When it comes to the bedroom, Viagra, Cialis and Levitra are all household words, thanks to TV, radio and Internet ads broadcasting information about erectile dysfunction around the clock, on all kinds of programming - even the Super Bowl. So when Rachel Braun Scherl, 45, a Stanford University business school graduate, co-founded Semprae Laboratories, which developed Zestra Essential Arousal Oils, a product described as a botanical aphrodisiac, she thought bringing its message to the airwaves would be a snap. Research had shown that tens of millions of American women had sexual difficulty and no products to remedy it. Scherl, 45, a married mother of two, and company co-founder Mary Jaensch, 58, a married mother of three, thought they had an answer for this unmet need, along with the cash to pay for ads on TV. In an apparent double standard, many networks and some websites have declined the company's ads; a few will air them during the daytime, and others only after midnight. The most frequent answer we get is, 'We don't advertise your category,' " Scherl said. "To which we say, 'What is the category? Because if it's sexual enjoyment, you clearly cover that category. If it's female enjoyment, you clearly don't.' And when you ask for information as to what we would need to change so they would clear the ad for broadcast, they give you very little direction. ... And yet they have no problem showing ads for Viagra and other men's drugs. Why?"