Table 2.

Knockout of β4 gene reduced somatic signs in morphine-treated mice

Individual somatic signs	β4 WT SAL	β4 KO SAL	β4 WT MOR	β4 KO MOR
Paw tremors	4.5 ± 0.8	7.2 ± 0.5	22.8 ± 5.1*	11.9 ± 2.5#
Head shakes	2.8 ± 0.8	4.3 ± 0.5	25.5 ± 6.1*	8.9 ± 2.0#
Backing	0 ± 0	0 ± 0	0 ± 0	0 ± 0
Ptosis	0 ± 0	0 ± 0	2.6 ± 0.7	1.3 ± 0.7
Jumping	0.7 ± 0.3	0 ± 0	15.6 ± 7.2*	14 ± 5.8*
Body tremor	0 ± 0	0 ± 0	6.9 ± 1.0*	2.7 ± 0.6*#
Occurrence of diarrhoea (% of mice)	0	0	50	0

Mice were made dependent on morphine for 8 days. On day 9, mice were administered naloxone (2 mg·kg⁻¹) before observing individual physical signs expressed as mean ± SEM and % occurrence of diarrhoea.

n = 8 mice per group.

^*P < 0.05 from saline group.

^#P < 0.05 from morphine WT group.

MOR, morphine; SAL, saline.