Comparison of effects of pentobarbital and ethanol on the neuronal activity in the posterior parietal association cortex.

Abstract

The problem of this study was whether the effects produced by alcohol in the posterior parietal association cortex are specific to this drug or shared by other centrally acting depressant drugs such as barbiturates. The effect of graded doses of pentobarbital on multineuronal impulse activity was recorded with transdural microelectrode technique in 30 expts. in Brodmann's area 7 of five stump-tailed monkeys (Macaca speciosa). The results were compared with those from 32 expts. performed with alcohol and published separately. The dosage of the two drugs was determined on the basis of the monkeys' sensori-motor coordination which was assessed with a rating scale of reaching accuracy for food rewards. There were several recording sites where the actions of the two drugs were similar at similar behavioural levels of intoxication. However, in the distribution of effects among various functional types of recording sites a significant difference was found between pentobarbital and alcohol. Alcohol commonly diminished cellular activity related to motor behaviour (reaching, grasping) and only rarely responses to somesthetic stimuli, whereas the effects of pentobarbital were the opposite being most common on somatosensory responses and least common on activity related to motor behaviour. Also responses to visual stimuli were more sensitive to pentobarbital than to alcohol. The actions of pentobarbital and alcohol on responses evoked by sensory stimulation differed significantly (P less than 0.01). We conclude that significant differences exist in the mechanisms of action of alcohol and barbiturate on the associative systems of the brain.