Arachidonic acid plays a role in rat vomeronasal signal transduction

Sensory neurons of the vomeronasal organ (VNO) detect volatile chemicals that are released by conspecific animals and convey information about social and reproductive behavior. The signal transduction pathway in vomeronasal receptor neurons (VRNs) is not known in detail, but is believed to be distinct from that of the sensory neurons of the main olfactory system. Many of the identified olfactory transduction components are not expressed by VRNs. Using Ca2+ imaging and electrophysiological recordings, we investigated the signal transduction pathway of urine perception and the possible role of polyunsaturated fatty acids (PUFAs) as intracellular messengers in freshly dissociated rat VNO neurons. We found that application of urine induced a transient increase in intracellular Ca2+ that was dependent on the activity of phospholipase C and diacylglycerol (DAG) lipase. The Ca2+ transient was not dependent on depletion of intracellular Ca2+ stores but was dependent on the presence of extracellular Ca2+. Furthermore, the urine response was not sensitive to modulators of adenylate cyclase and inhibitors of inositol 1,4,5-trisphosphate receptors. Application of PUFAs (linolenic acid and arachidonic acid, synthesized in living cells from DAG) also elicited Ca2+ transients in fura 2 measurements and inward currents in whole-cell voltage-clamp recordings. Pharmacological inhibition of lipoxygenase and cyclooxygenase induced a transient increase in intracellular Ca2+, possibly by increasing the endogenous level of PUFAs, leading to activation of transduction channels. These data provide evidence for a role of PUFAs in rat vomeronasal signal transduction.