Distribution Of Gastrin-releasing Peptide Research Articles

Distribution of gastrin‐releasing peptide in the rat trigeminal and spinal somatosensory systems

Gastrin-releasing peptide (GRP) has recently been identified as an itch-specific neuropeptide in the spinal sensory system in mice, but there are no reports of the expression and distribution of GRP in the trigeminal sensory system in mammals. We characterized and compared GRP-immunoreactive (ir) neurons in the trigeminal ganglion (TG) with those in the rat spinal dorsal root ganglion (DRG). GRP immunoreactivity was expressed in 12% of TG and 6% of DRG neurons and was restricted to the small- and medium-sized type cells. In both the TG and DRG, many GRP-ir neurons also expressed substance P and calcitonin gene-related peptide, but not isolectin B4 . The different proportions of GRP and transient receptor potential vanilloid 1 double-positive neurons in the TG and DRG imply that itch sensations via the TG and DRG pathways are transmitted through distinct mechanisms. The distribution of the axon terminals of GRP-ir primary afferents and their synaptic connectivity with the rat trigeminal sensory nuclei and spinal dorsal horn were investigated by using light and electron microscopic histochemistry. Although GRP-ir fibers were rarely observed in the trigeminal sensory nucleus principalis, oralis, and interpolaris, they were predominant in the superficial layers of the trigeminal sensory nucleus caudalis (Vc), similar to the spinal dorsal horn. Ultrastructural analysis revealed that GRP-ir terminals contained clear microvesicles and large dense-cored vesicles, and formed asymmetric synaptic contacts with a few dendrites in the Vc and spinal dorsal horn. These results suggest that GRP-dependent orofacial and spinal pruriceptive inputs are processed mainly in the superficial laminae of the Vc and spinal dorsal horn.

Ultrastructural localization of gastrin-releasing peptide (GRP) in the uterine gland of cow.

Gastrin-releasing peptide (GRP) is thought to act mainly as a neurotransmitter and localized almost exclusively to neurons and neuroendocrine cells. Recently, the localization of GRP in mammalian uterus and placenta has been demonstrated. Moreover, the exocrine manner of GRP release was deduced in ewes from the distribution of GRP on the uterine gland cells and its secretion as well as in the circulation. However, these reports have been examined at light-microscopic level. The present study was designed to make clear the localization of GRP in the uterine gland cells of nonpregnant and pregnant cows using an avidin-biotin-peroxidase complex (ABC) method at light-microscopic level and a pre-embedding immunogold with silver enhancement method at electron-microscopic level. The light-microscopic observation showed positive staining for GRP immunoreactivity in the supranuclear region and in the secreted materials of the uterine gland cells. At the electron-microscopic level, the supranuclear secretory granules and the secreted materials on the surface of the cell were labeled with immunogold particles representing GRP immunoreactivity in the uterine gland cells of nonpregnant and pregnant cows. Western blotting analysis showed a larger molecular form of GRP in the endometrial tissues taken from nonpregnant and pregnant cows. The present results revealed the localization of GRP in the uterine gland cells at light- and electron-microscopic levels and suggested the release of GRP from the cell into the lumen of the gland by exocrine manner.

Distribution of gastrin-releasing peptide/bombesin-like immunoreactivity in the rainbow trout brain

The distribution of gastrin-releasing peptide(14–27)/bombesin-like immunoreactivity was studied in the brain of the teleost Oncorhynchus mykiss using an indirect immunoperoxidase technique. Cell bodies were only found in the hypothalamic nuclei posterioris periventricularis, the anterior part of the recessus lateralis, and in the recessus posterioris. Immunoreactive fibers were widely distributed in the diencephalon, midbrain, and hindbrain. The highest density of immunoreactive fibers was found in the hypothalamus, whereas a moderate to low density of fibers was visualized in the periventricular thalamus. In the midbrain, a moderate density of fibers was observed at the level of the nuclei lateralis and centralis of the torus semicircularis, the stratum album centrale of the optic tectum, the nucleus of the rostral mesencephalic tegmentum, the nuclei lateralis valvulae, the lemnisci lateralis, istmi and locus coeruleus, as well as in the hindbrain at the level of the nuclei gustatorius secundarius, cerebelli, descendens nervi trigemini, and funiculi lateralis. These data suggest that the peptide could be involved in neuroendocrine (LT, nRL, nRP), visual (OT, nRTM, TS, Is), auditory (TS), and nociceptive (Vd, nufl) mechanisms.

Immunohistochemical study on gastrin-releasing peptide-containing peripheral nerve fibers in rat, macaque and human

Distribution of gastrin-releasing peptide (GRP)-containing peripheral nerve fibers in the respiratory organs, digestive tracts and hearts of rat, monkey and human was studied with immunohistochemical method. In the trachea, GRP-immunoreactive nerve fibers were observed in the lamina propria and surrounded ducts and acini of tracheal serous glands with a basket-like appearance. In the lung, immunoreactive nerve fibers were scattered in the lamina propria of bronchi and bronchioles, and also the adventitia of veins. In the digestive organs, such as esophagus, duodenum and jejunum, numerous GRP-immunoreactive nerve fibers were distributed in the lamina propria and muscle layer; especially in the former layer where they were seen running up to the apical part of villi. GRP-containing nerve bundles and branched fibers were also observed in the atrial muscle layer. These results gave a morphological basis to future studies of the functional significance of GRP on autonomic mechanisms.

Distribution of gastrin-releasing peptide (GRP)-like immunoreactivity in the rat.

Rat tissues were examined for gastrin-releasing peptide (GRP)-like immunoreactivity, using carboxy-terminus-specific antibody made against GRP (19-27), which is thought to be the biologically active site and to be common among species. The distribution of GRP-like immunoreactivity in the rat was similar to that of bombesin-like immunoreactivity. Sephadex G 50 chromatography revealed two peaks of GRP-like reactivity in the rat stomach. Immunohistochemical studies using the antiserum to GRP (19-27) revealed numerous nerve fibers in the mucosa of the rat stomach. In the antral mucosa, GRP-containing nerves were present mainly around the base of the antral glands. Some GRP-containing nerves were in contact with gastrin-containing cells and somatostatin-containing cells. GRP-containing nerve fibers were numerous in the middle portion of the oxyntic gland, where somatostatin-containing cells were also detected. None of the endocrine cells stained positively with anti-GRP serum. These results support the hypothesis that GRP is a neurotransmitter in the stomach and that the peptide plays a physiological role in the gastrointestinal tract.

Binding of GRP(14-27) but not bombesin or GRP(1-27) to hypothalamic magnocellular elements: an immunohistochemical study.

Bombesin, gastrin-releasing peptide (1-27), and gastrin-releasing peptide (14-27) abolished the specific immunocytochemical staining revealed by antiserum directed to the C-terminus of gastrin releasing peptide (GRP) and bombesin (BN) in rat hypothalamus. When the antiserum was preabsorbed with GRP(14-27), a strong reaction appeared in hypothalamic magnocellular neurons. This staining of magnocellular elements was produced by lower concentrations of GRP(14-27) than were needed to block immunocytochemical staining revealed by the antiserum in other hypothalamic locations. The distribution of GRP(14-27)-induced immunostaining was similar to that of neurophysin. Since only GRP(14-27) but not GRP(1-27) or bombesin was found to bind to magnocellular cells, it was concluded that binding was due to the N-terminus of GRP(14-27), which resembles the structure of oxytocin and vasopressin. In agreement with this, oxytocin and vasopressin were found to prevent the binding of GRP(14-27) to magnocellular cells. The similarity in localization and the effect of oxytocin and vasopressin suggest that GRP(14-27) may bind to neurophysin at low concentrations. The results suggest that enhancement of staining after preabsorption of antisera with antigens must be interpreted with care. Enhancement can occur at antigen concentrations lower than those required to block the immunostaining. These results fail to support the premise that antigen-induced enhancement of staining is due to antigen binding to specific receptors and subsequent detection of the receptor-bound antigen with the antiserum.

Localization of bombesin and GRP (gastrin releasing peptide) sequences in gut nerves or endocrine cells.

Five anti-gastrin releasing peptide (GRP) sera have been characterized against GRP, bombesin and related polypeptides spotted on cellulose acetate discs. Antibodies reacting with the C-terminal G-14 sequence of bombesin and the 19-27 sequence of GRP, were detected in all sera. Antibodies directed exclusively against the bombesin unrelated 1-17 sequence of GRP were found only in one serum (R-6902). With parallel immunohistochemical tests only the C-terminal immunoreactivity was detected in endocrine-paracrine cells of the chicken proventriculus, while both immunoreactivities were present in nerve fibres and a few nerve cell bodies of the mammalian gut. The distribution of GRP- and bombesin-like immunoreactive nerves in the gastric mucosa of both pyloric and oxyntic type the submucosal and myenteric plexus along the whole gastrointestinal wall and at sphincter regions is detailed.