The sciatic nerve in rats was cut and ligated, and 5-18 days later pathophysiological properties of the resulting neuroma were studied. We found that afferent fibers ending in the neuroma produced prolonged discharges following repetitive stimulation of the lumbar sympathetic trunk (LST) or i.v. adrenaline. Mean latencies of activation of afferent fibers were 10 +/- 2.1 sec and 12 +/- 3.4 sec (mean +/- S.D.) to LST stimulation and to adrenaline injection, respectively. The alpha-adrenergic antagonist phentolamine blocked responses to LST stimulation and adrenaline. The beta-adrenergic antagonist propranolol had no effect.