Description: The cell body of M1 is located subdorsally between the muscle and right marginal cell. A single process runs anteriorly in this position to the nerve ring where it then joins the dorsal nerve cord. Upon reaching the level of pm1, the process splits into two to send a vesicle-filled process to each of the subventral nerve cords, synapsing on pm1 and pm2 before reaching the cords. These then run posteriorly for a short length and form synapses on pm2 and pm3 (Albertson and Thomson, 1976).
Neurotransmitter: Possibly acetylcholine (Duerr et al., 2008, C. elegans Book II-Appendix 2).
Function: Unknown or redundant (Avery and Thomas, 1997).
Receptor Expression: Expresses glutamate receptor subunit, GLR-2 (Brockie et al., 2001). Suggested to express a subunit of the glutamate-gated chloride channel, AVR-14 (Cook et al., 2006; Brockie and Maricq, 2006).