ALTERATION OF SUBSTANCE P-MEDIATED VASODILATATION AND SYMPATHETIC VASOCONSTRICTION IN THE RAT KNEE-JOINT BY ADJUVANT-INDUCED INFLAMMATION

The effects of nerve stimulation and topical administration of substan ce P (SP) on the blood flow supplying the rat knee joint were measured using laser Doppler perfusion imaging. A comparison was made between the responses found in normal knees and those observed in a group of a nimals with unilateral chronic inflammation induced by intra-articular injection of Freund's adjuvant, 1 week prior to experimentation. In c ontrol knees, nerve stimulation produced a frequency-dependent vasocon striction over the range of 5-30 Hz and application of SP caused a dos e-dependent vasodilatation. Chronically inflamed joints showed virtual ly no response to either nerve stimulation or SP application, suggesti ng a radical alteration in sympathetic and neuropeptidergic actions.