Electrical coupling and intrinsic neuronal oscillations in Rana temporaria spinal cord

In the presence of TTX and NMDA, spinal cord neurons in Rana temporaria embryos generate membrane potential oscillations, but only when 5-HT is added to the perfusate. These oscillations are voltage-dependent due to magnesium block of the NMDA receptor ionophore and can vary in amplitude between 0 and 40 mV with imposed membrane polarization. In contrast, the intrinsic frequency of the oscillations is unaffected by changes in membrane potential. This could result from electrical coupling amongst homonymous motoneurons. Here we present initial evidence for such connections and discuss their implications for the segmental control of rhythmic motor behaviour.