Potassium stimulated calcium dependent release of immunoreactive somatostatin from incubated rat hypothalamus

Somatostatin (somatotropin release inhibiting factor, SRIF) is present in the median eminence of the hypothalamus in high concentration (Kronheim et al., 1976), is visualized in nerve endings (Hökfelt et al., 1974) and has been found to be concentrated in the synaptosome fraction of hypothalamic homogenates (Epelbaum et al., 1977; Berelowitz et al., 1978), suggesting a true neurosecretory role. To further explore this possibility we have studied the release of immunoreactive SRIF from the incubated rat hypothalamus (Bradbury et al., 1974: Rotsztein et al., 1977), basally and in response to depolarising concentrations of potassium, and have assessed the calcium dependence of this release.