Expression of neuropeptides and neuropeptide mRNAs in spinal cord after axotomy in the rat,with special reference to motoneurons and galanin

The extent to which the plasticity in peptide expression observed in developing spinal motoneurons occurs following proximal peripheral axotomy in the adult rat was examined using in situ hybridization and immunohistochemical techniques to visualize the changes. Transient upregulation of galanin, vasoactive intestinal polypeptide (VIP) and substance P messenger ribonucleic acids (mRNAs) was observed within subpopulations of motoneurons ipsilateral to lesion for periods lasting 2–3 weeks after injury. In contrast, the axotomy-induced heterogenous increases in somatostatin and neuropeptide tyrosine mRNA expression in ipsilateral motoneurons remained elevated, or, in the case of somatostatin, continued to increase for the time period studied (1 month). Immunohistochemical analysis agreed with the in situ hybridization results, showing some motoneurons within the injured ventral horn to contain galanin-, VIP-or somatostatin-like immunoreactivity. In some instances, galanin-immunoreactive motoneurons colocalized with calcitonin gene-related peptide immunoreactivity. Most of the neurons expressing the injury-induced peptides appeared large, presumably alpha-motoneurons, but there were also many small neurons expressing galanin in the ventral horn ipsilateral to lesion. This may represent evidence for peptide synthesis in gamma-motoneurons. The only peptide mRNA studied to be downregulated in response to axotomy was enkephalin. The results show that peptide expression in injured motoneurons is dramatically altered, the significance of which remains to be determined.     

Somatostatinoma syndrome. Biochemical, morphologic and clinical features.

Diabetes mellitus, steatorrhea, cholelithiasis and a tumor distorting the duodenum prompted a work-up for somatostatinoma in a 52-year-old man. The responses of pancreatic B-cells but not of A-cells to nutrient stimuli were inhibited, and growth-hormone release was suppressed, suggesting somatostatin resistance in some target tissues. Plasma somatostatin-like immunoreactivity ranged from 9000 to 13,000 pg per milliliter (normal: 88+/-8, mean +/- S.E.M.) and was distributed in four molecular forms, including free somatostatin. The primary tumor contained 5 microgram of somatostatin-like immunoreactivity per milligram of wet tissue, distributed in three of the molecular forms noted in plasma. Plasma calcitonin was also elevated (4650 pg per milliliter; normal: less than 120). Immunocytochemical studies showed that cells of the primary tumor contained somatostatin and calcitonin but no other peptide hormones. Only somatostatin was present in the metastases. Somatostatin was localized electron microscopically in all secretory granules, irrespective of size and shape, whereas calcitonin was present only within a single subpopulation of small granules in the same cells.     

Immunohistochemical evidence for separate populations of somatostatin-containing and substance P-containing primary afferent neurons in the rat

The localization of two small peptides, somatostatin and substance P, has been studied with the indirect immunofluorescence technique. Both peptides were present in small neuronal cell bodies in spinal ganglia, in fibers in the dorsal horn of the spinal cord and in fibers in the intestinal wall. By comparing consecutive sections incubated with antisera to somastostatin and to substance P respectively, it was established that somatostatin, or somatostatin-like immunoreactivity and substance P, or substance P-like immunoreactivity are present in different cells. This is possibly indicated also by a somewhat differential distribution of the immunoreactive fibers in the dorsal horn: the highest concentration of somatostatin-positive fibers was observed in lamina II, whereas abundant substance P-positive fibers were present also in lamina I. Furthermore, numerous substance P-, but no somatostatin-positive fibers, were found around the central canal and in the ventral horns. In the intestinal wall more substance P-positive than somatostatin-positive fibers were seen.The present results indicate that two subpopulations of primary sensory neurons exist, one containing somatostatin, or somatostatin-like immunoreactivity, and the other containing substance P, or substance P-like immunoreactivity.     

Kainic acid induced seizures: changes in somatostatin, substance P and neurotensin

The neuropeptides somatostatin, neurotensin and substance P were investigated in rats during and after limbic seizures induced by systemic injection of kainic acid (10 mg/kg, i.p.). Three hours after injection of the toxin, pronounced decreases (40-50%) in somatostatin-like immunoreactivity in frontal cortex, striatum, dorsal hippocampus and amygdala/pyriform cortex were observed. Concomitantly, neurotensin-like and substance P-like immunoreactivities were also reduced in the frontal cortex and the hippocampus. These early decreases in peptide levels may result from increased release and subsequent inactivation of the peptides during acute seizures. At later time intervals, 3, 10 and 30 days after injection of kainic acid, the initially decreased peptide levels were partially normalized. However, the reduction in somatostatin-like immunoreactivity in amygdala/pyriform cortex and striatum persisted up to 30 days. Neurotensin-like immunoreactivity remained decreased in the frontal cortex. On the other hand, neurotensin- and substance P-like immunoreactivities were increased in the striatum and substantia nigra 10-30 days after injection of kainic acid. These late changes in peptide levels may suggest destruction of peptidergic neurons or adaptive changes induced by the convulsions. Pretreatment of rats with cysteamine (100 mg/kg, i.p.), an agent which decreases brain somatostatin levels, had no effect on the intensity of kainic acid induced convulsions, although a slightly earlier onset of seizures was observed. The changes in peptide levels, especially the marked decreases in somatostatin content after systemic injection of kainic acid, suggest considerable acute and chronic alterations in peptidergic systems caused by limbic convulsions.     

Distribution of peptide- and catecholamine-containing neurons in the gastro-intestinal tract of rat and guinea-pig: immunohistochemical studies with antisera to substance P, vasoactive intestinal polypeptide, enkephalins, somatostatin, gastrin/cholecystokinin, neurotensin and dopamine beta-hydroxylase

The distribution of peptide-containing neurons in the oesophagus, stomach and small and large intestine of the rat and the guinea-pig has been studied with the indirect immunofluorescence technique ofCoons &; Co-workers (1958) using antisera to substance P, vasoactive intestinal polypeptide (VIP), enkephalin, somatostatin, gastrin and neurotensin. (The gastrin antiserum is to the C-terminal portion and consequently reacts also with cholecystokinin (CCK)-like peptides.) For comparison, the noradrenergic innervation was visualized with antiserum to dopamine β-hydroxylase. For improved visualization of peptide-containing cell bodies, a mitotic inhibitor (colchicine or vinblastine) was applied locally on the different parts of the gastro-intestinal tract of several animals.Substance P-, VIP-, enkephalin- and somatostatin-like immunoreactivity was observed in all parts of the gastro-intestinal tract studied. Gastrin/CCK had a more limited distribution, especially in the guinea-pig and neurotensin was seen only in certain regions and layers of the rat gastro-intestinal tract.Immunoreactivity to all peptides except neurotensin was observed both in cell bodies and fibres; immunoreactivity to neurotensin has so far only been seen in nerve fibres. Substance P and enkephalin immunoreactive cells were often numerous in the myenteric plexus, whereas VIP and somatostatin immunoreactive cells were preferentially located in the submucous plexus. Some VIP immunoreactive cells were observed in the lamina propria. Large numbers of especially substance P-, VIP- and enkephalin-containing fibres were often seen in the circular muscle layer and in the two ganglionic plexuses. Substance P immunoreactive fibres formed the densest network in the ganglionic plexuses, whereas VIP immunoreactive fibres constituted the most impressive network in the lamina propria and often extended into the most superficial parts of the mucosa. Enkephalin immunoreactive structures were mainly confined to the circular and longitudinal muscle layers and the myenteric plexus. Somatostatin immunoreactive fibres were mainly found in the ganglionic plexuses.Peptide-containing fibres, particularly these containing substance P and VIP were often seen along blood vessels, but never with such a density as the noradrenergic (dopamine β-hydroxylase immunoreactive) fibres. No somatostatin or neurotensin immunoreactive fibres were observed in relation to clearly identifiable blood vessels.The possible coexistence of two peptides in one neuron was studied. For this part of the study the proximal colon and five antisera, namely substance P, VIP, enkephalin. somatostatin and gastrin/CCK antisera were selected. Evidence was obtained for the occurrence of a somatostatin-like and a gastrin/ CCK-like peptide in the same neurons. This may indicate a common precursor for the two peptides in these particular neurons. Each of the substance P-, VIP- and enkephalin-like peptides. on the other hand, seem to be present in different neuronal populations, which were themselves distinct from the somatostatin-gastrin/CCK immunoreactive neurons. In addition, somatostatin immunoreactive neurons different from the gastrin/CCK immunoreactive ones seem to exist. The gastrin/CCK immunoreactive fibres around blood vessels may represent a further, separate population of fibres, since no somatostatin immunoreactive fibres were seen at this location.The findings indicate the existence of numerous subpopulations of enteric neurons, each characterized by its content of a certain peptide (or peptides). The axons of most of these neurons probably terminate in the wall of the gastro-intestinal tract, but some seem to project to other organs. In addition, some peptide-containing fibres in the gastro-intestinal wall may have an extrinsic origin. The relationship between these peptide-containing neurons and the cholinergic enteric neurons and any of the other non-cholinergic. non-adrenergic inhibitory and excitatory neurons present in the enteric nervous system is not known. It is, however, noteworthy that a somatostatin-like peptide seems to be present in noradrenergic neurons of prevertebral ganglia that project to the intestine. The possibility must be kept in mind that one or more of the peptides in the gut could be localized in neurons that contain other potential transmitters, e.g. acetylcholine.The wide variety of pharmacological actions of these neuronal peptides on smooth muscle and neurons in the gut and on its blood vessels raises the possibility that some of them may be neurotransmitters.     

Neurotensin-like and somatostatin-like immunoreactivity within amacrine cells of the retina

Neurotensin-like and somatostatin-like immunoreactivity was demonstrated in the pigeon retina, using both immunohistochemical and radioimmunoassay techniques.Immunohistochemical studies utilized both the indirect immunofluorescence and immunoperoxidase procedures with two well-characterized antisera to neurotensin and three well-characterized antisera to somatostatin. Specific immunoreactivity of each antiserum was established by absorption with either 10 μM synthetic neurotensin, somatostatin or leu⁵-enkephalin. Specific immunohistochemical staining for neurotensin and for somatostatin was observed within separate populations of multistratified amacrine cells. Neurotensin-like and somatostatin-like immunoreactivity were observed within somata located in the inner nuclear layer and within varicose processes ramifying in laminae 1, 3 and 4 of the inner plexiform layer. Immunoreactive somata and processes were observed throughout the retina and their density appeared to be greatest within central retinal regions. The somata-containing neurotensin-like and somatostatin-like immunoreactivity measured about 7 μm in diameter. The cell to cell spacing of neurotensin-like immunoreactive somata was approximately 30 μm and the cell to cell spacing of somatostatin-like immunoreactive somata was approximately 27 μm in central retinal regions. Within more peripheral retinal regions, immunoreactive cells were spaced farther apart.Radioimmunoassays utilizing well-characterized antisera to neurotensin and somatostatin demonstrate specific neurotensin-like and somatostatin-like immunoreactivity in acetic acid extracts of the retina. The concentration of immunoreactive neurotensin is 59 ± 7 fmoles per whole retina (mean ± S.E.M.) or 15.4 ± 2 fmoles per mg protein. The concentration of immunoreactive somatostatin is 2209 ± 440 fmoles per whole retina or 527 ± 76 fmoles per mg protein.These results demonstrate the existence of two additional neuropeptides within selected populations of retinal amacrine cells. The localization of several different neuropeptides within the retina suggests that neuropeptides play a specific role in retinal function.     

Somatostatin, galanin and peptide histidine isoleucine in the newborn and adult human trigeminal ganglion and spinal nucleus: Immunohistochemistry, neuronal morphometry and colocalization with substance P

By means of indirect immunofluorescence the neuropeptides somatostatin, galanin and peptide histidine isoleucine were localized in cell bodies, nerve fibres and terminal-like elements in the ganglion and spinal nucleus of the human trigeminal nerve in perinatal and adult ages. No immunoreactivity to vasoactive intestinal polypeptide was observed. In the gasserian ganglion somatostatin-, galanin- and peptide histidine isoleucine-containing neurons and nerve fibres occurred frequently in pre- and full-term newborns, but were scarce to absent in adults. Somatostatin- and galanin-positive pericellular basket-like structures around non-immunoreactive perikarya were observed in newborn specimens. Immunoreactivity to somatostatin, galanin and peptide histidine isoleucine labelled nerve fibers and punctate and felt-like nerve terminals in the pars interpolaris and subnucleus caudalis of the spinal trigeminal nucleus, with immunostaining and distribution patterns characteristic for each peptide. In addition, somatostatin-containing neuronal cell bodies frequently were detected. At variance with those containing somatostatin, the number of galanin- and peptide histidine isoleucine-like immunoreactive elements were dramatically reduced in the adult tissue compared to the newborn one. Double immunostaining revealed that each of the three peptides partially colocalizes with substance P, the degree of coexistence being very low for somatostatin/substance P and high for galanin/substance P and peptide histidine isoleucine/substance P both in the gasserian ganglion and in the spinal nucleus. The results obtained suggest that somatostatin, galanin and peptide histidine isoleucine may play functional roles in primary sensory neurons and at the first synaptic level of the human trigeminal sensory system.     

Colokinetic effect of somatostatin in the spinal defecation center in rats

Somatostatin and its receptors are expressed in the spinal cord, but the functional roles of the peptide remain unknown. In this study, we examined the colokinetic effect of somatostatin in the spinal defecation center in anesthetized rats. Intrathecal application of somatostatin into the lumbo-sacral cord caused propulsive contractions of the colorectum. However, somatostatin administered intravenously or intrathecally to the thoracic cord failed to enhance colorectal motility. Transection of the thoracic cord had no significant impact on the colokinetic action of somatostatin. The enhancement of colorectal motility by intrathecal administration of somatostatin was abolished by severing the pelvic nerves. Our results demonstrate that somatostatin acting on the spinal defecation center causes propulsive motility of the colorectum in rats. Considering that somatostatin is involved in nociceptive signal transmission in the spinal cord, our results provide a rational explanation for the concurrent appearance of chronic abdominal pain and colonic motility disorders in IBS patients.     

The immunocytochemical localization of somatostatin-containing neurons in the rat central nervous system

Somatostatin-containing neurons in the rat central nervous system were localized by immunocytochemical methods. The detection of somatostatin-like immunoreactivity was facilitated by (1) the use of brains from colchicine-treated rats, (2) the proteolytic pretreatment of sections with pronase and (3) a ‘double-bridge’ immunoperoxidase staining technique. In addition to the known distribution of somatostatin-like immunoreactivity we also observed immunoreactive perikarya in the following regions: the anterior olfactory nucleus, some areas of the preoptic and hypothalamic regions, the claustrum, the periaqueductal gray, the locus ceruleus, the central gray substance, the lateral parabrachial nucleus, the nucleus of the lateral lemniscus, the nucleus ambiguus, the spinal trigeminal nucleus, the nucleus of the solitary tract and various areas of the reticular formation. Immunoreactive neuronal processes were also observed in several major tracts of the brain, including the stria terminalis, the fornix and the medial forebrain bundle.Our results indicate that somatostatin-containing neurons may occur both as interneurons in some areas of the central nervous system and as projection neurons in others. The widespread but selective distribution of these neurons suggests that somatostatin is not only a hypothalamic regulator of neuroendocrine function, but may also function as a major neuromodulator mediating a variety of functions throughout the central nervous system.     

Existence and coexistence of calcitonin gene-related peptide, vasoactive intestinal polypeptide- and somatostatin-like immunoreactivities in spinal cord motoneurons of developing embryos and post-hatch chicks

By use of immunocytochemical methods, it is shown that immunoreactive calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and somatostatin (SOM) are present in motoneurons in the chicken spinal cord. While CGRP-like immunoreactivity (LI) is present in numerous motoneurons both before and after hatching, SOM- and VIP-LI markedly decline at the end of the embryonic period. Evidence is also provided for coexistence of some of these peptides in certain spinal motoneurons.     

The somatostatin systems of the guinea-pig brainstem

The tetradecapeptide somatostatin has been shown to have a widespread distribution in the rat brain. Except for its role in the inhibition of growth hormone secretion, the function of this molecule in the remainder of the central nervous system is unknown. To address this problem, the distribution of somatostatin-like immunoreactivity in the guinea-pig brainstem was examined systematically. Of 116 nuclei and/or areas, 34 nuclei had somatostatin neurons, 32 did not have any immunoreactivity and the remainder had immunoreactive fibers and/or terminals. Cranial nerve motor nuclei--somatic, branchiomeric and visceral--did not contain somatostatin neurons; somatostatin fibers were present in all nuclei with the exception of the somatic motor nuclei which innervate the ocular muscles. Of the cranial nerve sensory nuclei--both somatic and visceral--somatostatin neurons were present only in the somatic nuclei nervi spinal trigeminal caudalis, interpolaris and oralis; all of these nuclei, however, contained substantial numbers of immunoreactive fibers. Somatostatin neurons and fibers were also present in the spinal somatic sensory nuclei cuneatus medialis and gracilis. Of the cranial nerve special somatic sensory nuclei, somatostatin neurons were present in two vestibular nuclei--spinalis and medialis--and in the ventral cochlear nucleus. Not all of these nuclei contained somatostatin fibers. Of the nuclei related to the auditory system, somatostatin neurons were present only in the dorsal and ventral trapezoid nuclei and in the cortex of the inferior colliculus. In nuclei of the visual system in the brainstem, somatostatin neurons were present only in the superior colliculus. Of the raphe nuclei, four had somatostatin neurons--magnus, obscurus, pallidus and superior centralis; somatostatin fibers were present in all raphe nuclei. Of 24 nuclei in the reticular formation, 12 had somatostatin neurons--most notably nuclei gigantocellularis and paragigantocellularis--and only two nuclei, paranigralis and sagulum, did not contain any immunoreactive fibers. In the cerebellum, somatostatin fibers and terminals were restricted to the deep cerebellar nuclei. Of the 11 nuclei projecting to the cerebellum, five contained somatostatin neurons and the majority received somatostatin fibers. Of the limbic system nuclei, somatostatin neurons were confined to the central grey at both pontine and mesencephalic levels. Somatostatin neurons were present in the substantia nigra--compactus and lateralis, but not in reticularis--and absent from the nucleus ruber.(ABSTRACT TRUNCATED AT 400 WORDS)     

Somatostatin-immunoreactive amacrine cells of chicken retina: retinal mosaic, ultrastructural features, and light-driven variations in peptide metabolism

Somatostatin-like immunoreactive amacrine cells of the chicken retina have been characterized by immunohistochemistry at the light and electron microscope levels. The cell bodies were set back from the junction of the inner nuclear and inner plexiform layers, and prominent fibre plexuses were found in sublaminas 1 and 3-5 of the inner plexiform layer. The cells were distributed across the retinal surface with a centroperipheral gradient of cell density. Locally, the cells were organized in a non-random mosaic. Ultrastructurally, immunohistochemical reaction product was found throughout the cytoplasm of the cell bodies, particularly associated with membranous structures, including the cytoplasmic surfaces of the Golgi apparatus, and within large dense-core vesicles. In dendritic varicosities in the inner plexiform layer, reaction product was associated with the external surfaces of small, clear synaptic vesicles. The synaptic relationships of the somatostatin-immunoreactive terminals in sublamina 1 were distinct from those in sublaminas 3-5. Those in sublamina 1 received input predominantly, possibly exclusively, from bipolar cells. Feedback synapses onto bipolar terminals or to the other amacrine cell process at a synaptic dyad were observed. In sublaminas 3-5, input came predominantly, possibly exclusively, from other, non-immunoreactive amacrine cells, and output was primarily onto other amacrine cells. No synaptic contacts with ganglion cells or with other somatostatin-immunoreactive amacrine cells were identified. Changes in levels of somatostatin-like immunoreactivity in retinas of chicks kept on 12:12 light:dark cycles were detected by radioimmunoassay, and by light and electron microscopic immunohistochemistry. Levels of retinal somatostatin-like immunoreactivity increased in the light and decreased in the dark. The changes appear to be light-driven rather than circadian, since with prolonged exposure to light or dark, the levels of somatostatin-like immunoreactivity continued to increase or decrease until plateaus were reached. The light-driven change in levels of somatostatin-like immunoreactivity may be related to the predominance of bipolar input to the immunoreactive processes in sublamina 1 of the inner plexiform layer. The reduction in peptide levels in the dark may indicate greater release of somatostatin-like immunoreactivity from the amacrine cells in the dark, resulting in an inability of peptide synthesis to keep pace with breakdown. In the light, release of somatostatin-like immunoreactivity may be lower, leading to a net synthesis of peptide.     

Calcitonin gene-related peptide and somatostatin immunoreactivities in the rat lumbar spinal cord: sexually dimorphic aspects

The immunohistochemical distribution of calcitonin gene-related peptide and somatostatin in rat lumbar spinal laminae VII-X was investigated using the peroxidase-antiperoxidase technique. Within L1,2 laminae VII and X, calcitonin gene-related peptide and somatostatin fibers demarcate the location of preganglionic sympathetic neurons in a similar fashion in either sex but somatostatin is distributed in a sexually dimorphic manner in the lumbosacral (L5-S2) spinal cord with the male rat containing more somatostatin fibers and neurons than females. Within the ventral horn (lamina IX), calcitonin gene-related peptide has a sexually dimorphic distribution. Calcitonin gene-related peptide varicose fibers are found within the sexually dimorphic male cremaster nucleus but are virtually absent in the female cremaster nucleus. Calcitonin gene-related peptide varicose fibers are nearly absent in the remainder of the male and female lamina IX: this area includes the other two known sexually dimorphic spinal motonuclei: the dorsomedial and dorsolateral nuclei. Virtually all motoneurons in the lumbosacral spinal cord which are not sexually dimorphic contain calcitonin gene-related peptide. However, calcitonin gene-related peptide containing motoneurons have a heterogeneous distribution within sexually dimorphic nuclei. Calcitonin gene-related peptide containing motoneurons within the male and female cremaster nucleus are extremely rare. Some motoneurons within the male and female dorsomedial and dorsolateral nuclei contain calcitonin gene-related peptide with the female dorsomedial and dorsolateral nuclei containing a greater percentage of calcitonin gene-related peptide-containing motoneurons (c. 50%) than males (c. 20%). Somatostatin fibers are preferentially located in sexually dimorphic nuclei of either sex and are distributed in a sexually dimorphic manner within these nuclei with males containing a greater amount of somatostatin fibers than females. The amount of somatostatin immunoreactivity is most dense in the medial aspect of the dorsolateral nucleus, dense in the dorsomedial nucleus, moderate in the cremaster nucleus, and sparse in the lateral portion of the dorsolateral nucleus. In addition, a small column of motoneurons, between the dorsomedial and dorsolateral nuclei at the L5 level, is outlined by somatostatin fibers in females but is absent in males. Somatostatin containing motoneurons were not observed within the lumbar sexually dimorphic nuclei of either sex.     

The immunocytochemical distribution of seven peptides in the spinal cord and dorsal root ganglia of horse and pig

Summary The distribution of calcitonin gene-related peptide (CGRP), enkephalin, galanin, neuropeptide Y (NPY), somatostatin, tachykinins and vasoactive intestinal polypeptide (VIP) was compared in cervical, thoracic, lumbar and sacral segmental levels of spinal cord and dorsal root ganglia of horse and pig.In both species, immunoreactivity for the peptides under study was observed at all segmental levels of the spinal cord. Peptide-immunoreactive fibres were generally concentrated in laminae I–III, the region around the central canal, and in the autonomic nuclei. A general increase in the number of immunoreactive nerve fibres was noted in the lumbosacral segments of the spinal cord, which was particularly exaggerated in the case of VIP immunoreactivity. In the horse, some CGRP-, somatostatin- or tachykinin-immunoreactive cell bodies were present in the dorsal horn. In the pig, cells immunoreactive for somatostatin, enkephalin or NPY were noted in a similar location.In the ventral horn most motoneurones were CGRP-immunoreactive in both species. However, in pig many other cell types were CGRP-immunoreactive not only in the ventral horn, but also in laminae V–VI of the dorsal horn.With the exception of enkephalin and NPY immunoreactivity, which was not seen in pig dorsal root ganglia, all peptides studied were localised to neuronal cell bodies and/or fibres in the dorsal root ganglia. In both species, immunolabelled cell bodies were observed in ganglia from cervical, thoracic, lumbar and sacral levels, with the exception of VIP-immunoreactive cells that were detected only in the lumbosacral ganglia. Numerous CGRP- and tachykinin-immunoreactive cell bodies were visualised in both species, while the cells immunolabelled with other peptide antisera were much lower in number.In both species, immunostaining of serial sections revealed that a subset of CGRP-immunoreactive cells co-expressed tachykinin, galanin or somatostatin immunoreactivity. In the horse some enkephalin-immunoreactive cells were also CGRP positive and occasionally combinations of three peptides, e.g. CGRP, tachykinin and galanin or CGRP, tachykinin and enkephalin were identified.The results obtained suggest that the overall pattern of distribution of peptide immunoreactivities is in general agreement with that so far described in other mammals, although some species variations have been observed, particularly regarding the presence of immunoreactive cell bodies in the dorsal horn of the spinal cord.     

Somatostatin 28 and neuropeptide Y innervation in the septal area and related cortical and subcortical structures of the human brain. Distribution, relationships and evidence for differential coexistence

Somatostatin 28- and neuropeptide Y-containing innervations were mapped in the human medial forebrain (eight control brains) with immunohistochemistry, using the sensitive avidin-biotin-peroxidase method. Peptidergic perikarya and fibers had an extensive distribution: they were densest in the ventral striatum (nucleus accumbens, olfactory tubercle and bed nucleus of the stria terminalis) and infralimbic cortex, of intermediate density in the medial septal area and of lowest density in the dorsal and caudal lateral septal nucleus. Somatostatin-like immunoreactive perikarya and fibers were generally more numerous than the neuropeptide Y-like immunoreactive ones, but more faintly labeled. Their pattern of distribution was strikingly similar in some of the limbic structures studied but clearly distinct in others. Excellent overlap of neuropeptide Y and somatostatin-like immunoreactivity was detected in: (1) the medial septal area, where innervation occasionally formed perivascular clusters; (2) the nucleus accumbens and olfactory tubercle, characterized by dense patchy innervation; and (3) the laterodorsal septal nucleus, scarcely innervated. In the latter structures, most peptidergic neurons were double-labeled. On the other hand, both peptidergic innervations clearly differed in the lateroventral septal nucleus and the bed nucleus of the stria terminalis which contained distinct clusters of somatostatin-like immunoreactive neurons devoid of neuropeptide Y-like immunoreactivity. Also, the perineuronal and peridendritic axonal plexuses ('woolly fibers') present in these structures were only labeled with somatostatin. In the infralimbic cortex, the relation between the peptides varied according to the cortical laminae. Coexistence of somatostatin and neuropeptide Y frequently occurred in layer VI and in the subcortical white matter, whereas layer V and particularly layers II and III contained a contingent of neurons labeled only with somatostatin. Dense horizontal terminal networks in layers I and VI however were similar for both peptides. These findings support the existence of two different types of somatostatin-like immunoreactive perikarya as regards colocalization with neuropeptide Y. Their particular topographical segregation within the cortical and subcortical structures analysed suggest that they could have different connections and functional properties.(ABSTRACT TRUNCATED AT 400 WORDS)     

Characterization of the peptidergic afferent innervation of the stomach in the rat, mouse and guinea-pig

Retrograde tracing of the fluorescent marker, True Blue, has been used together with immunohistochemistry employing antibodies to substance P, calcitonin gene-related peptide, somatostatin, vasoactive intestinal polypeptide and morphine-modulating peptide to study the afferent innervation of the stomach in rat, mouse and guinea-pig. Up to 85% of spinal afferents to the stomach in all three species contained immunoreactive calcitonin gene-related peptide, and up to 50% contained substance P. In all three species less than 10% of vagal afferents to the stomach reacted with antibodies to calcitonin gene-related peptide, or substance P. Cacitonin gene-related peptide-immunoreactive fibres were found in the myenteric plexus, circular muscle and around submucosal blood vessels in the stomach. In the rat, removal of the coeliac ganglion, splanchnic nerve section, or capsaicin treatment virtually abolished calcitonin gene-related peptide immunoreactivity in the stomach. Capsaicin and splanchnic section also abolished the staining of immunoreactive calcitonin gene-related peptide fibres in the coeliac ganglion. The same treatments abolished substance P staining of fibres around submucosal blood vessels, but in the myenteric plexus and circular smooth muscle there were still abundant immunoreactive fibres, presumably arising from intrinsic cell bodies. No somatostatin-containing visceral afferents could be found, although somatostatin was localized to cell bodies in rat dorsal root ganglia. Immunoreactive vasoactive intestinal polypeptide-containing dorsal root ganglia neurons were not found; although antibodies to morphine-modulatory peptide revealed immunoreactive nerve cell bodies, we were unable to exclude the possibility that this result is attributable to cross reactivity with calcitonin gene-related peptide. These results provide direct evidence that calcitonin gene-related peptide is a marker for a major subset of visceral primary afferent neurons and suggest that this population of spinal afferents makes a major contribution to the total gastric content of calcitonin gene-related peptide.     

Substance P-, met-enkephalin- and somatostatin-like immunoreactivity distribution in the frog spinal cord

The distribution of substance P-, Met-enkephalin- and somatostatin-like immunoreactivity was studied in the thoracic spinal cord of the frog using immunohistochemical techniques. In fibres, probably nerve terminals, immunoreactivity was greatest in the grey matter (mainly dorsal horn), but it was also present in white matter regions. While substance P- and, perhaps, somatostatin-like immunoreactivity appeared to be contained in primary afferents, the presence of all 3 peptides in neuronal cells of the grey matter indicates the existence of a propriospinal peptidergic system.     

A double-label study demonstrating that enkephalin and somatostatin are localized in separate populations of amacrine cells in the larval tiger salamander retina.

Previous studies have localized enkephalin and somatostatin to amacrine cell populations in the larval tiger salamander retina. Double-label immunocytochemistry was utilized to examine if enkephalin- and somatostatin-like immunoreactivities are colocalized to tiger salamander amacrine cells. Of the more than 2000 labelled cells observed in double-labelled preparations, none were found to express both enkephalin and somatostatin immunoreactivity. Therefore, these studies demonstrate that in the larval tiger salamander retina, enkephalin and somatostatin are localized to separate populations of amacrine cells.     

Immunocytochemical identification of long ascending peptidergic neurons contributing to the spinoreticular tract in the rat

In the present study, we examined the peptidergic content of lumbar spinoreticular tract neurons in the colchicine-treated rat. This was accomplished by combining the retrograde transport of the fluorescent dye True Blue with the immunocytochemical labeling of neurons containing cholecystokinin-8, dynorphin A1-8, somatostatin, substance P or vasoactive intestinal polypeptide. After True Blue injections into the caudal bulbar reticular formation, separate populations of retrogradely labeled cells were identified as containing cholecystokinin-like, dynorphin-like, substance P-like or vasoactive intestinal polypeptide-like immunoreactivity. Retrogradely labeled somatostatin-like neurons were not identified in any of the animals examined. Each population of double-labeled cells showed a different distribution in the lumbar spinal cord. The highest yield of double-labeling occurred for cholecystokinin, with 16% of all intrinsic cholecystokinin-like neurons containing True Blue. These double labeled neurons were found predominantly at the border between lamina VII and the central canal region. About 11% of intrinsic vasoactive intestinal polypeptide-like neurons in the lumbar spinal cord were retrogradely labeled from the bulbar reticular formation. These neurons were found mostly in the lateral spinal nucleus, with only a few double-labeled cells located deep in the gray matter. Dynorphin-like double-labeled neurons were localized predominantly near the central canal; a smaller population was also seen in the lateral spinal nucleus. It was found that double-labeled dynorphin-like neurons made up 8% of all intrinsic dynorphin-like neurons. Retrogradely-labeled substance P-like neurons were rare; the few double-labeled neurons were found in the lateral spinal nucleus and lateral lamina V. These findings suggest a significant role for spinal cord peptides in long ascending systems beyond their involvement in local circuit physiology.