Impact of modified-release opioid use on clinical outcomes following total hip and knee arthroplasty: a propensity score-matched cohort study.

Modified-release opioids are often prescribed for the management of moderate to severe acute pain following total hip and knee arthroplasty, despite recommendations against their use due to increasing concerns regarding harm. The primary objective of this multicentre study was to examine the impact of modified-release opioid use on the incidence of opioid-related adverse events compared with immediate-release opioid use, among adult inpatients following total hip or knee arthroplasty. Data for total hip and knee arthroplasty inpatients receiving an opioid analgesic for postoperative analgesia during hospitalisation were collected from electronic medical records of three tertiary metropolitan hospitals in Australia. The primary outcome was the incidence of opioid-related adverse events during hospital admission. Patients who received modified with or without immediate-release opioids were matched to those receiving immediate-release opioids only (1:1) using nearest neighbour propensity score matching with patient and clinical characteristics as covariates. This included total opioid dose received. In the matched cohorts, patients given modified-release opioids (n = 347) experienced a higher incidence of opioid-related adverse events overall, compared with those given immediate-release opioids only (20.5%, 71/347 vs. 12.7%, 44/347; difference in proportions 7.8% [95%CI 2.3-13.3%]). Modified-release opioid use was associated with an increased risk of harm when used for acute pain during hospitalisation after total hip or knee arthroplasty.

Impact of an Australian/New Zealand organisational position statement on extended-release opioid prescribing among surgical inpatients: a dual centre before-and-after study.

Extended-release opioids are often prescribed to manage postoperative pain despite being difficult to titrate to analgesic requirements and their association with long-term opioid use. An Australian/New Zealand organisational position statement released in March 2018 recommended avoiding extended-release opioid prescribing for acute pain. This study aimed to evaluate the impact of this organisational position statement on extended-release opioid prescribing among surgical inpatients. Secondary objectives included predictors and clinical outcomes of prescribing extended-release opioids among surgical inpatients. We conducted a retrospective, dual centre, 11-month before-and-after study and time-series analysis by utilising electronic medical records from two teaching hospitals in Sydney, Australia. The primary outcome was the proportion of patients prescribed an extended-release opioid. For surgical patients prescribed any opioid (n = 16,284), extended-release opioid prescribing decreased after the release of the position statement (38.4% before vs. 26.6% after, p < 0.001), primarily driven by a reduction in extended-release oxycodone (31.1% before vs. 14.1% after, p < 0.001). There was a 23% immediate decline in extended-release opioid prescribing after the position statement release (p < 0.001), followed by an additional 0.2% decline per month in the following months. Multivariable regression showed that the release of the position statement was associated with a decrease in extended-release opioid prescribing (OR 0.54, 95%CI 0.50-0.58). Extended-release opioid prescribing was also associated with increased incidence of opioid-related adverse events (OR 1.52, 95%CI 1.35-1.71); length of stay (RR 1.44, 95%CI 1.39-1.51); and 28-day re-admission (OR 1.26, 95%CI 1.12-1.41). Overall, a reduction in extended-release opioid prescribing was observed in surgical inpatients following position statement release.

The Mouse Tumor Biology Database (MTB): a central electronic resource for locating and integrating mouse tumor pathology data.

The Mouse Tumor Biology Database (MTB) is designed to provide an electronic data storage, search, and analysis system for information on mouse models of human cancer. The MTB includes data on tumor frequency and latency, strain, germ line, and somatic genetics, pathologic notations, and photomicrographs. The MTB collects data from the primary literature, other public databases, and direct submissions from the scientific community. The MTB is a community resource that provides integrated access to mouse tumor data from different scientific research areas and facilitates integration of molecular, genetic, and pathologic data. Current status of MTB, search capabilities, data types, and future enhancements are described in this article.

Structure of nitrilotriacetate monooxygenase component B from Mycobacterium thermoresistibile.

Mycobacterium tuberculosis belongs to a large family of soil bacteria which can degrade a remarkably broad range of organic compounds and utilize them as carbon, nitrogen and energy sources. It has been proposed that a variety of mycobacteria can subsist on alternative carbon sources during latency within an infected human host, with the help of enzymes such as nitrilotriacetate monooxygenase (NTA-Mo). NTA-Mo is a member of a class of enzymes which consist of two components: A and B. While component A has monooxygenase activity and is responsible for the oxidation of the substrate, component B consumes cofactor to generate reduced flavin mononucleotide, which is required for component A activity. NTA-MoB from M. thermoresistibile, a rare but infectious close relative of M. tuberculosis which can thrive at elevated temperatures, has been expressed, purified and crystallized. The 1.6 Å resolution crystal structure of component B of NTA-Mo presented here is one of the first crystal structures determined from the organism M. thermoresistibile. The NTA-MoB crystal structure reveals a homodimer with the characteristic split-barrel motif typical of flavin reductases. Surprisingly, NTA-MoB from M. thermoresistibile contains a C-terminal tail that is highly conserved among mycobacterial orthologs and resides in the active site of the other protomer. Based on the structure, the C-terminal tail may modulate NTA-MoB activity in mycobacteria by blocking the binding of flavins and NADH.

The Mouse Gene Expression Database (GXD).

The Gene Expression Database (GXD) is a community resource of gene expression information for the laboratory mouse. By combining the different types of expression data, GXD aims to provide increasingly complete information about the expression profiles of genes in different mouse strains and mutants, thus enabling valuable insights into the molecular networks that underlie normal development and disease. GXD is integrated with the Mouse Genome Database (MGD). Extensive interconnections with sequence databases and with databases from other species, and the development and use of shared controlled vocabularies extend GXD's utility for the analysis of gene expression information. GXD is accessible through the Mouse Genome Informatics web site at http://www.informatics.jax.org/ or directly at http://www.informatics.jax.org/menus/expression_menu. shtml.

Association of melanoma tumor antigen activity with beta2-microglobulin.

The majority of melanoma tumor antigen activity present in melanoma extracts derived from fresh tumor tissue binds to a Sepharose-anti-beta2-microglobulin adsorbent. Removal of HLA antigens from the extracts of melanoma tissue by using a KBr flotation technique did not reduce either the tumor antigen activity of the extracts or the binding of melanoma tumor antigen (MTA) activity to the Sepharose-anti-beta2-microglobulin adsorbent. The complete blocking of MTA activity by pretreating the anti-beta2-microglobulin adsorbent with beta2-microglobulin and the lack of detectable MTA binding to a Sepharose anti-normal human serum adsorbent demonstrated the specificity of the binding of MTA to the anti-beta2-microglobulin adsorbent.

Myocardial bridging does not predict sudden death in children with hypertrophic cardiomyopathy but is associated with more severe cardiac disease.

OBJECTIVES: We sought to examine the association between systolic compression of sections of epicardial coronary vessels (myocardial bridging) with myocardial perfusion abnormalities and clinical outcome in children with hypertrophic cardiomyopathy (HCM). BACKGROUND: It has recently been suggested that myocardial bridging is an important cause of myocardial ischemia and sudden death in children with HCM. METHODS: Angiograms from 57 children with HCM were reviewed for the presence of bridging (50% or more maximum systolic arterial compression). QT interval indices, echocardiographic and cardiac catheterization findings, treadmill exercise tests, exercise thallium scintigraphy, Holter monitoring and electrophysiologic study findings were compared in children with and without bridging. The findings were also related to the presence or absence of compression of septal branches of the left anterior descending artery (LAD). RESULTS: Bridging was present in 23 (40%) of the children. Multiple coronary arteries were involved in four children. Bridging involved the LAD in 16 of 28 (57%) affected vessels. Myocardial perfusion abnormalities were present in 14 of 30 (47%) children without bridging and in 17 of 22 (94%) children with bridging, p = 0.002. However, bridging was associated with more severe septal hypertrophy (19+/-8 mm vs. 28+/-8 mm, p < 0.001), a higher septum:posterior wall thickness ratio (2.7+/-1.2 vs. 1.8+/-0.9, p < 0.001), and higher left ventricle (LV) outflow gradient (45+/-37 mm Hg vs. 16+/-28 mm Hg, p = 0.002). Compression of septal LAD branches was present in 37 (65%) of the children and was significantly associated with bridging, severity of LV hypertrophy and outflow obstruction. Multivariate analysis demonstrated that LV septal thickness and septal branch compression, and not bridging, were independent predictors of thallium perfusion abnormalities. There was a 90% power at 5% significance to detect an effect of bridging on thallium abnormalities at an odds ratio of 3. Bridging was also not associated with significantly greater symptoms, increased QT and QTc intervals and QTc dispersion, ventricular tachycardia on Holter or induced at EP study, or a worse prognosis. CONCLUSIONS: Bridging and compression of septal branches of the LAD are common in HCM children and are related to magnitude of LV hypertrophy. Left ventricular hypertrophy and compression of intramyocardial branches of the epicardial coronary arteries may contribute to myocardial perfusion abnormalities. Our findings suggest that bridging does not result in myocardial ischemia and may not cause arrhythmias or sudden death in HCM children.

Carrier-mediated delivery of metabotrophic glutamate receptor ligands to the central nervous system: structural tolerance and potential of the L-system amino acid transporter at the blood-brain barrier.

The brain endothelial large neutral amino acid carrier (L-system) is well suited for facilitated drug transport to the brain because of its high transport capacity and relatively broad structural substrate tolerance. The authors have examined the potential of this transporter for central nervous system (CNS) delivery of a new family of compounds derived from the large neutral amino acid phenylglycine. These compounds are highly selective for specific isoforms of metabotropic glutamate receptors (mGluRs) but will only become effective therapeutics for CNS diseases such as ischemic disorders, stroke, and epilepsy if they can effectively cross the blood-brain barrier. Using the immortalized rat brain endothelial cell line RBE4 as in vitro blood-brain barrier model, the authors have studied the interaction of phenylglycine and selected derivatives with the L-system-mediated transport of L-[3H]-histidine. The transport of L-histidine was characteristic of the L-system in vivo with the following kinetic parameters: Km 135 +/- 18 micromol/L, Vmax 15.3 +/- 1.13 nmol/min/mg protein, and K(D) 2.38 +/- 0.84 microL/min/mg protein. The affinities of the L-system for phenylglycine and the derivatives investigated increased in the order S-4-carboxyphenylglycine (Ki = 16 mmol/L) < R-phenylglycine (2.2 mmol/L) < S-3-hydroxy-phenylglycine (48 micromol/L) < S-phenylglycine (34 micromol/L), suggesting that a negative charge at the side chain or R-configuration is detrimental for carrier recognition, whereas neutral side chain substituents are well tolerated. The authors have further shown (1) that the mode of interaction with the L-system of S-phenylglycine and S-3hydroxy-phenylglycine is competitive, and (2) that the transporter carries these two agents into the cell as shown by high-performance liquid chromatography (HPLC) analysis of the RBE4 cell contents. The study provides the first evidence for the potential of S-phenylglycine derivatives for carrier-mediated delivery to the CNS and outlines the substrate specificity of the L-system at the blood-brain barrier for this class of mGluR ligands. As the affinities of S-phenylglycine and S-3-hydroxy-phenylglycine for the L-system carrier are even higher than those of some natural substrates, these agents should efficiently enter CNS via this route. Possible strategies for a synergistic optimization of phenylglycine-derived therapeutics with respect to desired activity at the CNS target combined with carrier-mediated delivery to overcome the blood-brain barrier are discussed.

Identification and sequence of human PKY, a putative kinase with increased expression in multidrug-resistant cells, with homology to yeast protein kinase Yak1.

We have previously shown that several protein kinases are present in higher activity levels in multidrug resistant cell lines, such as KB-V1. We have now isolated a gene that codes for a putative protein kinase, PKY, of over 130 kDa that is expressed at higher levels in multidrug-resistant cells. RNA from KB-V1 multidrug-resistant cells was reverse-transcribed and amplified by using primers derived from consensus regions of serine threonine kinases and amplified fragments were used to recover overlapping clones from a KB-V1 cDNA library. An open reading frame of 3648 bp of DNA sequence predicting 1215 aa, has been identified. This cDNA hybridizes to a mRNA of about 7 kb which is expressed at high levels in human heart and muscle tissue and overexpressed in drug-resistant KB-V1 and HL60/ADR cells. Because its closest homolog is the yeast serine/threonine kinase, Yak1, we have called this gene PKY. PKY is also related to the protein kinase family that includes Cdks, Gsk-3, and MAPK proline-directed protein kinases. This protein represents the first of its type known in mammals and may be involved in growth control pathways similar to those described for Yak1, as well as possibly playing a role in multidrug resistance.

Peptides and the blood-brain barrier: the status of our understanding.

In this limited review, it has only been possible to highlight some of the more significant interactions of peptides with the blood-brain barrier. The literature has been reviewed extensively in recent years, and the major reviews are included in the references. Certainly one of the major outstanding problems is an elucidation of the precise mechanism(s) by which centrally active peptides produce their effects. Without question peripherally administered peptides are able to modify central nervous activity; and for a rapidly growing number of peptides, an extraction by the cerebral endothelial cells can be demonstrated. For some of these peptides, the extraction involves highly specific transporters. What is far less clear is whether this internalization of peptide into the endothelial cells is the first step in a process of transcytosis, with an eventual abluminal exocytosis into brain extracellular fluid of the intact peptide, or an active fragment or whether their entry into brain extracellular fluid is via a different route. If, on the other hand, the mechanism of central action is via the circumventricular organs, a general entry into brain extracellular fluid may not be required. Clearly for different peptides the route and mechanism of action will differ and future attention should be focused on the precise mechanisms producing the central effects of defined peptides.

Changes in amino acid levels in rat plasma, cisternal cerebrospinal fluid, and brain tissue induced by intravenously infused arginine-vasopressin.

Circulating arginine-vasopressin (AVP) is known to reduce the blood-to-brain transfer of large neutral amino acids (AA). As a first step to examine whether the reduced uptake by brain endothelial cells is reflected in changes in large neutral amino acid levels of the extracellular fluid environment of cells within the nervous tissue, we measured the concentrations of amino acids in plasma, cerebrospinal fluid (CSF), and hippocampal tissue of rats before and after infusion of AVP (34 and 68 ng/min/kg, respectively) over the time period of 60 min. AA levels changed in all compartments investigated during both saline and AVP infusions. Whereas in the saline-infused controls changes in CSF AA levels paralleled those in plasma, this correlation was abolished by raising AVP concentrations. The effect of AVP was found to be i) dependent on the AA, ii) different with respect to direction and iii) magnitude of changes in AA levels, and iv) in some cases dose dependent. In summary, AVP infusion increased plasma levels of 10 AA, but decreased all 15 AA measured by some 30% in CSF. In contrast to CSF, levels of AA were slightly enhanced in the hippocampal tissue. The results are not solely explicable by a reduced blood-to-brain transfer of AA. We conclude that further mechanisms by which AVP affects the availability of AA to the brain may exist. The physiological significance of the findings might be related to brain osmoregulation, especially in situations of stress.

Saturable mechanism for delta sleep-inducing peptide (DSIP) at the blood-brain barrier of the vascularly perfused guinea pig brain.

Cellular uptake of [125I] labelled DSIP at the luminal interface of the blood-brain barrier (BBB) was studied in the ipsilateral perfused in situ guinea pig forebrain. Regional unidirectional transfer constants (Kin) calculated from the multiple-time brain uptake analysis were 0.93, 1.33 and 1.66 microliter.min-1 g-1 for the parietal cortex, caudate nucleus and hippocampus, respectively. In the presence of 7 microM unlabelled DSIP the brain uptake of [125I]-DSIP (0.3 nM) was inhibited, the values of Kin being reduced to 0.23-0.38 microliter.min-1 g-1, values that were comparable with the Kin for mannitol. The rapidly equilibrating space of brain, measured from the intercept of the line describing brain uptake versus time on the brain uptake ordinate, Vi, was greater for [125I]-DSIP than for mannitol; in the presence of unlabelled DSIP this was reduced to that of mannitol, and it was suggested that the larger volume for [125I]-DSIP represented binding at specific sites on the brain capillary membrane. L-tryptophan, the N-terminal residue of DSIP, in concentrations of 7 microM and 1 mM, inhibited Kin without affecting Vi. A moderate inhibition of Kin was obtained by vasopressin ([Arg8]-VP), but only at a concentration as high as 0.2 mM. The results suggest the presence of a high affinity saturable mechanism for transport of DSIP across the blood-brain barrier, with subsequent uptake at brain sites that are highly sensitive to L-tryptophan, and may be modulated by [Arg8]-VP.

Arginine vasopressin reduces the blood-brain transfer of L-tyrosine and L-valine: further evidence of the effect of the peptide on the L-system transporter at the blood-brain barrier.

Arginine vasopressin (AVP) coinjected into the carotid artery in physiological concentrations (0.1 nmol/l), with either L-[3H]tyrosine or L-[3H]valine, induced changes in the kinetic parameters of the blood-to-brain transfer of both large neutral amino acids (LNAA) without alterations in brain haemodynamics. The half-saturation constant (Km), the maximum velocity of transport (V(max)) and Kd, the nonsaturable transport constant, were estimated in 9 brain regions of male Wistar rats anaesthetized with ether. Apart from Kd, significant changes in Km and V(max) were observed in all brain regions investigated. On average Km decreased from 0.17 to 0.048 mmol/l for tyrosine, and from 0.61 to 0.059 mmol/l for valine, whereas V(max) declined from 22 to 9.9 nmol/min/g for tyrosine, and from 29 to 3.2 nmol/min/g for valine, respectively. The results provide further evidence that vasopressin-receptor interactions at the blood-brain barrier (BBB) induce changes in the properties of the common transporter, the L-system, which eventually result in a suppression of the blood-to-brain transfer of LNAA. Data analysis of the 5 LNAA tested so far reveals a significant negative correlation (R = 0.98, P < 0.05) between the respective substrate affinity for the transporter and the corresponding magnitude of transport reduction induced by circulating AVP. Calculations of the unidirectional influx (J) of the LNAA indicate that AVP (1) reduces J by approximately one-third for every LNAA, but (2) does not change the relative contribution for each single LNAA to the total influx across the BBB.

Blood-brain barrier permeability to dipeptides and their constituent amino acids.

The penetration of two [14C]-labelled dipeptides, glycyl-L-phenylalanine and glycyl-L-leucine, and of their constituent amino acids into the brain of the rat was measured employing an intracarotid injection technique. The brain-uptakes of the dipeptides were about equal to that of sucrose suggesting a negligible extraction from the blood during the 15-s period of exposure to the peptides. Brain uptakes for L-phenylalanine and L-leucine were large and in agreement with earlier work on these amino acids; self-inhibition by unlabelled amino acids was marked as also inhibition by the typical L-transport system substrate, 2-aminobicyclo (2, 2, 1) heptane-2 carboxylic acid (BCH), whilst the substrate for the A-system, N-methyl-L-aminoisobutyric acid (MeAIB) was without effect. Uptake of L-phenylalanine and L-leucine was not inhibited by dipeptides in 10 mM concentration. The uptakes of [14C]-labelled MeAIB and glycine were not significantly different from that of sucrose. It is concluded that peptide formation effectively excludes the rapidly penetrating L-system amino acids, L-leucine and L-phenylalanine, from access to the L-system channel.

S-adenosylmethionine is substrate for carrier mediated transport at the blood-brain barrier in vitro.

S-adenosylmethionine (SAM) is the sole methyl donor in the CNS where it is involved in a multitude of biochemical reactions. Peripherally administered SAM has been shown to increase SAM levels in cerebrospinal fluid and is reported to be effective in the treatment of numerous neurological disorders suggesting SAM crosses the blood-brain barrier (BBB). The mechanism of SAM entry into the brain remains unknown, but the presence of adenosyl and methionine residues in the molecule suggests probable entry via carrier mediated transport. We have investigated whether SAM utilises endogenous transport systems in cerebral endothelial cells, using RBE4 cells, an in vitro model of the BBB. SAM did not influence the transport of [(3)H]-methionine and only marginally reduced the uptake of [(3)H]-leucine in RBE4 cells. The inhibition constant for the latter was 2.11+/-0.29 mM (mean+/-S.E.M.). However, increasing concentrations of SAM strongly inhibited the transport of [3H]-adenosine in RBE4 cells in both the presence and the absence of sodium in the medium, with K(i) values of 199+/-32 and 139+/-8.4 microM, respectively. Lineweaver-Burk plots suggest a competitive mode of inhibition. The findings suggest that SAM is not recognised by the L-system transporter for large neutral amino acids at the brain endothelium. A significant interaction with the transport of adenosine, however, indicates that SAM has affinity for the nucleoside carrier systems; this is within the range of K(m) values of natural substrates and suggest that SAM may enter the CNS via the Na(+)-independent nucleoside carrier systems at the brain capillary endothelium.

Blood-brain barrier permeability to leucine-enkephalin, D-alanine2-D-leucine5-enkephalin and their N-terminal amino acid (tyrosine).

The permeability of the blood-brain barrier to [tyrosyl-3,5-3H]enkephalin-(5-L-leucine) (abbreviated to Leu-Enk) and of its synthetic analogue D-alanine2-[tyrosyl-3,5-3H]enkephalin-(5-D-leucine) (abbreviated to D-Ala2-D-Leu5-Enk) was studied, in the adult rat, by means of Oldendorf's27 intracarotid injection technique. The brain uptake index (BUI) corrected for residual vascular radioactivity was about the same for both peptides, indicating a low extraction from the blood during a 5- or 15-s period of exposure to the peptides. Transport of Leu-Enk was not saturated by unlabelled Enk at a concentration as high as 5 mM but was completely abolished by 5mM tyrosine and by the inhibitor of aminopeptidase activity, bacitracin (2 mM). Also the typical L-transport system substrate, 2-aminobicyclo(2,2,1)heptane-2 carboxylic acid (BCH)9 at 10 mM concentration markedly reduced (by 80%) Leu-Enk uptake by the brain. In contrast, brain uptake of D-Ala2-D-Leu5-Enk was reduced only to about one-half of its control value by bacitracin or by 25% by BCH. Brain uptake for L-tyrosine was typically large and markedly inhibited by BCH but not inhibited by 5 mM unlabelled Leu-Enk. These results show that the measurable but low first-pass extractions for enkephalins are not representative of the uptake of these peptides into the brain, but rather reflect their extreme sensitivity to enzymatic degradation with a release of the N-terminal tyrosine residue. The results also suggest that small amounts of D-Ala2-D-Leu5-Enk might cross the blood-brain barrier in an intact form.(ABSTRACT TRUNCATED AT 250 WORDS)

Permeability of the blood-cerebrospinal fluid and blood-brain barriers to thyrotropin-releasing hormone.

The permeability of the blood-cerebrospinal fluid (CSF) barrier to 3H-labelled thyrotropin-releasing hormone (TRH), was studied at the blood-tissue interface of the isolated perfused choroid plexus of the sheep, using a rapid (less than 30 s), single circulation paired-tracer dilution technique, in which D-[14C]mannitol serves as an extracellular marker. Arterio-venous loss of 14C radioactivity reflects the percentage of the D-mannitol dose that crosses the blood-CSF barrier using a non-specific pathway. This loss suggests that the choroidal epithelium is moderately leaky. Cellular uptake of TRH, estimated by directly comparing venous dilution profiles of [3H]TRH and D-[14C]mannitol was independent of this leakiness. The unidirectional transport of TRH could not be saturated with unlabelled TRH at a concentration as high as 10 mM, but was markedly reduced by 10 mM proline and by the inhibitor of amidase and aminopeptidase activity, bacitracin (2 mM). Permeability of the blood-brain barrier to [3H]TRH was studied in the adult rat, employing the intracarotid injection technique of Oldendorf in which [14C]butanol served as an 'internal standard'. Brain-uptake of 3H radioactivity corrected for residual vascular space indicated a low extraction from the blood of TRH during a 15 s period of exposure to the peptide. Self-inhibition of [3H]TRH uptake by unlabelled TRH (10 mM) could not be demonstrated, but L-proline (10 mM) and bacitracin (2 mM) strongly inhibited this uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic amphetamine intoxication and the blood-brain barrier permeability to inert polar molecules studied in the vascularly perfused guinea pig brain.

The brain vascular perfusion method, with a multiple-time brain uptake analysis, has been employed to study the effects of chronic amphetamine intoxication on the kinetics of entry of 2 inert polar molecules, D-[14C]mannitol (mol.wt. 180) and [3H]polyethylene glycol (PEG, mol.wt. 4000) into the forebrain of the guinea pig. The unidirectional transfer constants, Kin, determined from graphic analysis 14 and 20 days after chronic amphetamine treatment (5 mg/kg daily, i.p.) showed a marked time-dependent progressive enhancement of transfer for both molecules. The kinetic features of this entry suggest the opening up of pathways through the blood-brain barrier (BBB) which allows mannitol and PEG to pass into the brain at rates which are irrespective of their molecular size and/or lipophilia and these changes cannot be attributed to simple mechanical factors such as hypertension. This opening of the BBB was associated with changes in behaviour (increased locomotor activity, stereotypy, hypervigilance, social withdrawal, and loss of weight) seen in 14- and 20-day amphetamine-treated animals. At 7 and 28 days after the withdrawal of the amphetamine treatment, the behavioural manifestations were absent, and the Kin values for both molecules were not significantly different from those measured in normal control animals which had been treated with placebo injections. The present results suggest a reversible dysfunction of the BBB as a consequence of the chronic amphetamine intoxication which correlates with the behavioural syndrome induced in the guinea pig.

Interaction of poly(butylcyanoacrylate) nanoparticles with the blood-brain barrier in vivo and in vitro.

Poly(butylcyanoacrylate) nanoparticles were produced by emulsion polymerisation and used either uncoated or overcoated with polysorbate 80 (Tween 80). [3H]-dalargin bound to nanoparticles overcoated with polysorbate 80 or in the form of saline solution was injected into mice and the brain concentrations of radioactivity determined. Statistically significant, three-fold higher brain concentrations with the nanoparticle preparations were obtained after 45 minutes, the time of greatest pharmacological response assessed as analgesia in previous experiments. In addition the brain inulin spaces in rats and the uptake of fluoresceine isothiocyanate labelled nanoparticles in immortalised rat cerebral endothelial cells, (RBE4) were measured. The inulin spaces after i.v. injection of polysorbate 80-coated nanoparticles were significantly increased by 1% compared to controls. This is interpreted as indicating that there is no large scale opening of the tight junctions of the brain endothelium by the polysorbate 80-coated nanoparticles. In in vitro experiments endocytic uptake of fluorescent nanoparticles by RBE4 cells was only observed after polysorbate 80-overcoating, not with uncoated particles. These results further support the hypothesis that the mechanism of blood-brain barrier transport of drugs by polysorbate 80-coated nanoparticles is one of endocytosis followed by possible transcytosis. The experiments were conducted in several laboratories as part of an EEC/INTAS collaborative program. For various procedural and regulatory reasons this necessitated the use of both rats and mice as experimental animals. The brain endothelial cell line used for the in vitro studies is the rat RBE4.

Affinity for the P-glycoprotein efflux pump at the blood-brain barrier may explain the lack of CNS side-effects of modern antihistamines.

First generation H1 receptor antagonists are often associated with adverse CNS effects such as sedation, whereas modern, second generation antihistamines are generally non-sedating. The difference in therapeutic profile is mainly due to the poor CNS penetration of the modern derivatives. Current explanations for the differential ability of classical and modern antihistamines to cross the blood-brain barrier (BBB), based on differences in lipophilicity or protein binding, are inadequate. We have tested the hypothesis that non-sedating antihistamines fail to enter the CNS due to recognition by the P-glycoprotein (Pgp) drug efflux pump expressed on the luminal surface of cerebral endothelial cells forming the BBB in vivo. The ability of several sedating and non-sedating antihistamines to affect the uptake of the Pgp model substrate [3H]-colchicine was examined using the immortalised rat brain endothelial cell line, RBE4, an established in vitro model of the BBB expressing Pgp. All second generation antihistamines tested, significantly increased net accumulation of [3H]-colchicine to a level similar to that caused by the Pgp inhibitor verapamil. By contrast, the first generation antihistamines showed no affinity for Pgp. The results indicate that differences in the ability of classical and modern antihistamines to interact with Pgp at the BBB may determine their CNS penetration and as a consequence the presence or absence of central side-effects.