ABSTRACT
INTRODUCTION: In the present study, a model was developed to determine the effect of secretase inhibition on beta-amyloid peptide (Abeta) levels in the cerebrospinal fluid (CSF) of freely moving adult rats. METHODS: Rats were chronically implanted with a cannula into the cisterna magna and CSF samples were collected at different time points from the same animal without anaesthesia. The levels of CSF Abeta were measured by a sandwich ELISA assay. RESULTS: Administration of DAPT, a functional gamma-secretase inhibitor, resulted in a substantial reduction of Abeta40 and Abeta42, confirming the in vivo functionality of the CSF as a biomarker source for endogenous APP processing modulation by secretase inhibitors. DISCUSSION: Thus, the present work provides clear evidence for the usefulness of CSF sampling from the freely moving rat model for testing the effectiveness of small molecule inhibitors of Abeta production.
Subject(s)
Amyloid beta-Peptides/cerebrospinal fluid , Peptide Fragments/cerebrospinal fluid , Administration, Oral , Amyloid Precursor Protein Secretases , Amyloid beta-Protein Precursor/antagonists & inhibitors , Amyloid beta-Protein Precursor/metabolism , Animals , Chemistry, Clinical/methods , Endopeptidases/metabolism , Enzyme-Linked Immunosorbent Assay , Male , Movement/physiology , Rats , Rats, Sprague-Dawley , Time Factors , Triglycerides/administration & dosage , Triglycerides/pharmacology , Wakefulness/physiology , gamma-Aminobutyric Acid/administration & dosage , gamma-Aminobutyric Acid/analogs & derivatives , gamma-Aminobutyric Acid/pharmacologyABSTRACT
INTRODUCTION: There is a continuing need for increased throughput in the examination of new chemical entities (NCEs) in terms of the pharmacokinetic (PK) parameters. The aim was to validate a new study method designed to improve throughput and reduce inter-animal variability and animal number requirement in routine bioavailability and plasma PK studies of NCEs in awake rats. METHODS: The design uses a new method for intravenous (iv) administration via the saphenous vein in combination with serial blood sampling via the tail vein. The multiple sampling method was compared with single sampling (decapitation) and the effect on haematocrit (Hct) levels was studied. Direct injection in the saphenous vein was compared to iv administration using an indwelling jugular catheter. RESULTS: Using structurally different NCEs, it was shown that a combination of direct injection via the saphenous vein and multiple sampling from the tail vein produces comparable plasma concentrations and subsequent PK results to the comparator methods. Furthermore, Hct levels remained within recommended levels using a total blood sampling volume of up to 2.1 ml/day for rats with a body weight of around 250 g. DISCUSSION: The new model increases throughput by avoiding the time required for preparative surgery, increases quality by allowing inter-animal comparison of major PK parameters as concentration time curves can be obtained from each animal, and reduces the number of animals required.
