Choline enhances scopolamine-induced acetylcholine release in dorsal hippocampus of conscious, freely-moving rats.

We examined the effects of exogenous choline (30, 60, 120 mg/kg, i.p.) on basal and scopolamine-evoked acetylcholine (ACh) release in awake animals, using in vivo microdialysis. After collection of 3-4 baseline dialysate samples (15 min each), rats received either saline or choline chloride and 4 additional samples were collected. All animals then received scopolamine hydrochloride (0.5 mg/kg, i.p.) and 6 additional samples were collected. Basal ACh release in animals receiving choline did not differ from that in rats given saline, nor from ACh release prior to choline administration. Scopolamine alone increased average ACh levels in dialysates from 1.22 +/- 0.54 to 11.18 +/- 3.07 pmol/15 min (mean +/- SD; p = 0.001); administration of 60 mg/kg or 120 mg/kg of choline chloride significantly enhanced maximal scopolamine responses by about 55%. These results suggest that supplemental choline enhances evoked ACh release in hippocampus of freely-moving rats.