Aim: 

To further in vivo studies of spinal cord function in WT and KO mice we needed to measure averaged cord dorsum potentials evoked by electrical stimulation of hindlimb nerves as a guide to somatotopy. 33 CD1- mice (30-40g) were given 1.8 gm/kg Urethane, i.p. and after 15min, 0.4 gm/kg for sustained anaesthesia. Mice were supported prone by clamps at T13 and L3/4, the L1-2 laminae removed, dura opened and tissues covered by 4% agar. The sciatic nerve was stimulated in-continuity (mid-thigh) and the sural, medial and lateral popliteal nerves freed for stimulation at ankle level. Surface and depth recordings were amplified and processed by a CED 1401 and Spike 2 software.

Results: 

Sciatic stimulation at 1.0 -1.3 ( T evoked a synchronous, triphasic CAP (mean latency to ^+ve peak 2.0ms) followed at intensities >1.3T by a negative field potential. In 8 WT mice, systematic rostro-caudal recordings made 200m apart at 5T gave a maximal (averaged) CAP potential of 2.15 mV; SEM +/­ 0.22) and a mean field potential of -0.98mV; SEM +/­ 0.1 centered 1.6-2.0mm caudal to T13; in some mice T13 was removed to determine this maximum. Stimulation of the other nerves gave partial overlapping distributions with the field potential amplitude then dominating. Depth recordings showed phase reversal of the field potentials at different depths and the procedures aided the location of naturally evoked unit activities.

Conclusion: 

These results provide data for comparison with those from current studies on EphB1-KO mice exhibiting altered pain behaviour.