Role of spleen or spleen products in the reduced locomotor-enhancing effect of morphine in diabetic mice.

In the present study, we examined the possibility that factor(s) derived from spleen cells are involved in the reduced morphine-induced hyperlocomotion in diabetic mice. The mean total locomotor activity after s.c. administration of morphine (20 mg/kg) in non-diabetic mice was significantly greater than that in diabetic mice. Splenectomized diabetic mice had a significantly higher sensitivity to morphine-induced hyperlocomotion than untreated or sham-operated diabetic mice. However, morphine-induced hyperlocomotion in non-diabetic mice was unaffected by splenectomy or sham-operation. Furthermore, 7 days after adoptive transfer of the supernatant of spleen cell homogenate (SSCH) from diabetic mice (SSCH-D), naive mice that had been injected with SSCH-D showed lower morphine-induced locomotor activity than mice which had been injected with SSCH from non-diabetic mice (SSCH-ND). These results suggest that some factor(s) derived from spleen cells may play an important direct or indirect role in the selective reduction of morphine's locomotor-enhancing effect in diabetic mice.