Detergent-soaked HRP-chips: a new method for precise and effective delivery of small quantities of the tracer to nervous tissue.

We dissolved horseradish peroxidase (HRP) in a 5% aqueous detergent solution (Nonidet P-40) and dried it to a solid mass which was then fragmented into small chips of convenient size. These were applied to the cut or crushed oculomotor nerves of Xenopus laevis tadpoles. This method combines the advantages of solid HRP (high concentration) and the presence of a detergent (enhanced uptake). Moreover, as compared to chips of HRP alone, addition of the detergent facilitated the manipulation of the chips.