Effect of urethane on synaptic and amino acid-induced excitation in isolated spinal cord preparations.

Urethane (50 mM) produced a non-selective antagonism of depolarizations evoked by excitant amino acids or carbachol recorded from ventral roots of isolated spinal cord preparations of the frog or immature rat. Depolarizing responses to substance P or eledoisin-related-peptide were either unaffected or potentiated by this concentration of urethane. The threshold level for depression of dorsal to ventral root transmission was 10 mM urethane and transmission was completely blocked at 70-100 mM urethane. It is suggested that post-junctional blockade of the actions of excitant amino acids may be important in the anaesthetic action of urethane.