Interneuronal GABAA receptors inside and outside of synapses

- Many interneurons (INs) express different GABAARs than principal cells.
- Subclasses of INs have specific GABAARs mediating tonic and phasic conductances.
- In most INs, the tonic conductance is mediated by extrasynaptic α1/δ-GABAARs.
- On the basis of their ontogeny, we propose a binary view of tonic conductances in INs.
- There is hope for developing selective compounds altering GABAARs of INs.

About 20% of the total number of neurons in the brain are interneurons (INs) that utilize GABA as their neurotransmitter. The receptors for GABA have been well studied in principal cells, but INs also express GABA receptors, in particular the GABAA type (GABAARs), which may also be activated in an autocrine manner by the transmitter released by the INs themselves. As more and more neurological and psychiatric disorders are being discovered to be linked to malfunction or deficits of INs, this review will cover how INs communicate with each other through the activation of synaptic and extrasynaptic GABAARs. The properties of GABAARs specific to INs may differ significantly from those found on principal cells to open the prospect of developing IN-specific drugs.