Intrahypothalamic injection of somatostatin, not GRF, stimulates prolactin secretion

The distribution of somatostatin and growth hormone releasing factor (GRF) fibres in the hypothalamus suggests that they may be involved in physiological functions in addition to growth hormone control. GRF or somatostatin were stereotaxically injected into anterior or basal hypothalamic regions of unanesthetized male rats and effects on plasma prolactin measured. Somatostatin caused a small, significant, dose-responsive stimulation of prolactin secretion when injected in both hypothalamic regions, while GRF was without effect. Somatostatin may therefore have a minor intrahypothalamic role in regulating prolactin.