Measurements of postcoital sympathetic activity in females by means of vanillylmandelic acid

Urinary vanillylmandelic acid (VMA), the final metabolite of epinephrine and norepinephrine, and creatinine (Cr) were measured 1 hr before, within an hour after intercourse, and in a 23-hr pooled sample after intercourse in 11 females. The results were compared to a group of 8 normal females who abstained from intercourse. The control VMA/creatinine ratios were significantly lower than the preintercourse values (P < 0.01) as well as the postintercourse and 23-hr pooled postintercourse sample. This ratio, 1 hr postintercourse increased significantly (P < 0.01) over the preintercourse values. The pooled 23-hr postintercourse sample remained high and was significantly different from preintercourse but not from the postintercourse sample. The absolute values of VMA showed relatively similar significance. This study provides objective evidence in the female for the considerable involvement of the sympathetic system during sexual intercourse. In addition, it shows that the group that was planning to have sexual intercourse, 1 hr prior to intercourse, already had VMA/creatinine ratios double over the control group. Such objective information has hitherto not been available.