Somatostatin (SRIF) Prevents Natural Motoneuron Cell Death in Embryonic Chick Spinal Cord

A number of neuroactive peptides including calcitonin gene-related peptide (CGRP), substance P, neurokinin B, opioids, somatostatin (SRIF), galanin, neurotensin and vasoactive intestinal polypeptide (VIP) have been localized in adult rat spinal cord and are considered to participate either directly and/or indirectly in the processing of sensory, motor and autonomic functions. Most of these peptides appear early during development, leading to the suggestion that peptides, in addition to their neurotransmitter/neuromodulator roles, may possibly be involved in the normal growth and maturation of the spinal cord. To provide an anatomical substrate for a better understanding of the possible roles of peptides in the ontogenic development of the cord, we investigated the topographical profile as well as variation in densities of [125I]hCGRP alpha, [125I]substance P/neurokinin-1 (NK-1), [125I]eledoisin/neurokinin-3 (NK-3), [125I]FK 33-824 ([D-Ala2, Me-Phe4, Met(O)ol5]enkephalin)/mu-opioid, [125I]galanin, [125I]T0D8-SRIF14 (an analog of somatostatin); [125I]neurotensin and [125I]VIP binding sites in postnatal and adult rat spinal cord using in vitro quantitative receptor autoradiography. Receptor binding sites recognized by each radioligand are found to be distributed widely during early stages of postnatal development and then to undergo selective modification to attain their adult profile of distribution during the third week of postnatal development. The apparent density of various receptor sites, however, are differently regulated depending on the lamina and the stage of development studied. For example, the density of mu-opioid binding sites, following a peak at postnatal day 4 (P4), declines gradually in almost all regions of the spinal cord with the increasing age of the animal. [125I]substance P/NK-1 binding sites, on the other hand, show very little variation until P14 and then subsequently decrease as the development proceeds. In the adult rat, most of these peptide receptor binding sites are localized in relatively high amounts in the superficial laminae of the dorsal horn. To varying extents, moderate to low density of various peptide receptor binding sites are also found to be present in the ventral horn, intermediolateral cell column and around the central canal. Taken together, these results suggest that each receptor-ligand system is regulated differently during development and may each uniquely be involved in cellular growth, differentiation and in maturation of the normal neural circuits of the spinal cord. Furthermore, the selective localization of various receptor binding sites in adult rat spinal cord over a wide variety of functionally distinct regions reinforces the neurotransmitter/modulator roles of these peptides in sensory, motor and autonomic functions associated with the spinal cord.

Section: Adult Spinal Cordmentioning

confidence: 99%

Section: Adult Spinal Cordmentioning

confidence: 99%

Neuropeptide receptors in developing and adult rat spinal cord: An in vitro quantitative autoradiography study of calcitonin gene‐related peptide, neurokinins, μ‐opioid, galanin, somatostatin, neurotensin and vasoactive intestinal polypeptide receptors

Kar

Quirion

1995

“…In addition, SS has been shown to induce neurite sprouting in vitro (Bulloch, 1987;Grimm-Jorgensen, 1987) and in vivo (Gotow et al, 1989) and to rescue spinal cord motor neurons from naturally occurring cell death (Weil, 1991). SS-positive neurons of the mammalian hippocampal formation are generated prenatally (Rapp and Amaral, 1988).…”

Section: Comparison With Mammalsmentioning

confidence: 99%

“…Among peptide-containing neuronal populations, particular attention has been directed toward SS as a possible neurotrophic factor because of its relatively high levels during brain development, especially in transient structures such as the cortical subplate (Chun et al, 1987). In addition, SS has been shown to induce neurite sprouting in vitro (Bulloch, 1987;Grimm-Jorgensen, 1987) and in vivo (Gotow et al, 1989) and to rescue spinal cord motor neurons from naturally occurring cell death (Weil, 1991). SS-positive neurons of the mammalian hippocampal formation are generated prenatally (Rapp and Amaral, 1988).…”

Section: Comparison With Mammalsmentioning

confidence: 99%

Neuroactive substances in the developing dorsomedial telencephalon of the pigeon (Columba livia): Differential distribution and time course of maturation

Erichsen

Ciocchetti

Fontanesi

et al. 1994

The avian hippocampal formation has previously been shown to contain many of the same neurotransmitters and related enzymes that are found in mammals. In order to determine whether the relatively delayed development of the mammalian hippocampus is typical of other vertebrates, we investigated the maturation of a variety of neuroactive substances in the hippocampal formation of the homing pigeon. The distribution of two transmitter-related enzymes, choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH), the neurotransmitter GABA, and four neuropeptides (substance P, enkephalin, neuropeptide Y, and somatostatin) was studied by immunohistochemistry in the developing hippocampal complex. The pattern and/or the time course of changes in the distribution of immunoreactivity varied among the different neuroactive substances examined. Immunoreactivity to ChAT and TH was found exclusively in fibers and terminal-like processes, whereas GABA and peptide immunoreactivity was seen in cells and neuropil. Quantitative differences in the density, number, and size of stained cells were assessed by a computer-assisted image analyzer. For the majority of the substances, developmental patterns in the distribution of immunoreactivity differ between the hippocampus proper and the area parahippocampalis, the two major areas that together make up the avian hippocampal complex. The adult pattern of immunoreactivity was generally attained by 3 weeks after hatching. For many of the neuroactive substances found in cell bodies, there was a gradual decrease in the density of immunoreactive cells with a concomitant increase in the density of immunoreactive neuropil. The actual number of stained cells usually increased to a peak at 9 days posthatching and then declined until 3 weeks posthatching, when the adult value was reached. These results are discussed in relation to the advantages that the pigeon hippocampal complex may provide in the study of developmental processes. Parallels with the distribution of the same neuroactive substances in the mammalian hippocampus are used to suggest possible functional similarities between the avian and mammalian hippocampal regions.

“…Concurrently, somatostatin has been shown to exert neurotrophic activi- ties in various cell models (Bulloch, 1987;Weill, 1991;Takayuki and Schwartz, 1995) and to regulate neuronal cell migration in the mouse brain (Yacubova and Komuro, 2002). Whether somatostatin produced by ependymal glial cells may regulate the proliferation of stem cells and/or may control their differentiation into neural and glial cells deserves to be examined.…”

Section: Functional Considerationsmentioning

confidence: 99%

Somatostatin in the brain of the cave salamander, Hydromantes genei (Amphibia, Plethodontidae): Immunohistochemical localization and biochemical characterization

Mathieu

Bruzzone

Chartrel

et al. 2004

The distribution of somatostatin-like immunoreactivity in the brain of the cave salamander Hydromantes genei (Amphibia, Plethodontidae) was investigated by using two distinct antisera raised against somatostatin-14. Most somatostatin-positive cells were detected in the ependymal cell layer surrounding the ventricles. These cells possessed the typical morphological characteristics of tanycytes or radial glial cells. Double-labeling with an antiserum against somatostatin and a monoclonal antibody against glial fibrillary acidic protein showed that somatostatin-immunoreactive cells lining the ventricles also exhibited GFAP-like immunoreactivity. Injection of the neurotracer biocytin into the lateral ventricle revealed that neurons lining the ventricles did not contain somatostatin-like immunoreactivity. In the telencephalon, somatostatin-like immunoreactivity was confined to radial glial cells. In the diencephalon, in addition to somatostatin-immunoreactive cells in the ependyma, positive cell bodies were also found in the periventricular preoptic nucleus, the infundibular nucleus, the epiphysis, and the subcommissural organ. In the metencephalon, positive cell bodies were found in the auricula cerebelli, whereas in the rhombencephalon numerous somatostatin-immunoreactive cells were seen lining the ventricular cavity. Immunoreactive nerve fibers were observed in the hypothalamus-median eminence complex. In the pituitary, a discrete group of somatostatin-positive cells was found in the pars distalis. High-performance liquid chromatography analysis of brain extracts revealed that the immunoreactive material coeluted with somatostatin-14. The present results show that the somatostatin peptidergic system in the brain of the cave salamander has a more simple organization than those described in the brain of frog and other vertebrates. This feature is probably related to the expression of high pedomorphic characters in plethodontids. The distribution of somatostatin-like immunoreactivity suggests that, in the cave salamander, somatostatin may act as a neurotransmitter and/or neuromodulator, a central regulator of fluid homeostasis, and a hypophysiotropic neurohormone.