Presence of sst2(a) receptor immunoreactivity in rat ependyma and tanycytes

Somatostatin sst2(a) receptor was observed, by immunofluorescence, in ependymal cells and in tanycytes of the wall of the ventricle and the hypothalamic recess of the male rat median eminence. Strong immunoreactivity for the receptor protein was observed in lateral tanycytes (alpha-type) while a moderate signal was seen in medial tanycytes (beta-type). In high magnification the immunoreactive material, of moderate intensity, had a coarse granular appearance. Only few of the alpha-tanycytes also displayed immunoreactive GFAP. The apical portion of the ependymal cells as well as of tanycytes contained immunoreactive S-100 (alphabeta). Since rather high levels of somatostatin are demonstrated to occur in the cerebrospinal fluid of the third ventricle, it is suggested that somatostatin via the sst2(a) receptor may regulate the physiology of tanycytes.