Have We Neglected to Study Target-Site Drug Exposure in Children? A Systematic Review of the Literature

BACKGROUND AND OBJECTIVE

Drug dosing should ideally be based on the drug concentrations at the target site, which, for most drugs, corresponds to the tissue. The exact influence of growth and development on drug tissue distribution is unclear. This systematic review compiles the current knowledge on the tissue distribution of systemically applied drugs in children, with the aim to identify priorities in tissue pharmacokinetic (PK) research in this population.

METHODS

A systematic literature search was performed in the MEDLINE and Embase databases.

RESULTS

Forty-two relevant articles were identified, of which 71% investigated antibiotics, while drug classes from the other studies were anticancer drugs, antifungals, anthelmintics, sedatives, thyreostatics, immunomodulators, antiarrhythmics, and exon skipping therapy. The majority of studies (83%) applied tissue biopsy as the sampling technique. Tonsil and/or adenoid tissue was most frequently examined (70% of all included patients). The majority of studies had a small sample size (median 9, range 1-93), did not include the youngest age categories (neonates and infants), and were of low reporting quality. Due to the heterogeneous data from different study compounds, dosing schedules, populations, and target tissues, the possibility for comparison of PK data between studies was limited.

CONCLUSION

The influence of growth and development on drug tissue distribution continues to be a knowledge gap, due to the paucity of tissue PK data in children, especially in the younger age categories. Future research in this field should be encouraged as techniques to safely investigate drug tissue disposition in children are available.

Understanding the Conditions Under Which Drugs are Transferred from the Stomach Through the Upper Small Intestine After a High-Calorie, High-Fat Meal

Information on the conditions under which drugs are transferred from the stomach through the upper small intestine after a high-calorie, high-fat meal is very limited. To simulate the drug presence after disintegration and arrival in the antral region, paracetamol solution and Sporanox® amorphous solid dispersion pellets at two dose levels were administered to the antrum of 8 healthy adults 30 min after administration of a high-calorie, high-fat meal on a crossover basis. The overall median buffer capacity of antral contents was estimated to be 18.0 and 24.0 mmol/ml/ΔpH when titrating with NaOH and HCl, respectively. The corresponding values for the contents of upper the small intestine were 14.0 and 16.8 mmol/ml/ΔpH, respectively. The drug transfer process from the antrum through the upper small intestine occurred with apparent first-order kinetics. The best estimate for the antral emptying half-life was 39min and 45min for paracetamol and itraconazole, respectively, the apparent volume of contents of the upper small intestine was more than double compared with previously reported values in the fasted state, the half-life of drug elimination from the upper small intestine was similar to recent estimates for highly permeable drugs in the fasted state, and the apparent volume of antral contents during the first couple of hours post drug administration was 303mL. Information collected in this study could increase the reliability of in silico and/or in vitro modelling approaches applied in clinical drug development.

Microdialysis as a safe and feasible method to study target-site piperacillin-tazobactam disposition in septic piglets and children

OBJECTIVES

Knowledge on the tissue penetration of piperacillin-tazobactam in children with sepsis is lacking. In this study, the feasibility and performance of microdialysis experiments were explored in septic piglets and children as part of a translational research project.

METHODS

Multiple-day microdialysis investigations were performed in muscle tissue of 22 piglets (of which 11 were septic) and 6 children with sepsis. An in vitro experiment preceded the (pre)clinical trials to derive optimal experimental settings and calibration technique. Linear mixed-effects models quantified the impact of sepsis on relative recovery (RR) and intercatheter, interindividual, interoccasion, and residual variability.

RESULTS

In vivo microdialysis was well tolerated in piglets and children, with no significant adverse events reported. Using identical experimental settings, lower RR values were recorded in healthy and septic piglets (range: piperacillin, 17.2-29.1% and tazobactam, 23.5-29.1%) compared with the in vitro experiment (piperacillin, 43.3% and tazobactam, 55.3%), and there were unacceptably low values in children with sepsis (<10%). As a result, methodological changes were made in the pediatric trial. Realistic tissue concentration-time curves were derived in piglets and children. In piglets, sepsis reduced the RR. The greatest contributors to RR variability were residual (>40%) and interoccasion (>30%) variability. The internal standard method was the preferred calibration technique in both piglets and children.

CONCLUSIONS

Microdialysis is a safe and applicable method for the measurement of tissue drug concentrations in piglets and children. This study demonstrated the impact of experimental settings, sepsis, and target population on individual RR.

Projection of Target Drug Particle Size in Oral Formulations Using the Refined Developability Classification System (rDCS)

Dissolution limitations to oral absorption can occur if the time required for dissolution is longer than the transit time across the small intestine and/or if dissolution is slower than the drug's permeation through the gut wall. These limitations most often occur for poorly soluble drugs. A standard method for overcoming dissolution issues is to reduce the particle size of the (solid) drug. Building on the refined Developability Classification System (rDCS), this work establishes a novel set of equations with which the appropriate degree of particle size reduction needed to mitigate dissolution limitations to absorption can be calculated. According to the type of data available, the appropriate equation(s) for each situation can be applied. Three case examples are used to illustrate implementation of the equations: voriconazole, lemborexant and istradefylline. Although for voriconazole (rDCS Class I) target radius (r_target) estimates indicate that particle size reduction is unnecessary, for lemborexant (rDCS Class I) a radius of ≤20 µm would be required to improve absorption. For istradefylline (rDCS Class IIb) the r_target was approximately 12 µm. Results are commensurate with literature information for these three drugs, signaling that the equations are suitable for application to a wide variety of drug substances.

Long-term results of displaced intra-articular calcaneal fractures treated with minimal invasive surgery using percutaneous screw fixation

INTRODUCTION

Over the last 20 years, minimally invasive surgery using Percutaneous Screw Fixation (PSF) has been performed increasingly frequently in the treatment of Displaced Intra-Articular Calcaneal Fractures (DIACFs). The purposes of this study were to assess the long-term postoperative outcomes of mobility, foot function, stability, pain and patient satisfaction.

METHODS

All patients had DIACFs and underwent PSF between 1998 and 2006 according to the method reported by Forgon and Zadravecz. Functional outcomes, range of motion and change in footwear were evaluated with the American Orthopaedic Foot & Ankle Society (AOFAS) score and the Maryland Foot Score (MFS). All patients completed a general health status form (Short Form-36 [SF-36]) and visual analogue scale (VAS) for patient satisfaction. Anatomical restoration was assessed based on the pre- and postoperative radiographic images.

RESULTS

Sixty-six patients with an DIACF were observed in the period 1998-2006. Patients who had open fractures, died or were <18 years of age at trauma were excluded. A total of 46 patients were asked to complete the questionnaires, during the last quarter of 2018. Of these patients, 27 with 29 DIACFs responded (58%). Nineteen were males, and the mean age at trauma was 45 years. Seven cases were classified as Sanders type II, 14 as Sanders type III, and 8 as Sanders type IV. The mean pre- and postoperative Böhler angles were 10 ͦ and 26 ͦ, respectively. The average follow-up period was 16 years, and at the follow-up, the mean AOFAS, MFS, SF-36 and VAS scores were 76, 74, 63 and 7.7 points, respectively. In comparison to the results at 5-10 years postoperatively in a previous study, we observed a decline in the average AOFAS and MFS scores by 8 and 11 points, respectively. Patient satisfaction decreased by 0.1 points and general health by 14 points.

CONCLUSION

The long-term results of this study show relatively good functional outcomes is two-thirds of the treated patients. According to the reported scores, patients described their level of function as essentially normal. PSF should therefore be considered as a good option in patients with DIAC fractures, especially in patients with Sanders II and III fractures.

LEVEL OF EVIDENCE

Therapeutic Level III.

Optimizing the Use of Antibiotic Agents in the Pediatric Intensive Care Unit: A Narrative Review

Antibiotics are one of the most prescribed drug classes in the pediatric intensive care unit, yet the incidence of inappropriate antibiotic prescribing remains high in critically ill children. Optimizing the use of antibiotics in this population is imperative to guarantee adequate treatment, avoid toxicity and the occurrence of antibiotic resistance, both on a patient level and on a population level. Antibiotic stewardship encompasses all initiatives to promote responsible antibiotic usage and the PICU represents a major target environment for antibiotic stewardship programs. This narrative review provides a summary of the available knowledge on the optimal selection, duration, dosage, and route of administration of antibiotic treatment in critically ill children. Overall, more scientific evidence on how to optimize antibiotic treatment is warranted in this population. We also give our personal expert opinion on research priorities.

Quality of life after pelvic ring fractures: Long-term outcomes. A multicentre study

AIMS

This study was conducted to determine long-term (5-10 years) health-related quality of life (HRQOL) and ceiling effects in patients with a pelvic ring fracture.

PATIENTS AND METHODS

We identified all patients with pelvic ring fractures after high-energy trauma admitted at two level 1 trauma centres in the Netherlands from 2006 to 2011. Patients were asked to complete the Majeed Pelvic Score (MPS), EuroQol-5D (EQ-5D) and Short Musculoskeletal Function Assessment (SMFA) questionnaires. HRQOL analysis used a multiple linear regression model.

RESULTS

In total, 136 patients returned the questionnaires. The median follow-up period was 8.7 years. The mean MPS and EQ-5D-VAS scores were 85.1 and 74, respectively. The mean EQ-5D index scores were 0.87, 0.81 and 0.82 in Tile B, A and C patients, respectively. The mean SMFA index was 24. A ceiling effect was observed for 1/3 of the patients. After multiple linear regression analysis, no differences were identified among the various fracture types for each questionnaire, with the exception of 2 subscales of the MPS.

CONCLUSION

Patients who suffer pelvic ring fractures generally have good HRQOL outcomes after 5-10 years. No significant differences were found among different fracture types. Long-term follow-up of patients with Tile C fractures is warranted.

Open pelvic fracture: the killing fracture?

BACKGROUND

Open pelvic fractures are rare but represent a serious clinical problem with high mortality rates. The purpose of this study was to evaluate the outcomes of open pelvic fractures in our clinic and to compare the results from our patient group with those of closed fractures and with the literature from the past decade.

METHODS

Data of patients older than 16 years of age who were admitted to our hospital with a pelvic fracture between January 1, 2004, and December 31, 2014, were analyzed. The collected data were patient demographics, mechanism of injury, RTS, ISS, transfusion requirement during the first 24 h, Gustilo-Anderson and Faringer classification, number and type of interventions complications, mortality, and length of stay.

RESULTS

Twenty-four of 492 patients (5% of all pelvic fracture patients) had an open fracture. Their mean age was 36 years, the mean ISS was 31, and the mean number of transfused packed red blood cells was 5.5. These numbers were all significantly higher than in the patients with a closed fracture, although they were comparable to other studies with open fractures. The mortality was 4% in the open group versus 14% in the closed group (p = 0.23). The reported mortality in the literature ranges between 4 and 45%.

CONCLUSION

Open pelvic fractures are relatively rare but are a cause of significant morbidity. In this series, we treated patients with open pelvic fractures successfully, with a survival rate of 96%. There was no significant difference in survival rate between open and closed pelvic fractures. Compared with other studies, the mortality in our study was relatively low.

Paediatric pelvic fractures: how do they differ from adults?

BACKGROUND

The aim of this article was to review the incidence, presentation, treatment and complications of paediatric pelvic fractures of children who were admitted to our level 1 trauma centre and to compare them with our data from adult pelvic fracture patients.

METHODS

We conducted a retrospective chart review of all children with pelvic fractures who were managed at our institution between January 1993 and December 2013 and compared the data with our database on pelvic fractures in adults during the period 2007 to 2012.

RESULTS

We identified 51 children and 268 adults with pelvic fractures. The median age of the paediatric patients was 11 years. Children were significantly more involved in traffic accidents than adults (p < 0.001). Adults had a significantly higher Injury Severity Score (ISS) (31 vs 24.5; p < 0.03) and were significantly more often haemodynamically unstable (p < 0.01). Adults had a type C fracture more often, while children had a type B fracture (p < 0.001). Associated injuries were seen in both groups; however, thoracic injuries were significantly higher in adults (p < 0.01) and injuries to the extremities were higher in children (p < 0.01). Adults were significantly more often treated with open reduction and internal fixation (p < 0.001). Mortality in both groups, however, did not differ (6% vs 8%).

CONCLUSION

Paediatric pelvic fractures are rare. They differ from adult pelvic fractures in presentation, associated injuries and management. Mortality, however, is substantial and does not differ from the adult population. Mortality is often due to concomitant injuries and not to exsanguination from the pelvic fracture.

Lung surfactants and different contributions to thin film stability

The surfactant lining the walls of the alveoli in the lungs increases pulmonary compliance and prevents collapse of the lung at the end of expiration. In premature born infants, surfactant deficiency causes problems, and lung surfactant replacements are instilled to facilitate breathing. These pulmonary surfactants, which form complex structured fluid-fluid interfaces, need to spread with great efficiency and once in the alveolus they have to form a thin stable film. In the present work, we investigate the mechanisms affecting the stability of surfactant-laden thin films during spreading, using drainage flows from a hemispherical dome. Three commercial lung surfactant replacements Survanta, Curosurf and Infasurf, along with the phospholipid dipalmitoylphosphatidylcholine (DPPC), are used. The surface of the dome can be covered with human alveolar epithelial cells and experiments are conducted at the physiological temperature. Drainage is slowed down due to the presence of all the different lung surfactant replacements and therefore the thin films show enhanced stability. However, a scaling analysis combined with visualization experiments demonstrates that different mechanisms are involved. For Curosurf and Infasurf, Marangoni stresses are essential to impart stability and interfacial shear rheology does not play a role, in agreement with what is observed for simple surfactants. Survanta, which was historically the first natural surfactant used, is rheologically active. For DPPC the dilatational properties play a role. Understanding these different modes of stabilization for natural surfactants can benefit the design of effective synthetic surfactant replacements for treating infant and adult respiratory disorders.

Interfacial shear rheology of DPPC under physiologically relevant conditions

Lipids, and phosphatidylcholines in particular, are major components in cell membranes and in human lung surfactant. Their ability to encapsulate or form stable layers suggests a significant role of the interfacial rheological properties. In the present work we focus on the surface rheological properties of dipalmitoylphosphatidylcholine (DPPC). Literature results are confusing and even contradictory; viscosity values have been reported differ by several orders of magnitude. Moreover, even both purely viscous and gel-like behaviours have been described. Assessing the literature critically, a limited experimental window has been explored correctly, which however does not yet include conditions relevant for the physiological state of DPPC in vivo. A complete temperature and surface pressure analysis of the interfacial shear rheology of DPPC is performed, showing that the monolayer behaves as a viscoelastic liquid with a domain structure. At low frequencies and for a thermally structured monolayer, the interaction of the molecules within the domains can be probed. The low frequency limit of the complex viscosity is measured over a wide range of temperatures and surface pressures. The effects of temperature and surface pressure on the low frequency viscosity can be analysed in terms of the effects of free molecular area. However, at higher frequencies or following a preshear at high shear rates, elasticity becomes important; most probably elasticity due to defects at the edge of the domains in the layer is probed. Preshearing refines the structure and induces more defects. As a result, disagreeing interfacial rheology results in various publications might be due to different pre-treatments of the interface. The obtained dataset and scaling laws enable us to describe the surface viscosity, and its dependence under physiological conditions of DPPC. The implications on functioning of lung surfactants and lung surfactant replacements will be discussed.

PICK1 expression in reactive astrocytes within the spinal cord of amyotrophic lateral sclerosis (ALS) rats

AIMS

The protein interacting with C kinase 1 (PICK1), a PDZ domain-containing protein mainly expressed in the central nervous system, interacts with the glutamate receptor subunit GluR2, with the glutamate transporter GLT-1b and with the enzyme serine racemase. These three proteins appear as key actors in the glutamate-mediated excitotoxicity associated with amyotrophic lateral sclerosis (ALS), in both patients and animal models of the disease. In this study, we examined the expression of PICK1 in the spinal cord of transgenic rats expressing a mutated form of the human superoxide dismutase 1 (hSOD1(G93A) ) during the progression of the disease.

METHODS

Expression of PICK1 was examined by real-time qPCR at presymptomatic and symptomatic stages as well as at end-stage. The expression of PICK1 in the different cell types of the spinal cord was examined by immunohistochemistry.

RESULTS

The overall expression of PICK1 is not modified in cervical and lumbar spinal cord of transgenic (hSOD1(G93A) ) rats during the progression of the disease. Nonetheless, immunohistochemical studies of lumbar ventral horns revealed a shift of PICK1 expression from motor neurones in healthy rats to activated astrocytes in end-stage hSOD1(G93A) animals.

CONCLUSIONS

Considering the documented influence of PICK1 expression on d-serine release and glutamate transport in astrocytes, these findings point to a potential implication of PICK1 in the progression of ALS.

Multiplicity and regulation of G-protein couplings

During the last twenty years, molecular and biochemical data concerning G-protein coupled receptors have accumulated, providing a detailed characterisation of the structure and functions of this large family of receptors. Initially viewed as simple transducing proteins interacting with intracellular adapters which confer signalling specificity and amplification, the last decade has revealed the extreme complexity and flexibility offered by these membrane receptors. Indeed, there is accumulating evidence that these receptors can interact with several unrelated G-proteins and that some ligands can specifically orientate the functional response. This article summarizes my contributions to the study of the multiplicity and regulation of cell signallings associated with three unrelated systems: the neurotensin receptor, the type 1 metabotropic glutamate receptor and the type 1 cannabinoid receptor. Along with other studies, these experimental data emphasise on the importance of the emerging concept of functional selectivity which should lead to the development of drugs showing enhanced clinical efficacy with lower unwanted side effects.

[Neurobiology and psychology of addictions]

The clinical observation of patients that are addicted to drugs allows the distinction between physical dependence and psychic dependence (addiction). Empirical research has made important breakthrough in the understanding of the mechanisms involved in the development of dependence and opens new therapeutic options. Neurobiologic findings concerning dopaminergic brain reward circuit provide a better insight on the incentiv aspects of drug seeking. The present article is a review of current models of addiction with a specific focus on the link between biological aspects and psychological observations.

Adenylosuccinate lyase deficiency: study of physiopathologic mechanism(s)

Nucleotide concentrations were normal in adenylosuccinate lyase-deficient fibroblasts, and the succinylpurines were not toxic for cultured neuronal cells.

Transcriptional regulation of the tyrosine hydroxylase gene by neurotensin in human neuroblastoma CHP212 cells

The human neuroblastoma cell line CHP212 was found to express functional high affinity neurotensin (NTS-1) receptor subtype. Based on the functional interactions between neurotensin and dopamine transmission, we have used this cell line to investigate the short- and long-term modulation of tyrosine hydroxylase gene expression by the stable neurotensin agonist JMV 449. After exposure of the cells to 1 microM JMV 449 for 5 or 72 h, tyrosine hydroxylase protein and mRNA levels were significantly increased as detected by western blot analysis and quantitative RT-PCR, respectively. Transfection of CHP212 cells with a plasmid containing the luciferase reporter gene under the control of a limited proximal region of the cloned tyrosine hydroxylase promoter, revealed that the effect of JMV 449 results from an increase in the transcriptional activity of the TH gene. These results indicate that modulation of tyrosine hydroxylase gene expression may constitute one of the mechanisms involved in the control of dopamine transmission by neurotensin. Such neurotensin-mediated changes in tyrosine hydroxylase expression may also participate in multiple adaptation processes within the central nervous system to environmental conditions where neurotensin is released such as stress and food intake.

Parietal electroencephalogram beta asymmetry and selective attention to angry facial expressions in healthy human subjects

Research on cerebral affective processing in humans has concentrated on the lateralization of the prefrontal cortex. However, the parietal cortex also seems to play a role in motivation and emotion. In the present study the lateralized role of the parietal cortex in motivated attention was investigated, using an electrophysiological correlate of brain activity (electroencephalogram (EEG)) and a modified Dot probe task, which indexes selective, i.e. avoidant or vigilant attention for angry faces in a spatial display. Twenty-two participants underwent an EEG baseline recording from the F3, F4, P3 and P4 electrode positions, which was followed by the modified Dot probe task. Spectral power in 1 Hz frequency bins were derived for each electrode site and transformed to power density values in the 8-12 Hz (alpha) and 13-30 Hz (beta) frequency range. Log-transformed prefrontal and parietal asymmetries and bias scores for selective attention to angry and happy faces were calculated. Results showed a highly significant relationship between the asymmetry in parietal EEG beta activity and the attentional response to the angry face. Relative more right-sided parietal EEG activity in the beta frequency domain was predictive of a more avoidant response to angry facial expression. This finding suggests that asymmetrical parietal beta activity might be linked to the behavioural dimensions of approach and withdrawal.

Structural, signalling and regulatory properties of the group I metabotropic glutamate receptors: prototypic family C G-protein-coupled receptors

In 1991 a new type of G-protein-coupled receptor (GPCR) was cloned, the type 1a metabotropic glutamate (mGlu) receptor, which, despite possessing the defining seven-transmembrane topology of the GPCR superfamily, bore little resemblance to the growing number of other cloned GPCRs. Subsequent studies have shown that there are eight mammalian mGlu receptors that, together with the calcium-sensing receptor, the GABA(B) receptor (where GABA is gamma-aminobutyric acid) and a subset of pheromone, olfactory and taste receptors, make up GPCR family C. Currently available data suggest that family C GPCRs share a number of structural, biochemical and regulatory characteristics, which differ markedly from those of the other GPCR families, most notably the rhodopsin/family A GPCRs that have been most widely studied to date. This review will focus on the group I mGlu receptors (mGlu1 and mGlu5). This subgroup of receptors is widely and differentially expressed in neuronal and glial cells within the brain, and receptor activation has been implicated in the control of an array of key signalling events, including roles in the adaptative changes needed for long-term depression or potentiation of neuronal synaptic connectivity. In addition to playing critical physiological roles within the brain, the mGlu receptors are also currently the focus of considerable attention because of their potential as drug targets for the treatment of a variety of neurological and psychiatric disorders.

Functional coupling with Galpha(q) and Galpha(i1) protein subunits promotes high-affinity agonist binding to the neurotensin receptor NTS-1 expressed in Escherichia coli

To analyze the coupling of Galpha subunits to the rat neurotensin receptor NTS-1 (NTR), fusion proteins were expressed in Escherichia coli with various Galpha subunits covalently linked to the receptor C-terminus. The presence of Galpha(q) or Galpha(i/q), in which the six C-terminal residues of Galpha(i1) were replaced with those from Galpha(q), increased the percentage of receptors in the agonist high-affinity state. This effect was less pronounced for wild-type Galpha(i1) and not observed for Galpha(i/s). Functional coupling of neurotensin receptor to Galpha was demonstrated by neurotensin-induced [(35)S]GTPgammaS binding for the Galpha(q), Galpha(i/q) and Galpha(i1) subunits, but not for Galpha(i/s). Our results extend previous findings of the dual coupling of NTR to pertussis toxin-sensitive and -insensitive G-proteins in Chinese hamster ovary cells with preference for the latter.

Modulation of the neuronal dopamine transporter activity by the metabotropic glutamate receptor mGluR5 in rat striatal synaptosomes through phosphorylation mediated processes

There is considerable evidence that the activity of the neuronal dopamine transporter (DAT) is dynamically regulated and a putative implication of its phosphorylation in this process has been proposed. However, there is little information available regarding the nature of physiological stimuli that contribute to the endogenous control of the DAT function. Based on the close relationship between glutamatergic and dopaminergic systems in the striatum, we investigated the modulation of the DAT activity by metabotropic glutamate receptors (mGluRs). Short-term incubations of rat striatal synaptosomes with micromolar concentrations of the group I mGluR selective agonist (S)-3,5-dihydroxyphenylglycine were found to significantly decrease the DAT capacity and efficiency. This alteration was completely prevented by a highly selective mGluR5 antagonist, 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP). The effect of (S)-3,5-dihydroxyphenylglycine was also inhibited by staurosporine and by selective inhibitors of protein kinase C and calcium calmodulin-dependent protein kinase II. Co-application of okadaic acid prolonged the transient effect of the agonist, supporting a critical role for phosphorylation in the modulation of the DAT activity by mGluRs. In conclusion, we propose that striatal mGluR5 contribute to the control of the DAT activity through concomitant activation of both protein kinase C and calcium calmodulin-dependent protein kinase II.

A single administration of testosterone induces cardiac accelerative responses to angry faces in healthy young women

Recently, it was demonstrated how individuals with high levels of testosterone selectively attend toward angry faces. It was argued that this suggests that high levels of testosterone are associated with an aggressive, dominating personality style. In this study, the authors used a double-blind, placebo-controlled design to examine whether exogenous testosterone would induce cardiac acceleration in response to angry faces. Participants (healthy young women) were exposed to neutral, happy, or angry faces. Administration of a single dosage of testosterone (0.5 mg) induced an accelerative cardiac response to angry faces. It is argued that this effect is due to the encouragement of dominance behavior and the inclination toward aggression. Possible mechanisms behind testosterone-driven changes in behavior are discussed with relevance to steroid-responsive networks in the limbic system that drive and control motivational and physiological aspects of social behavior.

Evidence for the dual coupling of the rat neurotensin receptor with pertussis toxin-sensitive and insensitive G-proteins

We previously demonstrated the functional coupling of the rat neurotensin receptor NTS1 with G-proteins on transfected CHO cell homogenates by showing modulation of agonist affinity by guanylyl nucleotides and agonist-mediated stimulation of [(35)S]GTP gamma S binding. In the present study, we observed that G(i/o)-type G-protein inactivation by pertussis toxin (PTx) resulted in a dramatic reduction of the NT-induced [(35)S]GTP gamma S binding whereas the effect of guanylyl nucleotide was almost not affected. As expected, NT-mediated phosphoinositide hydrolysis and intracellular calcium mobilization were not altered after PTx treatment. This suggests the existence of multiple signaling cascades activated by NT. Accordingly, using PTx and the PLC inhibitor U-73122, we showed that both signaling pathways contribute to the NT-mediated production of arachidonic acid. These results support evidence for a dual coupling of the NTS1 with PTx-sensitive and insensitive G-proteins.

Increased dopamine uptake in striatal synaptosomes after treatment of rats with amantadine

The aim of the present study was to investigate the effect of short- and long-term treatments with amantadine on the activity of the neuronal dopamine transporter (DAT) in the rat striatum. For this purpose, the [3H]dopamine uptake was measured in striatal synaptosomes prepared from rats treated for 2, 7 and 14 days with amantadine (40 mg/kg; i.p.). After 7 days of treatment, amantadine increased the apparent V(max) by 30% without modification of the apparent K(m) of dopamine uptake whereas no change in these parameters was observed after 2 and 14 days treatment. Binding assays conducted with [3H]GBR-12935 on membranes prepared from animals treated with amantadine revealed no difference in the density and the affinity of striatal DAT binding sites as compared to control. This indicates that the increased dopamine uptake was not reflecting a modification at the level of the DAT expression. The activity of the DAT is regulated by phosphorylation and one may propose that ionotropic glutamate receptors present on presynaptic terminals directly modulate this phosphorylation. An indirect mechanism would involve presynaptic dopamine receptors that control the activity of the DAT in response to the increased dopamine concentration in the synaptic cleft.

Complex involvement of pertussis toxin-sensitive G proteins in the regulation of type 1alpha metabotropic glutamate receptor signaling in baby hamster kidney cells

Previously, we demonstrated that the coupling of the metabotropic glutamate receptor mGlu1alpha to phosphoinositide hydrolysis is enhanced by pertussis toxin (PTX) in stably transfected baby hamster kidney cells (BHK). Here, we show that the PTX effect on agonist-stimulated [(3)H]inositol phosphate accumulation can be resolved into two components: an immediate increase in agonist potency, and a more slowly developing increase in the magnitude of the response observed at maximally effective agonist concentrations. Using G(q/11)alpha- and G(i/o)alpha-selective antibodies to immunoprecipitate [(35)S]guanosine-5'-O-(3-thio)triphosphate-bound Galpha proteins, we also show that agonist stimulation of mGlu1alpha in BHK membranes increases specific [(35)S]guanosine-5'-O-(3-thio)triphosphate binding to both G(q/11) and G(i/o) proteins. Preincubation of BHK-mGlu1alpha with L-glutamate (300 microM) results in a progressive loss (60% in 30 min) of L-quisqualate-induced [(3)H]inositol phosphate accumulation (without a change in potency), providing evidence for agonist-induced receptor desensitization. Although such desensitization of mGlu receptor signaling was mimicked by a phorbol ester, agonist-induced phosphorylation of the receptor was not observed and protein kinase C inhibition by Ro 31-8220 did not prevent L-glutamate-mediated desensitization. In contrast, PTX treatment of the cells almost completely prevented L-glutamate-mediated desensitization. Together, these data provide evidence for a multifunctional coupling of mGlu1alpha to different types of G proteins, including PTX-sensitive G(i)-type G proteins. The latter are involved in the negative control of phospholipase C activity while also influencing the rate of desensitization of the mGlu1alpha receptor.

Laterality effects in selective attention to threat after repetitive transcranial magnetic stimulation at the prefrontal cortex in female subjects

Recently, several experiments have indicated that the left and right prefrontal cortex (PFC) are differently involved in emotional processing. The aim of this study was to investigate the role of the left and right PFC in selective attention to angry faces by using a pictorial emotional Stroop task. Slow repetitive transcranial magnetic stimulation (rTMS) was applied to the left and right PFC of 10 female subjects for 15 min on separate days. Results showed a significant effect of stimulation position: right PFC rTMS resulted in selective attention towards angry faces, whereas left PFC rTMS resulted in selective attention away from angry faces. This finding is in accordance with theoretical accounts of the neural implementation of approach and withdrawal systems.

Assessment of striatal D1 and D2 dopamine receptor-G protein coupling by agonist-induced [35S]GTP gamma S binding

The dopamine receptor-mediated modulation of guanosine 5'-O-(gamma-[35S]thio)triphosphate ([35S]GTP gamma S) binding has been characterized in rat striatal membranes. In optimized experimental conditions, the potency of dopamine was 4.47 microM [3.02-6.61 microM] and a maximal response representing 54.8 +/- 4.5% increase above basal level was observed. Data obtained with different agonists and antagonists clearly revealed that the most important fraction of this response was reflecting D2 receptor activation. Further analysis with specific antagonists also supported evidence for the involvement of D1 dopamine receptors. The potencies of compounds interacting with D1 and D2 receptors were deduced from [35S]GTP gamma S binding experiments and compared with their binding affinities for these receptors measured in similar experimental conditions. A good correlation between these parameters was observed, supporting the applicability of this technique for the study of dopamine receptors in the central nervous system.

Enhanced striatal dopamine D(2) receptor-induced [35S]GTPgammaS binding after haloperidol treatment

Dopamine receptor-G protein coupling and dopamine D(2) receptor density were assessed in rats treated for 3 weeks with either haloperidol (2 mg/kg; i.p.) or vehicle. After 3 days of withdrawal, agonist-induced guanosine 5'-O-(gamma-[35S]thio)triphosphate ([35S]GTPgammaS) and [3H]spiperone binding were determined in striatal homogenates. Maximal [3H]spiperone binding was increased (24.8%, P<0.01) following haloperidol treatment. The efficacy of dopamine and the dopamine D(2) receptor agonist R(-)-10, 11-dihydroxy-N-n-propylnorapomorphine (NPA) to induce [35S]GTPgammaS binding were found to be increased by 24.1% (P<0.01) and 44.6% (P<0. 001), respectively. When measured in the presence of a saturating concentration of a dopamine D(2) receptor antagonist, the response to dopamine was not significantly affected by haloperidol treatment. In addition, the measurement of haloperidol-induced catalepsy confirmed that the efficient dopamine receptor blockade was followed by a progressive development of dopaminergic supersensitivity. Taken together, these results indicate that a functional pool of dopamine D(2) receptors is increased after prolonged haloperidol administration.

Inhibition of N-linked glycosylation of the human type 1alpha metabotropic glutamate receptor by tunicamycin: effects on cell-surface receptor expression and function

The potential role of N-linked glycosylation of the human type 1alpha metabotropic glutamate (mGlu1alpha) receptor was studied in a recombinant, inducible expression system, where receptor expression was induced in the absence and presence of tunicamycin. In the absence of tunicamycin the mGlu1alpha receptor appeared to be expressed, at least in part, as a dimer consisting of monomers of approx. 145 and 160 KDa relative molecular mass (Mr). In the presence of tunicamycin only a single monomeric protein could be detected approximating the Mr predicted for the human mGlu1alpha receptor based on its primary amino acid sequence (130 KDa). Exposure to tunicamycin during receptor induction did not appear to affect the cell surface expression of the mGlu1alpha receptor as determined immunocytochemically or using a cell-surface biotinylation strategy, but reduced agonist-stimulated phosphoinositide hydrolysis by approximately 50% compared to control cell populations. Our data suggest that non-N-glycosylated human mGlu1alpha receptors can traffic to the cell surface and activate phospholipase C.

Analogues and homologues of N-palmitoylethanolamide, a putative endogenous CB(2) cannabinoid, as potential ligands for the cannabinoid receptors

The presence of CB(2) receptors was reported in the rat basophilic cell line RBL-2H3 and N-palmitoylethanolamide was proposed as an endogenous, potent agonist of this receptor. We synthesized a series of 10 N-palmitoylethanolamide homologues and analogues, varying by the elongation of the fatty acid chain from caproyl to stearoyl and by the nature of the amide substituent, respectively, and evaluated the affinity of these compounds to cannabinoid receptors in the rat spleen, RBL-2H3 cells and CHO-CB(1) and CHO-CB(2) receptor-transfected cells. In rat spleen slices, CB(2) receptors were the predominant form of the cannabinoid receptors. No binding of [(3)H]SR141716A was observed. [(3)H]CP-55,940 binding was displaced by WIN 55,212-2 and anandamide. No displacement of [(3)H]CP-55,940 or [(3)H]WIN 55,212-2 by palmitoylethanolamide derivatives was observed in rat spleen slices. In RBL-2H3 cells, no binding of [(3)H]CP-55,940 or [(3)H]WIN 55,212-2 could be observed and conversely, no inhibitory activity of N-palmitoylethanolamide derivatives and analogues was measurable. These compounds do not recognize the human CB(1) and CB(2) receptors expressed in CHO cells. In conclusion, N-palmitoylethanolamide was, in our preparations, a weak ligand while its synthesized homologues or analogues were essentially inactive. Therefore, it seems unlikely that N-palmitoylethanolamide is an endogenous agonist of the CB(2) receptors but it may be a compound with potential therapeutic applications since it may act via other mechanisms than cannabinoid CB(1)-CB(2) receptor interactions.

Dopamine receptor-modulated [35S]GTPgammaS binding in striatum of 6-hydroxydopamine-lesioned rats

The role of dopamine receptor-G protein coupling in the development of striatal dopamine receptor supersensitivity was studied in rats with a 6-hydroxydopamine (6-OHDA)-induced unilateral lesion of the nigrostriatal pathway. This coupling was assessed by the measurement of dopamine agonist-induced guanosine 5'-O-(gamma[35S]thio)triphosphate ([35S]GTP-gammaS) binding in striatal membranes, at different periods of time (1-5 weeks) following the microinjection of the neurotoxin. From the first to the fifth week following the lesion, basal and dopamine-stimulated [35S]GTPgammaS-specific binding were found to be enhanced in the denervated striata as compared to their control counterpart. D2 dopamine receptors were clearly demonstrated to be involved in this supersensitivity, as assessed by measuring N-propylnorapomorphine (NPA)-, quinpirole- and bromocriptine-induced [35S]GTPgammaS-specific binding. The involvement of D1 dopamine receptors was indirectly studied by the combination of dopamine with a saturating concentration of the selective and potent D2 antagonist domperidone. In these conditions, the remaining response to dopamine was also found to be significantly increased following the lesion. These results are consistent with the hypothesis that, in addition to D2 dopamine receptor upregulation, modulation of dopamine receptor-G protein interaction is involved in the hypersensitivity accompanying striatal dopamine depletion.

3-Alkyl-(5,5'-diphenyl)imidazolidineiones as new cannabinoid receptor ligands

Twenty-four 3-alkyl-(5,5'-diphenyl)imidazolidinediones were synthesized and evaluated as new cannabinoid receptor ligands. Three compounds exhibited a Ki value around 100 nM against [3H]-SR 141716A binding obtained from human CB1 transfected CHO cells membranes. The lack of change of affinity in the presence of a non hydrolyzable GTP analogue seems to indicate they are cannabinoid antagonists.

Effects of varying the expression level of recombinant human mGlu1alpha receptors on the pharmacological properties of agonists and antagonists

1. Different expression levels of the human type 1alpha metabotropic glutamate (mGlu1alpha) receptor were obtained in transfected Chinese hamster ovary cells using an isopropyl beta-D-thiogalactopyranoside (IPTG) inducible system. Expression of mGlu1alpha receptors could not be detected using immunoblotting or immunocytochemical approaches in non-induced cells, however, controlled expression could be induced following IPTG addition in a time- and concentration-dependent manner. 2. In induced cells (100 microM IPTG, 20 h) the agonists L-quisqualate or 1-aminocyclopentane-1S,3R-dicarboxylic acid stimulated large increases in [3H]-inositol (poly)phosphate (in the presence of Li+) and inositol, 1,4,5-trisphosphate levels. 3. Induction with 1-100 microM IPTG allowed the receptor density to be increased incrementally and this not only resulted in an increase in the maximum response to L-quisqualate, 1-aminocyclopentane-1S,3R-dicarboxylic acid and (S)-3,5-dihydroxy-phenylglycine, but also in an increase in the respective potencies of each agent to activate phosphoinositide hydrolysis. 4. The intrinsic activity of the partial agonist 1-aminocyclopentane-1S,3R-dicarboxylic acid dramatically increased with increasing receptor expression. 5. The activities of the competitive mGlu1alpha receptor antagonists (S)-alpha-methyl-4-carboxyphenylglycine and (S)-4-carboxy-3-hydroxyphenylglycine for inhibition of the effects of L-quisqualate or (S)-3,5-dihydroxyphenylglycine were found to be independent of the receptor expression level. 6. When the mGlu1alpha receptor was expressed at very high levels, no evidence for receptor constitutive activity could be detected, and none of the antagonists tested revealed either any intrinsic activity or negative efficacy. 7. These data demonstrate that both the potency and efficacy of mGlu1alpha receptor agonists are influenced by expression level, whilst mGlu1alpha receptor antagonist activities are independent of expression level.

Reversible and non-competitive antagonist profile of CPCCOEt at the human type 1alpha metabotropic glutamate receptor

In transfected CHO cells expressing the human metabotropic glutamate receptor mGlu1alpha, 7-(hydroxyimino)cyclopropan[b]-chromen-1a-carboxylic acid ethylester (CPCCOEt) was found to antagonize L-quisqualate-induced phosphoinositide hydrolysis in a non-competitive and reversible manner (apparent pKi value, 4.76+/-0.18; n=3). This suggests that CPCCOEt antagonizes type 1alpha metabotropic glutamate receptor activation by interacting with a site distinct from the agonist binding site.

Use of care by home-dwelling stroke patients during three years following hospital discharge

Of 82 stroke survivors who had been discharged from hospital, 49 were still living at home after a three-year period. Thirty-three of these patients formed the population of the present study of the use of care at home. Sixty-one percent had received professional care and 88% had received family care. Although their overall functional status indicated only mild handicaps, after three years patients still reported a large number of disabilities and problems. The average weekly amount of family care was 37 h, and many family carers experienced a high burden of care and had emotional problems coping with the patients' disabilities. Concerning factors related to the use of care, in spite of the relatively small number of study patients, some interesting hypotheses can be advanced.

Activation of receptor gene transcription is required to maintain cell sensitization after agonist exposure. Study on neurotensin receptor

Neurotensin (NT) acts through specific G protein-coupled receptors to induce effects in the central nervous system and periphery. In this study we have shown that in the human neuroblastoma cell line CHP 212, an NT agonist, JMV 449, induced high affinity neurotensin receptor (NTR) gene activation. 125I-NT binding of cells challenged with JMV 449 rapidly decreased then reappeared and subsequently stabilized at 50% of the control values after 48 h of agonist exposure. These receptors, which reappeared at the cell surface, are as active as those found in control cells as demonstrated by Ca2+ mobilization. Furthermore, the tyrosine hydroxylase (TH) gene, a known NT target gene, remained activated after prolonged NT agonist exposure in this cell line. In the murine neuroblastoma cell line, N1E-115, NT did not stimulate NTR gene activation but induced NTR mRNA destabilization after long term agonist exposure. In this cell line, NT binding dropped to 15% of control values and remained at this value after agonist treatment. The TH expression, which was originally activated upon NT agonist exposure, decreased to control values after prolonged agonist exposure. These observations combined with the data obtained from a complementary study with HT-29 cells (Souazé, F., Rostène, W., and Forgez, P. (1997) J. Biol. Chem. 272, 10087-10094) revealed the crucial role of agonist-induced receptor gene transcription in the maintenance of cell sensitivity. A model for G protein-coupled receptor regulation induced by prolong and intense agonist stimulation is proposed.

Mechanisms of regulation of neurotensin receptors

Since its discovery in 1973, the neuropeptide neurotensin has been demonstrated to be involved in the control of a broad variety of physiological activities in both the central nervous system and in the periphery. Pharmacological studies have shown that the biological effects elicited by neurotensin result from its specific binding to cell membrane neurotensin receptors that have been characterized in various tissue and in cell preparations. In addition, it is now well documented that most of these responses are subject to rapid desensitization. Such desensitization results in transient responses to sustained peptide applications, or to tachyphylaxis during successive stimulations in the same conditions. More recently, desensitization of neurotensin signalling was investigated at the cellular and molecular levels. In cultured cells, regulation at the second messenger level, receptor internalization, and receptor down-regulation processes have been reported. These are proposed to play a critical role in the control of cell responsiveness to neurotensin. This review aims to compile recent data on the different biochemical processes involved in the regulation of the neurotensin receptor and to discuss the physiological consequences of this regulation in vivo.

Effects of human type 1alpha metabotropic glutamate receptor expression level on phosphoinositide and Ca2+ signalling in an inducible cell expression system

Stable expression of the human type 1alpha metabotropic glutamate (mGlu 1alpha) receptor was achieved in Chinese hamster ovary cells using an isopropyl-beta-D-thiogalactoside (IPTG)-repressible expression system. Treatment of the cells with IPTG resulted in a time- and concentration-dependent induction of receptor expression. Maximal expression was obtained after treatment of the cells with 100 microM IPTG for 20 h, leading to a marked increase in receptor immunoreactivity detected by western blot, >30-fold stimulation of 3H-labelled inositol phosphate (3H-InsP) production, and a robust increase in intracellular calcium concentration in single cells after stimulation with 20 microM quisqualate. The basal level of 3H-InsP accumulation in cells induced with IPTG was increased by two- to threefold as compared with control cells; however, this basal activity was found to be dependent on glutamate released by the cells into the incubation medium. Following IPTG treatment, stable expression of the mGlu 1alpha receptor was maintained for at least 1 week. Taken together, these results clearly indicate the advantages of working with an inducible expression system when studying the biochemical and pharmacological properties of the human mGlu 1alpha receptor in transfected cells.

Down-regulation of neurotensin receptors after ligand-induced internalization in rat primary cultured neurons

When rat cultured neurons were incubated with unlabelled neurotensin (3 nM) for 1 or 24 h at 37 degrees C, the [3H]-neurotensin specific binding measured in cell homogenates was decreased to about 35 and 65% of control values, respectively. In these experiments, the decreases in binding corresponded to reductions of Bmax values without changes in the affinity. The slow neurotensin-induced receptor down-regulation is thought to result from receptor degradation since it was reduced by the lysosomotropic drugs chloroquine and methylamine and because no change in neurotensin mRNA level could be measured after the neurotensin stimulation. After their internalization, receptors slowly reappeared at the cell surface after further incubation in the absence of the peptide. Such receptor reappearance was prevented in the presence of the protein synthesis inhibitor cycloheximide and is therefore thought to result from new synthesis and not from recycling of internalized receptors. These results indicate that the neurotensin-induced receptor internalization in cultured neurons is irreversible and that it is followed by a down-regulation of the receptor through a degradative process.

Agonist and antagonist modulation of [35S]-GTP gamma S binding in transfected CHO cells expressing the neurotensin receptor

1. The functional interaction of the cloned rat neurotensin receptor with intracellular G-proteins was investigated by studying the binding of the radiolabelled guanylyl nucleotide analogue [35S]-GTP gamma S induced by neurotensin to membranes prepared from transfected Chinese hamster ovary (CHO) cells. 2. The agonist-induced binding of [35S]-GTP gamma S was only detected in the presence of NaCl in the incubation buffer. However, it was also demonstrated that the binding of [3H]-neurotensin to its receptor was inhibited by NaCl. In the presence of 50 mM NaCl, the binding of the labelled nucleotide was about 2 fold increased by stimulation with saturating concentrations of neurotensin (EC50 value of 2.3 +/- 0.9 nM). 3. The stimulation of [35S]-GTP gamma S binding by neurotensin was mimicked by the stable analogue of neurotensin, JMV-449 (EC50 value of 1.7 +/- 0.4 nM) and the neurotensin related peptide neuromedin N (EC50 value of 21 +/- 6 nM). 4. The NT-induced [35S]-GTP gamma S binding was competitively inhibited by SR48692 (pA2 value of 9.55 +/- 0.28), a non-peptide neurotensin receptor antagonist. SR48692 alone had no effect on the specific binding of [35S]-GTP gamma S. 5. The response to neurotensin was found to be inhibited by the aminosteroid U-73122, a putative inhibitor of phospholipase C-dependent processes, indicating that this drug may act at the G-protein level. 6. Taken together, these results constitute the first characterization of the exchange of guanylyl nucleotides at the G-protein level that is induced by the neuropeptide neurotensin after binding to its receptor.

Desensitization of neurotensin-induced phosphoinositide hydrolysis in transfected CHO cells

The regulation of neurotensin-induced phosphoinositide turnover was studied in transfected CHO cells expressing the rat neurotensin receptor. Stimulation of these cells with neurotensin resulted in an important, but transient, increase in inositol phosphate cell content. Preincubation of the cells with neurotensin dramatically decreased their response to further stimulation. This diminution, which was time-dependent and not related to the availability of phospholipase C substrate, is though to reflect a progressive homologous desensitization of the recombinant neurotensin receptor.

Home care--a realistic alternative for bed-blocking stroke victims in acute hospital wards? The conceptions of caregivers in six disciplines concerned

Up to half of the stroke patients admitted to acute hospital wards become bed-blockers. Investigations have been carried out in an effort to identify factors related to this problem. Very little is known about options which may lead to an alleviation of this problem. We investigated to what extent, in the opinions of professional representatives of six disciplines, home care can contribute to a solution. Sixty-nine stroke patients who were actually blocking beds in an acute hospital ward were described and examined on paper by a multidisciplinary panel. These patients were all moderately to severely disabled and needed a high degree of help in activities of daily life (ADL) and household activities. Estimations of the number of patients who were judged to be suitable for home care varied, although there was a fair degree of agreement between panel members concerning those patients who could and those who certainly could not return to their homes. Concerning one-third of the patients, the opinions of the caregivers diverged. Factors relating to the judgement of each panel member are identified. A method for selecting patients to be substituted to lower levels of care is suggested and discussed.

Role of [Ca2+]i in "Ca2+ stores depletion-Ca2+ entry coupling' in fibroblasts expressing the rat neurotensin receptor

1. Transfected Chinese hamster ovary fibroblasts expressing the rat neurotensin receptor were used to study the 'Ca2+ stores depletion-Ca2+ entry coupling' which follows stimulation with neurotensin and liberation of InsP3. 2. This coupling could be dissociated in time. Firstly, stores depletion was produced by neurotensin or thapsigargin which caused a first [Ca2+]i transient in a Ca(2+)-free external medium. Secondly, readmission of external Ca2+ produced an influx of Ca2+ and a second [Ca2+]i transient. 3. Various concentrations of thapsigargin (20 nM to 1 microM) were used to produce complete stores depletion with small or large first peaks of [Ca2+]i. Upon return to external Ca2+, small or large second [Ca2+]i peaks were observed. The amplitudes of both peaks were positively correlated. 4. The Ca2+ entry which followed stores depletion could occur at very low basal values of [Ca2+]i, was accelerated by okadaic acid and inhibited by staurosporine and the calmodulin antagonist W-7. 5. It is concluded that the rise in [Ca2+]i during Ca2+ stores depletion is an essential parameter which determines the size of the subsequent Ca2+ entry.