Effect of carrageenan on noxious pressure threshold and paw volume. The carrageenan was injected in the plantar surface of the right paw (2%, 0.1 ml). Left Graph. Noxious pressure threshold was measured by Analgesia-Meter (Ugo Basile). Right Graph. Volume measured by a plethysmometer. Data expressed as mean ± SD. The threshold to noxious pressure in the right hindpaw, decreased after carrageenan injection, recovered the next day and was equal to the threshold in the left hindpaw for the whole period of observation (up to 28d).