Dual effects of acetaldehyde on electrical activity in the isolated frog spinal cord

Acetaldehyde (1.4 X 10(-7)-1.4 X 10(-5) M) produced a transient depolarization followed by a distinct hyperpolarization of the ventral and dorsal roots as recorded by sucrose-gap in the isolated spinal cord. This effect occurred more frequently at lower concentrations than at higher concentrations of acetaldehyde, and the depolarization increased with doses increasing. The ventral root reflex potentials evoked by the dorsal root stimulation had decreased amplitudes during depolarization and increased during hyperpolarization. In the presence of Mg2+ or tetrodotoxin, acetaldehyde produced only hyperpolarization. Acetaldehyde slightly prolonged glutamate-induced depolarization of both roots. These results suggest that acetaldehyde acts not only on the spinal motoneuron resulting in membrane hyperpolarization but also on the presynaptic sites, which causes postsynaptic membrane depolarization probably through an increased release and decreased uptake or inactivation of the excitatory transmitter.