General principles of spinal motor circuit development: early contributions from research on avian embryos.

Abstract

Birds and mammals, both being amniotes, share many common aspects of development. Thus our understanding of how limb-innervating mammalian spinal motor circuits develop was greatly influenced by the use of the avian embryo (chick/quail) to bring about experimental perturbations to identify basic underlying mechanisms. These included embryonic surgery, the application of drugs to influence activity or molecular interactions, and the ability to observe motor behavior and make physiological recordings in intact developing embryos. This article will review some of these contributions, highlighting several areas including the acquisition of motoneuron subtype identity and target selection, as well as the role of spontaneous rhythmic activity in circuit development.