Formalin test
Rats were placed singly in perspex boxes (30 x 30 x 30cm,
with a mirror placed on the back panel to aid observation) for
approximately 15 minutes before the start of the test for
habituation.
Animals were pre-treated with standard analgesics
at different time points according to existing
pharmacokinetic/pharmacodynamic (PKPD) data (data not
shown).
Rats then received intraplantar injection into the right
hindpaw of a 50ul solution of either 1.25, 2.5, or 5.0%
formalin solution (saline vehicle) using a 29G needle, and
placed immediately back in the boxes.
Pain-like behaviours
(licking/biting and flinching) were recorded in 5 minute time
bins using the Pocket Observer (Noldus) for 45 minutes.
Data
were also considered in either the Early Phase (0-10mins) or
the Late Phase (11-45mins).
Animals were euthanased
immediately at the end of the study.
All experiments were
recorded using a video camera as back up information.