Electrical activities of the frog spinal cord are resistant to perfusion with hypoxic medium

Synaptic functions of the isolated and intra-arterially perfused frog spinal cord were investigated in terms of dorsal root-dorsal root potential (DR-DRP) and dorsal root-ventral root reflexes (DR-VRR), and under the influences of hypoxic Ringer solution, replacement of medium glucose with 2-deoxyglucose ('hypoglycemic Ringer'), and suspension of perfusion. The synaptic functions were markedly degraded during the suspension of perfusion, but they were remarkably resistant to hypoxic or hypoglycemic Ringer for more than 6 h, if the preparation was continuously perfused. The presynaptic inhibition of the first spike potential of the DR-VRR induced by a conditioning antidromic stimulation, however, was markedly reduced during prolonged exposure to hypoxic conditions. In contrast to earlier concepts that the spinal cord is vulnerable to hypoxia, the present results demonstrate that the frog spinal cord is resistant to prolonged perfusion with hypoxic and hypoglycemic media, although they suggest a latent deterioration of some processes which are believed to be more energy dependent.