Effect of protein cross-linking aldehydes on nerve activity

The changes in excitability and conduction properties of frog sciatic nerve under the influence of glutaraldehyde (GA), formaldehyde (FA), butyric aldehyde (BA) and crotonic aldehyde (CA) were examined in the concentration domain 0.01-1.00% (w/v) and at 20, 25, 30 and 35 degrees C. All these reagents irreversibly reduce the amplitude of the compound action potential of the nerve and decrease the conduction velocity up to the complete block. These changes occur as approximately exponential time decays. The decreasing order of efficiency is : CA greater than BA greater than FA greater than GA, showing no obvious correlation with the molecular weight of the aldehydes. The rise in temperature activates the decrease of amplitude but has a compensatory affect on the decrease of conduction velocity. The rising phase of the nervogram apparently remains unchanged, while the duration of the falling phase is up to threefold lengthened--more but slower at low temperatures and concentrations. These changes in the electrical response of the nerve are analysed as expressing the diffusion of aldehydes within the tissue, and their specific reactions with the proteins of the ionic channels.