The present investigation aimed to study two methodological concerns of an experimental model, where a spinal loop dialysis probe is used for administration of substances to the spinal cord and sampling of neurotransmitters by microdialysis from the same area of anaesthetized rats. [(3)H]Epibatidine in concentrations of 1, 10 and 100 nM was dissolved in Ringer's solution and administered through the dialysis membrane into the dorsal region of the cervical spinal cord. First, the outflow of [(3)H]epibatidine from the probe into the spinal cord was examined with respect to different concentrations and changes over time. Then, the distribution of the different [(3)H]epibatidine concentrations along the spinal cord was studied. It was found that the percentage of [(3)H]epibatidine entering the spinal cord did not differ between different administered concentrations after a stabilization period of 60 min. The administered [(3)H]epibatidine was found to be distributed to the area closest to the dialysis probe and not dispersed along the spinal cord, and the distribution was equal for all concentrations. The data presented in this investigation provide information, which is important for interpretation of data from intraspinal administration of substances through the spinal loop dialysis probe.