A NEW TECHNIQUE FOR THE DIRECT DEMONSTRATION OF OVERLAPPING CUTANEOUSINNERVATION TERRITORIES OF PEPTIDERGIC C-FIBER AFFERENTS OF RAT HINDLIMB NERVES

A new technique based on the phenomenon of vascular labelling has been devised for the direct visualisation of overlapping innervation terri tories of cutaneous nerves. The saphenous, peroneal and sural nerves o n one side in anaesthetised rats were exposed, cut centrally and succe ssively stimulated antidromically to induce a neurogenic inflammatory response after an intravenous injection of either a 1% colloidal silve r solution or a suspension of 3% Monastral Blue B. Light microscopic e xamination of transparent preparations of the dorsal hindpaw skin reve aled labelled blood vessels of different colours which represented cut aneous territories served by different nerves. Blood vessels labelled with both substances were regarded as areas of overlapping innervation . Such areas were typically localised along the border of adjacent inn ervation territories. In addition, distinct areas exhibiting double-la belled blood vessels were regularly encountered in regions separate fr om this border zone. Areas of interest were drawn with the aid of a ca mera lucida and measured by means of a computerised system. The result s indicate a significant, although topographically variable, degree of overlap of these cutaneous innervation areas. This new technique offe rs a possibility to explore the importance of normally existing overla p in the reinnervation of a denervated skin area by collateral nerve s prouting.