Re: What is the 'rat foot analgesia' test for testing pain killing drugs?

Hey Dave.. The FORMALIN TEST measures the analgesic (painkilling) effects 
of 
medications on
so-called tonic, or persistent pain. A dilute solution of formaldehyde and 
saline is
injected under the skin of a rat's paw, inducing pain that lasts for about 
90 minutes.
The rat licks its paw repeatedly, which is a sign of moderate pain (a pain 
rating of
3). Then. after a while, the animal holds the paw in the air (a rating of 
2), steps on it
gingerly (a rating of 1) and finally walks normally (a rating of 0). These 
criteria are used in testing the effectiveness of analgesias.... Mark