PROLONGED ALTERATION OF VASOCONSTRICTOR AND VASODILATOR RESPONSES IN RAT KNEE JOINTS BY ADJUVANT MONOARTHRITIS

Both neurogenic influences and the regulatory neuropeptide substance P (SP) have been implicated in the development of joint inflammation. U sing the laser Doppler perfusion imaging technique to quantify relativ e changes in joint blood flow, the effects of nerve stimulation and to pical SP application were examined in normal and chronically inflamed rat knee joints. Synovial inflammation was induced by unilateral intra -articular injection of Freund's complete adjuvant and experiments wer e carried out 1 week and 3 weeks later. Normal knees showed a frequenc y-dependent vasoconstriction in response to saphenous nerve stimulatio n over the range of 5-30 Hz and a dose-dependent vasodilatation in res ponse to SP administration. These vasoactive responses were completely abolished in the chronically inflamed knee joint, the abolition persi sting throughout the investigation. Since articular cartilage is criti cally dependent on synovial fluid formation for its nutrition, loss of neurovascular control of the synovial microcirculation could contribu te to the degenerative changes that commonly accompany chronic inflamm atory joint diseases.