Intraventricular Drug Delivery and Sampling for Pharmacokinetics and Pharmacodynamics Study

Abstract

Although the blood-brain barrier (BBB) protects the brain from foreign entities, it also prevents some therapeutics from crossing into the central nervous system (CNS) to ameliorate diseases or infections. Drugs are administered directly into the CNS in animals and humans to circumvent the BBB. The present protocol describes a unique way of treating brain infections through intraventricular delivery of antibiotics, i.e., polymyxins, the last-line antibiotics to treat multi-drug resistant Gram-negative bacteria. A straightforward stereotaxic surgery protocol was developed to implant a guide cannula reaching into the lateral ventricle in rats. After a recovery period of 24 h, rats can be injected consciously and repeatedly through a cannula that is fitted to the guide. Injections can be delivered manually as a bolus or infusion using a microinjection pump to obtain a slow and controlled flow rate. The intraventricular injection was successfully confirmed with Evans Blue dye. Cerebrospinal fluid (CSF) can be drained, and the brain and other organs can be collected. This approach is highly amenable for studies involving drug delivery to the CNS and subsequent assessment of pharmacokinetic and pharmacodynamic activity.

Figure 1:. Collection of CSF after injection of Evans Blue dye (1.1%) in the anesthetized rat to confirm cannula location.

CSF is extracted using a pulled glass pipette (A) and then collected in a tube for snap freezing and storage (B).

Figure 2:. Tracing of injection materials in the brain ventricles with Evan’s blue dye.

Whole brains are sliced with a blade at the injection site (A,B) or at more posterior locations (C) to confirm the successful injection in the ventricular system. Scale bar (B) = 1 mm.

Figure 3:. Bodyweight of representative animals.

Average body weight (+SD) of n = 174 representative animals (19 cohorts) before surgery (Day 0) and on the day of ICV injection (Day 1).