Abstract
Immature rat spinal motoneurons showed a slowly synchronized rhythmic activity (sSRA) in divalent cation- free solutions. This sSRA was attributed to rhythmic oscillations of extracellular potassium ions in spinal cord. So, possible occurrence of the same phenomena in the dorsal horn at this same special situation, was investigated in this experiment. In the isolated spinal cord preparation from newborn rats, extracellular neuronal activity was recorded from dorsal and ventral roots using suction electrodes. After removal of extracellular divalent cations, sSRA could be recorded from both the dorsal root (dorsal sSRA) and the ventral root (ventral sSRA). The dorsal and ventral sSRA had a mirror image, but ventral sSRA occurred slightly earlier. Both were recorded in rats soon after birth, but not in older rats. Sectioning the border between the dorsal and ventral horn eliminated ventral sSRA, but not dorsal sSRA. It is suggested that both dorsal and ventral sSRA depends on the activity of a rhythm generator located in the dorsal horn. Several characteristic features of these two sSRA will be discussed. [J Physiol Sci. 2006;56 Suppl:S164]
