A hypothermic miniaturized stereotaxic instrument for surgery in newborn rats.

We describe a simple, scaled-down instrument which enables accurate, reproducible stereotaxic placements into specific sites in the brain of the newborn rat. The instrument is specially designed for the administration of long-term hypothermia, yet permits the use of alternative methods of anesthesia. The design of the head-stabilizing mechanism allows head positioning to be finely adjusted to achieve precise horizontal and vertical zero planes. This adaptability also allows the device to accommodate a large range of animal sizes and levels of maturity. Furthermore, the apparatus can be fitted onto a conventional adult stereotaxic frame or used by itself in combination with a free-standing manipulator. As a model preparation, we describe a procedure for stereotaxic surgery in the post-natal day (P1) rat. The versatility of the instrument has permitted successful stereotaxic surgery in adolescent as well as neonatal rats, newborn and adult mice, and newborn hamsters.