Galanin is co-localized with noradrenaline and neuropeptide Y in dog pancreas and celiac ganglion

Noradrenergic and Cholinergic Reinnervation of Islet Grafts in Diabetic Rats

Grafted islets become denervated due to the islet transplantation procedure. The aim of the present study was 1) to examine whether islet grafts in the liver, the spleen, and under the kidney capsule in rats become reinnervated following the transplantation and experimental procedures used in our laboratory, 2) whether there is any difference in reinnervation at these different sites, and 3) how these results relate to previous physiological experiments. Isogeneic isolated islets were transplanted into diabetic Albino Oxford rats, resulting in normoglycaemia. After at least 5 wk, graft-receiving organs were removed and several antibodies were employed to detect insulin, neuron-specific proteins, and cholinergic and noradrenergic nerve fibers. Islets in all three receiving organs contained viable insulin-positive B-cells. Neuron-specific enolase (NSE) as well as the growth-associated protein B-50 was observed at all sites. The cholinergic marker choline acetyltransferase (ChAT) was localized in islets grafts at all sites, but with the lowest density in the spleen. Staining for the noradrenergic markers tyrosine hydroxylase (TH) and dopamine-β-hydroxylase (DBH) was observed in islet grafts at all sites with the lowest density in grafts under the kidney capsule. All these neurochemical substances were most frequently observed in fibers associated with blood vessels, which may be the route along which nerves grow into the graft. It can be concluded that 1) islet grafts in the liver, in the spleen and under the kidney capsule become reinnervated; 2) the innervation pattern of the islet grafts differs only slightly from that in the control pancreatic islets; and 3) in combination with our previously physiological data, we can conclude that these nerve fibers are, at least partly, functionally active.

Neurochemical Plasticity of the Coeliac-Superior Mesenteric Ganglion Complex Neurons Projecting to the Prepyloric Area of the Porcine Stomach following Hyperacidity

This study was designed to determine neurochemical properties of the coeliac-superior mesenteric ganglion (CSMG) neurons supplying the prepyloric area of the porcine stomach in physiological state and following experimentally induced hyperacidity. To localize sympathetic neurons innervating the studied area of stomach, the neuronal retrograde tracer Fast Blue (FB) was applied to control animals and hydrochloric acid infusion (HCl) groups. After 23 days, animals of the HCl group were reintroduced into a state of general anesthesia and intragastrically given 5 mL/kg of body weight of 0.25 M aqueous solution of hydrochloric acid. On the 28th day, all animals were sacrificed. The CSMG complexes were then collected and processed for double-labeling immunofluorescence. In the control animals, FB-positive perikarya displayed immunoreactivity to tyrosine hydroxylase (TH), dopamine β-hydroxylase (DβH), neuropeptide Y (NPY), and galanin (GAL). Experimentally induced gastric hyperacidity changed the neurochemical phenotype of the studied neurons. An upregulated expression of GAL and NPY and the de novo synthesis of neuronal nitric oxide synthase (nNOS) and leu5-enkephalin (LENK) as well as downregulated expression of TH and DβH in the stomach-projecting neurons were observed. These findings enrich existing knowledge about the participation of these active substances in adaptive mechanism(s) of the sympathetic neurons during pathological processes within the gastrointestinal tract.

The Influence of Prolonged Acetylsalicylic Acid Supplementation-Induced Gastritis on the Neurochemistry of the Sympathetic Neurons Supplying Prepyloric Region of the Porcine Stomach

This experiment was designed to establish the localization and neurochemical phenotyping of sympathetic neurons supplying prepyloric area of the porcine stomach in a physiological state and during acetylsalicylic acid (ASA) induced gastritis. In order to localize the sympathetic perikarya the stomachs of both control and acetylsalicylic acid treated (ASA group) animals were injected with neuronal retrograde tracer Fast Blue (FB). Seven days post FB injection, animals were divided into a control and ASA supplementation group. The ASA group was given 100 mg/kg of b.w. ASA orally for 21 days. On the 28^th day all pigs were euthanized with gradual overdose of anesthetic. Then fourteen-micrometer-thick cryostat sections were processed for routine double-labeling immunofluorescence, using primary antisera directed towards tyrosine hydroxylase (TH), dopamine β-hydroxylase (DβH), neuropeptide Y (NPY), galanin (GAL), neuronal nitric oxide synthase (nNOS), leu 5-enkephalin (LENK), cocaine- and amphetamine- regulated transcript peptide (CART), calcitonin gene-related peptide (CGRP), substance P (SP) and vasoactive intestinal peptide (VIP). The data obtained in this study indicate that postganglionic sympathetic nerve fibers supplying prepyloric area of the porcine stomach originate from the coeliac-cranial mesenteric ganglion complex (CCMG). In control animals, the FB-labelled neurons expressed TH (94.85 ± 1.01%), DβH (97.10 ± 0.97%), NPY (46.88 ± 2.53%) and GAL (8.40 ± 0.53%). In ASA group, TH- and DβH- positive nerve cells were reduced (85.78 ± 2.65% and 88.82 ± 1.63% respectively). Moreover, ASA- induced gastritis resulted in increased expression of NPY (76.59 ± 3.02%) and GAL (26.45 ± 2.75%) as well as the novo-synthesis of nNOS (6.13 ± 1.11%) and LENK (4.77 ± 0.42%) in traced CCMG neurons. Additionally, a network of CART-, CGRP-, SP-, VIP-, LENK-, nNOS- immunoreactive (IR) nerve fibers encircling the FB-positive perikarya were observed in both intact and ASA-treated animals. The results of this study indicate involvement of these neuropeptides in the development or presumably counteraction of gastric inflammation.

Galanin regulates blood glucose level in the zebrafish: a morphological and functional study

The present study has demonstrated the galaninergic innervation of the endocrine pancreas including sources of the galaninergic nerve fibers, and the influence of galanin receptor agonists on blood glucose level in the zebrafish. For the first time, a very abundant galaninergic innervation of the endocrine pancreas during development is shown, from the second day post-fertilization to adulthood. The fibers originated from ganglia consisting of galanin-IR, non-adrenergic (non-sensory) neurons located rostrally to the pancreatic tissue. The ganglia were found on the dorsal side of the initial part of the anterior intestinal segment, close to the intestinal branch of the vagus nerve. The galanin-IR neurons did not show immunoreactivity for applied antibodies against tyrosine hydroxylase, choline acetyltransferase, and vesicular acetylcholine transporter. Intraperitoneal injections of galanin analog NAX 5055 resulted in a statistically significant increase in the blood glucose level. Injections of another galanin receptor agonist, galnon, also caused a rise in blood glucose level; however, it was not statistically significant. The present findings suggest that, like in mammals, in the zebrafish galanin is involved in the regulation of blood glucose level. However, further studies are needed to elucidate the exact mechanism of the galanin action.

Neural control of the endocrine pancreas

The autonomic nervous system affects glucose metabolism partly through its connection to the pancreatic islet. Since its discovery by Paul Langerhans, the precise innervation patterns of the islet has remained elusive, mainly because of technical limitations. Using 3-dimensional reconstructions of axonal terminal fields, recent studies have determined the innervation patterns of mouse and human islets. In contrast to the mouse islet, endocrine cells within the human islet are sparsely contacted by autonomic axons. Instead, the invading sympathetic axons preferentially innervate smooth muscle cells of blood vessels. This innervation pattern suggests that, rather than acting directly on endocrine cells, sympathetic nerves may control hormone secretion by modulating blood flow in human islets. In addition to autonomic efferent axons, islets also receive sensory innervation. These axons transmit sensory information to the brain but also have the ability to locally release neuroactive substances that have been suggested to promote diabetes pathogenesis. We discuss recent findings on islet innervation, the connections of the islet with the brain, and the role islet innervation plays during the progression of diabetes.

Novel approaches to studying the role of innervation in the biology of pancreatic islets

The autonomic nervous system helps regulate glucose homeostasis by acting on pancreatic islets of Langerhans. Despite decades of research on the innervation of the pancreatic islet, the mechanisms used by the autonomic nervous input to influence islet cell biology have not been elucidated. This article discusses how these barriers can be overcome to study the role of the autonomic innervation of the pancreatic islet in glucose metabolism. It describes recent advances in microscopy and novel approaches to studying the effects of nervous input that may help clarify how autonomic axons regulate islet biology.

Pancreatic nociception--revisiting the physiology and pathophysiology

BACKGROUND

Pain management of many pancreatic diseases remains a major clinical concern. This problem reflects our poor understanding of pain signaling from the pancreas.

OBJECTIVES

This review provides an overview of our current knowledge, with emphasis on current pain management strategies and recent experimental findings.

METHODS

A systematic search of the scientific literature was carried out using EMBASE, PubMed/MEDLINE, and the Cochrane Central Register of Controlled Trials for the years 1965-2011 to obtain access to all publications, especially randomized controlled trials, systematic reviews, and meta-analyses exploring pain and its management in disease states such as acute pancreatitis (AP), chronic pancreatitis (CP) and pancreatic cancer (PC).

RESULTS

Over the last decade, numerous molecular mediators such as nerve growth factor and the transient receptor potential (TRP) cation channel family have been implicated in afferent nerve signaling. More recent animal studies have indicated the location of the receptive fields for the afferent nerves in the pancreas and shown that these are activated by agents including cholecystokinin octapeptide, 5-hydroxytryptamine and bradykinin. Studies with PC specimens have shown that neuro-immune interactions occur and numerous agents including TRP cation channel V1, artemin and fractalkine have been implicated. Experimental studies in the clinical setting have demonstrated impairment of inhibitory pain modulation from supraspinal structures and implicated neuropathic pain mechanisms.

CONCLUSIONS

Our knowledge in this area remains incomplete. Characterization of the mediators and receptors/ion channels on the sensory nerve terminals are required in order to facilitate the development of new pharmaceutical treatments for AP and CP.

Intrinsic choroidal neurons in the chicken eye: chemical coding and synaptic input

Intrinsic choroidal neurons (ICNs) exist in some primates and bird species. They may act on both vascular and non-vascular smooth muscle cells, potentially influencing choroidal blood flow. Here, we report on the chemical coding of ICNs and eye-related cranial ganglia in the chicken, an important model in myopia research, and further to determine synaptic input onto ICN. Chicken choroid, ciliary, superior cervical, pterygopalatine, and trigeminal ganglia were prepared for double or triple immunohistochemistry of calcitonin gene-related peptide (CGRP), choline acetyltransferase (ChAT), dopamine-beta-hydroxylase, galanin (GAL), neuronal nitric oxide synthase (nNOS), somatostatin (SOM), tyrosine hydroxylase (TH), vasoactive intestinal polypeptide (VIP), vesicular monoamine-transporter 2 (VMAT2), and alpha-smooth muscle actin. For documentation, light, fluorescence, and confocal laser scanning microscopy were used. Chicken ICNs express nNOS/VIP/GAL and do not express ChAT and SOM. ICNs are approached by TH/VMAT2-, CGRP-, and ChAT-positive nerve fibers. About 50% of the pterygopalatine ganglion neurons and about 9% of the superior cervical ganglion neurons share the same chemical code as ICN. SOM-positive neurons in the ciliary ganglion are GAL/NOS negative. CGRP-positive neurons in the trigeminal ganglion lack GAL/SOM. The neurochemical phenotype and synaptic input of ICNs in chicken resemble that of other bird and primate species. Because ICNs lack cholinergic markers, they cannot be readily incorporated into current concepts of the autonomic nervous system. The data obtained provide the basis for the interpretation of future functional experiments to clarify the role of these cells in achieving ocular homeostasis.

Galanin potentiates supramaximal caerulein-stimulated pancreatic amylase secretion via its action on somatostatin secretion

Galanin inhibits pancreatic amylase secretion from mouse lobules induced by physiological concentrations of caerulein via an insulin-dependent mechanism. We aimed to determine the effect and elucidate the mechanism of action of exogenous galanin on pancreatic amylase secretion induced by supramaximal concentrations of caerulein. Amylase secretion from isolated murine pancreatic lobules was measured. Lobules were coincubated with galanin (10(-12)-10(-7) M) and caerulein (10(-7) M). Lobules were preincubated with atropine (10(-5) M), tetrodotoxin (10(-5) M), diazoxide (10(-7) M), or the galanin antagonist galantide (10(-12)-10(-7) M) for 30 min followed by incubation with caerulein alone, or combined with galanin (10(-12) M). Lobules were also coincubated with combinations of galanin (10(-12) M), caerulein, octreotide (10(-12)-10(-7) M) or cyclo-(7-aminoheptanoyl-Phe-D-Trp-Lys-Thr[BZL]), a somatostatin receptor antagonist (10(-9) M). Amylase secretion was expressed as percent of total lobular amylase. Caerulein stimulated amylase secretion to 124% of control. Diazoxide pretreatment abolished the caerulein-stimulated amylase secretion, whereas atropine or tetrodotoxin caused a partial inhibition. Galanin (10(-12)-10(-7) M) potentiated caerulein-stimulated amylase secretion to 160% of control. Preincubation with a combination of atropine and diazoxide abolished the potentiating effect of galanin, indicating muscarinic receptor and insulin mediation. Preincubation with galantide abolished the galanin effect, implying galanin receptor involvement. Coincubation with caerulein, galanin, and octreotide significantly reduced the potentiating effect galanin. However, coincubation with the somatostatin receptor antagonist, alone or in combination with galanin, significantly increased caerulein-stimulated amylase secretion to a level comparable to the galanin potentiation. Taken together, these data suggest that, at supramaximal caerulein concentrations, galanin acts via its receptors to further increase caerulein-stimulated amylase secretion by inhibiting the caerulein-induced release of somatostatin.

A co-localization study on the ovine pancreas innervation

The expression of DbetaH and several neuropeptides was investigated in neuronal elements of the ovine pancreas using double immunocytochemical stainings. Immunoreactivities to DbetaH, NPY, VIP and SP were seen to various extents in nerve terminals associated with the acini, islets, ducts, blood vessels, interlobular connective tissue as well as in the neurons of intrapancreatic ganglia. The expression of CGRP was limited to nerve fibers lying in the connective tissue septa, amongst the acini and in close vicinity to the pancreatic blood vessels. Single GRP-positive nerve endings were located around the acini, ducts and in the interlobular connective tissue. With the exception of the ductal system in a co-localization of NPY with DbetaH was frequently found in all regions of the pancreas. Moderately numerous blood vessel-associated VIP-positive nerve fibers as well as the vast majority of VIP-containing intrapancreatic neurons were found to co-express DbetaH. Single SP-immunoreactive (IR) nerve fibers of the exocrine pancreas and interlobular connective tissue as well as SP-positive intrapancreatic neurons additionally showed the presence of DbetaH. The co-localization of VIP and NPY was found in nerve terminals located around the blood vessels and acini, in the connective tissue septa as well as in numerous pancreatic neuronal perikarya. Rare nerve terminals located between the acini and around small blood vessels as well as several neurons of intrapancreatic ganglia were VIP-IR/ SP-IR. Simultaneous expression of SP and CGRP was found in nerve fibers supplying large pancreatic arteries and veins, interlobular connective tissue and, occasionally, around the acini. Throughout the pancreas the population of CGRP-positive nerve endings showed lack of VIP and NPY. In a moderate number of GRP-containing nerve fibers, a co-expression of NPY was noted. Nerve terminals containing both GRP and VIP were detected sporadically, whereas none of the GRP-positive nerve terminals showed expression of SP. We conclude that the presented noradrenergic as well as peptidergic innervation patterns of the ovine pancreas are species-dependent. On the basis of the occurrence of DbetaH, NPY, VIP and SP (alone or in combination) in pancreatic neuronal elements we can suggest that these substances presumably act as regulators of the endocrine and/or exocrine pancreas. Involvement of CGRP and GRP in the ovine pancreas physiology seems to be of minor importance. The co-localization study indicated that the pancreas of the sheep is innervated from several sources including intrinsic as well as extrinsic ganglia.

Loss-of-function mutation of the galanin gene is associated with perturbed islet function in mice

The neuropeptide galanin is expressed in sympathetic nerve terminals that surround islet cells and inhibits insulin secretion. To explore its role for islet function, we studied mice with a loss-of-function mutation in the galanin gene [galanin knockout (KO) mice]. Intravenous 2-deoxy-glucose, which activates both the sympathetic and parasympathetic branches of the autonomic nervous system, caused an initial (1-5 min) inhibition of insulin secretion that was impaired in galanin KO mice (P = 0.027), followed by a subsequent stimulation of insulin secretion that was augmented in galanin KO mice (P < 0.01). Similar effects were seen after chemical sympathectomy by 6-hydroxydopamine. In contrast, galanin KO mice had a reduced insulin response to glucose, both in vivo (P < 0.001) and in isolated islets (P < 0.001), and to arginine, both in vivo (P = 0.012) and in vitro (P = 0.018). During an iv glucose tolerance test, galanin KO mice had impaired glucose disposal (P = 0.005) due to a reduced insulin response (P < 0.001) and a reduced insulin-independent glucose elimination (glucose effectiveness; P = 0.040). Insulin sensitivity, as judged by a euglycemic, hyperinsulinemic clamp technique, was slightly increased in galanin KO mice (P = 0.032). We conclude that 1) galanin may contribute to sympathetic influences inhibiting insulin secretion in mice, and 2) galanin KO mice have a reduced glucose-induced insulin secretion.

Coexistence of non-adrenergic non-cholinergic inhibitory and excitatory neurotransmitters in a large neuronal subpopulation in the vaginal segment of the chicken oviduct

The presence, distribution and smooth muscle motor effects of galanin and pituitary adenylate cyclase activating peptide (PACAP) were studied in the nerves of the vaginal part of the oviduct of egg-laying hens. Galanin and PACAP immunoreactivity were found both in neuronal perikarya and nerve fibres within the wall of the vaginal segment. Both populations showed a similar distribution pattern. Particularly the circular muscle and the intramural vascular net were richly innervated. A few galanin- and PACAP-IR nerve fibres extended up to the mucosal folds. Multiple labelling showed galanin to be colocalised with PACAP as well as with vasoactive intestinal polypeptide (VIP) and nitric oxide synthase (NOS) in a large, partly intrinsic neuronal subpopulation innervating the smooth muscle wall. Pharmacological in vitro experiments showed that isolated vaginal muscle strips had a spontaneous basal activity that was not affected by the neuronal conductance blocker tetrodotoxin (TTX). Galanin induced concentration-dependent contractions that were TTX-insensitive. PACAP, VIP, nitric oxide (NO) and the NO donor nitroglycerin caused concentration-dependent relaxations that were TTX-insensitive. Electrical field stimulation of isolated muscle strips induced frequency-dependent relaxations that were blocked by TTX and reduced by the NOS blocker L-nitroarginine. These data provide evidence that the vaginal part of the oviduct contains a largely intrinsic, neuronal subpopulation, capable of releasing multiple non-adrenergic, non-cholinergic (NANC) motor agents for the control of local muscular activities. In addition, we provided pharmacological evidence that VIP, NO and PACAP exert an inhibitory and galanin an excitatory action on isolated muscle strips of the vaginal part of the chicken oviduct. Our results suggest that these NANC neurotransmitters play an important role in the regulation of neuromuscular activity in this region.

Mechanisms and physiological significance of the cholinergic control of pancreatic beta-cell function

Acetylcholine (ACh), the major parasympathetic neurotransmitter, is released by intrapancreatic nerve endings during the preabsorptive and absorptive phases of feeding. In beta-cells, ACh binds to muscarinic M(3) receptors and exerts complex effects, which culminate in an increase of glucose (nutrient)-induced insulin secretion. Activation of PLC generates diacylglycerol. Activation of PLA(2) produces arachidonic acid and lysophosphatidylcholine. These phospholipid-derived messengers, particularly diacylglycerol, activate PKC, thereby increasing the efficiency of free cytosolic Ca(2+) concentration ([Ca(2+)](c)) on exocytosis of insulin granules. IP3, also produced by PLC, causes a rapid elevation of [Ca(2+)](c) by mobilizing Ca(2+) from the endoplasmic reticulum; the resulting fall in Ca(2+) in the organelle produces a small capacitative Ca(2+) entry. ACh also depolarizes the plasma membrane of beta-cells by a Na(+)- dependent mechanism. When the plasma membrane is already depolarized by secretagogues such as glucose, this additional depolarization induces a sustained increase in [Ca(2+)](c). Surprisingly, ACh can also inhibit voltage-dependent Ca(2+) channels and stimulate Ca(2+) efflux when [Ca(2+)](c) is elevated. However, under physiological conditions, the net effect of ACh on [Ca(2+)](c) is always positive. The insulinotropic effect of ACh results from two mechanisms: one involves a rise in [Ca(2+)](c) and the other involves a marked, PKC-mediated increase in the efficiency of Ca(2+) on exocytosis. The paper also discusses the mechanisms explaining the glucose dependence of the effects of ACh on insulin release.

Changes in the expression of neuropeptide Y (NPY) during maturation of human sympathetic ganglionic neurons: correlations with tyrosine hydroxylase immunoreactivity

Developmental patterns of neuropeptide Y (NPY) and tyrosine hydroxylase (TH)-immunoreactivities (IR) were investigated using the method of indirect immunohistochemistry in the stellate and thoracic sympathetic ganglia of human neonates ranging in gestational age from 24 to 27 weeks (premature group) and from 38 to 41 weeks (mature group). In the paravertebral ganglia of premature neonates a small (up to 7%) population of NPY-IR nerve cells was revealed. With the gestational age increase (a mature group), a marked elevation of the number of NPY-IR ganglionic neurons (up to 41%) was noted. In contrast, in the sympathetic ganglia of premature neonates almost all the neurons were tyrosine hydroxylase immunoreactive and any change in pattern during maturation was insignificant. The results demonstrate an age-related increase of neuropeptide Y-immunoreactivity in human paravertebral ganglia during maturation, and suggest that peptidergic co-transmission arises later in development than do the classical autonomic messengers. Adaptability of the fetus to a new external environment at birth demands a qualitatively new activity level of the autonomic nervous system, and this is provided side by side with the classical messengers noradrenaline and acetylcholine by the co-transmitter and modulating role of the neuropeptides. The appearance of neuropeptide Y in the principal sympathetic ganglionic neurons defines not only a qualitatively new level in the functional regulation of target organs at birth, but serves as an index of neonatal maturity.

An immunocytochemical study of intrapancreatic ganglia, nerve fibres and neuroglandular junctions in Brockmann bodies of the tompot blenny (Blennius gattoruggine), a marine teleost

The innervation of the Brockmann bodies in the teleost fish, Blennius gattoruggine, was studied using immunocytochemical techniques at both the light and electron microscopy levels. Islet innervation consisted of intrapancreatic ganglia, generally localized inside the rim of the exocrine tissue of the Brockmann bodies, in proximity to the islet, nerve fibres and nerve terminals with synaptic complexes. The intrapancreatic ganglia were of variable size, with different numbers of ganglionic cells, that appeared unipolar in section. The cell bodies showed immunoreactivity to galanin, oxytocin, peptide tyrosine tyrosine and glucagon. The extrinsic and intrinsic nerve fibres passed through the exocrine parenchyma and crossed the connectival septa and islet connectival sheath, penetrating into the islets, where they became increasingly thinner. They terminated on the endocrine cells with dilated nerve terminals. At least three types of terminals were detected, depending on the different vesicle content: peptidergic, cholinergic or adrenergic. They presented specialized synaptic structures, the neuroglandular junctions, some of which contained neurosecretory granules immunogold labelled by galanin antiserum. This new finding confirms the role of galanin as a neurotransmitter. This rich supply of innervation may be important in the regulation and integration of islet secretion.

Differential action of hepatic sympathetic neuropeptides: metabolic action of galanin, vascular action of NPY

Activation of hepatic nerves increases both hepatic glucose production (HGP) and hepatic arterial vasoconstriction, the latter best described by a decrease of hepatic arterial conductance (HAC). Because activation of canine hepatic nerves releases the neuropeptides galanin and neuropeptide Y (NPY) as well as the classical neurotransmitter norepinephrine (NE), we sought to determine the relative role of these neuropeptides vs. norepinephrine in mediating metabolic and vascular responses of the liver. We studied the effects of local exogenous infusions of galanin and NPY on HGP and HAC to predict the metabolic and vascular function of endogenously released neuropeptide. Galanin (n = 8) or NPY (n = 4) was infused with and without NE directly into the common hepatic artery of halothane-anesthetized dogs, and we measured changes in HGP and HAC. A low dose of exogenous galanin infused directly into the hepatic artery potentiated the HGP response to NE yet had little effect on HGP when infused alone. The same dose of galanin infused into a peripheral vein (n = 8) did not potentiate the HGP response to NE, suggesting that the locally infused galanin acted directly on the liver to modulate NE's metabolic action. In contrast, a large dose of exogenous NPY failed to influence HGP when infused either alone or in combination with NE. Finally, NPY, but not galanin, tended to decrease HAC when infused alone; neither neuropeptide potentiated the HAC response to NE. Therefore, both hepatic neuropeptides may contribute to the action of sympathetic nerves on liver metabolism and blood flow. It is likely that endogenous hepatic galanin acts directly on the liver to selectively modulate norepinephrine's metabolic action, whereas endogenous hepatic NPY acts independently of NE to cause vasoconstriction.

Galanin-like immunoreactive endocrine cells in bovine pancreas

Pancreata of fetal, neonatal and adult cattle were studied immunohistochemically for galanin. The results revealed galanin-like immunoreactivity both in the endocrine cells and in the neural elements. The galanin-like immunoreactive endocrine cells (Gal-LIEC) were confined to the large islets, and were not observed in the islets of Langerhans and exocrine pancreas. They were first detected at the third prenatal month. Their developmental profile showed an increase from fetal to early neonatal stage with a subsequent decrease towards adulthood. The considerable number of Gal-LIEC from late prepartum to early postpartum stage may imply functional significance of galanin during the perinatal development of cattle. Coexistence of galanin and insulin was also observed which may suggest autocrine interaction between the 2 hormones.

Galanin is localized in sympathetic neurons of the dog liver

Stimulation of canine hepatic nerves releases the neuropeptide galanin from the liver; therefore, galanin may be a sympathetic neurotransmitter in the dog liver. To test this hypothesis, we used immunocytochemistry to determine if galanin is localized in hepatic sympathetic nerves and we used hepatic sympathetic denervation to verify such localization. Liver sections from dogs were immunostained for both galanin and the sympathetic enzyme marker tyrosine hydroxylase (TH). Galanin-like immunoreactivity (GALIR) was colocalized with TH in many axons of nerve trunks as well as individual nerve fibers located both in the stroma of hepatic blood vessels and in the liver parenchyma. Neither galanin- nor TH-positive cell bodies were observed. Intraportal 6-hydroxydopamine (6-OHDA) infusion, a treatment that selectively destroys hepatic adrenergic nerve terminals, abolished the GALIR staining in parenchymal neurons but only moderately diminished the GALIR staining in the nerve fibers around blood vessels. To confirm that 6-OHDA pretreatment proportionally depleted galanin and norepinephrine in the liver, we measured both the liver content and the hepatic nerve-stimulated spillover of galanin and norepinephrine from the liver. Pretreatment with 6-OHDA reduced the content and spillover of both galanin and norepinephrine by > 90%. Together, these results indicate that galanin in dog liver is primarily colocalized with norepinephrine in sympathetic nerves and may therefore function as a hepatic sympathetic neurotransmitter.

Evidence that galanin is a parasympathetic, rather than a sympathetic, neurotransmitter in the baboon pancreas

To determine whether galanin is a pancreatic sympathetic neurotransmitter regulating insulin secretion in the baboon, as it is in the dog, we evaluated galanin for inhibitory effects on insulin secretion in conscious baboons, determined if baboon pancreatic islets are innervated by galaninergic fibers using immunohistochemistry, and measured galanin content in the major sympathetic ganglion supplying the pancreas. Surprisingly, infusion of galanin (1 microgram/kg per min) had no effect on arginine-stimulated secretion of either insulin (71 +/- 14 vs. 88 +/- 17 microU/ml; P = NS) or glucagon (104 +/- 12 vs. 94 +/- 9 pg/ml; P = NS). By contrast, growth hormone secretion was markedly increased during galanin infusion. In the baboon celiac ganglion, no galanin immunoreactivity was detectable in sympathetic neuronal cell bodies by immunostaining and their content of galanin-like immunoreactivity, determined by radioimmunoassay, was only 3% of that in dog celiac ganglion (5.2 +/- 0.8 vs. 158 +/- 13 pmol/g; P < 0.001). By contrast, galanin immunoreactivity was observed in many nerve fibers in the baboon exocrine pancreas and occasionally in baboon pancreatic islets. Moreover, galanin content of the baboon pancreas was similar to that of dog (8.7 +/- 1.5 vs. 5.5 +/- 1.2 pmol/g; P = NS). The finding of galanin immunoreactivity in many neuronal cell bodies in baboon intrapancreatic ganglia suggests a parasympathetic source for these galaninergic fibers in the baboon. Together these data demonstrate that galanin is likely to be a parasympathetic neurotransmitter in the baboon pancreas, without major effects on insulin or glucagon secretion.

Beta cells are important for islet innervation: evidence from purified rat islet-cell grafts

Pancreatic islets receive an extensive and complex innervation that includes sympathetic, noradrenergic nerve fibres also storing neuropeptide Y. Islets transplanted to the kidney capsule become progressively reinnervated, mainly by sympathetic fibres and to a lesser extent by parasympathetic and sensory fibres. The density of nerve fibres in the islet grafts is often higher than in the graft-bearing organ, suggesting that the grafted islets contain factors that promote ingrowth of nerve fibres. To find out if beta cells are of any importance for attracting nerve fibres, purified preparations of rat islet beta and non-beta cells were transplanted to the kidneys of nude mice. Some of the mice were rendered diabetic by alloxan injection before transplantation. Immunocytochemical analysis revealed that the beta-cell grafts became richly reinnervated by noradrenergic (tyrosine hydroxylase-containing) nerve fibres, also storing neuropeptide Y. Non-beta islet-cell grafts were virtually devoid of demonstrable nerve fibres. There was no discernible difference in the reinnervation pattern between diabetic and non-diabetic mice. The findings indicate that factors mediating islet neurotrophism are produced by the beta cells.

Immunochemical study of galanin in the cat digestive tract and autonomic ganglia

The presence of galanin was examined in the cat gut and related autonomic nervous structures using radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). In the gut wall, the concentration of galanin-like immunoreactivity (GAL-Lt) was assayed separately in the muscular layers with the nervous plexuses and in the mucosa and ranged from 0.35 to 0.55 pmol/g wet tissue. In the autonomic nervous structures, GAL-L1 concentrations ranged from 0.22 (thoracic spinal ganglia) to 0.81 (inferior mesenteric ganglion) pmol/g wet tissue. The presence of galanin was checked by HPLC in the antrum, intestine, and colon. HPLC of extractable material revealed a major peak coeluting with the synthetic porcine peptide and minor earlier peaks representing likely different molecular forms of galanin. Our study strengthens the notion that galanin acts in nervous control of the cat gut functions.

Noradrenergic and cholinergic reinnervation of islet grafts in diabetic rats

Grafted islets become denervated due to the islet transplantation procedure. The aim of the present study was 1) to examine whether islet grafts in the liver, the spleen, and under the kidney capsule in rats become reinnervated following the transplantation and experimental procedures used in our laboratory, 2) whether there is any difference in reinnervation at these different sites, and 3) how these results relate to previous physiological experiments. Isogeneic isolated islets were transplanted into diabetic Albino Oxford rats, resulting in normoglycaemia. After at least 5 wk, graft-receiving organs were removed and several antibodies were employed to detect insulin, neuron-specific proteins, and cholinergic and noradrenergic nerve fibers. Islets in all three receiving organs contained viable insulin-positive B-cells. Neuron-specific enolase (NSE) as well as the growth-associated protein B-50 was observed at all sites. The cholinergic marker choline acetyltransferase (ChAT) was localized in islets grafts at all sites, but with the lowest density in the spleen. Staining for the noradrenergic markers tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) was observed in islet grafts at all sites with the lowest density in grafts under the kidney capsule. All these neurochemical substances were most frequently observed in fibers associated with blood vessels, which may be the route along which nerves grow into the graft. It can be concluded that 1) islet grafts in the liver, in the spleen and under the kidney capsule become reinnervated; 2) the innervation pattern of the islet grafts differs only slightly from that in the control pancreatic islets; and 3) in combination with our previously physiological data, we can conclude that these nerve fibers are, at least partly, functionally active.

Immunohistochemical localization of galanin in bovine reproductive organs

The vagina, uterus and oviduct were shown to receive galanin immunoreactive (GAL-IR) nerve fibres, the number of which varied between particular organs. In the ovary, GAL-IR nerves were absent. A small number of these nerves were located in the layers of the oviduct. A moderate number of GAL-IR nerves were situated in the body and uterine horns, whereas the uterine cervix and vagina wall contained a large number of GAL-IR nerve fibres, evenly distributed throughout particular membranes of the organs. GAL-IR nerves were found to contain, simultaneously, either vasoactive intestinal polypeptide (VIP), substance P (SP) or Leu5-enkephalin (ENK). Many of the GAL-IR nerves contained tyrosine hydroxylase (TH). A group of GAL-IR nerves that did not possess immunoreactivity to VIP, SP, ENK or TH was also observed.

Distribution of immunoreactive neuropeptides in the pancreas of the bullfrog, Rana catesbeiana, demonstrated by immunofluorescence

Indirect double immunofluorescence labelling for eight neuropeptides in the pancreas of the bullfrog, Rana catesbeiana, demonstrated the occurrence, distribution, and coexistence of certain neuropeptides in the exocrine and endocrine pancreas. Immunoreactivity of substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), FMRFamide (FMRF), and galanin (GAL) was localized in nerve fibers distributed between the acini and around the duct system and vasculature of the exocrine pancreas. In these regions, CGRP-immunoreactive fibers were more numerous than those containing the other five peptides. Almost all SP fibers showed coexistence of SP with CGRP, and about one third of fibers also showed coexistence of SP with VIP, NPY, FMRF, and GAL. In the endocrine pancreas, SP, CGRP, VIP, and GAL were recognized in the nerve fibers around and within the islets of Langerhans, and VIP and GAL fibers were more numerous than SP and CGRP fibers. All CGRP fibers, and about half of the VIP and GAL fibers were immunoreactive for SP. NPY- and FMRF-immunoreactive cells were found at the periphery of the islets. These findings suggest that the exocrine and endocrine pancreatic functions of the bullfrog are under the control of peptidergic innervation.

Galanin immunoreactivity in autonomic innervation of the cat eye

In an immunohistochemical study, we find that galanin is much more widely distributed in the peripheral innervation of the cat eye than in other animals so far examined. Previous studies of rat and pig eyes have revealed sparse galanin-positive nerves that presumably originate in the trigeminal ganglion. In contrast, the cat has a rich supply of galanin-containing nerve fibers throughout the uvea. Galanin-positive varicose nerves concentrate densely in iris muscles and distribute more sparsely in the ciliary muscle. The ciliary processes have a plexus of galanin-positive nerves underlying the ciliary epithelium at their base and positive nerve fibers coursing within their stroma. The ciliary artery and its branch vessels in the uvea are invested with a dense plexus of galanin-positive nerves. All autonomic ganglia supplying the eye contain cells that express galanin. It is present in 97% of superior cervical ganglion cells, coexisting with both tyrosine hydroxylase and neuropeptide Y; in 80% of pterygopalatine ganglion cells, most of which also contain vasoactive intestinal peptide; and in approximately 25% of ciliary ganglion cells. After unilateral superior cervical ganglionectomy, galanin-positive nerves almost totally disappear from the iris muscles, demonstrating that they are predominantly of sympathetic origin. Galanin-positive nerves investing the ciliary artery and choroidal blood vessels are not detectably reduced by sympathectomy, indicating that perivascular parasympathetic nerves from the pterygopalatine ganglion also express galanin. Other galanin-containing nerves in the eye can originate from the trigeminal and ciliary ganglia. The prominence of galanin in the ocular autonomic innervation of the cat provides an opportunity to explore the physiological effects of this neuropeptide in the eye.

Galanin message-associated polypeptide (GMAP) does not affect insulin secretion from isolated islets

Galanin message-associated polypeptide (GMAP) is processed from preprogalanin. Recently, GMAP-like immunoreactivity was demonstrated in insulin cells in the endocrine pancreas. We therefore examined whether synthetic rat GMAP, like galanin, inhibits glucose-stimulated insulin secretion from isolated rat and mouse islets. We found, however, that over a wide dose range (0.1 nM to 1 microM) GMAP did not affect insulin secretion stimulated by 8.3 or 11.1 mM glucose during a 60-min incubation of single rat or mouse islets. In contrast, rat galanin, as expected, completely abolished glucose-stimulated insulin secretion at 100 nM. Thus, in contrast to galanin, GMAP does not affect insulin secretion in isolated rodent islets.

Coexistence of galanin and substance P in the mouse nasal mucosa, including the vomeronasal organ

Immunohistochemical fluorescent double labeling revealed the coexistence of galanin and substance P in nerve fibers in the mouse nasal mucosa. At the base of and in the epithelium, all galanin fibers also contained substance P, but around the blood vessels and glands, most of them did not. Since substance P fibers in the nasal mucosa originate from the trigeminal ganglion, these results suggest that galanin fibers in the submucosal region originate from ganglia other than the trigeminal.

Peptide-containing nerve fibers in the parathyroid glands of different species

Several neuropeptides, calcitonin gene-related peptide (CGRP), galanin, neuropeptide Y (NPY), pituitary adenylate cyclase activating peptide (PACAP), substance P (SP), vasoactive intestinal polypeptide (VIP), the noradrenergic marker dopamine beta-hydroxylase (DBH) and the general neuroendocrine marker PGP 9.5 were localized by immunocytochemistry in the parathyroid glands of chicken, rat, guinea-pig, cat, dog and sheep. The general density of innervation varied markedly among the species. Nerve fibers storing CGRP, NPY, PACAP, SP and VIP were present in all species examined. Galanin-containing fibers occurred in all species except guinea-pig and adrenergic (DBH-containing) fibers in all species except chicken and guinea-pig. Generally, the nerve fibers were distributed around blood vessels, in the parenchyma as single scattered fibers, and often also within the capsule. Coexistence studies were performed in cat and sheep. CGRP and SP invariably coexisted in the same nerve fibers. Further, CGRP partially coexisted with PACAP, NPY was observed in the same nerve fibers as DBH. A small population of NPY-containing fibers also seemed to contain galanin (cat only). VIP and NPY coexisted in a population of nerve fibers in the parenchyma. A population of VIP-containing fibers also seemed to contain PACAP. The results indicate the presence of several neuropeptides in the parathyroid glands. As judged by their distribution patterns they may regulate both secretory activity and blood flow, some of them possibly in a cooperative manner.

Canine galanin: sequence, expression and pancreatic effects

To determine if dog galanin is a potent inhibitor of dog insulin secretion we determined its primary structure from its cloned cDNA, evaluated its expression in celiac ganglia and determined its effect on islet hormone secretion. The predicted amino acid sequence differs from the other known species of galanin by three to six amino acids in the C-terminal half of the molecule. In situ hybridization revealed the presence of dog progalanin mRNA in every neuronal cell body in the dog celiac ganglion. The predicted dog galanin peptide was synthesized and infused i.v. at 0.25, 2.5, 25 or 250 pmol/kg/min. It potently inhibited insulin secretion, less potently inhibited pancreatic somatostatin release and stimulated glucagon secretion, similar to the effects of porcine galanin in the dog. In summary, dog galanin is expressed in the neuronal cell bodies that innervate the pancreas and the sequence of the dog galanin preserves the potent insulin inhibitory part of the galanin molecule. These data support the hypothesis that galanin is a sympathetic neurotransmitter in dog pancreas.

Distinct subsets of neuropeptide Y-negative principal neurons receive basket-like innervation from enkephalinergic and gabaergic axons in the superior cervical ganglion of adult rats

The distributions of axons immunoreactive for [Leu]- or [Met]enkephalin and GABA were studied in the superior cervical ganglion of adult rats. The antigens were visualized separately and in combination with neuropeptide Y by the immunoperoxidase technique, using reaction end-products of different colors. Similarities and differences were found in the light-microscopic innervation patterns of enkephalin- and GABA-immunoreactive nerve fibers. Both fiber systems were heterogeneously distributed within the superior cervical ganglion, forming denser networks in its rostral part than elsewhere in the ganglion. The appearance of labeled nerve fibers differed in the two systems. Enkephalin-immunoreactive axons exhibited dotted profiles due to a strong immunoreaction in the axonal varicosities as compared with that in the intervaricose segments, whereas GABA-positive fibers were evenly labeled in both parts of the axons. The most marked difference between the innervation patterns from enkephalin- and GABA-immunoreactive axons was the presence of bundles of varicose axons in conjunction with the basket-like aggregation of enkephalin-immunoreactive nerve terminals. The possibility that enkephalins and GABA are co-localized in certain axons was excluded in double-labeling studies, silver intensification being used for the first antigen and the nickel-enhanced diaminobenzidine reaction for the second antigen. Different subsets of principal neurons were richly innervated in a basket-like manner by axons immunoreactive for enkephalins and GABA. Additionally, combined staining with antisera against either enkephalin and neuropeptide Y or GABA and neuropeptide Y revealed that both subsets of principal neurons richly innervated either by enkephalin-immunoreactive or by GABA-immunoreactive axons were devoid of neuropeptide Y immunoreactivity. Thus, the enkephalinergic and GABAergic axons have different subpopulations of neuropeptide Y-negative principal neurons as targets in the superior cervical ganglion. These results provide further evidence that sympathetic ganglion cells can be classified on the basis of their receiving input from different sources.

Tissue-specific reduction of galanin content in the pancreas in alloxan diabetes in the mouse

Galanin inhibits insulin secretion and has been proposed to function as a sympathetic neurotransmitter in the endocrine pancreas in some species, for example in the dog. In this study, pancreatic and adrenal gland galanin content were measured following experimental diabetes induced by alloxan in mice. Three days after administration of alloxan (70 mg kg-1, i.p.) in normal mice, pancreatic content of galanin-like immunoreactivity (GLIR) was reduced to 65 +/- 11% of that in untreated controls (P < 0.01), whereas adrenal gland GLIR was unchanged. Similarly, 8 days after alloxan administration, pancreatic GLIR was reduced (P < 0.002), whereas adrenal gland GLIR was unaffected. Pancreatic GLIR also inversely correlated with plasma glucose levels (r = -0.5055, P < 0.005). To distinguish between the direct effects of alloxan vs. indirect metabolic effects induced by the drug, alloxan-diabetic mice were treated with insulin twice daily, which normalized the plasma glucose levels (7.6 +/- 0.3 mmol l-1). Pancreatic GLIR was then not significantly different from controls. Thus pancreatic but not adrenal gland GLIR content is reduced in alloxan-induced diabetes in mice. The data support a role for galanin as a pancreatic sympathetic neurotransmitter which may participate in the metabolic alterations seen in alloxan diabetes in mice.

On the effects of human galanin in man

Human galanin was recently isolated and sequenced and was found to differ from porcine galanin, hitherto used for studies in humans, in several important respects. We therefore synthesized and purified human galanin and infused it i.v. at a rate of 74 pmol.kg-1.min-1 into six healthy volunteers for 60 min during a hyperglycaemic clamp. The clamp was achieved by i.v. infusion of glucose at a rate which in a control experiment had been demonstrated to maintain the plasma glucose level at 12-13 mmol/l for 90 min. Galanin concentrations reached a plateau of approximately 1500 pmol/l throughout the infusion as opposed to pre-infusion and control levels of 20-30 pmol/l. The glucose levels obtained in the two experiments were indistinguishable. Plasma levels of C-peptide and insulin increased significantly in both experiments and the dynamic concentration curves were almost identical. Glucagon concentrations in plasma decreased significantly and similarly. Growth hormone levels, however, increased eight-fold during galanin infusions. Galanin was eliminated from plasma with a half-life of 3.7 +/- 0.4 min, similar to that of porcine galanin. It is concluded that human galanin powerfully stimulates growth hormone secretion in man, but has no effect on pancreatic endocrine secretion or glucose metabolism in the concentrations obtained in this study.

Perinatal development of galanin-like immunoreactivity in chromaffin tissues of the rabbit

We have analyzed the perinatal development of galanin-like immunoreactivity (GAL-LI) and catecholamines (CA) in the paraaortal paraganglia (PGGL) and adrenal glands. In the PGGL, the tissue content of GAL-LI was highest on the day of birth and decreased postnatally. The fetal levels were lower than at birth. In contrast, the content of CA in the PGGL increased with age. In the adrenal glands, the contents of both GAL-LI and CA also increased with age. During the first postnatal week the contents of both GAL-LI and CA in the PGGL were markedly higher than in the adrenal glands. Chromatographic analysis of GAL-LI in extracts of fetal and postnatal rabbit PGGL, respectively, indicated that most of the GAL-LI from both age groups co-eluted with synthetic porcine GAL. An additional, apparently more polar, component was also detected at both ages, which may represent a differently processed form of the peptide. The high content of GAL-LI in the PGGL at birth may reflect an enhanced synthesis associated with birth.

Galanin-like immunoreactivity in extrinsic and intrinsic nerves to the gut of the Atlantic cod, Gadus morhua, and the effect of galanin on the smooth muscle of the gut

The presence of galanin-like immunoreactivity in nerves to the stomach of the Atlantic cod has been investigated by immunohistochemistry. The distribution of ganglion cells showing galanin-like immunoreactivity was compared with the total distribution in nerves and ganglia. Projection studies were made to determine the origin of the galanin neurons. The effect of galanin was studied in smooth muscle strip preparations of the gut wall and arteries. Galanin-like immunoreactive ganglion cells frequently occurred along the vagal branches to the stomach. Most of them projected cranially. Immunoreactive nerve fibers were present in all layers of the gut and around arterial branches on the surface of the stomach. Ligations of the vagus and splanchnic nerves produced accumulations of immunoreactive material on both sides of the ligature. Galanin produced weak contractile effects unaffected by tetrodotoxin on the gut wall and on gut arteries. It is concluded that a population of the ganglion cells along the vagus nerve in the Atlantic cod contains a galanin-like peptide. Some of these cells may be parts of autonomic parasympathetic pathways innervating the gut of the Atlantic cod, having direct excitatory effects on the smooth muscles of the gut wall and gut arteries.

Immunohistochemical studies on the intrinsic pancreatic nerves in the chicken

A peroxidase anti-peroxidase method or an avidin-biotinylated complex method was used to visualize neural elements immunostained for several neuropeptides in the chicken pancreas. Pancreatic ganglion cells were only immunoreactive with vasoactive intestinal polypeptide (VIP), galanin and substance P (SP) antisera. VIP-immunoreactive (IR) ganglion cells were the most numerous, and most of them also showed the distinct immunoreaction with galanin. VIP- and galanin-IR nerve fibers were observed in the exocrine portion, the adventitia of the artery and the connective tissue of the ductal wall. The number and distribution of the VIP- and galanin-IR nerve fibers around the artery and duct were similar. SP-IR nerve fibers were found mainly close to the blood vessel. SP- and CGRP-IR nerve fibers were detected in the VIP-IR ganglion and extrapancreatic nerve bundle. Tyrosine hydroxylase (TH)- and aromatic L-amino acid decarboxylase (AADC)-IR nerve fibers were observed as nerve bundles in the interlobular space or extrapancreatic nerves. Consequently, VIP and galanin coexist in the intrinsic neural elements. SP is partially located in the intrinsic neural elements, but most of it seems likely to originate from the extrinsic ganglion. It is probable that calcitonin gene related peptide (CGRP)-, TH- and AADC-IR nerve fibers have an extrinsic origin.

Coexistence of calcitonin gene-related peptide and galanin immunoreactivity in female rat pelvic and lumbosacral dorsal root ganglia

Coexistence of immunoreactivity for calcitonin gene-related peptide (CGRP) and galanin (GAL) was examined in varicose nerve endings in female rat pelvic paracervical ganglia (PG) and in perikarya of lumbosacral dorsal root ganglia (DRG). Varicose peptide-containing nerves were closely adjacent to somata of neurons in the PG, certain somata being virtually surrounded by immunoreactive varicosities. Some nerve endings were immunoreactive for either CGRP or GAL; in others, immunoreactivity for CGRP and GAL coexisted. Likewise, many perikarya in DRG were CGRP immunoreactive, fewer were GAL immunoreactive, and in some immunoreactivity for CGRP and GAL coexisted. The results suggest there are subpopulations of neuropeptide-containing sensory nerve endings in the PG; some contain CGRP, some contain GAL, and in some CGRP and GAL coexist. These substances contained in sensory nerve endings could have important roles in pelvic ganglionic functions.

Corelease of galanin and NE from pancreatic sympathetic nerves during severe hypoglycemia in dogs

To determine whether norepinephrine (NE) and galanin are coreleased during reflex activation of the sympathetic nervous system by hypoglycemia, we administered insulin to halothane-anesthetized (0.8%) dogs and measured the spillover of NE and galanin-like immunoreactivity (GLIR) into pancreatic venous plasma. Insulin injection produced hypoglycemia [plasma glucose (PG) = 34 +/- 3 mg/dl] but did not activate pancreatic noradrenergic (delta pancreatic NE output = +20 +/- 130 pg/min) or galaninergic nerves (delta GLIR output = +40 +/- 50 fmol/min). To determine whether more severe hypoglycemia would activate these nerves, insulin was administered to dogs infused with somatostatin (SS; 2.5 micrograms/min) to block the counterregulatory increase of glucagon secretion. SS reduced the glucagon response to hypoglycemia by greater than 90%, which allowed PG to decrease to 14 +/- 1 mg/dl. Pancreatic NE output increased by 470 +/- 140 pg/min (P less than 0.005); however, pancreatic GLIR output did not increase significantly (delta = +70 +/- 50 fmol/min). When SS was discontinued, pancreatic NE output increased by 490 +/- 200 pg/min (P less than 0.025), and GLIR output increased by an additional +160 +/- 70 fmol/min (P less than 0.025; total delta from baseline = +230 +/- 90 fmol/min, P less than 0.025), suggesting that SS may restrain pancreatic NE and galanin release. Pancreatic NE and GLIR spillover were also increased during severe hypoglycemia when ganglionic neurotransmission was partially impaired with hexamethonium but not when the neural pathway was interrupted by spinal cord transection. We conclude that NE and galanin are coreleased from pancreatic sympathetic nerves when these nerves are centrally activated during severe hypoglycemia in halothane-anesthetized dogs.

Effects of noradrenaline and galanin on duodenal motility in the isolated perfused porcine pancreatico-duodenal block

The influence of neurotransmitters on gastrointestinal motility is different in different segments of the gastrointestinal tract. To clarify the regulation of duodenal motility, the aim of the present study was to investigate the effects of alpha-adrenoceptor agonism and blockade and of galanin on duodenal motility. The study was undertaken in the isolated perfused porcine pancreatico-duodenal block. The agents under investigation were administered arterially. Duodenal motility was measured by means of a low-compliance perfusion system using an intraluminal catheter. In addition the concentration of galanin was measured in the portal effluent. We found that spontaneous motility was abolished by noradrenaline by an effect that was counteracted by the alpha 2-adrenoceptor antagonist idazoxan. In contrast, the selective alpha 1-adrenoceptor antagonist prazosin did not influence the effect of noradrenaline. Galanin, like noradrenaline, abolished duodenal motility. Furthermore, the concentration of galanin in the portal effluent was decreased by noradrenaline by an alpha 2-adrenoceptor mediated mechanism. We conclude that alpha 2-adrenoceptor activation and galanin inhibit duodenal motility and that the release of galanin from the pancreatico-duodenal preparation is reduced by alpha 2-adrenoceptors.

Comparison of the inhibitory roles of neuropeptide Y and galanin on cardiac vagal action in the dog

Prolonged attenuation of cardiac vagal action occurs following cardiac sympathetic nerve stimulation or intravenous neuropeptide Y (NPY) injections in anaesthetised dogs. Equimolar intravenous injections of galanin (GAL) had no effect on cardiac vagal action in this species. Immunohistochemical analysis of dog stellate ganglia and cardiac muscle showed that most nerve cell bodies showing tyrosine hydroxylase immunoreactivity (TH-IR) also showed immunoreactivity to both NPY and GAL. The results are consistent with the proposal that NPY released from cardiac sympathetic nerves is responsible for the prolonged inhibition of cardiac vagal action known to be caused by such stimulation. A role for GAL, shown here to exist in cardiac sympathetic nerves in the dog, has yet to be determined.

Liver releases galanin during sympathetic nerve stimulation

To determine whether the gut or liver releases galanin during sympathetic neural activation, we performed bilateral thoracic splanchnic nerve stimulation (BTSNS) in halothane-anesthetized dogs. Using experimentally determined galanin extraction rates of 60% for gut and no extraction by liver, calculations demonstrated a minor increase in gut spillover during BTSNS (delta = +4.8 +/- 1.8 pmol/min), whereas liver spillover of galanin-like immunoreactivity (GLIR) increased markedly (delta = +27.9 +/- 9.5 pmol/min). To confirm the finding of liver galanin release, GLIR was measured in femoral artery, portal vein, and hepatic vein during hepatic nerve stimulation (HNS). GLIR spillover from gut was not increased by HNS (delta = +1.9 +/- 6.3 pmol/min). In contrast, liver GLIR spillover was greatly increased during HNS (delta = +53.3 +/- 16.4 pmol/min). Extracts of canine liver contained 2.7 +/- 0.4 pmol GLIR/g tissue. We conclude that, despite the known significant galanin content of the gut, little galanin is released from this organ during sympathetic activation. In contrast, the liver, heretofore not described to contain galanin, contains and releases significant amounts of the peptide during sympathetic activation.

Galanin inhibits rat pancreatic amylase release via cholinergic suppression

The effects of galanin on pancreatic exocrine function were examined using rat pancreatic tissues. In anesthetized rats, galanin (40 micrograms/kg/h) decreased amylase secretion stimulated by 2-deoxy glucose (5.8 +/- 0.1 vs. 3.1 +/- 0.1 times basal) and cholecystokinin octapeptide (21.5 +/- 0.6 vs. 16.8 +/- 0.5), while not inhibiting bethanechol-stimulated secretion. In dispersed acini, there was no effect of galanin alone (10(-8) to 10(-13) M) on amylase release, nor did galanin (10(-6) or 10(-8) M) coincubation affect amylase release stimulated by bethanechol (10(-3) to 10(-7) M) or CCK-8 (10(-8) to 10(-13) M). Using pancreatic lobules, coincubation with galanin (10(-6) M) suppressed 75 mM KCl-stimulated amylase secretion and ACh release (10.1 +/- 0.6% vs. 7.3 +/- 0.4%). Veratridine-stimulated (10(-4) M) amylase secretion and ACh release (12.4 +/- 1.7% vs. 8.5 +/- 0.7%) were similarly diminished.

Galanin is more common than NPY in vascular sympathetic neurons of the brush-tailed possum

The distribution of galanin (Gal) in sympathetic vascular neurons of adult and juvenile brush-tailed possums (Trichosurus vulpecula), was examined using double-labelling immunohistochemistry. This was compared with the distribution of neuropeptide Y (NPY) in the same tissues. Immunoreactivity (IR) to galanin was present in the majority (64-99%) of nerve cell bodies in paravertebral sympathetic ganglia, where it mostly co-existed with IR to the catecholamine-synthesizing enzyme, tyrosine hydroxylase (TH). Gal-IR also was present in most, if not all, TH-IR perivascular axons supplying systemic arteries and veins. NPY-IR was less common than Gal-IR in all sympathetic ganglia and perivascular axons examined. Some sympathetic, TH-IR axons supplying the abdominal aorta and renal artery contained both Gal-IR and NPY-IR, while TH-IR axons supplying cephalic and thoracic vessels contained Gal-IR but not NPY-IR. Limited observations on sympathetic neurons in two species of wallabies indicated that Gal-IR also was more common than NPY-IR in other marsupial species, but the incidence of NPY-IR was higher in these wallabies than in the brush-tailed possum. Together with previous studies, this work suggests that the coexistence of galanin and NPY may be the primitive condition for sympathetic neurons in tetrapods. The differential expression of these peptides in specific populations of sympathetic neurons may have important functional consequences in the autonomic control of the circulation.

Plasma neuropeptide Y (NPY) and galanin before and during exercise in type 1 diabetic patients with autonomic dysfunction

Plasma neuropeptide Y (NPY), plasma galanin and plasma catecholamines were determined before and during an ergometer exercise test in 11 type 1 diabetic patients (age 19-36 years, mean 30; duration of diabetes 2-18 years, mean 9) with autonomic dysfunction and in 13 age-matched healthy controls (age 24-36 years, mean 29). Before exercise, plasma NPY (100 +/- 6 pmol/l vs 144 +/- 7 pmol/l; P less than 0.001) and plasma galanin (54 +/- 3 pmol/l vs 77 +/- 5 pmol/l; P less than 0.005) were significantly lower in patients than in controls. During exercise, plasma NPY, plasma adrenaline, and plasma noradrenaline increased in patients and controls while galanin only increased in patients. Since there was a direct correlation between plasma NPY before exercise and the increment (delta 80%) in noradrenaline during exercise (r = 0.54; P less than 0.01), it is suggested that plasma NPY determined in the basal situation may be a useful marker of sympathetic nerve failure in diabetic patients.

Immunohistochemical demonstration of galaninlike immunoreactive nerves in the human pancreas

Galanin, the newly discovered 29 amino acid-residue peptide, has been shown to suppress glucose-induced insulin secretion in experimental animals, but its presence and physiological role in the human pancreas have not been established. In this study, the occurrence and distribution of galanin immunoreactivity in the human pancreas was investigated by immunohistochemistry. In addition, the possible coexistence of galanin and vasoactive intestinal peptide immunoreactivity in neural elements of the pancreas was examined. In the human pancreas, galanin immunoreactivity was localized in numerous nerve fibers around glandular acini, ductules and blood vessels, and in a few nerve fibers within islets. Nerve cells with galanin immunoreactivity were frequently noticed. Immunostainings for galanin and for vasoactive intestinal peptide on serial adjacent sections of intrapancreatic ganglia showed the coexistence of the two immunoreactivities in a large proportion (73.3%) of nerve cells. These observations may provide a morphological basis for the possible neurotransmitter or neuromodulator role of galanin in the human pancreas.

Galanin-induced inhibition of insulin secretion from rat islets: effects of rat and pig galanin and galanin fragments and analogues

The 29-amino acid neuropeptide galanin occurs in intrapancreatic nerves and inhibits insulin secretion. To study the structure-activity relations of galanin, we examined the effects of pig and rat galanin, three galanin fragments (galanin-(1-11), galanin-(1-16) and rat galanin-(17-29) and four galanin analogues ([Ala2]pig galanin, [Ala2]rat galanin, [D-Trp2]rat galanin and [D-Trp2]galanin-(1-16] on glucose-stimulated insulin secretion from isolated rat islets. Pig and rat galanin and galanin-(1-11) equipotently inhibited glucose-stimulated (8.3 mM) insulin secretion at and above 10(-7) M (P less than 0.05), whereas galanin-(1-16), inhibited insulin secretion at 10(-6) M (P less than 0.01). In contrast, the C-terminal rat galanin-(17-29) and the galanin analogues did not influence insulin secretion. Thus, rat and pig galanin are equipotent in inhibiting glucose-stimulated insulin secretion from rat islets. The active site resides in the N-terminal part of the molecule. Furthermore, the binding of galanin to its receptor depends on structural characteristics governed by the N-terminal position and in particular by the Trp2 residue.