Immunohistochemical studies on the somatostatin- and growth hormone-releasing factor (GRF)-neurons in the hypothalamus of the novel dwarf rat; the spontaneous dwarf rat (dr).

Immunoreactivities of somatostatin and growth hormone-releasing factor (GRF) in the hypothalamus of spontaneous dwarf rats (SDRs, gene symbol; dr), which show isolated growth hormone (GH) deficiency, and normal rats were studied with an avidin-biotin complex (ABC) immunohistochemical method. Somatostatin and GRF immunoreactivities were observed in the median eminence and each afferent nucleus with no difference between these animals. The observation suggests that the etiology of the GH deficiency lies in GH cells themselves and is not hypothalamic in origin. This observation indicates that the SDR is a new model animal for type I dwarfism.