[Long-term sensitization in the snail: the electrophysiological correlates in the command neurons of defensive behavior].

The long-term sensitization of defensive reflex led to an increase of excitability of the command neurons LPa3 and RPa3, controlling the defensive pneumostome contraction reaction due to a depolarization shift of the membrane potential and a decrease of the threshold potential. Depletion of dopamine by amphetamine injection also led to an increase of excitability in these command neurons mainly due to a decrease of the threshold potential. Sensitization of animals after amphetamine treatment resulted in a partial summation of effects--a reliable decrease of the threshold potential in comparison with the sensitized snails and amphetamine-treated ones. It was concluded that the increases of excitability during the long-term sensitization and amphetamine treatment were underlain by different mechanisms.