ANTIDROMIC VASODILATATION IN THE STRIATED-MUSCLE AND ITS SENSITIVITY TO RESINIFERATOXIN IN THE RAT

Antidromic stimulation at the L4-L5 dorsal roots elicited a blood flow increase in ipsilateral muscles of lower extremities in rats measured by laser-Doppler flowmetry. Stimulation with 0.5 Hz; 20 V; 0.5 ms; 50 impulses was much less effective in muscle (18.9 +/- 6.4 area under t he curve (%); mean +/- S.E.) than in the glabrous skin (80.5 +/- 8.25; P < 0.001). No significant difference was seen at 10 Hz (51.6 +/- 10. 6 muscle; 60.6 +/- 17.3 skin). In the muscle the latency period of the response was long (37.4 +/- 3.1 s; mean +/- S.E.) at 0.5 Hz stimulati on and was much shorter (8.8 +/- 0.8 s) at the higher frequency of 10 Hz, unlike in the skin where latency values at both frequencies were s imilar (9.7 +/- 0.8 s and 8.9 +/- 0.9 s, respectively). Antidromic vas odilatation in the muscle and the skin was abolished by resiniferatoxi n (RTX) in an i.v. dose of 1.0 mu g/kg. These results provide a direct evidence for the existence of antidromic vasodilatation in striated m uscle and suggest a mediating role for capsaicin/RTX sensitive afferen ts.