Effects of the GABA Receptor Agonist Phenibut on Spike Activity and Interactions between Neocortex and Hippocampus Neurons in Emotionally Negative Situations

Abstract

The nature of the spike activity of single neurons and interactions of neighboring cells in the hippocampus (field CA1) and parietal-temporal areas of the neocortex were compared in rabbits in emotionally negative situations in normal conditions and with decreased anxiety levels produced by systemic administration of the GABA receptor agonist phenibut. Analysis of the shapes of neuron spike activity autocorrelograms showed that phenibut increased the grouping of discharges in both structures, decreased interspike intervals within trains, increased the numbers of neurons with oscillations in the delta frequency range, and decreased the numbers of neurons with oscillations in the theta-1 range; in the hippocampus there was also an increase in frequencies in the theta-2 range. After phenibut, stimuli induced smaller rearrangements in neuron spike activity than in normal conditions. Analysis of cross-correlation histogram shapes showed that phenibut increased the numbers of common inputs to the neuron pairs being recorded and decreased the numbers of excitatory connections between cells in both structures; the hippocampus also showed an increase in the number of inhibitory connections. These changes provide evidence of a reduced level of activation of the hippocampus and neocortex after phenibut, with increases in neuron synchronization and decreases in the propagation of excitation between cells within structures, which correlated with decreases in the animals’ behavioral reactivity and anxiety.