Chronic pain has been associated with changes in forebrain regions, as well as impairments in related cognitive functions, including memory and cognitive flexibility. Here, we examine the impact of osteoarthritis(OA)-associated chronic pain on selected cognitive functions in a rat model. 
First, we adapted the monoiodoacetate (MIA) model of chronic OA-like joint pain to adult male Lister hooded (LH) rats, which are more suitable for cognitive testing than the commonly used albino strains. Then, we used the watermaze delayed-matching-to-place(DMP) test, the novel object recognition test and an operant response shifting task to examine the impacts of MIA-induced OA-like pain on memory and cognitive flexibility in LH. Nociceptive behaviour and sensorimotor activity were also measured at baseline and after model induction.  Joint pathology was confirmed.
MIA injection (3mg/50μL,n=8) caused robust pain behaviour, including weight-bearing asymmetry and changes in paw-withdrawal threshold, as well significant cartilage damage and synovitis, compared to saline controls(n=8). MIA-injected rats showed minor motor deficits (reduced rearing and swim speed). Mild PPI disruption was also observed in MIA rats, indicating impact on the forebrain regions involved in sensorimotor gating mechanisms. However, there was no significant impairment in hippocampus-dependent rapid place learning performance in the watermaze-DMP task, indicating that MIA treated LH rats do not have substantially altered hippocampal function. This finding is consistent with previous human imaging findings indicating that the hippocampus may be less affected by OA pain, than in other chronic pain conditions. Effects of this model of OA-like joint pain on cognitive flexibility will also be presented.

MIA-INDUCED OSTEOARTHRITIS-LIKE KNEE PAIN IMPACTS ON COGNITIVE FUNCTIONS IN LISTER HOODED RATS