Fig. 9. Activity-dependent depression during bursting motor output. (A) (i) Mean level of activity before and after bursts in wild-type embryos (n=3, 15 pre-burst and 15 post-burst sequences) (error bars=s.e.m.). (ii) Number of muscle contractions (in 1-minute time bins) from start of second burst until the end of third burst in five embryos. Data are normalised so that each cycle duration=1. (iii) Regression lines for number of contractions per minute during inter-burst interval. (B) Activity-dependent depression in embryos expressing channel rhodopsin 2 in all neurons (elav-GAL4;UAS-ChR2). Average response scores are shown for different intervals from the end of a naturally occurring burst of activity (n=5 at each time interval and error bars indicate s.e.m.). Response scores correspond to shortest stimulus pulse producing a long-lasting (over 15 seconds) vigorous contractile response (response to 25 mseconds scores 5, 50 mseconds 4, 100 mseconds 3, 200 mseconds 2, 400 mseconds 1, no response to any pulse 0). Stimuli: 488 nm light and control wavelengths that do not activate ChR2 (568 and 638 nm).