Table 2.

Summary of the effects of NGF and NT-3 on rat nociceptive threshold and the release of SP-LI from the isolated spinal cord

Neurotrophin	Treatment	Thermal threshold	Mechanical threshold	Electrically-evoked release of SP-LI
In vivo
NGF	Single injection	↓	↓	No effect
NT-3	Single injection	No effect	↓, ↑	No effect
NGF	Prolonged	No effect	↓*	↑
NT-3	Prolonged	No effect	–	↓
In vitro
NGF	1–100 ng/ml	–	–	No effect
NT-3	1–100 ng/ml	–	–	↓
NT-3 + naloxone	10 ng/ml + 0.1 μm	–	–	No effect
NT-3 + CGP 36742	10 ng/ml + 100 μm	–	–	↓

↓, Decrease; ↑, increase; –, not measured; ↓*, Lewin et al. (1993).