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. 2023 Jul 14;14:4218. doi: 10.1038/s41467-023-39955-8

Fig. 6. Working model for the aBoc step.

Fig. 6

During the defecation motor program, a calcium oscillation occurs in the intestine every 50 s, which leads to NLP-40 release from the intestine. NLP-40 activates its receptor, AEX-2, on AVL which results in a calcium spike. The calcium spike triggers secretion of the neuropeptide FLP-22 from AVL, which in turn activates its receptor, FRPR-17, on hmc. Activation of FRPR-17 leads to a calcium spike in hmc possibly by activating a signaling cascade composed of, GSA-1/Gαs and KIN-1/PKA. The calcium spike in hmc is transmitted to muscles through the gap junction protein UNC-9, resulting in a contraction of anterior body-wall muscles which is aBoc. Additional GABAergic neuron(s) may also secrete FLP-22 to activate hmc. FLP-9 activates its receptor, FRPR-21, on hmc which inhibits hmc activation. Additional peptidergic input to hmc, possibly from AVL, contributes to hmc activation in some cycles.