Growth hormone releasing factor immunoreactivity in rat hypothalamus.

Neurones immunoreactive to antibodies against human pancreatic growth hormone releasing factor1-40 (hpGRF) were identified in the hypothalamus of the rat after pretreatment with colchicine. Reactive perikarya were concentrated in the arcuate nucleus and were also present around the anterior commissure. hpGRF immunoreactive fibres were observed in the median eminence and preoptic area where they tended to complement the distribution of somatostatin immunoreactive fibres. The distribution of GRF-immunoreactive perikarya in the rat hypothalamus is similar to that reported in monkey, and is consistent with other studies which suggest that neural mechanisms stimulatory for growth hormone secretion in the rat are situated in the medial basal hypothalamus.