Dorsal root vasodilatation in cat skeletal muscle.

1. A study has been made, in the cat anaesthetized with chloralose, of the effects of antidromic stimulation of dorsal roots L6-S1 on the blood flow through the gastrocnemius muscle. 2. Stimulation of the peripheral ends of the ligated dorsal roots with current pulses of 0.3-0.5 msec duration and at intensities most effective in activating the smaller afferent fibres, for periods of 15-20 sec, produced a 50-60% increase in muscle vascular conductance which was slow in onset and long outlasted the stimulus. 3. This muscle vasodilatation could be evoked in the paralysed animal and was unaffected by guanethidine or atropine. It was, however, greatly reduced or even abolished by the prostaglandin synthetase inhibitors, indomethacin or acetylsalicylic acid, in doses which had no effect on the dilatation produced by a local injection of acetylcholine or the functional hyperaemia induced by muscle contraction. 4. It is concluded that activity in the smaller myelinated or unmyelinated afferent fibres of skeletal muscle produces an increase in muscle blood flow which is mediated, at least in part, by prostaglandins locally synthesized within the muscle.