In vivo dynamics and distribution of intracerebroventricularly administered gadodiamide, visualized by magnetic resonance imaging

Direct injections into the cerebroventricles have been extensively utilized in neurophysiological studies. Mapping the distribution of injectate after intracerebroventricular injection has been made only by post mortem analys is, and the dynamic distribution of injectate within the brain has not been well characterized. In this report, we apply contrast-enhanced magnetic re sonance imaging to study the pharmacokinetics and extent of non-ionic gadod iamide transport into brain tissue in vivo after intracerebroventricular ad ministration. The results indicate that intracerebroventricular injectate t ravels quickly throughout the ventricular system from the lateral ventricul ar site of injection to the fourth ventricle and foramina of Luschka and Ma gendie within 2 min. After this, the signal intensity begins to increase in the periventricular and paraventricular brain parenchyma. Contrast enhance ment is visible 2 mm into the brain tissue from the ventricles. Quantitativ e analysis of the data shows that the transport of gadodiamide across the e pendymal layer that lines the cerebrospinal fluid space characterized a rat e constant of 0.066 +/- 0.017 min(-1). These results provide a better understanding of chemical transport and diff usion following direct injection into the cerebroventricles. They provide i nformation on the in vivo dynamics of injectate after intracerebroventricul ar administration, and show that contrast enhanced magnetic resonance imagi ng may be used to more precisely define the target sites of chemicals after intracerebroventricular administration into the brain. (C) 1999 IBRO. Publ ished by Elsevier Science Ltd.