Squidy

Hi all, I've got an essay to write on the activation of cell surface receptors, specifically hormones and neurotransmitters. My local library hasn't been much help, so I was hoping someone here might be able to point me in the direction of useful literature on the subject. I have a couple of books, but not enough to write 1500 words. I'd prefer to steer clear of wikipedia if possible. Many thanks in advance!