2.6.2 Hargreaves test
Paw withdrawal latency to radiant heat was evaluated by the Hargreaves
test (Hargreaves, Dubner, Brown, Flores &
Joris, 1988). Animals were placed individually in Plexiglas cages
positioned on a heated glass floor (30°C) and allowed to habituate for
at least 30 min before testing. A radiant heat source was positioned
underneath the animal and aimed at the plantar surface of each hind paw.
The time interval before the animal withdrew its paw from the heat
stimulus was measured by an automatic plantar stimulator meter (IITC
model 390, Woodland Hills, CA) and recorded as the paw withdrawal
latency (PWL). This test was repeated three times at 5-min intervals. If
no behavioral response was elicited after 30 s (cutoff time), the
stimulus was discontinued to avoid sensitization and prevent tissue
damage. The average PWL across the three trials was used for data
analysis.