Penetration of phosphorothioate oligodeoxynucleotides into rainbow trout brain in vivo. A technique for chronic infusion of substances into the brain of free‐living adult fish

Abstract

This paper describes a method for infusing chronically substances into the cranial cavity of free‐living rainbow trout Oncorhynchus mykiss for several weeks. The efficacy of the method was established by examining the penetration of radioactively labelled phosphorothioate oligodeoxynucleotides and a blue‐coloured dye, xylene cyanole, into brain tissue. No problems with pump patency were encountered, and the contents of the pump diffused consistently throughout the brain ventricular system, including the anterior lateral ventricles of the olfactory lobes, the third ventricle under the optic tecta and into the hypothalamus, including the lateral ventricular recesses. Autoradiographic examination of frozen sections demonstrated variable penetration of labelled probe into brain interstitium to a depth of up to approximately 200 μm. At the end of the experiment, >50% of radioactivity within brain tissue was shown to be of similar size to intact, labelled oligodeoxynucleotides.