抄録
In the previous studies we showed that when the rat medullary pyramid was stimulated the negative potentials were recorded from everywhere in the spinal cord at postnatal day 7 (P7), however, after P14 the positive potentials instead of the negative potentials were recorded in the ventrolateral side of spinal cord. In this study we investigated the properties of the negative and positive potentials electrophysiologically and pharmacologically. The CS tract was stimulated at the level of medullary pyramid and field potentials were recorded from the cervical cord (C7). Pharmacological agents were applied to recording sites by micro pressure ejection through the multi-barrel pipettes along with recording. The negative field potentials were evoked with constant latency and showed paired-pulse depression and frequency depression. Those potentials were reversibly blocked by an AMPA receptor antagonist, CNQX. The positive potentials were not affected by glycine receptor blocker, strychnine, GABA-A receptor blocker, bicuculline and CNQX. These indicate that the negative potentials evoked by the medullary pyramid stimulation are active sinks generated by the monosynaptic action of CS synapses, whereas the positive potentials recorded in ventrolateral side represent the passive sources. Together with the change of the distribution of the potentials during the development we conclud that the CS synapses are distributed widely in the spinal cord at P7 and subsequently they are eliminated from the vetrolateral side and restricted to the dorsomedial side of spinal cord. [Jpn J Physiol 54 Suppl:S227 (2004)]
