Influence of Brain Neurochemical Systems on Frequency Spectra of Hippocampal Theta Rhythm

Chronic experiments with rabbits have shown that electrical destruction of dorsal amygdalofugal pathways leads to complete and persisted blockade of hippocampal theta rhythm in contrast to ventral one. In intact animals, electro- and chemostimulation of amygdala nuclei, hypothalamus, reticular formation and medial septum nucleus lead to the formation of well pronounced theta rhythm in hippocampus, but after destruction of the amygdalofugal pathway any theta-rhythm in this structure is not observed. Restoration of hippocampal EEG took place under intrahippocampal application of carbocholine and strychnine. It is proposed that one of the necessary conditions for the regulation of excitability of hippocampal neurons is the integrity of dorsal amygdalofugal pathways by means of which regulatory influence of amygdale on the hippotalamic neurosecretory cells is realized.