Occurrence of galanin-like immunoreactivity in growth hormone-releasing factor (GRF)-containing neurons of the monkey (Macaca fascicularis) infundibular nucleus and median eminence.

The distribution of growth hormone-releasing factor (GRF)- and galanin (GAL)-immunoreactive (-IR) neurons in the mediobasal hypothalamus of the monkey (Macaca fascicularis) was studied with immunohistochemistry using a direct double-labelling method. GRF- and GAL-IR cell bodies were demonstrated in the ventral part of the infundibular nucleus and dense aggregations of GRF- and GAL-IR fibers were seen in the external layer of the median eminence, closely surrounding portal vessels. Double-staining revealed that GRF and GAL were colocalized in cell bodies of the infundibular nucleus and in nerve fiber varicosities in the external layer of the median eminence. GAL has been reported to stimulate the secretion of growth hormone in both rats and humans, most likely via hypothalamic mechanism(s).