Trans-Uterine Tracer Injections in Mammalian Foetuses

Intra-uterine manipulation of mammalian foetuses for experimental purposes was first described at the beginning of this century (Wolff, 1919). Though numerous publications have appeared since which bear witness to the feasibility of intra-uterine manipulation, its application has remained rather restricted. In this paper we describe a technique for the trans-uterine injection of neuronal tracers into rat foetuses. Uterine wall and foetal membranes are pierced only with a micro pipette, and are thus left virtually intact, preventing loss of amniotic fluid. Surgical mortality is 24% overall, but the experimental success rate is much lower (23%). Even so these results are comparable to more complicated procedures, because the technique is simple (i.e. requires no micro surgical skill), and because up to 6 foetuses can be injected per dam. Technical problems, such as foetal anaesthesia and the detection of false-negative results due to imponderable factors are discussed.