RT Journal Article SR Electronic T1 Differential GABAB-Receptor-Mediated Effects in Perisomatic- and Dendrite-Targeting Parvalbumin Interneurons JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 7961 OP 7974 DO 10.1523/JNEUROSCI.1186-12.2013 VO 33 IS 18 A1 Sam A. Booker A1 Anna Gross A1 Daniel Althof A1 Ryuichi Shigemoto A1 Bernhard Bettler A1 Michael Frotscher A1 Matthew Hearing A1 Kevin Wickman A1 Masahiko Watanabe A1 Ákos Kulik A1 Imre Vida YR 2013 UL http://www.jneurosci.org/content/33/18/7961.abstract AB Inhibitory parvalbumin-containing interneurons (PVIs) control neuronal discharge and support the generation of theta- and gamma-frequency oscillations in cortical networks. Fast GABAergic input onto PVIs is crucial for their synchronization and oscillatory entrainment, but the role of metabotropic GABAB receptors (GABABRs) in mediating slow presynaptic and postsynaptic inhibition remains unknown. In this study, we have combined high-resolution immunoelectron microscopy, whole-cell patch-clamp recording, and computational modeling to investigate the subcellular distribution and effects of GABABRs and their postsynaptic effector Kir3 channels in rat hippocampal PVIs. Pre-embedding immunogold labeling revealed that the receptors and channels localize at high levels to the extrasynaptic membrane of parvalbumin-immunoreactive dendrites. Immunoreactivity for GABABRs was also present at lower levels on PVI axon terminals. Whole-cell recordings further showed that synaptically released GABA in response to extracellular stimulation evokes large GABABR-mediated slow IPSCs in perisomatic-targeting (PT) PVIs, but only small or no currents in dendrite-targeting (DT) PVIs. In contrast, paired recordings demonstrated that GABABR activation results in presynaptic inhibition at the output synapses of both PT and DT PVIs, but more strongly in the latter. Finally, computational analysis indicated that GABAB IPSCs can phasically modulate the discharge of PT interneurons at theta frequencies. In summary, our results show that GABABRs differentially mediate slow presynaptic and postsynaptic inhibition in PVIs and can contribute to the dynamic modulation of their activity during oscillations. Furthermore, these data provide evidence for a compartment-specific molecular divergence of hippocampal PVI subtypes, suggesting that activation of GABABRs may shift the balance between perisomatic and dendritic inhibition.