Differential sensitivity of dorsal and ventral root activity to magnesium and 2-amino-5-phosphonovalerate (APV) in an isolated mammalian spinal cord preparation

Abstract

Spontaneous activity emerging from the isolated hamster spinal cord simultaneously along the ventral and dorsal lumbar roots was shown by inter-spike interval analysis to have different firing patterns. Ventral root firing was reduced in solutions containing 1 mM magnesium or sub-micromolar concentrations of 2-amino-5-phosphonovalerate (APV), whereas the activity in the dorsal roots was unchanged. Differences in sensitivity to magnesium and APV were also shown on the evoked ventral and dorsal root reflexes, with the dorsal root reflex being unaffected, and the ventral root reflex exhibiting a long latency component that was sensitive to magnesium and APV. These results indicate that NMDA receptors are involved in the generation of part of the ventral root responses in the spinal cord, but not in the generation of the dorsal root reflex and spontaneous dorsal root activity.