Table 1 Time line for experiments

Experiment #1

−13

▪ Male Sprague–Dawley rats from Harlan Industries arrive

−8

▪ Rats placed in the feeder chambers

−1

▪ A ligature is placed around the tendon of the masseter muscle, the sham group has the tendon exposed but no ligature is placed

11

▪ Rats are sacrificed

Experiment #2

−16

▪ Male Sprague–Dawley rats from Harlan Industries arrive

−13

▪ Gentled for filament testing

−8

▪ Rats placed in the feeder chambers

−7

▪ von Frey filament testing is performed

−4

▪ Innoculate regions around the mouth with five 3 μl injections of vehicle, SHZ virus (control virus), or SHPE virus (enkephalin expressing virus)

−1

▪ von Frey filament testing is performed before surgery

▪ A ligature is placed around tendon of the masseter muscle for those rats in the chronic pain group, the sham group has the tendon exposed but no ligature is placed

4

▪ von Frey filament testing is performed

▪ Rats removed from feeders after the enkephalin transgene effect on meal duration was no longer significant

11

▪ von Frey filament testing is performed

18

▪ von Frey filament testing is performed

▪ Rats are sacrificed and the trigeminal ganglia is isolated for ELISA

Experiment #3

−13

▪ Male Sprague–Dawley rats from Harlan Industries arrive

−4

▪ Innoculate regions around the mouth with five 3 μl injections of vehicle, SHZ virus, or SHPE virus

−1

▪ A ligature is placed around the tendon of the masseter muscle

1

▪ Rats are sacrificed and tissue is isolated for RIA

Experiment #4

−13

▪ Male Sprague–Dawley rats from Harlan Industries arrive

−10

▪ Gentled for filament testing

−8

▪ Rats placed in the feeder chambers

−4

▪ Osmotic pumps surgically implanted subcutaneously contained either vehicle, naloxone or naloxone methiodide

−1

▪ Gentled for filament testing

▪ Innoculate regions around the mouth with five 3 μl injections of SHPE virus

3

▪ A ligature is placed around the tendon of the masseter muscle

7

▪ von Frey filament testing is performed