The effect of the systemic administration of carbachol on consolidation of the passive avoidance skill and the characteristics of evoked responses in the CA1 field of the hippocampus

Abstract

We studied the effect of carbachol, a non-selective agonist of cholinergic receptors (at a dose of 0.1 mg/kg), on the synaptic plasticity of the hippocampus during the consolidation of memory traces. We elaborated the reaction of passive avoidance of the dark compartment of the chamber after a single electric pain stimulation in this section. A significant increase in the latent period before entry to the dark chamber compartment served as a criterion of learning. The electrophysiological studies were performed on freely moving rats. The efficacy of synaptic transmission was evaluated on the basis of an analysis of the changes in the focal potentials (the amplitude and slope of the response front edge) in the CA1 field in the response to the stimulation of Schaffer collaterals before electric pain stimulation, for 1.5 h (the consolidation period), and 24 h after training during the retention test. Administration of the agonist induced a considerable increase in the amplitude of the focal field potentials in the hippocampal CA1 area of rats that were not trained during first 1.5 h after the injection and 24 h after primary placement into the chamber. However, the drug had no effect on the elaboration of the passive avoidance skill.