An easily constructed pipette for pressure microinjections into the brain

A simple device for making pressure microinjections into the brain, its application for delivery of a tracer substance, biotin dextran amine, and an example of the resulting axonal transport are described. The device is based on the use of a Luer tip Hamilton microliter syringe mated directly to the plastic hub of an injection needle assembly in which the metal needle has been replaced by a glass pipette. In model experiments, the injection sites were measured in brain sections of rats, which were perfused with fixative immediately after administration of the tracer, and the relationship between the injected volume and the area of the injection site was evaluated. The results showed that the device provided accurate and reproducible delivery of the fluid.