We are responsible pet owners. We neuter all the cats that we share our lives with. Buster is a gentle loving cat. He was very playful with his male cat buddy Twinkie (our original cat) and gets along with the older male cat Pickles. However Twinkie got ill and passed on. We tried to introduce another male cat "Sam" but that was disastrous. Buster was very aggressive to the poor guy. Finally poor Sam went outside one evening and never returned. He may have been a victim of a Fisher Cat attack.
When my daughter moved into an apartment that didn't allow pets we ended up with a neutered female cat "Paris". She is a feisty little thing and Buster hates her. He's attacked her and has picked up the very disgusting habit of spraying around the house. Besides convincing us that we will never own another male cat, I tried a few remedies. After chasing him around with a spray bottle (taste of his own medicine) I decided that negative responses is going to work with this cat. I purchased an aerosol pheromone spray that is supposed to calm cats. It is called "Feliway" and as the disclaimer in the literature mentions that it may not work on all cats. It is supposed to mimic the "calming" pheromones that a cat releases when it rubs against objects instead of the territorial spraying "MY SPACE" pheromones. Buster scoffed at this product.
Finally we settled on a vet visit with female hormones for good old Buster. He was okay for a day or two, obviously in a state of sex confusion. I actually had a pang of guilt... but he's back to his nasty spraying attitude. He is so gently with human (especially me) but can't deal with this particular female cat. We have given it over a year to work to no avail.
I've decided to teach her some defensive moves with a bit of sparring and although she can draw human blood (mine), I can see that this is going to be a long process.