Experiment 2

Constant Object

Novel Object

Saline (i.c.v.) /
Saline (i.p.)

11 ± 2

18 ± 3

Saline (i.c.v.) /
U50,488 (0.3 mg/kg, i.p.)

16 ± 3

14 ± 2

NXM (30 nmol, i.c.v.) /
Saline (i.p.)

8 ± 1†

16 ± 2

NXM (30 nmol, i.c.v.) /
U50,488 (0.3 mg/kg, i.p.)

7 ± 1†

16 ± 3

 

Experiment 3

Constant Object

Novel Object

Saline (i.c.v.) /
Saline (i.p.)

10 ± 2

22 ± 3

Saline (i.c.v.) /
ffir-NH2 (1 mg/kg, i.p.)

12 + 3

22 ± 4

ffir-NH2 (3 nmol, i.c.v.) /
Saline (i.p.)

8 ± 1

6 ± 1‡

ffir-NH2 (3 nmol, i.c.v.) /
nor-BNI* (5 mg/kg, i.p.)

11 ± 2

19 ± 3


*nor-BNI = nor-binaltorphimine

Table 1: Presents the amount of time (sec ± SEM) that mice (n = 12 / group) spent investigating the constant and novel objects in the novel object recognition task. † indicates a main effect wherein naloxone methiodide (NXM)-infused mice significantly differed from saline-infused mice on exploration of the constant object, irrespective of peripheral injection condition (p < 0.05). ‡ indicates a significant interaction wherein mice infused with ffir-NH2 significantly differed from salineinfused controls on exploration of the novel, but not constant, object (p < 0.05).