This is an interesting study performed in rats showing that the inhibitory effect on micturition (urination) by acupuncture takes place in the brainstem. This is surprising to me, since I would have thought it was more of a spinal reflex/gating mechanism. (info on my practice here)

Acupuncture of the sacral vertebrae suppresses bladder activity and bladder activity-related neurons in the brainstem micturition center.
Wang H, Tanaka Y, Kawauchi A, Miki T, Kayama Y, Koyama Y.
Department of Physiology, Guiyang College of Traditional Chinese Medicine, Guiyang 550001, China
Acupuncture of the sacral vertebrae has therapeutic effects in patients with overactive bladders. The mechanism of these effects, however, remains unclear. The present study, using urethane-anesthetized rats, investigated the effects of acupuncture stimulation of the sacral vertebrae on bladder activity and bladder activity-related neurons in and around Barrington’s nucleus. In 95 of 147 trials (64.6%), acupuncture stimulation of the sacral vertebrae for 1 min suppressed bladder contraction for 27-2347s…These findings suggest that acupuncture stimulation of the sacral vertebrae suppresses bladder contraction and changes the firing properties of bladder activity-related neurons in and around Barrington’s nucleus, and that these changes are mediated by GABAergic systems.