The inositol trisphosphate receptor regulates a 50-second behavioral rhythm in C-elegans

The C. elegans defecation cycle is characterized by the contraction of thre e distinct sets of muscles every 50 s. Our data indicate that this cycle is regulated by periodic calcium release mediated by the inositol trisphospha te receptor (IP3 receptor). Mutations in the IF, receptor slow down or elim inate the cycle, while overexpression speeds up the cycle. The IP3 receptor controls these periodic muscle contractions nonautonomously from the intes tine. In the intestinal cells, calcium levels oscillate with the same perio d as the defecation cycle and peak calcium levels immediately precede the f irst muscle contraction. Mutations in the IF, receptor slow or eliminate th ese calcium oscillations. Thus, the IP3 receptor is an essential component of the timekeeper for this cycle and represents a novel mechanism for the c ontrol of behavioral rhythms.