Cyclic adenosine monophosphate signaling in the rat vomeronasal organ: Role of an adenylyl cyclase type VI

The present study indicates that male rat urinary components in female rat vomeronasal organ microvillar preparations not only induce a rapid and tran sient IP3 signal, but in addition, the level of cAMP decreases with a delay ed and sustained time course. This decrease seems to be a consequence of th e preceding activation of the phosphoinositol pathway rather than the resul t of an enhanced phosphodiesterase activity or an inhibition of adenylyl cy clase (AC) via G alpha(i) or G alpha(o). This notion is supported by the fi nding that activation of the endogenous protein kinase C suppresses basal a s well as forskolin-induced cAMP formation. Furthermore, it was observed th at elevated levels of calcium inhibit cAMP formation in rat VNO microvillar preparations. These properties of cAMP signaling in the VNO of rats may be mediated by a calcium- and protein kinase C-inhibited AC VI subtype, which is localized in microvillar preparations of the VNO.