TY - JOUR T1 - Cell Type- and Input-Specific Differences in the Number and Subtypes of Synaptic GABA<sub>A</sub> Receptors in the Hippocampus JF - The Journal of Neuroscience JO - J. Neurosci. SP - 2513 LP - 2521 DO - 10.1523/JNEUROSCI.22-07-02513.2002 VL - 22 IS - 7 AU - Thomas Klausberger AU - J. David B. Roberts AU - Peter Somogyi Y1 - 2002/04/01 UR - http://www.jneurosci.org/content/22/7/2513.abstract N2 - Networks of parvalbumin (PV)-expressing basket cells are implicated in synchronizing cortical neurons at various frequencies, through GABAA receptor-mediated synaptic action. These cells are interconnected by GABAergic synapses and gap junctions, and converge with a different class of cholecystokinin-expressing, PV-negative basket cells onto pyramidal cells. To define the molecular specializations in the synapses of the two basket cell populations, we used quantitative electron microscopic immunogold localization of GABAA receptors. Synapses formed by PV-positive basket cells on the somata of pyramidal cells had several-fold higher density of α1 subunit-containing receptors than synapses made by PV-negative basket cells, most of which were immunonegative. The density of the β2/3 subunits was similar in the two populations of synapse, indicating similar overall receptor density. Synapses interconnecting parvalbumin-expressing basket cells contained a 3.6 times higher overall density of GABAA receptor (β2/3 subunits) and 3.2 times higher density of α1 subunit labeling compared with synapses formed by boutons of PV-positive basket cells on pyramidal cells. Thus, PV-positive basket cells mainly act through α1subunit-containing GABAA receptors, but the receptor density depends on the postsynaptic cell type. These observations, together with previously reported enrichment of the α2subunit-containing receptors in synapses made by PV-negative basket cells, indicate that the number and subtypes of GABAAreceptors present in different synapse populations are regulated by both presynaptic and postsynaptic influences. The high number of GABAA receptors in synapses on basket cells might contribute to the precisely timed phasing of basket cell activity. ER -