Table 3.

Parameter estimates when mean A and h varied freely across dose groups (Model A, h in Table 2) including only those animals that had acquired nicotine self-administration based on the curve-fitting criterion. Values are the asymptote (A), baseline (B), and half-life (h; i.e., sessions to reach 50% of asymptote) parameters that were obtained from the selected model. The selected model suggests that B did not vary with dose, while A and h varied dose-dependently.

Dose group	A (reinforcers)	h (sessions)	B (reinforcers)	s (sessions)
0.015 mg/kg	31.25	12.32	3.62	0.58
0.03 mg/kg	24.12	11.49	3.62	0.85
0.06 mg/kg	21.37	11.18	3.62	1.95
SD	9.64†	4.00†	2.90†	2.01*

Dagger (^†) represents the estimated standard deviation (SD) of parameter estimates in every dose group (SDs were constrained to the same value across groups).

Asterisk (*) represents the SD of the slope (s) pooled across dose groups (SD was not constrained).