Lack of evidence for adrenergic innervation of the external urethral sphincter

Catecholamine histofluorescence studies of the external urethral sphincter in 11 normal dogs, 4 dogs treated with tranylcypromine and 4 humans have demonstrated that this striated muscle does not possess adrenergic innervation. This finding suggests that the sympathetic nervous system affects outlet resistance only through its influence on the smooth musculature of the bladder neck and urethra.