We studied the release of immunoreactive somatostatin (IR-SRIF) from hypothalamic cells that were obtained from rats and dispersed with the aid of collagenase. Twenty-four hours after dispersion, cells were placed in a column supported by a matrix of preswollen Biogel P2 and perifused. Fractions were collected on ice and subsequently assayed for SRIF. SRIF release was stimulated markedly by potassium depolarization (KCl, 56 mM), by the Na+-K+-ATPase inhibitor ouabain (10(-4) M), and by dopamine at concentrations as low as 10(-11) M. The stimulatory effects of membrane depolarization were calcium dependent and were not observed in the absence of exogenous calcium in the perifusion medium or in the presence of EDTA (0.05 M). Metoclopramide, the dopamine antagonist, abolished the stimulatory effect of dopamine. In conclusion, release of IR-SRIF by dispersed rat hypothalamic cells can be studied in a simple perifusion apparatus. Release is stimulated by membrane depolarization in a calcium-dependent manner and by dopamine at physiological concentrations.