Pharmacological analysis of conditioning in sensorimotor cortex neurons in a model.

In awake mobile rabbits, with electrodes implanted in the medial lemniscus, midbrain tegmental reticular nucleus, and pyramidal tract, combined stimulation of two brain of two brain structures resulted in elaboration of conditional connections in sensorimotor cortex neuronal populations. The main criterion of the conditioning was the appearance of changes in the neuronal activity on omission of the second stimulus. These changes represented a complex of electrical events, some of which were similar to and others different from the evoked responses to the second stimulus. Application of atropine, sulfate, chlorpromazine hydrochloride, serotonin creatinine sulfate, and gamma-aminobutyric acid (GABA) to the cortex at the site of the recording exerted a modulating effect on the conditional neuronal activity patterns. Of the above substances, GABA and atropine had the most pronounced effect. The GABA removed the short-latency components of the conditional changes which were similar to evoked responses. The atropine abolished the long-latency changes which differed from evoked responses.