Supplementary Figure 1: Machining of the cannula holder adapter.

This adapter is specifically designed for use with the KOPF Model 1966 Cannula Holder. The adapter is fashioned from aluminum with an 8 mm stalk (3 mm in diameter) that can be held by the Model 1966. The main body of the adapter is 14 mm in length with a 7 mm diameter. There are two orthogonal bore holes through the body. The first is a 5 mm hole from which the center slit is created through to the tip of the adapter. The second is a 2 mm screw-hole so that a screw can be tightened to reduce the size of the center slit to hold the μ-needle. It is important that the center point of the adapter be in-line with the center point of the cannula holder itself to ensure accurate device injection. Note that this adapter is merely a suggestion, but we acknowledge there can be many other solutions to the problem of accurate injection of the devices. Most stereotaxic instrument manufacturers offer custom-built holders and it is likely that many standard electrode holders can be modified to suit the needs of the individual laboratory (e.g. KOPF Model 1768).