Recently a new GABA receptor has been described...the GABAc receptor.
Like the GABAa receptor, it is a chloride channel.
The GABAc receptor is believed to be a homo-oligometric structure, composed of 5 identical subunits.
The subunit is the pico subunit, which has a low homology with the subunits used to construct a GABAa receptor.
The GABAc is highly expressed in the retina and there are indications that it, or related receptors, may be present in other parts of the CNS.
How important it becomes to the GABA story in the brain remains to be seen.