Effect of ethanol on hippocampal neurons depends on their behavioural specialization

Acute effect of ethanol on hippocampal neurons was studied during food acquisition behaviour in seven rabbits. The rabbits were taught to acquire food from a feeder by pressing a pedal on the same side of the cage. The behaviourally specialized units (L units related to newly learned behaviour and M units related to behaviour formed before learning, e.g. certain movements) were comparable with the 'place' (projectional pyramidal and granular cells) and 'displace' (non-pyramidal interneurons) units of the current classification. The same direction of ethanol effects was found as for the limbic cortex; the number of certain kinds of L units decreased and that of M units increased but there was no significant change in the relative number of L and M units as a whole. The background frequency of L units decreased, but the frequency within activations increased. The results confirm our earlier findings on the most marked depressive effect of ethanol on L units and show that it is the behavioural specialization, not the morphological unit type, which is a major determinant of the ethanol influence.