Quote:
In animals, Valium appears to act on parts of the limbic system, the thalamus and hypothalamus, and induces calming effects. Valium, unlike chlorpromazine and reserpine, has no demonstrable peripheral autonomic blocking action, nor does it produce extrapyramidal side effects; however, animals treated with Valium do have a transient ataxia at higher doses. Valium was found to have transient cardiovascular depressor effects in dogs.
Basically it will make him more relaxed but high doses may make him clumsy (ataxia). It can also depress the cardiovascular system (heart), although it will come and go.