Distribution of V0v interneurons in the spinal cord.

(A,B) Lateral views of a spinal segment from two different preparations showing the distribution of GFP-expressing V0v interneurons. Images are the maximum intensity projections from 164 and 193 optical sections respectively. Most V0v interneurons project ventrally before crossing the midline as indicated in expansions (right panels). (C) Dorsal view of the spinal cord showing two V0v interneurons and their crossing axonal projections (neurons are colored and expanded in the right panels for clarification). The image is the maximum intensity projections from 90 optical sections (D) Graph showing the dorso-ventral and rostro-caudal distribution of V0v interneurons within one hemisegment. Data are from three different preparations (black, grey and open circles). The ventral edge is defined as 0 and the dorsal edge as 1. V0v interneurons are evenly distributed along the rostro-caudal axis, with an average of 21 ± 6 neurons per hemisegment (mean ± SEM).