Parvalbumin, but not calretinin, neurons express high levels of α1-containing GABAA receptors, α7-containing nicotinic acetylcholine receptors and D2-dopamine receptors in the basolateral amygdala of the rat

Abstract

The generation of emotional responses by the basolateral amygdala is largely determined by the balance of excitatory and inhibitory inputs to its principal neurons − the pyramidal cells. The activity of these neurons is tightly controlled by g-aminobutyric acid (GABA)ergic interneurons, especially by those expressing parvalbumin (PV) and calretinin (CR). Although it is known that GABAergic, cholinergic and dopaminergic fibres make synapses on PV and CR cells, knowledge of the various receptors which are used by these cells is still incomplete. Thus, the present study investigates whether neurons expressing PV or CR co-express specific GABA, acetylcholine and/or dopamine receptors in the basolateral amygdala of the rat. The results show that almost two-thirds of PV neurons co-express high concentrations of α1 subunit of GABAA receptor, and more than half of them co-express high levels of α7 subunit of nicotinic acetylcholine receptor and/or D2-subtype of dopamine receptor. In contrast, a smaller percentage of CR neurons had detectable amounts of these receptors and at lower levels of abundance in most cases. In conclusion, the present results indicate that not only principal neurons but also GABAergic interneurons have specific receptors, which allow these cells to respond to the GABAergic, cholinergic and dopaminergic inputs coming to the basolateral amygdala of the rat. Since these cells receive intrinsic GABAergic inputs, they are strongly interconnected. Since they also receive extrinsic cholinergic and dopaminergic inputs, such stimulation may result in stimulus-driven feed-forward control of the principal neurons. The effects of such control may be either feed-forward inhibition of the principal neurons via α7 nicotinic acetylcholine receptors or disinhibition of these cells via D2-dopamine receptors.