Age-dependent differences in sensitivity to aconitine of rat hippocampal slices

The effect of aconitine, a plant alkaloid known to bind at site 2 of the sodium channel, was investigated on neuronal excitability in hippocampal slices of adult and juvenile rats. Aconitine (0.01-1 microM) diminished the extracellularly recorded population spike in a concentration-dependent manner. At each concentration, the inhibitory action of aconitine was significantly stronger and was obtained after a shorter latency in slices of juvenile rats (20-25 days) as compared with slices of adult rats (45-50 days). When maximal inhibition was achieved, a prolonged application of aconitine evoked an increase in spike amplitude of up to 15% in slices of juvenile but not of adult rats. The latency of recovery from the aconitine-induced inhibition was also significantly shorter in slices of juvenile rats. This effect was concentration-dependent and significantly stronger in slices of juvenile rats. These observations indicate that juvenile hippocampi have a higher susceptibility to the effect of aconitine, but also provide a partial protective mechanism.