A comparison of drug transport in pulmonary absorption models: isolated perfused rat lungs, respiratory epithelial cell lines and primary cell culture

Purpose: To evaluate the ability of human airway epithelial cell layers and a simple rat isolated perfused lung (IPL) model to predict pulmonary drug absorption in rats in vivo. Method: The permeability of seven compounds selected to possess a range of lipophilicity was measured in two airway cell lines (Calu-3 and 16HBE14o-), in normal human bronchial epithelial (NHBE) cells and using a simple isolated perfused lungs (IPL) technique. Data from the cell layers and ex vivo lungs were compared to published absorption rates from rat lungs measured in vivo. Results: A strong relationship was observed between the logarithm of the in vivo absorption half-life and the absorption half-life in the IPL (r = 0.97; excluding formoterol). Good log-linear relationships were also found between the apparent first-order absorption rate in vivo and cell layer permeability with correlation coefficients of 0.92, 0.93, 0.91 in Calu-3, 16HBE14o- and NHBE cells, respectively. Conclusion: The simple IPL technique provided a good prediction of drug absorption from the lungs, making it a useful method for empirical screening of drug absorption in the lungs. Permeability measurements were similar in all the respiratory epithelial cell models evaluated, with Calu-3 having the advantage for routine permeability screening purposes of being readily availability, robust and easy to culture

Anaesthesia and PET of the Brain

Although drugs have been used to administer general anaesthesia for more than a century and a half, relatively little was known until recently about the molecular and cellular effects of the anaesthetic agents and the neurobiology of anaesthesia. Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) studies have played a valuable role in improving this knowledge. PET studies using 11C-flumazenil binding have been used to demonstrate that the molecular action of some, but not all, of the current anaesthetic agents is mediated via the GABAA receptor. Using different tracers labelled with 18F, 11C and 15O, PET studies have shown the patterns of changes in cerebral metabolism and blood flow associated with different intravenous and volatile anaesthetic agents. Within classes of volatile agents, there are minor variations in patterns. More profound differences are found between classes of agents. Interestingly, all agents cause alterations in the blood flow and metabolism of the thalamus, providing strong support for the hypothesis that the anaesthetic agents interfere with consciousness by interfering with thalamocortical communication.</p

Biofluid Biomarkers in Huntington's Disease

Huntington's disease (HD) is a chronic progressive neurodegenerative condition where new markers of disease progression are needed. So far no disease-modifying interventions have been found, and few interventions have been proven to alleviate symptoms. This may be partially explained by the lack of reliable indicators of disease severity, progression, and phenotype.Biofluid biomarkers may bring advantages in addition to clinical measures, such as reliability, reproducibility, price, accuracy, and direct quantification of pathobiological processes at the molecular level; and in addition to empowering clinical trials, they have the potential to generate useful hypotheses for new drug development.In this chapter we review biofluid biomarker reports in HD, emphasizing those we feel are likely to be closest to clinical applicability

Discriminative stimulus effects of pentobarbital in pigeons

Pigeons were trained to discriminate the IM injection of pentobarbital (5 or 10 mg/kg) from saline in a task in which 20 consecutive pecks on one of two response keys produced access to mixed grain. Pentobarbital (1.0–17.8 mg/kg) produced a dose-related increase in the percentage of the total session responses that occurred on the pentobarbital-appropriate key. The concomitant administration of bemegride (5.6–17.8 mg/kg) antagonized the discriminative control of behavior exerted by the training dose of pentobarbital. Benzodiazepines, diazepam (1.0 mg/kg) and clobazam (3.2 mg/kg), and barbiturates, methohexital (10 mg/kg), phenobarbital (56 mg/kg), and barbital (56 mg/kg), produced responding on the pentobarbital-appropriate key similar to that produced by pentobarbital. In contrast, narcotics such as morphine, ethylketazocine, cyclazocine, and SKF-10,047, at doses up to and including those that markedly suppressed response rates, produced responding predominantly on the saline-appropriate key. Similarly, the anticonvulsants, valproate, phenytoin, and ethosuximide occasioned only saline-appropriate behavior, indicating that not all anticonvulsants share discriminative stimulus effects with pentobarbital. Muscimol, a direct GABA agonist, and baclofen, a structural analogue of GABA, also failed to produce pentobarbital-appropriate responding. Ketamine, dextrorphan, and ethanol (0.3–3.2 g/kg, orally) produced intermediate levels of pentobarbital-appropriate responding, suggesting that the discriminative effects of these drugs may be somewhat like those of pentobarbital.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46416/1/213_2004_Article_BF00433247.pd