Multiple modes of synaptic excitation of olfactory bulb granule cells - PubMed (original) (raw)

Cortical synaptic input gates dendrodendritic inhibition onto mitral cells. A, Diagram of experiment. B1, Dendrodendritic inhibitory responses in mitral cells to steps to +20 mV for 1, 2, 3, and 5 ms duration in Mg-free ACSF (0 m

m

Mg). Dendrodendritic responses were blocked by 50 μ

m d

-APV. B2, Dendrodendritic inhibition evoked by a step to +20 mV was blocked by 1.2 m

m

Mg. C, Near coincident mitral cell (MC) depolarization and APC stimulation (stim) evokes dendrodendritic inhibition in mitral cells. Example responses to voltage-clamp depolarization alone (DDI, to +20 mV, 2 ms duration; left), APC stimulation alone (APC Tetanus; 5 × 50 Hz; middle traces), and both intracellular depolarization and APC stimulation (DDI + APC; right traces). The last set of traces shows the effect of the GABAA receptor antagonist gabazine (10 μ

m

) on the DDI + APC responses. The combination of intracellular depolarization and APC stimulation evoked trains of GABAA receptor-mediated outward currents. D, Summary graph of the results from five experiments using the protocol shown in C. Dendrodendritic inhibition, as assayed by current variance, was significantly increased after depolarization plus APC stimulation, compared with either stimulation method alone. The GABAA receptor antagonist gabazine (10 μ

m

) blocked the dendrodendritic inhibition associated variance increase (*p < 0.05; **p < 0.01). All experiments in C and D were conducted with normal ACSF (containing 1.2 m

m

Mg).