AC can be activated by at least three distinct pathways: First, a novel NF1/Ras-dependent pathway stimulated by growth factors such as EGF and TGFα that activates an unidentified AC (AC-X), and does not involve Gαs; secondly, an NF1/Gαs-dependent pathway, acting through Rutabaga-AC (Rut-AC), stimulated by serotonin and histamine, and possibly PACAP38 (see discussion), that does not require Ras; thirdly, a classical NF1-independent pathway, involving Gαs but not NF1 or Ras, stimulated by FMRFamide and dopamine that activates an unidentified AC (AC-Y).