Representative histopathology of left ankle joints of (A) normal control rats (normal synovial lining, articular cartilage and subchondral bone), (B) untreated adjuvant arthritic rats, (C) adjuvant arthritic rats treated with 30 mg·kg−1·day−1 theophylline from day 16 to day 25, (D) adjuvant arthritic rats treated with 45 mg·kg−1·day−1 theophylline from day 16 to day 25, (E) adjuvant arthritic rats treated with 30 mg·kg−1·day−1 theophylline in combination with 0.01 mg·kg−1·day−1 sodium nitroprusside (SNP) from day 16 to day 25, (F) adjuvant arthritic rats treated with 30 mg·kg−1·day−1 theophylline in combination with 30 mg·kg−1·day−1 L-NG-monomethyl arginine from day 16 to day 25. Note the dramatic inhibition of inflammatory cellular infiltrate and alleviation of articular cartilage erosion by therapeutic administration of theophylline in combination with a low dose of SNP.