The nematode C. elegans has become an important model for understanding how genes influence behavior. However, in this organism the available approaches for identifying the neuron(s) where the function of a gene is required for a given behavioral trait are time consuming and restricted to non essential genes for which mutants are available. We describe a simple reverse genetics approach for reducing, in chosen C. elegans neurons, the function of genes. The method is based on the expression, under cell specific promoters, of sense and antisense RNA corresponding to a gene of interest. By targeting the genes osm-10, osm-6 and the Green Fluorescent Protein gene, gfp, we show that this approach leads to efficient, heritable and cell autonomous knock-downs of gene function, even in neurons usually refractory to classic RNA interference (RNAi). By targeting the essential and ubiquitously expressed gene, gpb-1, which encodes a G protein beta subunit, we identify for the first time two distinct sets of neurons in which the function of gpb-1 is required to regulate two distinct behaviors: egg-laying and avoidance of repellents. The cell specific knock-downs obtained with this approach provide information that is complementary to that provided by the cell specific rescue of loss-of-function mutations and represents a useful new tool for dissecting the role that genes play in selected neurons.