ACUTE EFFECT OF ETHANOL ON THE PATTERN OF BEHAVIORAL SPECIALIZATION OF NEURONS IN THE LIMBIC CORTEX OF THE FREELY MOVING RABBIT

Single-unit activity was studied in the limbic cortex of eight freely moving rabbits in order to find out what kind of changes in the organization of unit activity correlate with behavioural disturbances following an acute administration of ethanol (1 g kg-1). The rabbits were taught to acquire food by pressing pedals in the experimental cage. Unit activity was recorded during this behaviour in a control experiment and the alcohol experiment took place the next day. The number of behavioural mistakes significantly increased in the alcohol experiments. The pattern of behavioural specialization of the units also differed between the control and alcohol experiments. In the control experiments 55% of units did not show any constant activations in relation to the behavioural phases (non-involved units), 28% of the units were constantly activated in relation to one or more behavioural phases learned in the cage (e.g. use of pedals; L units) and 17% of units showed activations in relation to the behaviour learned before the teaching of food acquisition (e.g. movements in general; M units). In the alcohol experiments the number of active units decreased by one-third compared with that found in the control experiments. The relative number of non-involved units did not change, whereas the relation between L and M units was reversed (11% L units and 34% M units). This was the result of a decrease in the number of active L units, mainly in the upper layers of the cortex. The results indicate that ethanol has a selective depressing effect on cortical neurons with different behavioural specialization, which could explain the behavioural disturbances observed in the alcohol experiments.