High potassium-induced, calcium-dependent monoamine release from brain slices of the newborn rat

To determine the functional significance of monoamines taken up into the newborn rat brain, a high K+-induced, Ca2+-dependent release of noradrenaline (NA), dopamine (DA) or serotonin (5-HT) from brain slices of the newborn rat was investigated and compared with that of the adult animal. Depolarization by increasing the potassium concentration in the medium induced the release of L-[3H]NA,[3H]DA or [3H]5-HT from brain slices prelabelled with the radioactive monoamines in the 2-day- or 3-day-old rat as well as in the adult. The release of three [3H]amines was markedly inhibited by perfusing with Ca2+- free medium in the presence of EGTA (2.0 mM) at both newborn and adult stages, although the inhibitory potency of Ca2+- deficiency in the newborn preparation was lower than in the adult. The degree of the release against [3H]amines initially taken up in the newborn was of the same order of magnitude as those in the adult. It is suggested that NA, DA and 5-HT are stored in a functionally releasable pool of the nerve terminals of the central monoamine neurons in the rat and that these compounds act as neurotransmitters at birth and at the adult stage.