Effect of the forebrain on flexion reflexes in rats with ankle joint urate arthritis

Ankle joint urate arthritis in rats is associated with increased responses to ankle stimulation and decreased responses to stimulation of the distal foot. To determine the influence of the forebrain on flexion reflexes in this model, responses to ankle and foot stimulation were examined in chronic decerebrate rats, decerebrated either before or after the induction of the arthritis. The increased responsiveness to stimulation of the arthritic ankle which had been observed after 24 h of urate arthritis was equally apparent in animals decerebrated 24 h before the induction of the arthritis and in those decerebrated 24 h after the urate injection. However, the decreased responsiveness of the distal foot to pressure or temperature stimuli, which had been observed in arthritic animals with an intact forebrain, was still apparent in animals decerebrated 24 h after the induction of the arthritis but did not appear in animals who had been decerebrated before the arthritis induction. It is concluded that the forebrain is required for the production of the reduced responsiveness of the distal foot but is not required for its maintenance once the insensitive state has been acquired.