding to only 388 amino acids instead of 406 amino acids. This difference is due to a frame shift caused by an additional cytosine found in the human sequence after position 1,154. Moreover, we also found the same additional cytosine in the rat 5-HT4 sequence. We confirmed the occurrence of the sequence by examining this part of the sequence in genomic DNA of 10 human volunteers and in rat genomic DNA. Based on a part of the genomic 5-HT4 receptor sequence that was identified in the cloning process, there seem to be at least two possible splice sites in the coding region of the gene. The human 5-HT4 receptor, transiently expressed in COS-7 cells, showed radioligand binding properties similar to 5-HT4 receptors in guinea pig striatal tissue. [3H]GR 113808 revealed K(D) values of 0.15 +/- 0.01 nM for the human receptor and 0.3 +/- 0.1 nM in the guinea pig tissue. Binding constants were determined for four investigated 5-HT4 antagonists and three agonists, and appropriate binding inhibition constants were found in each case. Stimulation of transfected COS-7 cells with 5-HT4-specific agonists caused an increase in cyclic AMP levels.

In vivo cell kinetic measurements in human oesophageal cancer: what can be learned from multiple biopsies?

The importance of intratumour variability of cell kinetics was studied in 60 patients with cancer of the oesophagus. Five biopsies per tumour were taken. The labelling index, S-phase duration and potential doubling time (Tpot) were measured using flow cytometry. The mean Tpot value was 5.56 +/- 4.43 days (+/- 1S.D.) for adenocarcinomas and 4.40 +/- 2.45 days (+/- 1S.D.) for squamous cell carcinomas. These values were statistically significantly different. Although intratumour variation in Tpot measurements occurred, the intertumour variability was more important (P < 0.00001). This feature permits classification of tumours into slow and fast proliferating groups, leaving an intermediate group of tumours that could not be unequivocally categorised. The relative distribution of tumours into these three categories depends on the intratumour and intertumour variability of Tpot, and on the cut-off values used. Increasing the number of biopsies from one to five reduces the number of non-classifiable tumours.

Eosinophilic granuloma of the head and neck: CT and MRI features in three cases

We report the radiological findings and more specifically the MRI features in three typical cases of Langerhans' cell histiocytosis of the head and neck. All three cases were of solitary eosinophilic granuloma of bone: two mandibular and one temporal bone lesion. Reports on the MRI features of head and neck eosinophilic granulomas are rare.

Predictability of the individual outcome of a physical training program of an Army Special Forces Unit

In a search for parameters that could predict the chances of success in a 3-month basic training program of a Special Forces unit, 293 conscripts were studied before the start of the training period. Physical activities, smoking habits, and dietary and drinking habits were evaluated by questionnaire. Anthropometric values were noted. A blood sample was taken for determination of serum cholesterol, high-density lipoprotein (HDL)-cholesterol and gamma-glutamyltranspeptidase (GGT). Physical capacity was assessed by bicycle ergometry. Sixty-five trainees were discontinued from the program for intercurrent diseases or trauma, 132 went successfully through the whole program (group S), and 96 trainees failed (group F). More candidates of group S stated that they participated in sports (p less than 0.01) and fewer smoked (p less than 0.01) than in group F. Trainees of group F had a higher consumption of spirits (p less than 0.05) than trainees of group S. There was no difference between the two groups in weight, percentage body fat, physical capacity, total serum cholesterol, and GGT values. HDL-cholesterol was higher in group S compared to group F (p less than 0.01). Stepwise discriminant analysis applied to anthropometric, biochemical, and cycloergometric data indicated HDL-cholesterol, height, resting heart rate, heart frequency at maximal exercise, and serum cholesterol as significant discriminating variables (p less than 0.001), giving only a 63% chance of correctly classifying the candidates.

In vitro pharmacological profile of 3-N-(2-fluoroethyl)spiperone

The binding affinities of spiperone and 3-N-(2-fluoroethyl)spiperone (FESP) have been compared for several rodent brain receptor sites and for inhibition of monoamine release and uptake sites. FESP and spiperone have almost identical profiles, namely a high affinity for dopamine-D2 and serotonin-S2 receptors, a low affinity for alpha 1-adrenergic receptors, and negligible binding to other sites. These results suggest that available data on spiperone binding may be applied to the interpretation of PET data obtained with FESP.

Evidence for functional 5-HT2 receptor sites on human blood platelets

The aggregation of normal human platelets by 5-hydroxytryptamine (5-HT) is the result of a specific interaction of the monoamine with a platelet receptor since it is not influenced by adrenergic receptor blockade, inhibition of fatty acid cyclo-oxygenase or ADP-scavenging. The 5-HT induced platelet reaction is inhibited in a concentration-dependent way by various serotonergic antagonists; the potency of these compounds in this respect correlates strongly with their potential to inhibit the specific binding of [3H] ketanserin, a selective label for 5-HT2 binding sites, to rat prefrontal cortex and striatum and to cat platelet membranes. This study thus provides evidence for a functional role as true receptor initiating a physiological response of the 5-HT2 receptor on human platelets.

Problems in in vitro receptor binding studies and identification and role of serotonin receptor sites

The principles and problems in neurotransmitter receptor radioligand binding studies are discussed. Various types of ligand-membrane interactions are described and criteria and ways for identification of specific receptor binding sites are evaluated. It is questioned whether the endogenous neurotransmitters must have binding affinities of nanomolar order for their receptor sites. The relationship between the numbers of receptor binding sites and functional activity of the receptors is investigated. Serotonin-S1 binding sites are sites labelled at nanomolar concentrations by [3H]serotonin. Various alleged roles for these sites are considered and found to be insufficiently substantiated. Therefore these sites should not yet be regarded as receptor sites. Serotonin-S2 binding sites are sites labelled by potent serotonin antagonists. The sites show a typical distribution in the mammalian brain and are present on blood platelets. The neuronal localization of the sites, investigated by lesion studies is discussed. Serotonin-S2 sites have a role in serotonin-induced behavioural excitation in laboratory animals. A presumed role for the sites in depression and anxiety is to be investigated. Serotonin-S2 sites were also shown to mediate serotonin-induced vasoconstriction and platelet aggregation. The sites were hypothesized from pharmacological and electrophysiological studies. Appropriate tools are lacking for a clear characterization of the multiple sites.

The involvement of 5-HT2-receptor sites in the activation of cat platelets

5-Hydroxytryptamine (5-HT) induces a concentration-dependent aggregation/release of/by cat platelets (Km = 6.2 x 10(-7) M); this activation is inhibited (Ki = 5.24 x 10(-9) M) or reversed by ketanserin, a selective 5-HT2 receptor antagonist. Comparison of the inhibition of specific [3H] ketanserin binding to cat platelet membranes and rat pre-frontal cortex membranes with that of 5-HT-induced aggregation of cat platelets obtained with various drugs, displaying various receptor binding profiles, reveals a highly significant correlation between the ligand binding and the physiological response (Spearman correlation coefficient r = 0.92 and r = 0.91 respectively, p less than 0.0001; n = 14); inhibition of platelet activation by 5-HT and of uptake of 5-HT are not correlated. Secondary aggregation induced by ADP as well as collagen-induced aggregation are inhibited by the 5-HT receptor antagonists suggesting a primary role of 5-HT in the secondary platelet recruitment subsequent to a release reaction. This study demonstrates a functional role for the 5-HT2 receptors in the primary activation of the platelets by 5-HT and in the secondary aggregation induced by other agonists, especially in platelets superreactive to 5-HT2 receptor activation.

Narcotic dosage and central nervous system opiate receptor binding

Increasing doses of lofentanil (0, 0.08, 0.16, 0.31, 0.63, 1.25, 2.50, 5.00, and 10.0 micrograms/kg), a potent long-acting narcotic, were administered intravenously to rats to examine the relationship among narcotic dosage, degree of analgesia (inhibition of tail withdrawal reflex), anesthesia (no response to bone-crush injury), and central nervous system (CNS) opiate-receptor occupancy (inhibition of [3H] sufentanil binding). Our results demonstrate that increasing doses of lofentanil produce increasing analgesia and anesthesia and eventually complete opiate receptor occupancy. Analgesia occurs with doses of lofentanil (0.31 micrograms/kg) that result in levels of CNS opiate-receptor binding too low to be measured and anesthesia occurs with doses of lofentanil (1.25 micrograms/kg) that produce occupancy of about 25% of the available opiate receptors in subcortical areas and cortex. These findings in rats cannot be applied to narcotic usage in humans, but the data do indicate that in rats a dose eight times the anesthetic dose of lofentanil is needed to saturate virtually all available CNS opiate receptors (10.0 micrograms/kg). Whether saturation of most or all available CNS opiate receptors during narcotic anesthesia is of clinical importance remains to be determined.

Differentiation of opiate and neuroleptic receptor binding in rat brain

For 6 large series of compounds derived from the piperidine moieties of spiperone, pimozide, haloperidol, pethidine, fentanyl and 4-methocarboxy-fentanyl, IC50 values were determined in the opiate and neuroleptic binding assay using [3H]-fentanyl and [3H]-haloperidol as ligands, respectively. The specificity and difference between both receptors were demonstrated on the basis of several criteria (1) the sterospecificity of the binding (2) the significant correlation between the in vitro activity of the drugs and their pharmacological potency in vivo, not withstanding some discrepancies which are probably of pharmacokinetic and/or metabolic origin (3) the ability to discriminate between morphinomimetic and neuroleptic drugs by the differential affinity for their specific receptro (4) the structure--activity relationships derived from the in vitro data indicating that the structural requirements for high affinity binding in vitro parallel those for high in vivo potency (5) a demonstration, on the basis of physicochemical principles, of the difference in binding mechanism between morphinomimetics and neuroleptics to their respective receptor.

Specific effect of haloperidol on dopamine turnover in the frontal cortex

A single injection of haloperidol (0.08 mg/kg) produced marked increases in HVA in rabbit brain. Of the dopamine-containing areas studied, the elevation of HVA was significantly greater in the frontal cortex than in the striatum, the tuberculum olfactorium or the parietal cortex. After chronic treatment, a tolerance phenomenon to the effects of haloperidol on HVA was observed only in the striatal and limbic areas. The present results suggest that the frontal cortex may be a preferential target for the antipsychotic activity of neuroleptic agents.

Discrimination of narcotic drugs on 3H-fentanyl receptor binding

Stereospecific opiate receptor binding was measured using specifically labeled fentanyl in the presence of an excess of either dextromoramide or levomoramide, only the former being the analgesic isomer. In a very large series of chemically related drugs, but of different pharmacological activity, it was possible to recognize compounds endowed with a potential morphine-like activity. Attempts were made to localize the opiate receptors within the neuronal cell.

Identification of alkaloids; the condensation products of biogenic amines with formaldehyde, enzymatically formed from 5-methyltetrahydrofolic acid

The use of thin-layer chromatography has demonstrated that incubations of indoleamines with 5-methyl[14-C]tetrahydrofolic acid and an enzyme previously described as an N-methyltransferase, do not yield Nw, N1, or O-methylated products. Further elucidation by thin-layer chromatography, gas chromatography, mass spectrometry and selected ion monitoring enabled us to identify the reaction products as tetrahydroisoquinolines and tetrahydro-beta-carbolines in mixtures incubated respectively with catecholamines and indoleamines in the presence of 5-methyl[14-C]tetrahydrofolic acid and enzyme. The alkaloids have been shown to originate from a spontaneous condensation of the corresponding amines with formaldehyde, this latter being formed in the first stage of the reaction by enzymatic conversion from 5-methyltetrahydrofolic acid.

Ontogenetic development of a 5-methyltetrahydrofolate requiring enzyme in rats and mice

Developmental characteristics of 5-methyltetrahydrofolate requiring N-methyltransferase (5 MT-NMT) have been studied in rats and mice and compared to the development pattern of marker enzymes. In rat and mouse brain, the 5 MT-NMT activity expressed in units per mg protein, was found to decrease rapidly during the first five days after birth and then more slowly, whereas two other enzymes, dopa-decarboxylase and histamine N-methyltransferase increased gradually during maturation. In kidney, the ontogenetic development of 5 MT-NMT was first characterized by an increasing activity from birth until a different age, depending on the species, and then followed by an abrupt decline. In contrast to this, histamine N-methyltransferase activity in mouse kidney was about 60 times higher at maturity than at birth. When the enzyme activities are expressed in units per g tissue, the changes in the course of the development of 5 MT-NMT were less apparent, but in any way differed markedly from those of dopa-decarboxylase and histamine N-methyltransferase. The results suggest that 5 MT-NMT does not behave as a synaptosomal or perhaps even as a neuronal enzyme. Although its physiological role remains to be elucidated, it must have a more general function in the cellular economy than merely N-methylating biogenic amines.