Light and Electron Microscopic Immunocytochemical Evidence that Delta Sleep-Inducing Peptide and Gonadotropin-Releasing Hormone Are Coexpressed in the Same Nerve Structures in the Guinea Pig Median Eminence

Abstract

The relationships between delta sleep-inducing peptide (DSIP) and GnRH immunoreactivity within the guinea pig median eminence are investigated by light and electron microscopic immunocytochemistry. Indirect immunofluorescence and elution-restaining experiments show that at the light microscopic level the distribution patterns of DSIP and GnRH immunoreactivity are indistinguishable. This suggested the possible coexistence of both immunoreactivities within the same fibers and neurosecretory endings. At the electron microscopic level, a preembedding double-immunolabeling technique using both indirect immunoperoxidase and immunogold methods, clearly indicate that DSIP and GnRH immunoreactivity are frequently colocalized within single secretory granules. In addition DSIP/GnRH immunoreactive nerve endings were also observed often in close proximity to tanycyte elements. Taken together, the present results provide for the first time ultrastructural evidence for the presence of DSIP immunoreactivity and demonstrate that DSIP and GnRH immunoreactivities may be coexpressed within the same neuronal elements in the median eminence.

Fetal Development of Delta-Sleep-Inducing-Peptide-Like Immunoreactivity in Hypothalamus of Guinea Pig with Special Regard to the Prenatal Colocalization with Gonadotropin-Releasing-Hormone-Like Immunoreactivity

“…The controls, previously reported [14,21] and again repeated for this study, have shown that rat antiserum to DSIP did not recognize LHRH, angiotensin II, ACTH, TRH and vasopressin. In addition, the rabbit antiserum to GnRH did not cross-react with DSIP and other heterologous antigens, such as oxytocin, vasopres sin, TRH, somatostatin and neuropysin.…”

“…We used the same primary antisera as previously [14]: rat antiserum to DSIP (1:500-1,000, reference GO, a gift from Dr. Y. Charnay, Genève, Switzerland); rabbit antiserum to GnRH (1:2,000-4,000, a gift from M.P. Dubois, Nouzilly, France), goat antirat immunoglobulin G (IgG).…”

“…The single immunolabeling procedure was performed according to the indirect immunofluorescence method [19] as previously described [14]. Briefly, two adjacent sections were incubated with either rat antise rum to DSIP or rabbit antiserum to GnRH at optimal dilution for 48 h at 4 °C.…”

“…Recently, by using light or/and electron microscopy immunocytochemistry, DS1P and gonadotropin-releasing hormone (GnRH) have been shown to be colocalized within the same neurons in the basal forebrain and hypothalamus [7,8] and in the same neurosecretory granules of these neu rons as observed in the guinea pig median eminence [14].…”

Induction of Pituitary Cell Type Differentiation by Delta Sleep-Inducing Peptide

“…Immunoreactive DSIP has been found in biological fluids, the brain and endocrine glands of several species [6][7][8]. Recent immu nocytochemical studies using light and electron microsco-py have shown that in the adult DSIP colocalizes with GnRH in neurons of several species including man [9], rabbit [10], guinea pig [11] and rat [12]. GnRH is known to influence the differentiation of gonadotropes in vitro [13], and is detected as early as embryonic day (ED) 12 in the rat hypothalamus [14].…”