Receptor for short chain fatty acids. The activity of this receptor is coupled to the formation of inositol 1,4,5- trisphosphate, intracellular Ca2+ mobilization, the activation of ERK 1/2 and inhibition of intracellular cAMP accumulation. Coupled exclusively to the pertussis toxin-sensitive G(i/o)-alpha protein. The rank order of potency for agonists of this receptor is propionate = pentanoate = butyrate > acetate > formate.