Purpose of vehicle during oral gavage - (Aug/14/2013 )

Hi and good afternoon. 

Not sure if this is the right group to post my question, but I'll give it a try. 

Im just started on my masters-project and are performing oral gavage on rats in a couple of weeks. I read that you can use different 'vehicles' when introducing pharmaceuticals into the rodents, one which was methylcellulose. I cant seem to find any articles on the sole purpose of the vehicle. I understand that you must dissolve your pharmaceutics in something before introducing it into the rodent, but how do I know what the best vehicle is? 

- Magnus

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