Table 1

ED₅₀ of compounds tested for substitution in rats trained to discriminate 5 mg/kg pregnanolone

	Drug	ED₅₀	95% CI
		mg/kg
Neurosteroids	Pregnanolone	1.7	1.3–2.2
	Allopregnanolone	5.0	0.8–6.6
	Epipregnanolone	5.5	4.4–6.8
	Androsterone	21.5	10.5–44.0
	DHEAS	NS	NS
GABA_A	Pentobarbital	2.9	2.2–3.8
	Midazolam	0.5	0.2–1.2
	Zolpidem	1.5	0.7–3.3
	THIP	NS	NS
	Muscimol	NS	NS
NMDA	MK-801	0.09	0.07–0.12
Alcohol	Ethanol	900	700–1100
5-HT₃	SR 57227A	5.5	4.4–6.8
	CPBG	8.8	7.3–10.8
	Tropisetron	NS	NS
ς₁	SKF 10047	9.7	6.0–15.6
Opiate	Morphine	NS	NS

NS, no substitution.