Table 1.
Mean (±SEM) days to stability, days between retest, age at stability (days), mean weight (grams), and mean intake (grams) for the 3 days of stability for each group and condition
| Cocaine
|
Food
|
||||||||
|---|---|---|---|---|---|---|---|---|---|
| Adolescent → adult
|
Adult → adult
|
Adolescent → adult
|
Adult → adult
|
||||||
| Female | Male | Female | Male | Female | Male | Female | Male | ||
| First test | Days to stability | a16.5 (3.9) | a20.1 (1.8) | 34.0 (8.0) | 28.9 (3.7) | 13.8 (1.4) | 13.3 (1.7) | b14.4 (2.7) | b11.8 (2.4) |
| Age (days) | 50.0 (2.1) | 49.8 (1.9) | 143.2 (14.6) | 123.7 (4.9) | 43.0 (4.2) | 40.1 (1.2) | 98.6 (2.3) | 102.0 (4.3) | |
| Weight (g) | 159.5 (11.2) | 155.4 (12.4) | 295.3 (10.7) | 391.6 (20.4) | 144.8 (17.0) | 146.3 (10.6) | 297.3 (5.0) | 383.8 (6.1) | |
| Food intake (g) | 14.2 (0.8) | 15.3 (0.7) | 15.1 (0.7) | 19.2 (0.5) | 15.8 (0.2) | 20.0 (0) | 16.0 (0) | 19.2 (0.8) | |
| Retest | Days to retest | 28.0 (3.2) | 34.3 (4.1) | 30.0 (1.9) | 28.0 (3.7) | 35.7 (2.1) | 33.0 (3.8) | 23.8 (5.8) | 34.8 (2.6) |
| Days to stability | 15.0 (3.6) | 19.8 (6.2) | c20.8 (3.7) | c14.6 (2.6) | 7.0 (1.8) | 7.1 (0.9) | c5.2 (0.7) | c10.4 (4.2) | |
| Age (days) | 96.5 (3.1) | 102.6 (6.7) | 193.4 (14.1) | 166.0 (3.5) | 84.2 (2.2) | 90.3 (7.2) | 127.0 (6.3) | 144.4 (3.5) | |
| Weight (g) | 278.7 (15.9) | 390.8 (26.8) | 333.2 (15.0) | 471.1 (21.4) | 270.3 (10.0) | 401.8 (31.5) | 334 (13.5) | 495.2 (13.7) | |
| Food intake (g) | 14.2 (0.8) | 18.8 (0.3) | 14.1 (1.4) | 18.4 (0.7) | 16.0 (0.0) | 20.0 (0) | 16.0 (0) | 20.0 (0) | |
a
Adolescent rats reached stability for cocaine self-administration faster than adults (between- and within-subject comparisons) (p<0.05)
b
Adult rats took significantly fewer days to reach stability for food than for cocaine (p<0.05)
c
Adults took significantly fewer days to reach acquisition of lever pressing for iv cocaine and food under the retest vs. the initial testing conditions (p<0.05)