Coeliac-superior Mesenteric Ganglion Complex Research Articles

Noninvasive focused ultrasound stimulation of the celiac-superior mesenteric ganglion complex regulates inflammation in murine endotoxemia

The nervous system has an important role in the regulation of cytokines and inflammation ( Nature, 2002). The celiac-superior mesenteric ganglion complex (CSMGC) is an important component of the vagus nerve based inflammatory reflex, which controls inflammation ( Nat Neuroscience 2017). In addition to receiving cholinergic innervations from the efferent vagus nerve, the CSMGC is innervated by preganglionic sympathetic splanchnic nerves, which also are involved in the inflammatory regulation. Both neuronal types - vagal and preganglionic sympathetic - interact with catecholaminergic neurons, which reside in this ganglionic complex and innervate the liver, spleen, and other abdominal organs. Despite being a prominent locus of neuronal interactions, the possibilities of directly targeting the CSMGC to regulate cytokine responses and inflammation remains unexplored. To provide insight, we subjected the CSMGC in mice to focused ultrasound stimulation (FUS) - a non-invasive approach, which has been increasingly utilized in neuromodulation. We used ultrasound imaging and doppler to localise the complex in anesthetized 10–14-week-old male C57BL/6J mice. To perform stimulation, the FUS transducer was placed on the abdominal surface over the CSMGC and FUS (1.1MHz and 200mV per pulse, 150 burst cycles, 500μs burst period) or sham stimulation was delivered for 2 mins or 5 mins. Five mins post FUS, mice were injected with lipopolysaccharide (endotoxin, 0.25mg/kg, i.p.) and euthanized after 90 mins. Blood and liver were collected and processed for cytokine analysis. Compared to sham stimulation, FUS of the CSMGC for 5mins (n=11,12/group) significantly decreased serum TNF levels (1,875 ± 750 pg/ml vs 672.9 ± 335 pg/ml, P< 0.0001) and hepatic TNF levels (27.8 ± 8.6 pg/mg vs 16.0 ± 7.1 pg/mg, P= 0.0018) in endotoxemic mice. In contrast, FUS of CSMGC for 2 mins (n=15/group) did not significantly alter serum TNF levels (1,458 ± 599.9 pg/ml vs 1,120 ± 332.5 pg/ml, P=0.1607). These results demonstrate the anti-inflammatory effcacy of noninvasive FUS of the CSMGC. Our findings also identify the CSMGC as an easily targetable new therapeutic site for controlling systemic and hepatic inflammation with a potential for clinical translation. This work was partially supported by NIGMS. R01GM128008. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Optogenetic stimulation of cholinergic neuronal endings in the celiac‐superior mesenteric ganglion complex suppresses inflammation in murine endotoxemia

The vagus nerve plays a key role in the regulation of inflammation within the inflammatory reflex (Annu Rev Immunol, 2018, 36:783). In this major physiological neuroimmunoregulatory mechanism, efferent vagus nerve cholinergic axons interact with catecholaminergic neurons of the splenic nerve in the celiac‐superior mesenteric ganglion (CSMG) complex(Proc Natl Acad Sci USA, 2020, 117(47):29803).Previous studies utilizing electrical and optogenetic neuromodulation have demonstrated that vagus nerve cholinergic signalling suppresses pro‐inflammatory cytokine levels during endotoxemia and other inflammatory conditions. However, the specific role of cholinergic axonal terminals in the CSMG complex in this regulation remained enigmatic. To provide insight, we investigated the effect of selective optogenetic stimulation of cholinergic neuronal endings in the CSMG complex on cytokine and chemokine levels during murine endotoxemia. We used transgenic female 10–14‐week‐old mice expressing channelrhodopsin 2 coupled with yellow fluorescent protein on cholinergic, i.e., choline acetyltransferase positive neurons (ChAT‐ChR2‐eYFP). Anesthetized mice were subjected to abdominal surgery and the CSMG complex was localized medial to the upper pole left kidney and along the branch of the abdominal aorta, above the left renal vein. Blue laser light stimulation at 473nm was delivered in square pulses for 10mins at 20Hz, 25% duty cycle through an optic fiber cannula placed in contact with the CSMG complex. 30mins following optogenetic stimulation or sham stimulation, lipopolysaccharide (0.25mg/kg) was injected intraperitoneally and 90mins later mice were euthanized and blood, and spleen were collected and processed for cytokine and chemokines. Optogenetic stimulation of the CSMG complex in ChAT‐ChR2 mice (n=14) suppressed serum pro‐inflammatory cytokines and chemokines compared with sham stimulation (n=13), including TNF(401.7 ± 102.9 pg/ml vs 766.1 ± 207.2 pg/ml; P<0.0001) and MIP‐1α (6,523 ± 3,041 pg/ml vs 10,672 ± 3,915 pg/ml, P=0.0066), while the serum levels of the anti‐inflammatory cytokine IL‐10 were significantly increased (30,779 ± 10,035 pg/ml vs 22,979 ± 9,669 pg/ml, P=0.0427). There was also a significant reduction in splenic TNF levels in the stimulated vs the sham group(P=0.0023). Of note, optogenetic stimulation of the CSMG complex in littermate mice that do not express ChR2 on cholinergic neurons did not alter serum and splenic cytokine levels. These results provide the first experimental evidence that selective stimulation of cholinergic neuronal endings in the CSMG complex attenuates cytokine and chemokine levels. Future studies examining the specific contribution of vagal and sympathetic preganglionic cholinergic neurons in the CSMG complex in the regulation of immune responses will be instrumental for developing new targeted therapeutic anti‐inflammatory approaches.

Effect of selective β-adrenoceptor blockade and surgical resection of the celiac-superior mesenteric ganglion complex on delayed liquid gastric emptying induced by dipyrone, 4-aminoantipyrine, and antipyrine in rats.

There is evidence for participation of peripheral β-adrenoceptors in delayed liquid gastric emptying (GE) induced in rats by dipyrone (Dp), 4-aminoantipyrine (AA), and antipyrine (At). The present study aimed to determine whether β-adrenoceptors are involved in delayed GE induced by phenylpyrazole derivatives and the role of the prevertebral sympathetic nervous system in this condition. Male Wistar rats weighing 220-280 g were used in the study. In the first experiment rats were intravenously pretreated with vehicle (V), atenolol 30 mg/kg (ATE, β1-adrenergic antagonist), or butoxamine 25 mg/kg (BUT, β2-adrenergic antagonist). In the second experiment, rats were pretreated with V or SR59230A 2 mg/kg (SRA, β3-adrenergic antagonist). In the third experiment, rats were subjected to surgical resection of the celiac-superior mesenteric ganglion complex or to sham surgery. The groups were intravenously treated with saline (S), 240 µmol/kg Dp, AA, or At, 15 min after pretreatment with the antagonists or V and nine days after surgery. GE was determined 10 min later by measuring the percentage of gastric retention (%GR) of saline labeled with phenol red 10 min after gavage. The %GR (means±SE, n=6) values indicated that BUT abolished the effect of Dp (BUT+Dp vs V+Dp: 35.0%±5.1% vs 56.4%±2.7%) and At (BUT+At vs V+At: 33.5%±4.7% vs 52.9%±2.6%) on GE, and significantly reduced (P<0.05) the effect of AA (BUT+AA vs V+AA: 48.0%±5.0% vs 65.2%±3.8%). ATE, SRA, and sympathectomy did not modify the effects of treatments. These results suggest that β2-adrenoceptor activation occurred in delayed liquid gastric emptying induced by the phenylpyrazole derivatives dipyrone, 4-aminoantipyrine, and antipyrine. Additionally, the released neurotransmitter did not originate in the celiac-superior mesenteric ganglion complex.

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.

Alterations of neurochemical expression of the coeliac-superior mesenteric ganglion complex (CSMG) neurons supplying the prepyloric region of the porcine stomach following partial stomach resection.

The purpose of the present study was to determine the response of the porcine coeliac-superior mesenteric ganglion complex (CSMG) neurons projecting to the prepyloric area of the porcine stomach to peripheral neuronal damage following partial stomach resection. To identify the sympathetic neurons innervating the studied area of stomach, the neuronal retrograde tracer Fast Blue (FB) was applied to control and partial stomach resection (RES) groups. On the 22nd day after FB injection, following laparotomy, the partial resection of the previously FB-injected stomach prepyloric area was performed in animals of RES group. On the 28th day, all animals were re-anaesthetized and euthanized. The CSMG complex was then collected and processed for double-labeling immunofluorescence. In control animals, retrograde-labelled perikarya were immunoreactive to tyrosine hydroxylase (TH), dopamine β-hydroxylase (DβH), neuropeptide Y (NPY) and galanin (GAL). Partial stomach resection decreased the numbers of FB-positive neurons immunopositive for TH and DβH. However, the strong increase of NPY and GAL expression, as well as de novo-synthesis of neuronal nitric oxide synthase (nNOS) and leu5-Enkephalin (LENK) was noted in studied neurons. Furthermore, FB-positive neurons in all pigs were surrounded by a network of cocaine- and amphetamine-regulated transcript peptide (CART)-, calcitonin gene-related peptide (CGRP)-, and substance P (SP)-, vasoactive intestinal peptide (VIP)-, LENK- and nNOS- immunoreactive nerve fibers. This may suggest neuroprotective contribution of these neurotransmitters in traumatic responses of sympathetic neurons to peripheral axonal damage.

Sympathetic Activity Controls Fat-Induced Oleoylethanolamide Signaling in Small Intestine

Ingestion of dietary fat stimulates production of the small-intestinal satiety factors oleoylethanolamide (OEA) and N-palmitoyl-phosphatidylethanolamine (NPPE), which reduce food intake through a combination of local (OEA) and systemic (NPPE) actions. Previous studies have shown that sympathetic innervation of the gut is necessary for duodenal infusions of fat to induce satiety, suggesting that sympathetic activity may engage small-intestinal satiety signals such as OEA and NPPE. In the present study, we show that surgical resection of the sympathetic celiac-superior mesenteric ganglion complex, which sends projections to the upper gut, abolishes feeding-induced OEA production in rat small-intestinal cells. These effects are accounted for by suppression of OEA biosynthesis, and are mimicked by administration of the selective β2-adrenergic receptor antagonist ICI-118,551. We further show that sympathetic ganglionectomy or pharmacological blockade of β2-adrenergic receptors prevents NPPE release into the circulation. In addition, sympathetic ganglionectomy increases meal frequency and lowers satiety ratio, and these effects are corrected by pharmacological administration of OEA. The results suggest that sympathetic activity controls fat-induced satiety by enabling the coordinated production of local (OEA) and systemic (NPPE) satiety signals in the small intestine.

Identification of intestinofugal neurons projecting to the coeliac and superior mesenteric ganglia in the rat

Intestinofugal neurons are parts of the afferent limbs of inhibitory intestino-intestinal reflexes. These neurons have been mapped in guinea-pigs, where they have a gradient of increasing frequency of occurrence from oral to anal, but not in other species. In the present work in the rat, a species that is more amenable to physiological study than the guinea-pig, we have used retrograde tracing to map the distribution of the cell bodies of intestinofugal neurons projecting to the coeliac–superior mesenteric ganglion complex. Labelled nerve cells were found in the myenteric, but not the submucosal plexus. They were mono-axonal neurons, most with Dogiel type I morphology, and were immunoreactive for choline acetyltransferase, implying that they are cholinergic, which is consistent with functional studies. The cells increased in number per unit area from the stomach, through the small intestine, to the caecum. The results are consistent with physiological studies that reveal distal to proximal inhibitory reflexes that are more potent from distal compared to proximal sites.

5-Hydroxytryptamine-immunoreactive nerve fibers in the rat and porcine prevertebral sympathetic ganglia: effect of precursor loading and relation to catecholaminergic neurons

Localization of 5-hydroxytryptamine immunoreactivity was studied in the rat coeliac-superior mesenteric ganglion complex and in the porcine superior and inferior mesenteric ganglia by the indirect immunofluorescence technique. In normal rats, only 5-hydroxytryptamine immunoreactive SIF cells were seen in the coeliac-superior mesenteric ganglion complex. In the rats, pretreated with a 5-hydroxytryptamine precursor, l-tryptophan, and with a monoamine oxidase inhibitor, nialamide, a large number of 5-hydroxytryptamine-immunoreactive nerve fiber terminals were detected. In normal porcine superior and inferior mesenteric ganglia, intense 5-hydroxytryptamine immunoreactivity was found in numerous nerve fibers which were located around tyrosine hydroxylase-immunoreactive principal neurons. The origin and function of these fibers are discussed.

Immunohistochemical demonstration of galanin-, and galanin message-associated peptide-like immunoreactivities in sympathetic ganglia and adrenal gland of the guinea pig.

Using the indirect immunofluorescence method, the distribution of galanin (GAL)- and galanin message-associated peptide (GMAP)-like immunoreactivities (LI) were studied in sympathetic ganglia and the adrenal gland of the guinea pig. A rather dense network of GAL-immunoreactive nerve fibers was found in the inferior mesenteric ganglion (IMG) and in the superior mesenteric pole of the celiac-superior mesenteric ganglion complex (C-SMG). The celiac pole of the C-SMG, the stellate ganglion, and the superior cervical ganglion contained fewer, mostly scattered fibers. SIF-cells in prevertebral and paravertebral ganglia contained GAL-LI, as did the adrenal medullary cells. The GAL fibers in the IMG surrounded mainly principal ganglion cells containing somatostatin-immunoreactivity (SOM-IR), whereas fewer fibers were seen around neuropeptide Y (NPY) cells and cells in which SOM and NPY coexisted. Application of colchicine or vinblastine onto the IMG did not result in the appearance of GAL-IR in the principal ganglion cells. In denervation experiments it was revealed that most of the GAL fibers reach the IMG via the lumbar splanchnic nerves. GAL-IR appears to be colocalized with substance P (SP) in fibers of the IMG, indicating an origin of the GAL-containing fibers in dorsal root ganglia (DRG). This conclusion was supported by the finding in lumbar DRGs of GAL-positive cell bodies that contained SP. The role of GAL in prevertebral ganglia is unclear. It may be suggested that GAL modulates the slow, long-lasting membrane depolarization of the principal ganglion cells caused by SP in the primary afferents related to the IMG. GMAP-LI was detected in SIF cells and adrenal medullary cells in which GMAP-LI parallels the immunoreactivity of GAL. GMAP-LI was not observed in neuronal cell bodies or nerve fibers of the ganglia.

Distribution of NADPH-diaphorase activity in rat paravertebral, prevertebral and pelvic sympathetic ganglia.

Paravertebral (superior cervical and stellate), prevertebral (coeliac-superior mesenteric, inferior mesenteric) and pelvic (hypogastric) sympathetic ganglia of the rat were investigated by enzyme histochemistry to ascertain the distribution of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase) activity. In the paravertebral ganglia the majority of the sympathetic neuronal perikarya contained lightly and homogeneously distributed formazan reaction product but there was a range of staining intensities amongst the neuron population. In contrast, in the prevertebral ganglia, intense NADPH-diaphorase staining was present in certain neurons. Firstly, a population of neurons of the coeliac-superior mesenteric ganglion complex were surrounded by densely NADPH-diaphorase-positive 'baskets' of fibres and other stained fibres were seen in interstitial nerve bundles and in nerve trunks connected to the ganglion complex. Secondly, in both the inferior mesenteric ganglion and hypogastric ganglion there were many very intensely NADPH-diaphorase positive neurons. Stained dendritic and axonal processes emerged from these cell bodies. In both ganglia this population of neurons was smaller in size than the lightly stained ganglionic neurons and commonly had only one long (presumably axonal) process. The similarity of these highly NADPH-diaphorase-positive neurons with previously described postganglionic parasympathetic neurons in the hypogastric ganglion is discussed.

Reflex gastric motor inhibition caused by intraperitoneal bradykinin: Antagonism by Hoe 140, a bradykinin antagonist

Bradykinin (BK) has been reported to have mixed excitatory/inhibitory effects on gastrointestinal motility. The present study examined the mechanism responsible for the inhibition of gastric motor activity caused by intraperitoneal administration of BK. Gastric motor activity was measured by recording the intragastric pressure (IGP) of phenobarbital-anesthetized rats via a transesophageal catheter. To facilitate the study of inhibitory influences, gastric motility was stimulated by neurokinin A (NKA), which on intravenous injection evoked reproducible gastric contractions as measured by a rise of IGP. Intraperitoneal injection of BK (0.1–10 nmol) inhibited the NKA-induced increase in IGP in a dose-dependent manner, and the effect of epigastric administration of BK was not significantly different from that of intraperitoneal administration. The inhibitory effect of intraperitoneal BK on gastric motility was due to an effect on BK 2 receptors because it was blocked by prior intraperitoneal injection of the BK 2 antagonist Hoe 140. The specificity of this BK antagonist was demonstrated by its inability to antagonize the effect of intraperitoneal hydrochloric acid (HCl), which, like BK, inhibited the NKA-induced gastric contractions. Because the BK- and HCl-induced inhibition of the NKA-induced rise of IGP was abolished by acute removal of the celiac-superior mesenteric ganglion complex, but left unaltered by acute bilateral subdiaphragmatic vagotomy, it is inferred that intraperitoneal BK inhibits gastric motor activity via activation of an autonomic reflex that involves prevertebral ganglia.

Gastric mucosal hyperemia due to acid backdiffusion depends on splanchnic nerve activity.

Acid backdiffusion through a disrupted gastric mucosal barrier leads to an increase in gastric mucosal blood flow (MBF). This response involves afferent neurons that pass through the celiac ganglion. The present study examined the neural pathways that underlie the rise in MBF caused by gastric perfusion with 15% ethanol in 0.15 N HCl. MBF was measured by the hydrogen gas clearance technique in urethan-anesthetized rats. Mucosal hyperemia due to acid backdiffusion was not changed by acute bilateral subdiaphragmatic vagotomy but was blocked by acute removal of the celiac-superior mesenteric ganglion complex or acute bilateral transection of the greater splanchnic nerves. Hexamethonium (85 mumol/kg iv) also attenuated the rise in MBF due to acid backdiffusion, whereas guanethidine (0.225 mmol/kg sc) had no effect. None of the procedures and drug treatments altered basal MBF to a significant extent. Transection of the splanchnic nerves, hexamethonium, and guanethidine lowered mean arterial blood pressure, but hypotension as such did not significantly influence the hyperemic response under study. Taken together, the previous and present data indicate that the rise in MBF caused by acid backdiffusion depends on the integrity of afferent and efferent neural pathways that run in the splanchnic nerves and through the celiac ganglion. The efferent pathway involves ganglionic transmission through nicotinic acetylcholine receptors but is independent of noradrenergic neurons.

L-glutamate decarboxylase immunoreactivity in developing sympathetic tissues of the rat

An indirect immunofluorescence method was used to study the appearance and distribution of l-glutamate decarboxylase (GAD), the enzyme synthesizing γ-aminobutyric acid, in developing rat retroperitoneal sympathetic tissues. GAD immunoreactivity was analyzed in correlation with immunoreactivity to the catecholamine-synthesizing enzyme, tyrosine hydroxylase (TH), in the main retroperitoneal paraganglion, adrenal medullae and abdominal sympathetic ganglia. In different abdominal sympathetic tissues TH-immunoreactive cells first appeared on embryonic days 12.5–14.5, while GAD immunoreactivity was first observed in all these tissues in 14.5-day-old embryos (E 14.5). This suggests that the first expression of GAD is not coupled to the onset of catecholamine synthesis. In developing chain ganglia, GAD immunoreactivity was localized prenatally only in cell clusters with bright TH immunoreactivity, suggesting that GAD is expressed only in the cell lineage leading to ganglionic small intensely fluorescent (SIF) cells. The coeliac-superior mesenteric ganglion complex developed from the preaortic sympathetic tissue, starting from E 16.5 embryos, when the cranial, moderately TH-immunoreactive cells of this tissue were seen to form compact cell islets around the branches of the abdominal aorta. The caudal, intensely TH-immunoreactive cells of preaortic sympathetic tissue were seen to form the main retroperitoneal paraganglion from day E 15.5. During the prenatal period GAD immunoreactivity in preaortic sympathetic tissue was present caudally only in these paraganglionic cells and cranially in some brightly TH-immunoreactive cells, representing SIF and/or paraganglionic cells. In the adrenal medulla, only some of the TH-immunoreactive cells showed GAD immunoreactivity during early developmental stages. The moderately TH-immunoreactive, noradrenaline-synthesizing, cell clusters were seen for the first time in E 16.5 embryos, and they exhibited no GAD immunoreactivity. Thereafter, GAD was expressed only in the intensely TH-immunoreactive, adrenaline-synthesizing, cell clusters. The results of this study indicate that in the developing rat sympathetic tissues GAD is present only in the cell lineages which differentiate into SIF cells of abdominal sympathetic ganglia, preaortic paraganglionic cells and adrenaline cells of the adrenal medulla.

Distribution of peptidergic terminals of enteric origin in the rat celiac ganglion

We examined the distribution of enterofugal nerve terminals of bombesin-, cholecystokinin- and vasoactive intestinal polypeptide-like immunoreactivity in the rat celiac-superior mesenteric ganglion complex. The majority of these nerve terminals were concentrated in the mesenteric side of the ganglion. The present findings suggest that some functional specialization occurs in the celiac ganglion of the rat.

An electron microscopic study on VIP-, BOM- and CCK-like immunoreactive terminals in the celiac-superior mesenteric ganglion complex of the guinea pig

The distribution and fine structure were studied of the following 3 peptide-containing fibers of enteric origin, vasoactive intestinal polypeptide (VIP), bombesin (BOM) and cholecystokinin (CCK)-like immunoreactive peptide in the celiac-superior mesenteric ganglion complex (CMG) of the guinea pig. These peptides, especially VIP, were distributed more densely on the mesenteric side than on the celiac side of the CMG, and their distribution shared a similar mosaic pattern. Immunoelectron microscopic analysis revealed that the fibers formed synaptic contacts with the proximal dendrites of the principal ganglion cells, however, the profiles of these synaptic junctions differed between fibers. Those containing VIP or CCK formed symmetrical synapses, while those containing BOM formed assymetrical ones. This suggests that there are some functional differences between these enterofugal fibers in the CMG.

Localization of bombesin-, neuropeptide Y-, enkephalin-and tyrosine hydroxylase-like immunoreactivities in rat coeliac-superior mesenteric ganglion

The localization of bombesin- (BOMB) and enkephalin- (ENK) immunoreactive (IR) nerves was studied in rat coeliac-superior mesenteric ganglion complex in relation to neuropeptide Y (NPY)- and tyrosine hydroxylase (TH)-immunoreactive neurons with an immunofluorescence double-staining method. Very dense networks of BOMB-IR nerve terminals surrounded the majority of the principal ganglion cells, whether or not they were TH-IR. BOMB-IR nerves were specifically related to the non-NPY-IR neurons. Moderately dense networks of ENK-IR fibers were unevenly distributed among the ganglion cells. Majority of these neurons exhibited TH-IR and some of them also contained NPY-IR. In sections double stained with antibodies to ENK and BOMB some nerve fibers contained both peptides. The findings suggest that BOMB-IR nerves, which have been previously demonstrated to originate from gut, control the function of non-NPY-IR ganglion cells. ENK-IR nerves apparently control the adrenergic neurons which project to gut and also some NPY-IR vasomotoric neurons. The finding that ENK- and BOMB-IR coexist in some nerves suggests that some ENK-IR nerves may originate from gut, although the major part probably represents preganglionic fibers originating from spinal cord.

Stimulation of afferent nerve endings by intragastric capsaicin protects against ethanol-induced damage of gastric mucosa

Ablation of capsaicin-sensitive afferent neurons enhances experimentally induced ulceration in the rat gastric mucosa, which suggests that these neurons are involved in gastric mucosal protection. To provide direct evidence for such a function it was investigated whether stimulation of afferent nerve endings by the intragastric administration of capsaicin could counteract the ulcerogenic effect of 25% ethanol. Capsaicin (3.2–640μM), administered together with ethanol, inhibited the development of haemorrhagic lesions in a concentration-dependent fashion but did not alter the ethanol-induced fall in the gastric potential difference. This suggests that capsaicin does not prevent ethanol from damaging gastric epithelial cells but can counteract the vascular lesions caused by ethanol. The anti-lesion effect of intragastric capsaicin was absent in adult rats which had been treated with a high dose of systemic capsaicin as neonates in order to achieve a permanent degeneration of unmyelinated afferent neurons. It would appear, therefore, that intragastric capsaicin reduces lesion formation by an action on afferent neurons. The protective effect of intragastric capsaicin was not altered following acute subdiaphragmatic vagotomy, acute removal of the coeliac-superior mesenteric ganglion complex, acute bilateral ligation of the adrenal glands, or pretreatment of the rats with atropine or guanethidine. These findings indicate that stimulation of afferent neurons by intragastric capsaicin affords protection of the rat gastric mucosa against ethanol-induced damage. As the autonomic nervous system is not involved gastroprotection appears to represent a local effector function of sensory nerve endings in the stomach.

Sympathetic and afferent neurons projecting in the splenic nerve of the cat

Afferent and sympathetic postganglionic nerve cell bodies projecting in the splenic nerve of the cat have been labeled retrogradely with horseradish peroxidase (HRP) in order to study numbers and locations of these neurons. Labeled somata were found bilaterally in dorsal root and sympathetic paravertebral ganglia T3-L2 with a maximum in T10-T13 and in the coeliac superior mesenteric ganglion complex. About 13,200 neurons project into the splenic nerve of the cat, 12,550 being postganglionic and 650 afferent. About 98% of the postganglionic neurons were located in prevertebral and 2% in paravertebral sympathetic ganglia. About 73% of the afferent and 66% of the postganglionic paravertebral neurons were located on the left side. The density of the splenic innervation is about 3-4 times higher than that of the kidneys when normalized to the weight of both organs. It is discussed whether the afferent and sympathetic innervation of the spleen is not only involved in cardiovascular functions but also in regulation of the immune response of this organ.

The origin and distribution of 5-hydroxytryptamine-like immunoreactive nerve fibres to major mesenteric blood vessels of the rat

5-Hydroxytryptamine-like immunoreactive nerve plexuses were demonstrated by indirect immunofluorescence histochemistry in whole-mount preparations and cryostat sections of blood vessels from the mesenteric vasculature of the adult rat. The major veins showed a density of innervation greater than that of the accompanying arteries. Removal of the coeliac-superior mesenteric ganglion complex resulted in almost total loss of 5-hydroxytryptamine-like immunoreactive nerves from superior mesenteric blood vessels. The results of crush lesions applied to distal vessels of the superior mesentery indicate that there were no 5-hydroxytryptamine-like immunoreactive nerve fibres extending from the enteric nervous system to these vessels. The administration of 6-hydroxydopamine resulted in a large reduction in the noradrenergic innervation, accompanied by a similar fall in the number of 5-hydroxytryptamine-like immunoreactive nerve fibres. It is suggested that the cell bodies of the 5-hydroxytryptamine-like immunoreactive nerve fibres demonstrated in the superior mesenteric vasculature are located within the sympathetic ganglia which supply the noradrenergic innervation to the same region and that the 5-hydroxytryptamine-like immuno-reactivity may be co-localized with noradrenaline within sympathetic nerve fibres.

Localization of L-glutamate decarboxylase immunoreactivity in the major pelvic ganglion and in the coeliac-superior mesenteric ganglion complex of the rat.

The localization of L-glutamate decarboxylase (GAD), the GABA-synthesizing enzyme, was studied in the rat major pelvic ganglion and in the coeliac-superior mesenteric ganglion complex by indirect immunofluorescence technique with a specific antiserum raised in rabbits. GAD immunoreactivity was demonstrated in small cells of these ganglia. The GAD-immunoreactive small cells were 10-20 microns in diameter and formed clusters or occurred as solitary cells. The principal neurons were non-reactive but they were surrounded by immunoreactive processes. Studies on colocalization of GAD with tyrosine hydroxylase (TH), the rate-limiting enzyme of the catecholamine synthesis, in the major pelvic ganglion and in the coeliac-superior mesenteric ganglion complex indicated that all GAD-immunoreactive small cells were also labelled with TH. In the major pelvic ganglion all TH-immunoreactive SIF cells were also immunoreactive for GAD. However, in the coeliac-superior mesenteric ganglion complex there occurred TH-immunoreactive small cells which showed no immunoreactivity to GAD. It is suggested that the small GAD-immunoreactive cells represent small intensely fluorescent (SIF) cells.