SUBSTANCE-P INNERVATION OF EQUINE SYNOVIAL MEMBRANES - JOINT DIFFERENCES AND NEURAL AND NONNEURAL RECEPTOR LOCALIZATIONS

Substance P (SP) immunocytochemistry and receptor autoradiography were used to define the innervation of the equine synovial membrane of joi nts equivalent to the wrist and knuckle of man. SP-immunoreactive fibe rs were mainly concentrated around blood vessels in the subsynovial la yer, although not exclusively, while in the more distal joint, SP fibe rs were more frequently seen in the synovial surface layer. Iodinated SP receptor autoradiography studies revealed silver grain concentratio ns in the advential layer of blood vessels associated with the vasa va sorum, on the vascular endothelium and in the synovial surface. These findings suggest that SP has various sites of action within the synovi al membrane, each of which may contribute both a sensory function and a different component of the inflammatory process to the joint.