my new rat is coughing/squeaking?

Question
Hello,
We just bought a male rat from a petstore... I know not ideal. He is about 3months old and since we brought him home 3/1/11 he has been sneezing and doing this cough squeak noise pretty frequently. We own 4 other rats and none of them have ever done this. He is coming out of his shell a little bit. But, when we brought him home he just sat at the bottom of the cage frozen. He is actually walking around the cage now but still making a coughing noise. It sounds more like a cough than sneeze with a little squeak he doesnt have any noticeable discharge from his nose or eyes yet. We have also kept him seperate from our other rats and they all use the same bedding type so I dont know whats wrong with him. We have a 14 day health guarantee so I can take him back to petco and have them look at him I just wanted to get an idea what a expert thinks. I am worried they will try to brush his problem off until the 14 days is up and he will get worse. Any advice would be wonderful. I am still learning and have never had a health problem with my others so this is new to me and I just want him to get better so we can start enjoying our new family memeber. Thank you for reading :)

-Jessica and ratties

Answer
Sounds like Myco already. I would refrain from going back to the petco. They will only want to exchange him and I feel sorry for the rat, as he is now coming out of his shell and learning to love his new life with you.  I would take him to the vet and DEMAND petco pay you back. Enough fussing and they usually do.  He needs to be on medications for a bit to get better and the vet should know what to do for rats.  Please read my site, sandyscrittercity.com and you will find all of the info needed to know about pet rats, and more.  Start out with the page on rat illness and check out the page on myco. THis may help you better understand what it is all about and how to treat it.  I can help find a vet for you as well, but I need to know your location.