Cadmium modulates diabetes-induced alterations in murine neuromuscular junction

Skeletal muscle function is compromised in diabetes mellitus and exposure t o heavy metals may further complicate neuromuscular impairments. The presen t study investigated the effects of cadmium on diabetes induced dorsiflexor muscle dysfunction in C57 BL adult male mice. Forty mice were divided rand omly into 2 groups (n=20 each). One group served as control and the other w as injected once with i.p. streptozotocin (STZ) solution (60 mg/kg) to indu ce experimental diabetes. Each group was then divided into two sub-groups ( n=10) of which one received 5 mM cadmium. Utilizing intracellular recording method, resting membrane potential (RMP) and miniature endplate potentials (MEPPs) were measured in dorsiflexor muscle obtained from urethane-anaesth etized (2 mg/g, i.p.) four weeks diabetic and matched control mice. Compara tive analyses of isometric contractile characteristics of in situ dorsiflex or muscle were also conducted in both groups. In control mice, flexor muscl e exposure to 5 mM cadmium for 10 min resulted in significant reduction in MEPPs frequencies and isometric twitch tensions without affecting RMP. In S TZ-diabetic mice, the same exposure did not modify resting membrane potenti al and further decreased MEPPs frequencies and isometric twitch tensions. C urrent results indicated that cadmium probably via a Ca2+ antagonist and ch elating activity at nerve terminals exacerbates diabetes complications.