INTRODUCTION: The amygdala mediates unconscious reactions and is responsible for emotional memory formation and attachment of subjective emotional valence to various stimuli. The amygdala complex expresses 5-HT7 receptors in a high density, however, their function in this structure remains poorly investigated. AIM(S): The present experiments were aimed at determining the effects of 5-HT7 receptor activation on membrane properties and synaptic transmission in pyramidal‑like basal amygdala (BA) neurons. METHOD(S): Whole-cell patch clamp recordings were performed on the brain slices containing a part of the amygdala. Spontaneous excitatory and miniature postsynaptic currents (sEPSCs and mEPSCs) were recorded at a holding potential of ‑70 mV. Spontaneous and miniature inhibitory postsynaptic currents (sIPSCs and mIPSCs) were recorded at a holding potential of 0 mV with pipette filled with cesium gluconate-containing solution. RESULTS: Activation of 5-HT7 receptors decreased the mean frequency of sEPSCs without changing sEPSCs amplitude. The mean frequency and amplitude of sIPSCs were enhanced after 5-HT7 receptor activation. Administration of 5-HT7 receptors agonist 5-CT induced a hyperpolarization and an increase of the membrane resistance in a majority of recorded cells. The frequency and amplitude of mEPSCs and mIPSCs were not changed after 5‑CT administration. The observed effects of 5‑HT7 receptors activation were absent in the presence of the 5-HT7 receptor antagonist SB 269970. The application of 5-CT had no effect in slices prepared from 5-HT7 knockout mice. CONCLUSIONS: These data suggest that the observed decrease in sEPSCs and an increase in sIPSCs frequency and amplitude result from activation of 5-HT7 receptors located on GABAergic interneurons that, in turn, innervate BA projection neurons. FINANCIAL SUPPORT: Supported by grant 2016/21/B/NZ4/03618 financed by the National Science Center, Poland, and by statutory funds from Maj Institute of Pharmacology, Polish Academy of Sciences.
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