Accumulation of prion protein in the vagus nerve in creutzfeldt-jakob disease.

Disease-associated proteins are thought to propagate along neuronal processes in neurodegenerative diseases. To detect disease-associated prion protein (PrPSc ) in the vagus nerve in different forms and molecular subtypes of Creutzfeldt-Jakob disease (CJD), we applied 3 different anti-PrP antibodies. We screened the vagus nerve in 162 sporadic and 30 genetic CJD cases. Four of 31 VV-2 type sporadic CJD and 7 of 30 genetic CJD cases showed vagal PrPSc immunodeposits with distinct morphology. Thus, PrPSc in CJD affects the vagus nerve analogously to α-synuclein in Parkinson disease. The morphologically diverse deposition of PrPSc in genetic and sporadic CJD argues against uniform mechanisms of propagation of PrPSc . Ann Neurol 2019;85:782-787.

Vagal nerve endings in visceral pleura and triangular ligaments of the rat lung.

The inner thoracic cavity is lined by the parietal pleura, and the lung lobes are covered by the visceral pleura. The parietal and visceral plurae form the pleural cavity that has negative pressure within to enable normal respiration. The lung tissues are bilaterally innervated by vagal and spinal nerves, including sensory and motor components. This complicated innervation pattern has made it difficult to discern the vagal vs. spinal processes in the pulmonary visceral pleura. With and without vagotomy, we identified vagal nerve fibres and endings distributed extensively in the visceral pleura ('P'-type nerve endings) and triangular ligaments ('L'-type nerve endings) by injecting wheat germ agglutinin-horseradish peroxidase as a tracer into the nucleus of solitary tract or nodose ganglion of male Sprague-Dawley rats. We found the hilar and non-hilar vagal pulmonary pleural innervation pathways. In the hilar pathway, vagal sub-branches enter the hilum and follow the pleural sheet to give off the terminal arborizations. In the non-hilar pathway, vagal sub-branches run caudally along the oesophagus and either directly enter the ventral-middle-mediastinal left lobe or follow the triangular ligaments to enter the left and inferior lobe. Both vagi innervate: (i) the superior, middle and accessory lobes on the ventral surfaces that face the heart; (ii) the dorsal-rostral superior lobe; (iii) the dorsal-caudal left lobe; and (iv) the left triangular ligament. Innervated only by the left vagus is: (i) the ventral-rostral and dorsal-rostral left lobe via the hilar pathway; (ii) the ventral-middle-mediastinal left lobe and the dorsal accessory lobe that face the left lobe via the non-hilar pathway; and (iii) the ventral-rostral inferior lobe that faces the heart. Innervated only by the right vagus, via the non-hilar pathway, is: (i) the inferior (ventral and dorsal) and left (ventral only) lobe in the area near the triangular ligament; (ii) the dorsal-middle-mediastinal left lobe; and (iii) the right triangular ligament. Other regions innervated with unknown vagal pathways include: (i) the middle lobe that faces the superior and inferior lobe; (ii) the rostral-mediastinal inferior lobe that faces the middle lobe; and (iii) the ventral accessory lobe that faces the diaphragm. Our study demonstrated that most areas that face the dorsal thoracic cavity have no vagal innervation, whereas the interlobar and heart-facing areas are bilaterally or unilaterally innervated with a left-rostral vs. right-caudal lateralized innervation pattern. This innervation pattern may account for the fact that the respiratory regulation in rats has a lateralized right-side dominant pattern.

A recurrent vagal schwannoma in the middle mediastinum after surgical enucleation.

A 50-year-old man underwent repeat surgery for a benign vagal schwannoma in the middle mediastinum. He had undergone tumor enucleation at another hospital 4 months before presentation. The tumor (99 × 88 × 76 mm) was located in the aortopulmonary window and arose from the left vagus nerve. It had been enucleated, leaving its sheath behind to preserve the nerve. Imaging studies showed tumor regrowth without distant metastasis, and the tumor was extirpated along with the involved nerve during cardiopulmonary bypass. There was no nerve dysfunction, recurrence, or metastasis 6 months after the operation. A benign vagal schwannoma can be excised with nerve transection or enucleated without nerve transection. The present case suggests that a vagal mediastinal schwannoma should be extirpated along with the nerve because insufficient enucleation might lead to tumor regrowth.

Alterations in TH- and ChAT-immunoreactive neurons in the DMV and gastric dysmotility in an LPS-induced PD rat model.

To study movement disorder in Parkinson's disease (PD), an animal model of PD can be created by injecting lipopolysaccharide (LPS) into the substantia nigra of rats. In addition to body movement disorders, patients with PD often experience gastrointestinal (GI) dysfunction, such as gastroparesis. However, the underlying mechanism of these disorders remains unclear. The dorsal motor nucleus of vagus (DMV) is a well-known visceral nucleus that regulates GI function. The present study investigated alterations in DMV neurons and gastric motility in rats with LPS-induced PD (LPS-PD rats). Gastric motility was recorded using a strain gauge force transducer in vivo. The distributions of tyrosine hydroxylase (TH)- and choline acetyltransferase (ChAT)-positive neurons in the DMV were determined using immunofluorescence and confocal laser microscopy. Our results indicated that in LPS-PD rats, the number of neurons in the substantia nigra, including neurons with TH immunoreactivity, was markedly reduced, although glial cell proliferation was clearly observed. However, enhanced TH immunoreactivity and decreased ChAT immunoreactivity were found in the DMV. Furthermore, weakened gastric motility was recorded in anesthetized LPS-PD rats. In conclusion, rats with LPS-induced PD exhibited gastric dysmotility with an alteration in DMV neurons. This PD model may be used to study autonomic nervous system disorders that are often observed in patients with early-stage PD.

Distribution of dopamine receptors D1- and D2-immunoreactive neurons in the dorsal motor nucleus of vagus in rats.

The dorsal motor nucleus of vagus (DMV) plays an important role in the regulation of gastrointestinal function. Dopamine (DA) exerts potent neuromodulatory effects on the motoneurons in the DMV via dopamine receptors (DRs). However, the distribution of DRs and their neurochemical phenotypes in the DMV are unclear. In the present study, the distribution of DRs D1- and D2-immunoreactive (IR) neurons and their neurochemical phenotypes in the DMV of rats were investigated using a double-labeling immunofluorescence technique combined with confocal microscopy. The results indicated that a considerable quantity of D1 and D2 was expressed throughout the DMV. A large amount of choline acetyltransferase (ChAT)-IR and a few tyrosine hydroxylase (TH)-IR neurons were observed in the DMV. Nearly all of the neurons were also D1-IR and D2-IR. In conclusion, the present study demonstrates the wide distribution of D1 and D2 in the cholinergic and catecholaminergic neurons in the DMV of rats. The DRs might play an important role in the regulation of DA on the activity of cholinergic and catecholaminergic neurons in the DMV.

Disease phenotype in sheep after infection with cloned murine scrapie strains.

Prion diseases exhibit different disease phenotypes in their natural hosts and when transmitted to rodents, and this variability is regarded as indicative of prion strain diversity. Phenotypic characterization of scrapie strains in sheep can be attempted by histological, immunohistochemical and biochemical approaches, but it is widely considered that strain confirmation and characterization requires rodent bioassay. Examples of scrapie strains obtained from original sheep isolates by serial passage in mice include ME7, 79A, 22A and 87V. In order to address aspects of prion strain stability across the species barrier, we transmitted the above murine strains to sheep of different breeds and susceptible Prnp genotypes. The experiment included 40 sheep dosed by the oral route alone and 36 sheep challenged by combined subcutaneous and intracerebral routes. Overall, the combined route produced higher attack rates (~100%) than the oral route (~50%) and 2-4 times shorter incubation periods. Uniquely, 87V given orally was unable to infect any sheep. Overall, scrapie strains adapted and cloned in mice produce distinct but variable disease phenotypes in sheep depending on breed or Prnp genotype. Further re-isolation experiments in mice are in progress in order to determine whether the original cloned murine disease phenotype will reemerge.

Abdominal vagal afferent pathways and their distributions of intraganglionic laminar endings in the rat duodenum.

We examined abdominal vagal afferents (n = 33) and the distributions of their intraganglionic laminar endings (IGLEs) in the duodenum. Rats (male, Sprague-Dawley) received a partial subdiaphragmatic vagotomy that spared a single branch. Wheat germ agglutinin-horseradish peroxidase (0.5-1.0 µl) was injected into the nodose ganglion ipsilateral to the vagotomized side. We observed that the hepatic branch does not project to the stomach, that the accessory celiac and celiac branches course along the celiac artery and innervate the intestines, and that the left nodose afferents innervate predominantly the duodenum. The hepatic branch innervates the duodenum via the "hepatoduodenal" subbranch and has the densest IGLE distribution in both the dorsoventral and the rostrocaudal extensions of the first 4-cm segment. Both gastric branches have two subbranches that innervate the duodenum; the "lesser curvature" subbranches follow the lesser curvature artery and may join the "hepatoduodenal" subbranch, whereas the "pyloric" subbranches run through the antrum and pylorus to reach the proximal duodenum. Moreover, the subbranches of ventral and dorsal gastric branches innervate more in the ventral and dorsal parts of the duodenum, respectively, and have more IGLEs in the rostral region than in the caudal. A posteriori comparisons indicate that, in the first-centimeter segment, the ventral gastric branch has significantly more IGLEs, whereas, in the third- and fourth-centimeter segments, the hepatic branch has more IGLEs. The finding that three different vagal branches innervate the duodenum with different densities of afferent endings might indicate a viscerotopic receptive field that coordinates digestive functions in feeding.

Chemical coding and central projections of gastric vagal afferent neurons.

Vagal afferents that innervate gastric muscle or mucosa transmit distinct sensory information from their endings to the nucleus of the tractus solitarius (NTS). While these afferent subtypes are functionally distinct, no neurochemical correlate has been described and it is unknown whether they terminate in different central locations. This study aimed to identify gastric vagal afferent subtypes in the nodose ganglion (NG) of ferrets, their terminal areas in NTS and neurochemistry for isolectin-B4 (IB4) and calcitonin gene-related peptide (CGRP). Vagal afferents were traced from gastric muscle or mucosa and IB4 and CGRP labelling assessed in NG and NTS. 7 +/- 1% and 6 +/- 1% of NG neurons were traced from gastric muscle or mucosa respectively; these were more likely to label for CGRP or for both CGRP and IB4 than other NG neurons (P < 0.01). Muscular afferents were also less likely than others to label with IB4 (P < 0.001). Less than 1% of NG neurons were traced from both muscle and mucosa. Central terminals of both afferent subtypes occurred in the subnucleus gelatinosus of the NTS, but did not overlap completely. This region also labelled for CGRP and IB4. We conclude that while vagal afferents from gastric muscle and mucosa differ little in their chemical coding for CGRP and IB4, they can be traced selectively from their peripheral endings to NG and to overlapping and distinct regions of NTS. Thus, there is an anatomical substrate for convergent NTS integration for both types of afferent input.

Detection of PrP(CWD) in postmortem rectal lymphoid tissues in Rocky Mountain elk (Cervus elaphus nelsoni) infected with chronic wasting disease.

Preclinical diagnostic tests for transmissible spongiform encephalopathies have been described for mule deer (Odocoileus hemionus), using biopsy tissues of palatine tonsil, and for sheep, using lymphoid tissues from palatine tonsil, third eyelid, and rectal mucosa. The utility of examining the rectal mucosal lymphoid tissues to detect chronic wasting disease (CWD) was investigated in Rocky Mountain elk (Cervus elaphus nelsoni), a species for which there is not a live-animal diagnostic test. Postmortem rectal mucosal sections were examined from 308 elk from two privately owned herds that were depopulated. The results of the postmortem rectal mucosal sections were compared to immunohistochemical staining of the brainstem, retropharyngeal lymph nodes, and palatine tonsil. Seven elk were found positive using the brainstem (dorsal motor nucleus of the vagus nerve), retropharyngeal lymph nodes, and palatine tonsil. Six of these elk were also found positive using postmortem rectal mucosal sections. The remaining 301 elk in which CWD-associated abnormal isoform of the prion protein (PrP(CWD)) was not detected in the brainstem and cranial lymphoid tissues were also found to be free of PrP(CWD) when postmortem rectal mucosal sections were examined. The use of rectal mucosal lymphoid tissues may be suitable for a live-animal diagnostic test as part of an integrated management strategy to limit CWD in elk.

Ghrelin-containing neuron in cerebral cortex and hypothalamus linked with the DVC of brainstem in rat.

Ghrelin is a newly discovered brain-gut peptide and an endogenous ligand for growth hormone secretagogues receptor (GHS-R). Ghrelin and GHS-R present extensively in central and peripheral tissues such as stomach, brain and other organs of rodent and human, which suggest it has multiple biological effects. It has been reported that ghrelin has significant role in the regulation of energy homeostasis, food intake and appetite. The organization of central circuitry appears to play an important role in integrating orexigenic effects of ghrelin, but the detail is not fully clear. In this study, we examined the expression of ghrelin, ghrelin mRNA and GHS-R mRNA in cerebrum and brainstem by RT-PCR and immunofluorescence histochemistry, and analyzed the connection among the cerebral cortex, hypothalamus, dorsal vagal complex (DVC). The results showed that the positive staining of ghrelin was found on the pyramidal neuron of layer V in the sensorimotor area of cerebral cortex, cingulate gyrus, as well as in the neuron of lateral hypothalamus (LH), PVN and ARC. The expression of ghrelin mRNA and GHS-R mRNA were also found in the sensorimotor cortex and hypothalamus by method of RT-PCR. The GHS-R mRNA was also found in the DVC of medulla oblongata. Other finding is that the FG/ghrelin dual labeled neurons were found in LH of hypothalamus (not in cortex). The ghrelin-containing neuron in the LH projects its axon to the DVC with the method of retrograde tracing. In conclusion, the ghrelin neurons are located not only in hypothalamus (LH, PVN, ARC), but also in the cortex (sensorimotor area, cingular gyrus), and the fibers of ghrelin neurons in hypothalamus projected directly to the DVC. It suggests that ghrelin plays its role from hypothalamus to brainstem as a neurotransmitter or neuromodulator to regulate function of vagal nuclei in brainstem.

First localization and biochemical identification of chromogranin B- and secretoneurin-like immunoreactivity in the fetal human vagal/nucleus solitary complex.

The human vagal/nucleus solitary complex is a primary visceral relay station and an integrative brain stem area which displays a high density of chromogranin B- and secretoneurin-like immunoreactivity. In this study, we localized and biochemically identified these proteins during prenatal development. At prenatal week 11, 15, 20 and 37, we performed a chromatographic analysis to identify the molecular forms of PE-11, a peptide within the chromogranin B sequence, and secretoneurin, a peptide within secretogranin II. Their localization was studied with immunocytochemistry, and was compared to that of substance P which is well established as a functional neuropeptide in the vagal/nucleus solitary complex. At prenatal week 11, chromogranin B-, secretoneurin- and substance P-like immunoreactivities were detected consisting of varicosities, varicose fibers and single cells. At the same time, PE-11 and secretoneurin appeared as a single peak in chromatographic analysis. Prohormone convertases PC1- and PC2-like immunoreactivities were also present at week 11. In general, the density for each peptide increased during later fetal stages with the highest density at week 37. These results demonstrate that each chromogranin peptide is expressed during human fetal life in neurons of the vagal/nucleus solitary complex indicating that these peptides could be important during prenatal development.

[Properties of lung surfactant during changes in capsaicin-sensitive vagal afferents under conditions of emotional stress].

In this work, we investigated surface active properties and biochemical composition of pulmonary surfactant under emotional stress in condition of neuropeptides pool exhaustion in capsaicin-sensitive afferents of the vagus nerve. It is shown that stress is accompanied by decrease of lung surface active properties and increase of total phospholipids content as result of phosphatidylcholine and lysophospholipid fraction rise. After capsaicin application on the cervical part of the right vagus nerve stress-induced alterations in ipsilateral lung become less considerable, whereas all spectra of changes in contralateral lung is remained.

TNF alpha-p55 receptors: medullary brainstem immunocytochemical localization in normal and vagus nerve-transected rats.

Tumor necrosis factor alpha (TNF(alpha)) is a potent modulator of autonomic reflex mechanisms that control the stomach. Evidence suggests that TNF(alpha) action directly on vago-vagal reflex control circuits causes the autonomic misregulation of digestion manifested as gastrointestinal stasis, nausea, and emesis associated with illness. Neurophysiological studies indicated that TNF(alpha) may have effects on vagal afferents in the solitary nucleus, as well as neurons of the solitary nucleus (NST) and dorsal motor nucleus (DMN) of the vagus. The aim of this study was to determine the location of the TNFR1 receptor (p55) in the medulla using immunocytochemical methods. We devised a technique for localizing the p55 receptor using heat-induced antigen recovery in fixed tissue sections. This protocol allowed us to demonstrate that dense p55-immunoreactivity (p55-ir) is constitutively present on central (but not peripheral) vagal afferents in the solitary tract (ST) and nucleus; p55-ir is also present on afferents entering the spinal trigeminal nucleus. Unilateral supra-nodose vagotomy eliminated p55-ir from ipsilateral central vagal afferents. Virtually all neurons in the brainstem appeared to express p55-ir at a low level, i.e., just above background. However, vagotomy caused a dramatic up-regulation of p55-ir in vagal motor neurons. This increase in p55-ir in axotomized neurons may play a pivotal role in the connection between the occurrence of the injury and the initiation of apoptotic processes resulting in elimination of damaged neurons.

[Neurotransmitter stage in the development of peripheral part of autonomic nervous system]. / Mediatornyi étap v razvitii perifericheskogo otdela vegetativnoi nervnoi sistemy

The dynamics of neurotransmitter stage in the development of autonomic nervous system (ANS) was studied in rats starting from the moment of initial appearance of neurotransmitters acetylcholine and adrenalin in ANS peripheral part main nervous plexuses. Cryostat sections of embryos on developmental days 13.5, 16.5 and 18.5 and of neonatal rats aged 0.5 and 1.5 days were treated with glyoxilic acid, using Karnovsky-Roots method and impregnated with silver nitrate according to Bielschowsky-Gross method. Acetylcholinesterase in vagus and in spinal ganglia was found on day 13.5, while catecholamine in sympathetic trunc was detected in animals immediately after the birth. Periods of the beginning of neurotransmitter stage in ANS development in rat and man were compared and it was established that it was delayed in rat as in immature-born animal.

Angiotensin II subtype 1A (AT1A) receptors in the rat sensory vagal complex: subcellular localization and association with endogenous angiotensin.

Angiotensin II (Ang II) type 1 (AT1) receptors are prevalent in the sensory vagal complex including the nucleus tractus solitarii (NTS) and area postrema, each of which has been implicated in the central cardiovascular effects produced by Ang II. In rodents, these actions prominently involve the AT1A receptor. Thus, we examined the electron microscopic dual immunolabeling of antisera recognizing the AT1A receptor and Ang II to determine interactive sites in the sensory vagal complex of rat brain. In both the area postrema and adjacent dorsomedial NTS, many somatodendritic profiles were dually labeled for the AT1A receptor and Ang II. In these profiles, AT1A receptor-immunoreactivity was often seen in the cytoplasm beneath labeled portions of the plasma membrane and in endosome-like granules as well as Golgi lamellae and outer nuclear membranes. In addition, AT1A receptor labeling was detected on the plasma membrane and in association with cytoplasmic membranes in many small axons and axon terminals. These terminals were morphologically heterogeneous containing multiple types of vesicles and forming either inhibitory- or excitatory-type synapses. In the area postrema, AT1A receptor labeling also was detected in many non-neuronal cells including glia, capillary endothelial cells and perivascular fibroblasts that were less prevalent in the NTS. We conclude that in the rat sensory vagal complex, AT1A receptors are strategically positioned for involvement in modulation of the postsynaptic excitability and intracrine hormone-like effects of Ang II. In addition, these receptors have distributions consistent with diverse roles in regulation of transmitter release, regional blood flow and/or vascular permeability.

The co-expression of VR1 and VRL-1 in the rat vagal sensory ganglia.

Immunohistochemistry for two nociceptive transducers, the vanilloid receptor 1 (VR1) and vanilloid receptor 1-like receptor (VRL-1), was performed on the vagal sensory ganglia. In the jugular ganglion, VR1-immunoreactive (IR) neurons were small to medium-sized (range 49.7-1,125.6 microm(2), mean+/-S.D. 407.7+/-219.7 microm(2)), whereas VRL-1-IR neurons were medium-sized to large (range 223.6-1,341.1 microm(2), mean+/-S.D. 584.3+/-253.5 microm(2)). In the nodose ganglion, VR1- and VRL-1-IR neurons were mostly small to medium-sized (VR1: range 148.5-1464.4 microm(2), mean+/-S.D. 554.3+/-207.4 microm(2); VRL-1: range 161.7-1166.2 microm(2), mean+/-S.D. 541.9+/-186.2 microm(2)). The double immunofluorescence method revealed that co-expression of VR1-immunoreactivity among VRL-1-IR neurons was more abundant in the nodose ganglion (63%) than in the jugular ganglion (4%). The present study suggests that co-expression of VR1 and VRL-1 may be more common in visceral sensory neurons than in somatic sensory neurons.

Antiemetic effect of a tachykinin NK1 receptor antagonist GR205171 on cisplatin-induced early and delayed emesis in the pigeon.

Cisplatin (4 mg/kg, i.v.) induced both early emesis, which appears within the first 8-h period, and delayed emesis, which appears between 8 and 48 h after its administration to pigeons. GR205171 ([(2S-cis)-N-((2-methoxy-5(5-(trifluoromethyl)-1H-tetrazol-1-yl)-phenyl) methyl)-2-phenyl-3-piperidinamine dihydrochloride]) administered intramuscularly (1-10 mg/kg) reduced significantly the number of emetic response to cisplatin: this reduction was 60-81% (P < 0.05) for early emesis and 48-64% (P < 0.05) for the delayed response. Intracerebroventricularly administered GR205171 (30 microg/kg) also reduced the number of emetic responses: 53% (P < 0.05) in early emesis and 88% (P < 0.05) in the delayed response. However, the latency time to the first emesis was not affected by GR205171. Direct injection of cisplatin (10 microg/kg) into the fourth ventricle produced emesis, which was reduced by GR205171 administered via the peripheral or central route. Substance P-immunoreactive fibres were distributed throughout the dorsal vagal complex. These results suggest that the antiemetic effect of GR205171 on both emetic responses to cisplatin acts on a central site, and that the onset of the emetic response may be mediated partly via GR205171-insensitive mechanisms.

Expression of metabotropic glutamate receptor 8 in autonomic cell groups of the medulla oblongata of the rat.

Metabotropic glutamate receptors (mGluRs) in the medulla oblongata have been suggested to have a functional role in the regulation of cardiovascular baroreflexes. The present study examines the localization of mGluR8 autonomic nuclei of the medulla of the rat. mGluR8 immunoreactivity was observed in the cell bodies and/or processes of the dorsolateral, interstitial, medial, intermediate, ventral, ventrolateral, subpostremal, commissural, parvicellular and gelatinosus subnuclei of the nucleus tractus solitarius (NTS). The intensity of mGluR8 staining was highest in the commissural and interstitial subnuclei at the level of the area postrema. Commissural NTS is involved in regulation of baro-, and chemo-reflexes whereas the interstitial nucleus mediates respiratory reflexes. In the area postrema, diffuse staining was observed in the cell bodies, dendrites and fibers of the dorsal and central regions. In vagal outflow nuclei, mGluR8 immunoreactivity was observed in: (1). the cell bodies and processes of the dorsal motor nucleus of the vagus (DMN) throughout the rostro-caudal extent; and (2). the cell bodies and fibers throughout the rostro-caudal extent of the dorsal and ventral division the nucleus ambiguus (NA). Staining in the ventrolateral medulla was restricted to regions ventral to the nucleus ambiguus and dorsal to the lateral reticulate nucleus. The present study is the first to provide a detailed mapping of mGluR8 within the autonomic nuclei of the medulla and suggests that this subtype may be involved in shaping synaptic transmission in these central nuclei.

Streptozotocin-induced diabetes and the neurochemistry of vagal afferent neurons.

To assess whether diabetes alters the content and/or expression of neuroactive agents and protooncogenes in afferent neurons of the vagus nerve, the nodose ganglia of streptozotocin (STZ)-induced diabetic rats were studied at 8, 16, and 24 weeks after induction of diabetes. Neuronal nitric oxide synthase (nNOS), tyrosine hydroxylase (TH), the immediate early gene c-Jun, vasoactive intestinal peptide (VIP) and calcitonin gene related peptide (CGRP) content and expression were measured in nodose ganglia of control, diabetic, and diabetic+insulin-treated rats using immunocytochemistry and reverse transcription-polymerase chain reaction (RT-PCR). The numbers of nNOS-immunoreactive (ir) neurons were increased in the nodose ganglion of diabetic compared to control rats at the 8- and 16-week time points. However, no change was noted in the nNOS mRNA content of the diabetic nodose ganglion at either time point. Moreover, no alterations in the numbers of vagal efferent NOS-containing neurons (labeled with NADPH-diaphorase histochemistry) were noted in the dorsal motor nucleus of the vagus (DMV) or the nucleus ambiguous (NA) of control, diabetic, and diabetic+insulin-treated rats at any time point. Neither the numbers of TH-ir neurons nor the content of TH mRNA was altered in the diabetic rats at the 8- and 16-week time points. However, 24 weeks of diabetes resulted in a reduction in the numbers of TH-ir neurons in the diabetic nodose ganglia when compared to control, an effect not seen in diabetic rats receiving insulin. The number of nodose ganglion neurons labeled for the protooncogene, c-Jun, was small yet slightly increased in the diabetic nodose ganglia at the 8-week time point and was reversed with insulin treatment. The increase in c-Jun-ir neurons was not found at 16 or 24 weeks of diabetes. VIP-ir and CGRP-ir were unchanged at any of the time points. These data show that diabetes affects the content of some, but not all, neuroactive agents in the nodose ganglion and may reflect a modest level of diabetes-induced damage and/or alterations in axonal transport in the vagus nerve.

GABA(B)R expressed on vagal afferent neurones inhibit gastric mechanosensitivity in ferret proximal stomach.

GABA(B)-receptor (GABA(B)R) agonists reduce transient lower esophageal sphincter relaxation (TLESR) and reflux episodes through an action on vagal pathways. In this study, we determined whether GABA(B)R are expressed on vagal afferent neurones and whether they modulate distension-evoked discharge of vagal afferents in the isolated stomach. Vagal mehanoreceptor activity was recorded following distensions of the isolated ferret proximal stomach before and after perfusion with the GABA(B)R-selective agonists baclofen and 3-aminopropylphosphinic acid (3-APPiA). Retrograde labeling and immunohistochemistry were used to identify GABA(B)R located on vagal afferent neurones in the nodose ganglia. Vagal afferent fibers responded to isovolumetric gastric distension with an increase in discharge. The GABA(B)-receptor agonists baclofen (5 x 10(-5) M) and 3-APPiA (10(-6) to 10(-5) M) but not muscimol (GABA(A)-selective agonist: 1.3 x 10(-5) M) significantly decreased afferent distension-response curves. The effect of baclofen (5 x 10(-5) M) was reversed by the GABA(B)-receptor antagonist CGP 62349 (10(-5) M). Over 93% of retrogradely labeled gastric vagal afferents in the nodose ganglia expressed immunoreactivity for the GABA(B)R. GABA(B)R expressed on vagal afferent fibers directly inhibit gastric mechanosensory activity. This is likely a contributing mechanism to the efficacy of GABA(B)-receptor agonists in reducing TLESR and reflux episodes in vivo.