Development of transmitter-releasing capacity in neuron-enriched tissue cultures

Dissociated cell cultures derived from whole brains of foetal rats (17 days of gestation) were maintained for periods of up to 21 days in vitro for the purpose of studying the transmitter-releasing properties of the dopaminergic neuronal cells and glial cells. In the neuron-enriched cultures, after 3 days in vitro, [3H]dopamine was released in response to depolarizing stimuli. Both the potassium and veratrine-evoked release of dopamine was Ca2+ dependent. Veratrine-evoked release was reduced in the presence of the calcium channel blocker verapamil and was tetrodotoxin sensitive. Glial cultures, after 7 days in vitro, did not respond to any depolarizing stimuli, although they displayed a significant ability to take up [3H]dopamine. Comparison between static incubations and perfused cultures showed no difference in the patterns of release resulting from veratrine stimulation. Tyrosine hydroxylase activity increased progressively in neuron-enriched cultures but was not detectable in glial cultures. These results show that neuron-enriched cultures respond to depolarizing stimuli in a manner similar to excised adult basal ganglia tissue, with the appearance of functional ionic channels after 3 days in vitro.