Ontogenetic Development of High Potassium- and Acetylcholine-induced Release of Dopamine from Striatal Slices of the Rat

The high K+- and acetylcholine (ACh)-induced release of [3H]dopamine (DA) were investigated in whole brain slices of fetuses and striatal slices of postnatal rats. A high K+-induced, Ca2+-dependent release of [3H]DA was demonstrated in brain on day 18 of gestation and the amount of release from the striatum increased during postnatal development. ACh induced [3H]DA release in striatal slices from 3-, 7- and 70-day-old rats but not from 1-day-old animals. ACh-induced [3H]DA release on both day 7 and day 70 was dependent on Ca2+ and significantly reduced by the addition of 5 x 10(-6) M atropine or 10(-5) M hexamethonium. It is suggested that DA is taken up into functionally releasable pools at a late fetal stage and that from around 3 days after birth, ACh may begin to regulate DA release by stimulating muscarinic and/or nicotinic receptors located on DA nerve terminals in the striatum.