Table 1 Methods to induce LTP.

Electrical nerve stimulation: C-fibres

HFS

100 Hz for 1 s, repeated 2-20 times at 10-20 s intervals

[3, 4, 6, 17, 40, 65, 70, 90, 92, 101, 102, 108, 110, 113, 133, 134, 143, 144, 268, 269] (superficial dorsal horn), [14, 29, 114, 270] (deep dorsal horn)

LFS

2 Hz, 120 s

[4, 7]

1-2 Hz, 40-100 s paired with postsynaptic depolarisation

[38, 271]

IFS

10 Hz for 1 s, repeated 12 times at 10 s

[83]

20 Hz for 5 s, repeated 4 times at 10 s intervals

[3]

Electrical nerve stimulation: Aδ-fibres

HFS

100 Hz for 1 s, repeated 90 times at 10 s intervals

LTP only in spinalised rats

[36]

Natural noxious stimulation

Noxious heat, pinching (hindpaw)

LTP only in spinalised rats

[13]

Formalin, capsaicin injection (hindpaw)

[4, 13]

Sciatic nerve transsection or crush

[11]

Sural nerve crush

LTP only in spinalised rats

[13]

Pharmacological stimulation

NMDA, substance P, neurokinin A

LTP only in spinalised rats

[272]

ATP

[122]

BDNF, SKF 38393 (Dopamine receptor D1/D5 agonist), 8-Br-cAMP (PKA activator)

Late, protein-synthesis- dependent phase of LTP

[91, 140]

Abrupt withdrawal of remifentanil or DAMGO

No LTP upon tapered withdrawal

[21, 42]

TNF-α

LTP only in neuropathic animals

[111]