This study was performed to elucidate the effects of glutamate, aspartate, substance P and GABAergics on the intracellular membrane potential and membrane input resistance of isolated medullary dorsal horn, and the interrelations between EAA,
substance
P and GABA in medullary dorsal horn. Transectional slices of caudal part of trigeminal sensory nucleus were prepared from rats about 5 weeks old, then transferred and fixed in the recording chamber where it was preincubated and continuously
perfused
with airated modified Koreas-Ringer solution. Intracellular recordings were carried out with glass microelectrode to record the changes of membrane potential and membrane resistance induced by perfusion of glutamate, aspartate, substance P, GABA,
baclofen and/or bicuculline.
@ES Results obtained as follows:
@EN 1. Glutamate and aspartate respectively depolarized medullary dorsal horn neurons and decreased membrane input resistance in a dose-dopendent manner. Effect of glutamate and aspartate applied simultaneously on medullary dorsal horn neuron was
not
different from that of glutamate or aspartate, respectively. Substance P also depolarized medullary dorsal horn neurons.
2. Medullary dorsal horn neurons responding to glutamate also responded to aspartate and substance P.
3. GABA and baclofen showed little effects on menbrane potential and input resistance.
4. Bicuculline evoked a depolarization of neurons of medullary dorsal horn.
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