Molecular and functional properties of neurons in the human lateral amygdala

Neuronal properties were investigated through patch-clamp recording in situ in surgical specimens of the human lateral amygdala (LA) obtained from patients with intractable temporal lobe epilepsy. Projection neurons displayed spiny dendrites, action potentials with varying degree of frequency adaptation, and an inwardly rectifying K⁺ (Kir) conductance coupled to GABA_B receptors. In interneurons, dendrites were spineless or sparsely spiny, action potentials were shorter than those in projection neurons and often occurred spontaneously, and GABA_B receptor-mediated responses were lacking. Single-cell RT-PCR demonstrated expression of Kir channel subunits Kir3.1 and Kir3.2 and of vesicular glutamate transporters VGLUT1 and VGLUT2 in projection neurons. It is concluded that projection neurons and interneurons of the human LA can be distinguished based upon morphological, electrophysiological, and molecular biological criteria. The most striking difference relates to the expression of postsynaptic GABA_B receptors coupled to Kir3 channels in projection neurons and the lack of functional GABA_B receptors in interneurons.