Peripheral reinnervation patterns and dorsal root ganglion topography in skin-grafted frogs: a behavioral and histological examination.

Cutaneous respective fields for the first ventrolateral (VL1) and dorsomedial nerve trunks were mapped out behaviourally in normal and in skin-grafted Discoglossus pictus frogs. Ventrally directed wiping responses were obtained from stimulation of dorsally located belly skin grafts in all experimental animals. These misdirected responses were abolished completely by cutting either the dorsomedial nerve trunk or both the dorsomedial and the VL1 nerve trunks. The topography of cutaneous neurons of the dorsal root ganglion innervating dorsal skin areas was demonstrated by back-filling the dorsomedial nerve trunk with cobalt. In both normal and skin-grafted frogs, twice as many cobalt-filled neurons were observed in the dorsal half of the ganglion as in the ventral half although the absolute number of filled cells in different regions was the same in both groups. It was concluded that misdirected responses following skin rotation cannot be explained on the basis of a re-establishment of the original peripheral nerve connections.