Table 2.

Continuous morphine dose-dependently decreases the weights of P18-24 rats across the course of the exposure as well as during abstinence (average ± SEM). The days on which animals were exposed to morphine are indicated by the gray shading. The experimental day (ED) is indicated for each of the three morphine dosing schedules.

Postnatal age	P18	P19	P20	P21	P22	P23	P24
Acute (n=5−6/group)			ED 1	ED 2	ED 3	ED 4	ED 5
Saline			56.9 ± 1.3	61.0 ± 1.6	65.0 ± 1.7	68.8 ± 2.4	74.3 ± 1.2
1 mg/kg morphine			53.9 ± 1.6	57.6 ± 1.8	62.2 ± 1.8	65.8 ± 1.5	72.8 ± 1.8
3 mg/kg morphine			56.1 ± 1.5	61.9 ± 1.8	66.8 ± 1.9	69.4 ± 2.2	74.6 ± 2.5
12 mg/kg morphine			50.3 ± 1.0	55.4 ± 1.1	60.1 ± 0.8	63.3 ± 0.9	71.5 ± 2.1
Continuous - pump (n=5−6/group)	ED 1	ED 2	ED 3	ED 4	ED 5	ED 6	ED 7
saline	46.6 ± 1.6	49.9 ± 1.0	55.7 ± 1.6	60.6 ± 2.1	65.6 ± 2.5	71.6 ± 2.6	76.9 ± 2.7
sham	46.3 ± 1.1	49.5 ± 1.6	56.4 ± 1.6	60.1 ± 1.5	66.0 ± 1.5	71.6 ± 1.8	76.8 ± 1.8
0.175 mg/kg/h morphine	47.4 ± 1.4	49.4 ± 0.7	55.3 ± 1.0	58.5 ± 1.2	63.2 ± 1.2	68.8 ± 0.9	73.2 ± 1.1
0.7 mg/kg/h morphine	46.0 ± 1.8	46.5 ± 1.2	52.2 ± 1.9	55.7 ± 2.2	59.0 ± 2.3*	64.1 ± 2.0*	70.3 ± 2.2*
1.4 mg/kg/h morphine	46.5 ± 0.7	47.1 ± 0.6	51.9 ± 0.8	55.5 ± 1.0*	57.1 ± 1.4*	61.3 ± 1.2*	66.8 ± 1.2*
Continuous - pellet (n=5−6/group)	ED 1	ED 2	ED 3	ED 4	ED 5	ED 6	ED 7
Sham	45.6 ± 1.1	48.1 ± 1.0	54.0 ± 0.9	61.3 ± 1.6	63.9 ± 1.2	68.4 ± 0.7	74.7 ± 2.6
Pellet	44.4 ± 1.1	44.7 ± 2.0	48.8 ± 2.6	55.4 ± 2.4*	51.5 ± 2.6*	57.9 ± 2.7*	63.8 ± 2.1*
Intermittent (n=5−6/group)	ED 1	ED 2	ED 3	ED 4	ED 5	ED 6	ED 7
saline	46.3 ± 1.1	49.8 ± 1.4	56.2 ± 1.5	63.2 ± 1.8	66.8 ± 2.0	72.0 ± 2.0	76.6 ± 2.1
1 mg/kg morphine	45.3 ± 0.8	48.6 ± 0.8	53.8 ± 1.0	59.9 ± 1.1	62.5 ± 1.5	68.6 ± 1.7	74.4 ± 2.1
3 mg/kg morphine	44.4 ± 0.8	46.4 ± 0.9	51.0 ± 1.1	57.7 ± 1.3	60.1 ± 1.5*	65.5 ± 1.5	72.1 ± 2.1

^*p<0.05 compared to sham or vehicle control rats at the same postnatal age