Properties of dendritic unitary IPSPs
| Amplitude (mV) | Latency to onset (ms) | Rise time (10-90 %) (ms) | Duration at half-amplitude (ms) | |
|---|---|---|---|---|
| Pair 1 (n= 72) | 1.4 ± 0.3 | 0.9 ± 0.1 | 2.8 ± 0.3 | 24.6 ± 1.6 |
| Pair 2 (n= 11) | 0.9 ± 0.3 | 1.7 ± 0.6 | 8.0 ± 1.1 | 47.8 ± 8.1 |
| Pair 3 (average of 22 traces) | 0.4 | 2.3 | 12.7 | 55.5 |
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IPSPs were recorded in CA1 pyramidal cell apical dendrites that were synaptically coupled to histologically identified bistratified cells. Data from 3 different pairs are listed separately (pairs 1-3). Analysis of pairs 1 and 2 is based on individual IPSPs (see Fig. 7); analysis of pair 3 is based on averaged traces (see Fig. 11A). Strong coupling was observed in pair 1 (no failure in response to single interneuron AP), and weak coupling in pair 3 (only averaged traces revealed IPSPs in response to a single interneuron AP). Synaptic coupling of pair 2 was of intermediate strength (single IPSPs in response to a single interneuron AP were detectable in 61 %). Criteria for coupling strength were IPSP amplitude and probability of elicitation in response to a single interneuron AP (or failure). The detection criterion for IPSPs was > 0.2 mV hyperpolarization within 4 ms following the AP peak in the presynaptic interneuron. The 0.2 mV limit was based on the size of random membrane fluctations (noise), and the 4 ms latency limit was based on the maximal latency to onset of a clearly distinguishable IPSP.