SYNCHRONIZED SPONTANEOUS CA2-PITUITARY SLICES( TRANSIENTS IN ACUTE ANTERIOR)

We investigated the organization of spontaneous rises in cytosolic fre e Ca2+ concentration ([Ca2+](i)) due to electrical activity in acute p ituitary slices. Real time confocal imaging revealed that 73% of the c ells generated fast peaking spontaneous [Ca2+](i) transients. Striking ly, groups of apposing cells enhanced their [Ca2+](i) in synchrony wit h a speed of coactivation >1,000 mu m/s. Single-cell injection of Neur obiotin or Lucifer yellow labeled clusters of cells, which corresponde d to coactive cells. Halothane, a gap junction blocker, markedly reduc ed the spread of tracers. Coupling between excitable cells was mainly homologous in nature, with a prevalence of growth hormone-containing c ells. We conclude that spontaneously active endocrine cells are either single units or arranged in synchronized gap junction-coupled assembl ies scattered throughout the anterior pituitary gland. Synchrony betwe en spontaneously excitable cells may help shape the patterns of basal secretion.