Degenerate primers were used in the polymerase chain reaction (PCR) to investigate the expression of genes encoding regulators of G-protein signaling (RGS) in olfactory rosettes and in isolated olfactory receptor neurons from channel catfish. Five cloned PCR products were obtained from olfactory rosettes that shared 78% amino acid sequence similarity to the mammalian RGS3 gene product. Southern blotting of PCR products from isolated olfactory receptor neurons showed that the catfish RGS3 homology was expressed in the neurons. These results suggest that the RGS3 gene may be involved in regulating G-protein signaling in olfactory receptor neurons. These results are also the first demonstration of RGS gene expression in a vertebrate sensory system.