AbstractThe role of extracellular calcium in monoamine responses of central neurons was investigated using explant cultures of tuberal hypothalamus. The spontaneous activity of neurons in cultures was recorded in balanced salt and calcium‐deficient salt solutions. The firing rate was reversibly augmented during perfusion with calcium‐free salt solutions. This increased firing rate was counteracted by the addition of magnesium. Addition of magnesium also regularized the pattern of firing. Iontophoretic application of putative monoamine neurotransmitters reversibly decreased the rate of firing in both normal and calcium‐deficient salt solutions. These results suggest that monoamine inhibitions are not primarily mediated by transmembrane calcium f