Theoretical and practical applications of the intracerebroventricular route for CSF sampling and drug administration in CNS drug discovery research: a mini review

Clinically, central nervous system (CNS) disorders account for more hospitalisations and prolonged care than almost all other diseases combined. In the preclinical setting, the intracerebroventricular (ICV) route for cerebrospinal fluid (CSF) sampling or dose administration in rodent models of human CNS disorders has potential to provide key insight on the pathobiology of these conditions. Low level neuroinflammation is present in >40% of patients with severe depression or schizophrenia and so comparative assessment of CSF composition between patients and rodent models of CNS disorders is potentially invaluable for hypothesis generation and for assessing rodent model validity. As molecules in the CSF have relatively low protein binding and are freely exchanged into the extracellular fluid of the brain parenchyma, supraspinal drug administration into the CSF can produce therapeutic drug concentrations in the brain. Direct administration of investigational agents into the CSF of the lateral ventricle of the brain enables intrinsic efficacy and adverse effect profiles to be evaluated without the confounding effects of drug metabolism, due to the low capacity of the CNS to metabolise exogenous compounds. It is our view that the ICV route for CSF sampling and for administration of novel drugs in development is under-utilised in preclinical research on CNS disorders. This is due to the high degree of technical skill and low margin for error associated with correct ICV guide cannula implantation in the rat. However, these technical challenges can be overcome by using standardised procedures and attention to detail during surgery and in the post-operative period. (C) 2014 Elsevier B.V. All rights reserved

La Carta forestale della Basilicata.

A comment is made on the Forest Map of Regione Basilicata (Southern Italy)

Morphine hyposensitivity in STZ-diabetic rats: reversal by dietary L-arginine treatment

Painful diabetic neuropathy (PDN) is a long-term complication of diabetes. Defining symptoms include mechanical allodynia (pain due to light pressure or touch) and morphine hyposensitivity. In our previous work using the streptozotocin (STZ)-diabetic rat model of PDN, morphine hyposensitivity developed in a temporal manner with efficacy abolished at 3 months post-STZ and maintained for 6 months post-STZ. As this time course mimicked that for the temporal development of hyposensitivity to the pain-relieving effects of the furoxan nitric oxide (NO) donor, PRG150 (3-methylfuroxan-4-carbaldehyde) in STZ-diabetic rats, we hypothesized that progressive depletion of endogenous NO bioactivity may underpin the temporal loss of morphine sensitivity in STZ-diabetic rats. Furthermore, we hypothesized that replenishment of NO bioactivity may restore morphine sensitivity in these animals. Diabetes was induced in male Dark Agouti rats by intravenous injection of STZ (85 mg/kg). Diabetes was confirmed on day 7 if blood glucose concentrations were ≥15 mmol/L. Mechanical allodynia was fully developed in the bilateral hindpaws by 3 weeks of STZ-diabetes in rats and this was maintained for the study duration. Morphine hyposensitivity developed in a temporal manner with efficacy abolished by 3 months post-STZ. Administration of dietary l-arginine (NO precursor) at 1 g/d to STZ-diabetic rats according to a 15-week prevention protocol initiated at 9 weeks post-STZ prevented abolition of morphine efficacy. When given as an 8-week intervention protocol in rats where morphine efficacy was abolished, dietary l-arginine at 1 g/d progressively rescued morphine efficacy and potency. Our findings implicate NO depletion in the development of morphine hyposensitivity in STZ-diabetic rats. Clinical and Experimental Pharmacology and Physiolog

An improved liquid chromatography tandem mass spectrometry (LC-MS/MS) method for quantification of dexmedetomidine concentrations in samples of human plasma

Dexmedetomidine (DMET) is a sedative, analgesic and anxiolytic with minimum adverse respiratory effects. An LC-MS/MS bioanalytical method has been developed and validated to accurately measure DMET concentrations in samples of human plasma. The method overcomes difficulties in the extraction and quantification of DMET due to the fact that it binds strongly to glass and plastic tubes, as well as solid phase extraction (SPE) cartridges. Human plasma (50 μL) was mixed with the internal standard (IS) (DMET-d4) solution (100 μL) and 0.1% formic acid (50 μL) and extracted using Oasis HLB 1 CC (30 mg) solid phase extraction (SPE) cartridges (Waters®). The glass tubes were coated with bovine serum albumin (BSA) 0.5% (20 μL) before eluting DMET and the IS. After evaporation under nitrogen at room temperature, the analytes were reconstituted in 20% acetonitrile in 0.1% formic acid in water and transferred to silanized glass vials. An electrospray ionisation (ESI) mass spectrometry method in positive mode was created and the precursor/product transitions (m/z) were 201.1 → 95.0 (DMET) and 204.9 → 99.0 (IS). The method was robust and fully validated based on the 2012 EMEA guideline for bioanalytical method validation in the concentration range of 0.5-20 ng/mL. Using this assay, we showed that DMET binds strongly to Extracorporeal Membrane Oxygenation (ECMO) circuits, consistent with expectations for small lipophilic compounds

Incomplete, Asymmetric, and Route-Dependent Cross- Tolerance between Oxycodone and Morphine in the Dark Agouti Rat 1

ABSTRACT Our previous studies indicate that oxycodone is a putative -opioid agonist, whereas morphine is a well documented -opioid agonist. Because there is limited information regarding the development of tolerance to oxycodone, this study was designed to 1) document the development of tolerance to the antinociceptive effects of chronically infused i.v. oxycodone relative to that for i.v. morphine and 2) quantify the degree of antinociceptive cross-tolerance between morphine and oxycodone in adult male Dark Agouti (DA) rats. Antinociceptive testing was performed using the tail-flick latency test. Complete antinociceptive tolerance was achieved in 48 to 84 h after chronic infusion of equi-antinociceptive doses of i.v. oxycodone (2.5 mg/24 h and 5 mg/24 h) and i.v. morphine (10 mg/24 h and 20 mg/24 h, respectively). Dose-response curves for bolus doses of i.v. and i.c.v. morphine and oxycodone were produced in naive, morphine-tolerant, and oxycodone-tolerant rats. Consistent with our previous findings that oxycodone and morphine produce their intrinsic antinociceptive effects through distinctly different opioid receptor populations, there was no discernible cross-tolerance when i.c.v. oxycodone was given to morphine-tolerant rats. Similarly, only a low degree of crosstolerance (Ϸ24%) was observed after i.v. oxycodone administration to morphine-tolerant rats. By contrast, both i.v. and i.c.v. morphine showed a high degree of cross-tolerance (Ϸ71% and Ϸ54%, respectively) in rats rendered tolerant to oxycodone. Taken together, these findings suggest that, after parenteral but not supraspinal administration, oxycodone is metabolized to a -opioid agonist metabolite, thereby explaining asymmetric and incomplete cross-tolerance between oxycodone and morphine. Morphine is recommended by the World Health Organization as the drug of choice for the management of moderate to severe cancer pain (WHO, 1986). Tolerance to the pain-relieving effects of opioids is a problem that may be encountered in a clinical setting in patients receiving these drugs for the relief of chronic pain. Antinociceptive tolerance is well documented in experimental animals such as rats and mice and is characterized by a marked reduction in the painrelieving effects of an opioid such as morphine after chronic administration. This phenomenon has been shown by numerous laboratories for a range of antinociceptive tests Oxycodone has been used clinically for over 80 years, but its pharmacology has been studied only relatively recently. The analgesic actions of oxycodone are comparable to those of morphine and are mediated primarily in the central nervous system. Oxycodone has been reported to be ϳ1.5 times more potent than morphine when administered by both the i.v. and oral routes for postoperative and cancer pain relief with fewer side-effects than morphine The intrinsic antinociceptive effects of oxycodone are mediated by central nervous system opioid receptors, because they are completely attenuated by i.c.v. naloxone, a universal opioid receptor antagonis

Current developments in MRI for assessing rodent models of multiple sclerosis

MRI is a key radiological imaging technique that plays an important role in the diagnosis and characterization of heterogeneous multiple sclerosis (MS) lesions. Various MRI methodologies such as conventional T 1/T 2 contrast, contrast agent enhancement, diffusion-weighted imaging, magnetization transfer imaging and susceptibility weighted imaging have been developed to determine the severity of MS pathology, including demyelination/remyelination and brain connectivity impairment from axonal loss. The broad spectrum of MS pathology manifests in diverse patient MRI presentations and affects the accuracy of patient diagnosis. To study specific pathological aspects of the disease, rodent models such as experimental autoimmune encephalomyelitis, virus-induced and toxin-induced demyelination have been developed. This review aims to present key developments in MRI methodology for better characterization of rodent models of MS

Sustained-release hydromorphone microparticles produced by supercritical fluid polymer encapsulation

Chronic cancer pain remains prevalent and severe for many patients, particularly in those with advanced disease. The effectiveness of analgesic/adjuvant drug treatments in routine practice has changed little in the last 30 years. To address these issues herein, we have developed sustained-release poly(lactic-co-glycolic acid) microparticles of hydromorphone for intrathecal injection aimed at producing prolonged periods of satisfactory analgesia in patients, as a novel strategy for alleviation of intractable cancer-related pain. These hydromorphone-loaded microparticles were produced successfully using organic solvent-free supercritical fluid polymer encapsulation. Drug loading at 9.2% and encapsulation efficacy at 92% were achieved for particles in the desired size range (20-45 μm) with sustained release over a 5-week period in vitro

SYSTEMIC COADMINISTRATION OF CHLORAMPHENICOL WITH INTRAVENOUS BUT NOT INTRACEREBROVENTRICULAR MORPHINE MARKEDLY INCREASES MORPHINE ANTINOCICEPTION AND DELAYS DEVELOPMENT OF ANTINOCICEPTIVE TOLERANCE IN RATS 1

This paper is available online at http://www.dmd.org ABSTRACT: Chloramphenicol, an in vitro inhibitor of the glucuronidation of morphine to its putative antianalgesic metabolite, morphine-3-glucuronide (M3G), was coadministered with morphine in adult male Sprague-Dawley rats to determine whether it inhibited the in vivo metabolism of morphine to M3G, thereby enhancing morphine antinociception and/or delaying the development of antinociceptive tolerance. Parenteral chloramphenicol was given acutely (3-h studies) or chronically (48-h studies). Morphine was administered by the i.v. or i.c.v. route. Control rats received chloramphenicol and/or vehicle. Antinociception was quantified using the hotplate latency test. Coadministration of chloramphenicol with i.v. but not i.cv. morphine increased the extent and duration of morphine antinociception by Ϸ5.5-fold relative to rats that received i.v. morphine alone. Thus, the mechanism through which chloramphenicol enhances i.v. morphine antinociception in the rat does not directly involve supraspinal opioid receptors. Acutely, parenteral coadministration of chloramphenicol and morphine resulted in an Ϸ75% increase in the mean area under the serum morphine concentration-time curve but for chronic dosing there was no significant change in this curve, indicating that factors other than morphine concentrations contribute significantly to antinociception. Antinociceptive tolerance to morphine developed more slowly in rats coadministered chloramphenicol, consistent with our proposal that in vivo inhibition of M3G formation would result in increased antinociception and delayed development of tolerance. However, our data also indicate that chloramphenicol inhibited the biliary secretion of M3G. Whether chloramphenicol altered the passage of M3G and morphine across the blood-brain barrier remains to be investigated. Morphine is recommended by the World Health Organization as the drug of choice for the management of moderate to severe cancer pain (World Health Organization, 1986). However, chronic administration of morphine by systemic routes may result in the development of analgesic/antinociceptive tolerance, manifested as a diminution of the pain-relieving effect or the requirement for an increase in morphine dose to maintain satisfactory pain relief, without an underlying progression in the disease state. Sprague-Dawley (SD) 2 rats are commonly used for studies of morphine tolerance. In both rats and humans, more than half of every morphine dose is metabolized to morphine-3-glucuronide (M3G). However, in both SD and Wistar strains of rat (unlike humans), glucuronidation of morphine at the 6-position to form morphine-6-glucuronide (M6G), the analgesically active metabolite of morphine, does not occur in detectable quantitie

Digitally enabled aged care and neurological rehabilitation to enhance outcomes with Activity and MObility UsiNg Technology (AMOUNT) in Australia: A randomised controlled trial

Background: Digitally enabled rehabilitation may lead to better outcomes but has not been tested in large pragmatic trials. We aimed to evaluate a tailored prescription of affordable digital devices in addition to usual care for people with mobility limitations admitted to aged care and neurological rehabilitation. Methods and findings: We conducted a pragmatic, outcome-assessor-blinded, parallel-group randomised trial in 3 Australian hospitals in Sydney and Adelaide recruiting adults 18 to 101 years old with mobility limitations undertaking aged care and neurological inpatient rehabilitation. Both the intervention and control groups received usual multidisciplinary inpatient and post-hospital rehabilitation care as determined by the treating rehabilitation clinicians. In addition to usual care, the intervention group used devices to target mobility and physical activity problems, individually prescribed by a physiotherapist according to an intervention protocol, including virtual reality video games, activity monitors, and handheld computer devices for 6 months in hospital and at home. Co-primary outcomes were mobility (performance-based Short Physical Performance Battery [SPPB]; continuous version; range 0 to 3; higher score indicates better mobility) and upright time as a proxy measure of physical activity (proportion of the day upright measured with activPAL) at 6 months. The dataset was analysed using intention-to-treat principles. The trial was prospectively registered with the Australian New Zealand Clinical Trials Registry (ACTRN12614000936628). Between 22 September 2014 and 10 November 2016, 300 patients (mean age 74 years, SD 14; 50% female; 54% neurological condition causing activity limitation) were randomly assigned to intervention (n = 149) or control (n = 151) using a secure online database (REDCap) to achieve allocation concealment. Six-month assessments were completed by 258 participants (129 intervention, 129 control). Intervention participants received on average 12 (SD 11) supervised inpatient sessions using 4 (SD 1) different devices and 15 (SD 5) physiotherapy contacts supporting device use after hospital discharge. Changes in mobility scores were higher in the intervention group compared to the control group from baseline (SPPB [continuous, 0–3] mean [SD]: intervention group, 1.5 [0.7]; control group, 1.5 [0.8]) to 6 months (SPPB [continuous, 0–3] mean [SD]: intervention group, 2.3 [0.6]; control group, 2.1 [0.8]; mean between-group difference 0.2 points, 95% CI 0.1 to 0.3; p = 0.006). However, there was no evidence of a difference between groups for upright time at 6 months (mean [SD] proportion of the day spent upright at 6 months: intervention group, 18.2 [9.8]; control group, 18.4 [10.2]; mean between-group difference −0.2, 95% CI −2.7 to 2.3; p = 0.87). Scores were higher in the intervention group compared to the control group across most secondary mobility outcomes, but there was no evidence of a difference between groups for most other secondary outcomes including self-reported balance confidence and quality of life. No adverse events were reported in the intervention group. Thirteen participants died while in the trial (intervention group: 9; control group: 4) due to unrelated causes, and there was no evidence of a difference between groups in fall rates (unadjusted incidence rate ratio 1.19, 95% CI 0.78 to 1.83; p = 0.43). Study limitations include 15%–19% loss to follow-up at 6 months on the co-primary outcomes, as anticipated; the number of secondary outcome measures in our trial, which may increase the risk of a type I error; and potential low statistical power to demonstrate significant between-group differences on important secondary patient-reported outcomes. Conclusions: In this study, we observed improved mobility in people with a wide range of health conditions making use of digitally enabled rehabilitation, whereas time spent upright was not impacted. Trial registration: The trial was prospectively registered with the Australian New Zealand Clinical Trials Register; ACTRN1261400093662