I want to use a beta blocker in vivo but first I want to ensure the drug is working and for how long the effects last after the drug is withdrawn. I'm thinking I can administer the drug and then do RT-PCR for the beta adrenergic receptor type and check to see if it is changed in mice that got the drug vs. saline treated? I'd expect treatment with the antagonist will cause upregulation?
Any other ideas? Is this necessary?
Seems like it would sort of depend on what you are using the drug for. Collecting tissue and doing PCR would, in my opinion, be a roundabout way of verifying your drug dose if your main interest is in some type of behavior or phenotypic endpoint. However, it might be appropriate if the goal of your research is to look at differences in receptor expression following chronic treatment, for example.
It would seem easier, if you have the appropriate equipment, to look at some simple physiological measurements that have been previously reported for your drug. Maybe your drug was shown to affect heart rate, blood pressure, body temperature, or locomotion/activity levels. If you can replicate some previous data reported for your drug or one in its class, you have good idea you are working somewhere near the effective dose for your drug and would be able to measure a time course of its effects. Ideally the effect you measure will be the one your conclusions most heavily depend upon.
Alternatively, if the drug has previously been reported to have robust effects at a certain range of doses you should just be able to cite that prior research, as long as you trust it.