Author's permanent address
Temporal overlap of excitatory and inhibitory afferent input in guinea-pig CA1 pyramidal cells
Article first published online: 8 SEP 2004
The Journal of Physiology
Volume 516, Issue 2, pages 485–504, April 1999
How to Cite
Karnup, S. and Stelzer, A. (1999), Temporal overlap of excitatory and inhibitory afferent input in guinea-pig CA1 pyramidal cells. The Journal of Physiology, 516: 485–504. doi: 10.1111/j.1469-7793.1999.0485v.x
S. Karnup: Institute of Theoretical and Experimental Biophysics, 142292 Puschino, Russia.
- Issue published online: 8 SEP 2004
- Article first published online: 8 SEP 2004
- (Received 13 July 1998; accepted after revision 11 January 1999)
- 1The temporal interaction of evoked synaptic excitation and GABAA-mediated inhibition was examined in CA1 pyramidal cells. Single and paired intracellular recordings were carried out in pyramidal cell dendrites and somata, and interneurons of the guinea-pig hippocampal slice. Current-clamp, sharp electrode and whole-cell voltage-clamp recordings were made.
- 2Kinetics of dendritic and somatic inhibitory responses were similar. Notably, kinetics of dendritic unitary IPSPs were as fast as kinetics of somatic unitary IPSPs.
- 3GABAA-mediated influences were present throughout the orthodromic pyramidal cell EPSP/EPSC. Comparison of the kinetics of pharmacologically isolated monosynaptic IPSPs, IPSCs and inhibitory conductances (gGABAA), showed fastest kinetics for gGABAA. Close temporal overlap was observed between monosynaptic gGABAA and the rising phase of the evoked EPSP/EPSC. The onset of gGABAA coincided with or preceded onset of the EPSP/EPSC.
- 4Onsets of feedforward IPSPs coincided with the rising phase of the pyramidal cell EPSP in > 80 % of paired recordings. Fastest feedforward inhibitory responses exerted near complete overlap with evoked excitation.
- 5Onsets of recurrent IPSPs did not occur during the rising phase of the evoked EPSP, but > 3·0 ms after the peak of the pyramidal cell EPSP.
- 6Orthodromically evoked interneuron spikes were observed at stimulation intensities that were below the threshold for eliciting EPSPs in concomitantly recorded pyramidal cells. The activation of feedforward inhibitory responses by weakest excitatory input, and the large temporal overlap between feedforward inhibition and evoked excitation, suggest that in situ any excitatory input in CA1 is effectively controlled by fast synaptic inhibition.