Touch Assay for C. elegans

Obtain embyros by treating gravid worms by Hypochlorite solution of the differrent strains. After incubate the worms in M9 for 17-24 hours at 20°C to obtains synched L1 stage in a 15 ml falcon tube on shaker.   

Next plate the worms on 60 mm plates with OP50-1. When plating centrifuge at 2000 rpms for a minute so worms collect at bottom of tube and aspirate out to 1 ml of M9 liquid,  then plate worms. After the M9 dries, incubate it at 20°C to L4 to young adult.

On a population of synchronized animals ranging between L4 and young adult stage, a pick designed for gentle-touch (adapted from Hobert et al., 1999) was used in a set of thirty touch replicates per worm, with each replicate consisting of a touch above the AVM in the head followed by a touch above the PVM in the tail. On each head touch, the ratios of positive response (counted as animal reversal or omega turn) versus negative response (no reversal or turn) were recorded. Positive/negative responses were only counted for the touches on the head region; the tail touch stimuli was used to reset the response in the head. 

Final result is quanitfy by the touch index which is generated by the total number of positive responses divided by the number of negative responses within the 30 touches per animal.