SYNCHRONOUS DEVELOPMENT OF SPONTANEOUS AND EVOKED CALCIUM-DEPENDENT PROPERTIES IN HYPOTHALAMIC NEURONS

The development of various related parameters was compared in hypothal amic neurons grown in primary culture. We measured: (i) low- and high- voltage-activated calcium currents; (ii) spontaneous and N-methyl-D-as partate (NMDA)-induced fluctuations of intracellular calcium concentra tion; (iii) basal and NMDA- or potassium-evoked somatostatin release. Spontaneous calcium fluctuations appeared after 5 days in culture and increased progressively in amplitude and frequency over the next 8 day s studied. Basal release of somatostatin was not detectable in 3 day-o ld cultures and reached a plateau at day 5. Responses evoked by exogen ous stimulations (voltage-activated calcium currents, agonist-induced intracellular calcium rise and somatostatine release) appeared early i n culture, increased in amplitude during 7-10 days and then stabilized . We conclude that, in hypothalamic neurons, the main neuronal functio ns develop in synchrony over a limited period of time.