Pharynx pharmacology

I am studying some pharynx related behavior in Pristionchus, and I was wondering if there might be a way in C. elegans to pharmacologically paralyze the body wall muscles, but allow the pharynx to keep pumping normally. This would greatly assist me in observing behavior! I am looking into other means of immobilizing them as well, but if I could do it pharmacologically it would be experimentally convenient.