Hippocampal Theta Input to the Amygdala Shapes Feedforward Inhibition to Gate Heterosynaptic Plasticity.
Bottom Line: These effects are mediated by GABAB receptors and change in the Cl(-) driving force.Hence, feedforward inhibition, known to enforce temporal fidelity of excitatory inputs, dominates hippocampus-amygdala interactions to gate heterosynaptic plasticity.VIDEO ABSTRACT.
Affiliation: MRC Brain Network Dynamics Unit, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3TH, UK.Show MeSH
Related in: MedlinePlus
Mentions: Because vCA1 pyramidal cells are glutamatergic, we hypothesized that the inhibition of PNs was due to the disynaptic activation of feedforward INs, while the monosynaptic excitation of PNs would remain subthreshold. To test this hypothesis, we optogenetically dissected the BA circuit activated by vCA1 HPC ex vivo. We prepared acute brain slices 3 to 4 weeks after the ChR2 injection and recorded single BA neurons in cell attached mode (see Supplemental Experimental Procedures). This configuration did not alter the intracellular milieu of the recorded cell and mimicked our extracellular in vivo conditions. PNs and INs could be distinguished according to their soma size (diameter ≥ 20 μm for PNs, < 15 μm for INs). After cell-attached recordings, 8/40 PNs and 6/18 INs were re-patched in whole-cell mode to confirm their identity. Optical stimulations were delivered through the microscope objective to excite vCA1 axons within an area of ∼200 μm diameter around the soma of the recorded neurons. We observed that the power of a single light pulse stimulation had to be significantly higher (p < 0.0001) to trigger one action potential in PNs (9.5 ± 0.3 mW/mm2, n = 33) compared to INs (2.5 ± 0.2 mW/mm2, n = 11) (Figure 3).
Affiliation: MRC Brain Network Dynamics Unit, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3TH, UK.