Heterotrimeric GTP binding proteins (G proteins) mediate signal generated by neurotransmitter and hormones. Among all G proteins, Go is the most abundant in brain but its role in brain is not clearly understood. To determine the function of the alpha subunit of Go (Go$alpha$), we search for the interacting partner of Go$alpha$ in brain using yeast two-hybrid system. A resistant to inhibitor of cholinesterase (Ric-8B) was identified as a Go$alpha$ interacting protein. We confirmed interaction between Go$alpha$ and Ric-8b employing in vitro affinity binding assay and showed that the Ric-8b increased the function of Go$alpha$. Our findings indicate that Ric-8b is possible guanine nucleotide exchange factor for Go$alpha$.