Acute hyperglycemia attenuates nerve conduction velocity and nerve blood flow in male Sprague-Dawley rats: reversal by adenosine.

Hyperglycemia is implicated to play a major role in development of diabetic neuropathy. Since most of the diabetics are hyperglycemic much before they develop full-blown diabetes, we felt, it would be very important to know the effects of acute hyperglycemia on nerve function so that early pathophysiological events could be understood and appropriate therapeutic intervention can be made. Moreover, effect of acute hyperglycemia on motor nerve conduction velocity (MNCV) and nerve blood flow (NBF) is not known. Hence, we studied the effects of acute hyperglycemia on sciatic MNCV and sciatic NBF in healthy male Sprague-Dawley (SD) rats. Three different animal models of acute hyperglycemia (50% glucose (3 g kg(-1), i.v. (intra-venous) or i.p. (intra-peritoneally)) or 24 h post-streptozotocin (STZ) injected rats were used. Acute hyperglycemia but not mannitol or sucrose significantly attenuated MNCV and NBF. Adenosine (10 mg kg(-1), i.p.) prevented the acute hyperglycemia-induced attenuation of MNCV and NBF in all the three rat models of acute hyperglycemia. Adenosine effects were blocked by theophylline (50 mg kg(-1), i.p.) suggesting the role of adenosinergic receptor mediated mechanisms in acute hyperglycemia-induced neuropathy. Acute glucose administration in 8 weeks, STZ diabetic rats did not further affect MNCV or NBF. Adenosine (10 mg kg(-1), i.p.) did not produce any adverse effects on the blood pressure and heart rate. From the results, we conclude that acute hyperglycemia attenuates MNCV and NBF via an adenosinergic receptor-dependent mechanism.