PARVALBUMIN-IMMUNOREACTIVE NEURONS MAKE INHIBITORY SYNAPSES ON PYRAMIDAL CELLS IN THE HUMAN AMYGDALA - A LIGHT AND ELECTRON-MICROSCOPIC STUDY

In the present study we investigate the inhibitory circuitries that re gulate the neuronal activity in the lateral and basal nuclei, which ar e the main sensory input regions of the amygdala. Axon terminals immun oreactive for parvalbumin, a calcium-binding protein known to colocali ze with GABA, were examined in these regions with electron microscopy, and their postsynaptic targets were identified and characterized. In the lateral nucleus, parvalbumin-immunoreactive (PV-ir) axons formed t erminal rows which made symmetric synaptic contacts on the axon initia l segments of the pyramidal cells. In the basal nucleus, pericellular baskets of PV-ir fibers established symmetric synapses on pyramidal ce ll somata and proximal dendrites. Our data suggest that PV-ir neurons play a crucial inhibitory role in the control of pyramidal cell activi ty in the human amygdala.