Xue-Ying Jiang and Tom Abrams' paper (1998)

The first EPSP and the second EPSP in a paired pulse are evoked at distinct loci.

Paired-pulse ratio decreases with repeated testing.

Paired-pulse ratio depends on the size of the initial EPSP size.
The second EPSP size does not do much in determining the PPR.

The decrease in PPR is independent from synaptic depression.
The decrease of PPR occurs even without the depression of the 1st EPSP.
The decrease of PPR develops much faster than the depression of the 1st EPSP.
The PPR is not affected by the depression of the 1st EPSP.

Depresssion reduces EPSP2 along with EPSP1

Does synaptic depression change large synapses into small synapses?
No, they are different.
The paired pulse ratio is independent from the initial synaptic strength.

Use-dependent plasticity of paired-pulse facilitation provides evidence that a separate set of release sites contributes to EPSP2
A dramatic reduction in the 2nd EPSP after a single paired-pulse trial, when there was minimal change in the first.

Post-tetanic potentiation persists through repeated testing
Facilitation is not simply a modest form of PTP.

Interaction of serotonin-induced facilitation with the paired-pulse ratio
Serotonin-induced facilitation persisted only in the 1st EPSP. The 2nd EPSP shows a transient increase.

Contribution of Ca²⁺ and phosphorylation to paired-pulse facilitation
Facilitation is Ca dependent, but not phosphatase-dependent.