Table 1.

Gα_i/o subunits mediating analgesia, hyperalgesia, and priming induced by sub-ADs and ADs of systemic fentanyl and morphine

	Fentanyl		Morphine
	Sub-AD	AD	Sub-AD	AD
OIH	↓ Gαi2, Gαi3 and Gαo	NS	↓ Gαi1, Gαi2 and Gαi3	NS
Analgesia	NS	↑ Gαi1 and Gαi2	NS	↓ Gαi1
Priming	↓ Gαi3	↓ Gαo	None	None

NS, Not studied; ↑, enhances; ↓, attenuates.