Dopamine is released spontaneously from developing midbrain neurons in organotypic culture

While neuronal activity is important in CNS development, little is known of the behaviour of the actual neurotransmitters released during this period. None the less, indirect evidence has suggested that the neurotransmitter dopamine actually has a morphogenic role. This study is the first attempt to monitor directly and in real-time, the release of dopamine from midbrain neurons developing as an isolated organotypic slice culture. The observed release of dopamine was both spontaneous and synchronized and occurred with an average periodicity that is two orders of magnitude longer than the characteristic neuronal discharge activity of midbrain dopamine cells. Moreover, elevations in the extracellular concentrations of dopamine were markedly more prolonged in these and other developing systems than in axon terminal regions in mature striatum in which dopaminergic innervation is fully established. Thus, dopamine may have an action in developing circuits over spatial and temporal scales that vastly exceed those in mature, synaptic-like transmission.