Compartmental distribution of GABAB receptor-mediated currents along the somatodendritic axis of hippocampal principal cells

23.03.2015

Degro CE, Kulik A, Booker SA, Vida I.

Front Synaptic Neurosci. 2015 Mar 23;7:6.

Front Synaptic Neurosci.            online article

Activity of cortical principal cells is controlled by the GABAergic system providing inhibition in a compartmentalized manner along their somatodendritic axis. The role of GABABRs is unknown. We investigated the localization of GABABRs and Kir3 channels by combining electrophysiological recordings, immunoelectron microscopic analysis and single cell simulations. Spatially restricted currents were assessed along the axis of principal cells by uncaging GABA in the different hippocampal layers. GABABR-mediated currents were present along the entire somatodendritic axis of principal cells, but not uniformly distributed: largest currents and the highest conductance densities determined in the simulations were found on the distal apical dendrites. Immunocytochemical localization of GABABRs and Kir3 channels showed that distributions overlap but their densities diverge on basal dendrites of pyramidal cells. Current amplitudes and the conductance densities correlated better with Kir3 density, suggesting a bottlenecking effect defined by the effector channel. These data demonstrate a compartmentalized distribution of the GABABR-Kir3 signaling cascade and suggest differential control of synaptic transmissio, dendritic integration and synaptic plasticity at pathways onto cells.