Effect of leptin on nitrergic neurons in the lateral hypothalamic area and the supraoptic nucleus of rats

The adipocyte-derived hormone, leptin, plays a key role in the maintenance of energy homeostasis. Leptin binds to the long form of its receptor, which is predominantly expressed in various hypothalamic regions, including the lateral hypothalamic area (LH) and supraoptic nucleus (SO). Several studies have suggested that leptin directly activates neuronal nitric oxide synthase, leading to increased nitric oxide production. We used histochemistry for nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) as a marker for nitric oxide synthase activity and assessed the effect of leptin on nitrergic neurons in the LH and SO of rats. We found that intraperitoneal administration of leptin led to a significant increase in the number of NADPH-d-positive neurons in the LH and SO. In addition, the intensity (optical density) of NADPH-d staining in LH and SO neurons was significantly elevated in rats that received leptin compared with saline-treated rats. These findings suggest that nitrergic neurons in the LH and SO may be implicated in mediating the central effects of leptin.

Aryl hydrocarbon receptor activation affects nitrergic neuronal survival and delays intestinal motility in mice

Despite progress describing the effects of persistent organic pollutants (POPs) on the central nervous system, the effect of POPs on enteric nervous system (ENS) function remains underexplored. We studied the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a POP, and a potent aryl hydrocarbon receptor (AHR) ligand, on the ENS and intestinal motility in mice. C57Bl/6J mice treated with TCDD (2.4 µg/kg body weight) for 8 weeks (once per week) exhibited significant delay in intestinal motility as shown by reduced stool frequency, prolonged intestinal transit time, and a persistence of dye in the jejunum compared to control mice with maximal dye retention in the ileum. TCDD significantly increased Cyp1a1 expression, an AHR target gene, and reduced the total number of neurons and affected nitrergic neurons in cells isolated from WT mice, but not Ahr-/- mice. In immortalized fetal enteric neuronal cells, TCDD-induced nuclear translocation of AHR as well as increased Cyp1a1 expression. AHR activation did not affect neuronal proliferation. However, AHR activation resulted in enteric neuronal toxicity, specifically, nitrergic neurons. Our results demonstrate that TCDD adversely affects nitrergic neurons and thereby contributes to delayed intestinal motility. These findings suggest that AHR signaling in the ENS may play a role in modulating TCDD-induced gastrointestinal pathophysiology.

Involvement of nitrergic neurons in colonic motility in a rat model of ulcerative colitis

BACKGROUND

The mechanisms underlying gastrointestinal (GI) dysmotility with ulcerative colitis (UC) have not been fully elucidated. The enteric nervous system (ENS) plays an essential role in the GI motility. As a vital neurotransmitter in the ENS, the gas neurotransmitter nitric oxide (NO) may impact the colonic motility. In this study, dextran sulfate sodium (DSS)-induced UC rat model was used for investigating the effects of NO by examining the effects of rate-limiting enzyme nitric oxide synthase (NOS) changes on the colonic motility as well as the role of the ENS in the colonic motility during UC.

AIM

To reveal the relationship between the effects of NOS expression changes in NOS-containing nitrergic neurons and the colonic motility in a rat UC model.

METHODS

Male rats (n = 8/each group) were randomly divided into a control (CG), a UC group (EG1), a UC + thrombin derived polypeptide 508 trifluoroacetic acid (TP508TFA; an NOS agonist) group (EG2), and a UC + NG-monomethyl-L-arginine monoacetate (L-NMMA; an NOS inhibitor) group (EG3). UC was induced by administering 5.5% DSS in drinking water without any other treatment (EG1), while the EG2 and EG3 were gavaged with TP508 TFA and L-NMMA, respectively. The disease activity index (DAI) and histological assessment were recorded for each group, whereas the changes in the proportion of colonic nitrergic neurons were counted using immunofluorescence histochemical staining, Western blot, and enzyme linked immunosorbent assay, respectively. In addition, the contractile tension changes in the circular and longitudinal muscles of the rat colon were investigated in vitro using an organ bath system.

RESULTS

The proportion of NOS-positive neurons within the colonic myenteric plexus (MP), the relative expression of NOS, and the NOS concentration in serum and colonic tissues were significantly elevated in EG1, EG2, and EG3 compared with CG rats. In UC rats, stimulation with agonists and inhibitors led to variable degrees of increase or decrease for each indicator in the EG2 and EG3. When the rats in EGs developed UC, the mean contraction tension of the colonic smooth muscle detected in vitro was higher in the EG1, EG2, and EG3 than in the CG group. Compared with the EG1, the contraction amplitude and mean contraction tension of the circular and longitudinal muscles of the colon in the EG2 and EG3 were enhanced and attenuated, respectively. Thus, during UC, regulation of the expression of NOS within the MP improved the intestinal motility, thereby favoring the recovery of intestinal functions.

CONCLUSION

In UC rats, an increased number of nitrergic neurons in the colonic MP leads to the attenuation of colonic motor function. To intervene NOS activity might modulate the function of nitrergic neurons in the colonic MP and prevent colonic motor dysfunction. These results might provide clues for a novel approach to alleviate diarrhea symptoms of UC patients.

Evaluation of myenteric neurons in the colon of rats exposed to 2,4 dichlorophenoxyacetic acid herbicide

The assessment of the enteric nervous system provides a better understanding of the effects that contaminants can have on the health and well-being of organisms. It has been reported that 2,4-dichlorophenoxyacetic acid (2,4-D) is a highly persistent herbicide in the environment that is responsible for neurotoxic changes in different myenteric neuronal subpopulations. The current study aimed to evaluate the effects of 2,4-D on myenteric neurons in the colon of Rattus norvegicus for the first time. A dose of 2,4-D (5 mg/kg/day) was administered to the experimental group (2,4-D) for 15 days. Then, the proximal colon was collected and submitted to Giemsa and NADPH-d histochemical techniques for the disclosure of total and nitrergic neurons. The 2,4-D group presented a higher density of total neurons (p = 0.05, t-test), which together with the maintenance of nitrergic neuronal density, may be related to the increase in the expression of the neurotransmitter acetylcholine by colocalization, responsible for stimulating the intestinal smooth muscle and increasing the chances of the expulsion of the harmful content present in the lumen. Over 15 days, the neurotoxic effects of 2,4-D in the myenteric plexus influenced an increase in the general population of myenteric neurons in the colon.

The effect of Xenin25 on spontaneous circular muscle contractions of rat distal colon in vitro

Xenin25 has a variety of physiological functions in the Gastrointestinal (GI) tract, including ion transport and motility. However, the motility responses in the colon induced by Xenin25 remain poorly understood. Therefore, the effect of Xenin25 on the spontaneous circular muscle contractions of the rat distal colon was investigated using organ bath chambers and immunohistochemistry. Xenin25 induced the inhibition followed by postinhibitory spontaneous contractions with a higher frequency in the rat distal colon. This inhibitory effect of Xenin25 was significantly suppressed by TTX but not by atropine. The inhibitory time (the duration of inhibition) caused by Xenin25 was shortened by the NTSR1 antagonist SR48692, the NK1R antagonist CP96345, the VPAC2 receptor antagonist PG99-465, the nitric oxide-sensitive guanylate-cyclase inhibitor ODQ, and the Ca2+ -dependent K+ channel blocker apamin. The higher frequency of postinhibitory spontaneous contractions induced by Xenin25 was also attenuated by ODQ and apamin. SP-, NOS-, and VIP-immunoreactive neurons were detected in the myenteric plexus (MP) of the rat distal colon. Small subsets of the SP-positive neurons were also Calbindin positive. Most of the VIP-positive neurons were also NOS positive, and small subsets of the NK1R-positive neurons were also VIP positive. Based on the present results, we propose the following mechanism. Xenin25 activates neuronal NTSR1 on the SP neurons of IPANs, and transmitters from the VIP and apamin-sensitive NO neurons synergistically inhibit the spontaneous circular muscle contractions via NK1R. Subsequently, the postinhibitory spontaneous contractions are induced by the offset of apamin-sensitive NO neuron activation via the interstitial cells of Cajal. In addition, Xenin25 also activates the muscular NTSR1 to induce relaxation. Thus, Xenin25 is considered to be an important modulator of post prandial circular muscle contraction of distal colon since the release of Xenin25 from enteroendocrine cells is stimulated by food intake.

Nitrergic Enteric Neurons in Health and Disease-Focus on Animal Models

Nitrergic enteric neurons are key players of the descending inhibitory reflex of intestinal peristalsis, therefore loss or damage of these neurons can contribute to developing gastrointestinal motility disturbances suffered by patients worldwide. There is accumulating evidence that the vulnerability of nitrergic enteric neurons to neuropathy is strictly region-specific and that the two main enteric plexuses display different nitrergic neuronal damage. Alterations both in the proportion of the nitrergic subpopulation and in the total number of enteric neurons suggest that modification of the neurochemical character or neuronal death occurs in the investigated gut segments. This review aims to summarize the gastrointestinal region and/or plexus-dependent pathological changes in the number of nitric oxide synthase (NOS)-containing neurons, the NO release and the cellular and subcellular expression of different NOS isoforms. Additionally, some of the underlying mechanisms associated with the nitrergic pathway in the background of different diseases, e.g., type 1 diabetes, chronic alcoholism, intestinal inflammation or ischaemia, will be discussed.

High-Fat Diet During the Perinatal Period Induces Loss of Myenteric Nitrergic Neurons and Increases Enteric Glial Density, Prior to the Development of Obesity

Diet-induced obesity induces peripheral inflammation accompanied by a loss of myenteric neurons. Few studies, however, have investigated the effects of a high-fat diet (HFD) on either the development of myenteric neurons or prior to the occurrence of obesity. The present study assessed the effects of maternal HFD on the density and neurochemical phenotype of myenteric ganglia in the upper gastrointestinal tract. Sprague-Dawley rats were fed either a control or HFD (14% or 60% kcal from fat, respectively) from embryonic day 13; the fundus, corpus and duodenum were fixed thereafter at postnatal 2, 4, 6 and 12 weeks of age for subsequent immunohistochemical studies. While myenteric ganglion size did not differ throughout the study, HFD exposure decreased the number of nitrergic neurons by 6 weeks of age in all regions. This decrease was accompanied by a loss of PGP-immunoreactive neurons, suggesting a decline in myenteric neuronal number. HFD also increased myenteric plexus glial cell density in all regions by 4 weeks of age. These changes occurred in the absence of an increase in serum or gastric inflammatory markers. The present study suggests that exposure to a HFD during the perinatal time period results in glial proliferation and loss of inhibitory nitrergic neurons prior to the onset of obesity, suggesting that dietary alterations may affect gastrointestinal functions independently of increased adiposity or glycemic dysregulation.

In human brain ornithine transcarbamylase (OTC) immunoreactivity is strongly expressed in a small number of nitrergic neurons

There is recent evidence for ornithine transcarbamylase (OTC) expression in adult human brain. We decided to immunocytochemically map OTC throughout brain, and to further characterize OTC-immunopositive neurons. By using double immunolabeling technique for OTC and neuronal nitric oxide synthase (nNOS) OTC protein expression was revealed in a small subset of nitrergic (nNOS) neurons. Since citrulline (the reaction product of OTC) enhances the bioavailability of L-arginine, the substrate of nNOS, it is conceivable that OTC activity supports NO production in nitrergic neurons.

Nitrergic neurons of the dorsal raphe nucleus encode information about stress duration

Nitrergic neurons of the dorsal raphe nucleus (DRN) may play a role in physiological stress responses. The caudal lateral wings (CLW) are unique compared to other rostral-caudal DRN sub-regions because they contain distinct nitric oxide (NO) synthase (NOS) populations that are independent of tryptophan hydroxylase (TPH). NOS neurons in the CLW are also highly activated during acute restraint stress. However, the effects of acute stress duration on NOS activation in the CLW are unclear. Here NADPH-d, an index of NOS activity, is used to show that sub-regions of the DRN have differential NOS activation in response to 6 hours of restraint stress in rats. We report increased NOS activity through 6 hours of restraint in the caudal lateral wings and ventromedial sub-regions. These data suggest that, NOS neurons may play a dynamic role in the response to stress duration.

Bowel dysfunction following pullthrough surgery is associated with an overabundance of nitrergic neurons in Hirschsprung disease

PURPOSE

Recent evidence suggests that patients with Hirschsprung disease (HD) have abnormal neurotransmitter expression in the ganglionated proximal colon. These alterations may cause persistent bowel dysfunction even after pullthrough surgery. We sought to quantify the proportion of nitrergic neurons in the ganglionic colon of HD patients and relate these findings to functional outcome.

METHODS

The proximal resection margin from 17 patients with colonic HD who underwent a pullthrough procedure and colorectal tissue from 4 age-matched controls were immunohistochemically examined to quantify the proportion of nitrergic neurons. The incidence of constipation, incontinence, and enterocolitis in HD patients was assessed retrospectively and correlated with the proportion of nitric oxide synthase (NOS) expressing neurons. Neuronal subtypes in the ganglionic colon of the Edrnb^-/- mouse model of HD were also studied.

RESULTS

Mice with HD had a significantly higher proportion of NOS+ neurons in ganglionic colon than normal littermates (32.0±5.6% vs. 19.8±1.2%, p<0.01). Patients with HD also had significantly more NOS+ neurons than controls (18.4±4.6% vs. 13.1±1.9%, p<0.01). Patients who experienced constipation or enterocolitis postoperatively tended toward a higher proportion of NOS+ neurons (21.4±3.9% vs. 17.1±4.1%, p=0.06). Furthermore, patients with a proportion of NOS+ neurons above the median of all HD patients (18.3%) were significantly more likely to have constipation than those below the median (75% vs. 14%, p<0.05).

CONCLUSION

An overabundance of nitrergic neurons in the proximal resection margin is associated with HD and may predict bowel dysfunction following pullthrough surgery.

[INVOLVEMENT OF THE NITRERGIC SYSTEM OF THE PREFRONTAL CORTEX IN FEAR EXPRESSION INDUCED BY CONTEXTUAL SIGNALS OF DANGER]

In Sprague-Dawley rats by means of in vivo microdialysis, we have shown that presentation to rats a conditioned chamber in which a ton was previously paired with footshock (acquisition of a conditioned fear response to the tone) produces an increase in extracellular levels of citrulline (an NO co-product) in the medial prefrontal cortex and results in freezing response (fear index). This increase was not observed in control rats (same procedure, no footshock) and it was prevented by infusions into the medial prefrontal cortex of N®-propyl-L-arginine (1 mM), a neuronal NO synthase inhibitor. The infusion of 1mM N®-propyl-L-arginine into the medial prefrontal cortex reduced freezing to the conditioned chamber, but did not affect movement activity of the rats. Data obtained indicate that the nitrergic system of the medial prefrontal cortex implicates in regulation of fear expression produced by contextual signals of danger.

Distribution and trafficking of the μ-opioid receptor in enteric neurons of the guinea pig

The μ-opioid receptor (MOR) is a major regulator of gastrointestinal motility and secretion and mediates opiate-induced bowel dysfunction. Although MOR is of physiological and therapeutic importance to gut function, the cellular and subcellular distribution and regulation of MOR within the enteric nervous system are largely undefined. Herein, we defined the neurochemical coding of MOR-expressing neurons in the guinea pig gut and examined the effects of opioids on MOR trafficking and regulation. MOR expression was restricted to subsets of enteric neurons. In the stomach MOR was mainly localized to nitrergic neurons (∼88%), with some overlap with neuropeptide Y (NPY) and no expression by cholinergic neurons. These neurons are likely to have inhibitory motor and secretomotor functions. MOR was restricted to noncholinergic secretomotor neurons (VIP-positive) of the ileum and distal colon submucosal plexus. MOR was mainly detected in nitrergic neurons of the colon (nitric oxide synthase positive, 87%), with some overlap with choline acetyltransferase (ChAT). No expression of MOR by intrinsic sensory neurons was detected. [d-Ala(2), MePhe(4), Gly(ol)(5)]enkephalin (DAMGO), morphiceptin, and loperamide induced MOR endocytosis in myenteric neurons. After stimulation with DAMGO and morphiceptin, MOR recycled, whereas MOR was retained within endosomes following loperamide treatment. Herkinorin or the δ-opioid receptor agonist [d-Ala(2), d-Leu(5)]enkephalin (DADLE) did not evoke MOR endocytosis. In summary, we have identified the neurochemical coding of MOR-positive enteric neurons and have demonstrated differential trafficking of MOR in these neurons in response to established and putative MOR agonists.

Quantification of nitrergic neurons in the myenteric plexus of gastric antrum and ileum of healthy and diabetic dogs

Diabetes mellitus (DM) determines a wide array of severe clinical complications including gastrointestinal motility disorders. The present study investigates the effects of spontaneous DM on the intramural innervation and in particular on nitrergic neurons of the myenteric plexus (MP) of the canine gastric antrum and ileum. Specimens of antrum and ileum from eight control-dogs and five insulin-dependent DM-dogs were collected. MP neurons were immunohistochemically identified with the anti-HuC/HuD antibody, while nitrergic neurons were identified with the antibody anti-neuronal nitric oxide synthase (nNOS). The density of HuC/HuD-immunoreactive (IR) neurons was determined and the nitrergic neurons were quantified as a relative percentage, in consideration of the total number of HuC/HuD-IR neurons. Furthermore, the density of nitrergic fibers in the muscular layers was calculated. Data were expressed as mean±standard deviation. Compared to control-dogs, no significant differences resulted in the density of HuC/HuD-IR neurons in the antrum and ileum of DM-dogs; however, HuC/HuD-immunolabeling showed nuclear localization and fragmentation in DM-dogs. In the stomachs of control- and DM-dogs, the percentages of nitrergic neurons were 30±6% and 25±2%, respectively (P=0.112). In the ileum of the control-dogs, the percentage of nitrergic neurons was 29±5%, while in the DM-dogs, it was significantly reduced 19±5% (P=0.006). The density of nNOS-IR nervous fibers was meaningful reduced in either the tracts considered. Notably, the ganglia of DM-dogs showed also a thickening of the periganglionic connective tissue. These findings indicate that DM in dogs induce modification of the myenteric neurons and, in particular, of the nitrergic neuronal subpopulation.

Cytoarchitecture of nitrergic neurons in the human striatum and subthalamic nucleus

BACKGROUND

Nitric oxide (NO) is a gaseous molecule that modulates several physiological processes, including signal transmission in the central nervous system. There is evidence supporting NO as a major neurotransmitter involved in motor and emotion/behavior control. We investigated the distribution and morphology of nitrergic neurons in the two main input structures of the basal ganglia of human brain: the striatum and subthalamic nucleus.

METHODS

We studied samples of striatum (caudate and putamen) and subthalamic nucleus of 20 human brains from subjects without neurological/psychiatric diseases. The tissues were stained by histochemistry for nicotinamide adenine dinucleotide phosphate diaphorase activity and by immunohistochemistry for neuronal NO synthase (nNOS). Subsequently, we analyzed the nitrergic neuronal profile and its morphometric parameters.

RESULTS

Our data corroborate that approximately 2% of neurons in striatum express nNOS and these exhibited morphology characteristic of interneurons. Posterior regions of the striatum have a higher nitrergic neuronal profile than anterior regions of this nucleus suggesting an anteroposterior gradient of nitrergic neurons. Posterior limbic-associated areas of the striatum have a higher nitrergic neuronal profile compared to other functional subdivisions. Also, approximately 90% of neurons in the subthalamic nucleus express nNOS.

CONCLUSIONS

A remarkable presence of nitrergic neurons in the human striatum and subthalamic nucleus suggests that NO may play a critical role in the physiology of these nuclei.

Toxoplasma gondii causes death and plastic alteration in the jejunal myenteric plexus

AIM: To assess the effects of ME-49 Toxoplasma gondii (T. gondii) strain infection on the myenteric plexus and external muscle of the jejunum in rats.

METHODS: Thirty rats were distributed into two groups: the control group (CG) (n = 15) received 1 mL of saline solution orally, and the infected group (IG) (n = 15) inoculated with 1 mL of saline solution containing 500 oocysts of M-49 T. gondii strain orally. After 36 d of infection, the rats were euthanized. Infection with T. gondii was confirmed by blood samples collected from all rats at the beginning and end of the experiment. The jejunum of five animals was removed and submitted to routine histological processing (paraffin) for analysis of external muscle thickness. The remaining jejunum from the others animals was used to analyze the general population and the NADH-diaphorase, VIPergic and nitrergic subpopulations of myenteric neurons; and the enteric glial cells (S100-IR).

RESULTS: Serological analysis showed that animals from the IG were infected with the parasite. Hypertrophy affecting jejunal muscle thickness was observed in the IG rats (77.02 ± 42.71) in relation to the CG (51.40 ± 12.34), P < 0.05. In addition, 31.2% of the total number of myenteric neurons died (CG: 39839.3 ± 5362.3; IG: 26766.6 ± 2177.6; P < 0.05); hyperplasia of nitrergic myenteric neurons was observed (CG: 7959.0 ± 1290.4; IG: 10893.0 ± 1156.3; P < 0.05); general hypertrophy of the cell body in the remaining myenteric neurons was noted [CG: 232.5 (187.2-286.0); IG: 248.2 (204.4-293.0); P < 0.05]; hypertrophy of the smallest varicosities containing VIP neurotransmitter was seen (CG: 0.46 ± 0.10; IG: 0.80 ± 0.16; P < 0.05) and a reduction of 25.3% in enteric glia cells (CG: 12.64 ± 1.27; IG: 10.09 ± 2.10; P < 0.05) was observed in the infected rats.

CONCLUSION: It was concluded that infection with oocysts of ME-49 T. gondii strain caused quantitative and plastic alterations in the myenteric plexus of the jejunum in rats.

Diabetic neuropathy: an evaluation of the use of quercetin in the cecum of rats

AIM

To investigate the effect of quercetin supplementation on the myenteric neurons and glia in the cecum of diabetic rats.

METHODS

Total preparations of the muscular tunic were prepared from the ceca of twenty-four rats divided into the following groups: control (C), control supplemented with quercetin (200 mg/kg quercetin body weight) (CQ), diabetic (D) and diabetic supplemented with quercetin (DQ). Immunohistochemical double staining technique was performed with HuC/D (general population)/nitric oxide synthase (nNOS), HuC-D/S-100 and VIP. Density analysis of the general neuronal population HuC/D-IR, the nNOS-IR (nitrergic subpopulation) and the enteric glial cells (S-100) was performed, and the morphometry and the reduction in varicosity population (VIP-IR) in these populations were analyzed.

RESULTS

Diabetes promoted a significant reduction (25%) in the neuronal density of the HuC/D-IR (general population) and the nNOS-IR (nitrergic subpopulation) compared with the C group. Diabetes also significantly increased the areas of neurons, glial cells and VIP-IR varicosities. Supplementation with quercetin in the DQ group prevented neuronal loss in the general population and increased its area (P < 0.001) and the area of nitrergic subpopulation (P < 0.001), when compared to C group. Quercetin induced a VIP-IR and glial cells areas (P < 0.001) in DQ group when compared to C, CQ and D groups.

CONCLUSION

In diabetes, quercetin exhibited a neuroprotective effect by maintaining the density of the general neuronal population but did not affect the density of the nNOS subpopulation.

The stem bark extracts of Cenostigma macrophyllum attenuates tactile allodynia in streptozotocin-induced diabetic rats

CONTEXT. Cenostigma macrophyllum Tul. var. acuminata Teles Freire (Leguminosae- Caesalpinioideae) is popularly known as "caneleiro". Previous studies showed antioxidant action and analgesic effects of the ethanol extract from the leaves of C. macrophyllum. The phytochemical evaluation of the stem bark revealed the presence of antinociceptive compounds.

OBJECTIVE

To investigate the antinociceptive actions of the ethanol extract and ethyl acetate fraction from C. macrophyllum stem bark in streptozotocin (STZ)-induced diabetic rats and the involvement of opioid and nitrergic mechanisms.

MATERIALS AND METHODS

STZ-rats received the ethanol extract (E.EtOH 200 and 300 mg/kg, p.o.) during 5 weeks. In acute experiments, untreated diabetic rats were treated with the ethyl acetate fraction (F.EtOAc 250 and 500 mg/kg, p.o.), on the 28th day of diabetes induction when the opioid and nitrergic mechanisms were investigated. The mechanical nociceptive threshold (MNT) was determined by application of von Frey filaments.

RESULTS

Data show that STZ-induced diabetic rats developed a significant tactile allodynia during 5 weeks. Diabetic rats that received E.EtOH (200 and 300 mg/kg) and F.EtOAc (250 and 500 mg/kg) had a pain threshold higher than those in the STZ-vehicle group. F.EtOAc effects were inhibited by pretreatment with naloxone and were not influenced by .-arginine.

DISCUSSION AND CONCLUSION

The results suggest that the ethanol extract and ethyl acetate fraction of C. macrophyllum presented antinociceptive activity. Thus, F.EtOAc may be exerting its effect by affecting the opioid system, but nitrergic mechanisms are not detectable. The observed activity may be due to its gallic acid, lupeol and bergenin content.

Anticonvulsant, anxiolytic and hypnotic effects of aqueous bulb extract of Crinum glaucum A. chev (Amaryllidaceae): role of GABAergic and nitrergic systems

Crinum glaucum A. Chev (Amaryllidaceae) (CG) is a bulbous plant widely used in folk medicine in the treatment of cough, asthma and convulsions. This study was carried out to investigate the anticonvulsant, anxiolytic and hypnotic effects of the aqueous bulb extract of C. glaucum and its possible mechanism (s) of action. The anticonvulsant activity of C. glaucum extract (400-1200 mg kg(-1) p.o.) was investigated using picrotoxin, strychnine, isoniazid, pentylenetetrazol and N-methyl-D-aspartate (NMDA)-induced seizures in mice while the elevated plus maze test (EPM) and hexobarbitone-induced sleeping time (HIST) were used to evaluate the anxiolytic and hypnotic effects, respectively. Animals were pretreated with flumazenil (3 mg kg(-1); i.p. GABA(A) receptor antagonist), cyproheptadine (4 mg kg(-1); i.p. 5-HT2 receptor antagonist), L-arginine (500 mg kg(-1); p.o. Nitric Oxide (NO) precursor) and L-Nitroarginine (L-NNA) (10 mg kg(-1) i.p. Nitric Oxide Synthase (NOS) inhibitor) were used to investigate the probable mechanism (s) of anticonvulsant activity. Oral administration of CG significantly (p < 0.001) delayed the onset of seizures induced by picrotoxin, strychnine, isoniazid and pentylenetetrazol with peak effect at 1200 mg kg(-1) in comparison to control groups. CG (800 and 1200 mg kg(-1)) strongly antagonized NMDA-induced turning behavior. Pretreatment of mice with cyproheptadine could not reverse the anticonvulsant effect of CG. However, pretreatment with flumazenil and L-NNA significantly (p < 0.05) reversed the anticonvulsant effect of CG while L-arginine pretreatment significantly (p < 0.001) delayed the onset of seizures when compared with control and extract (1200 mg kg(-1) only). CG potentiated hexobarbitone-induced sleeping time with peak effect at 400 mg kg(-1) and also significantly (p < 0.05) increased open arm exploration in EPM and had its peak anxiolytic effect at 100 mg kg(-1). The data obtained suggests that aqueous bulb extract of Crinum glaucum possess anticonvulsant, anxiolytic and hypnotic activities which involve an interaction with GABAergic, nitrergic and glutaminergic systems to exert its effects.

The increasing burden of imported chronic hepatitis B--United States, 1974-2008

Mitochondrial dysfunction is a central mediator of disease progression in diverse neurodegenerative diseases that often present with prominent gastrointestinal abnormalities. Gastrointestinal dysfunction in these disorders is related, at least in part, to defects in the enteric nervous system (ENS). The role of mitochondrial deficits in ENS neurodegeneration and their relative contribution to gastrointestinal dysfunction, however, are unclear. To better understand how mitochondrial abnormalities in the ENS influence enteric neurodegeneration and affect intestinal function, we generated mice (Tfam-ENSKOs) with impaired mitochondrial metabolism in enteric neurons and glia through the targeted deletion of the mitochondrial transcription factor A gene (Tfam). Tfam-ENSKO mice were initially viable but, at an early age, they developed severe gastrointestinal motility problems characterized by intestinal pseudo-obstruction resulting in premature death. This gastrointestinal dysfunction was caused by extensive, progressive neurodegeneration of the ENS involving both neurons and glia. Interestingly, mitochondrial defects differentially affected specific subpopulations of enteric neurons and regions of the gastrointestinal tract. Mitochondrial deficiency-related neuronal and glial loss was most prominent in the proximal small intestine, but the first affected neurons, nitrergic inhibitory neurons, had the greatest losses in the distal small intestine. This regional and subtype-specific variability in susceptibility to mitochondrial defects resulted in an imbalance of inhibitory and excitatory neurons that likely accounts for the observed phenotype in Tfam-ENSKO mice. Mitochondrial dysfunction, therefore, is likely to be an important driving force of neurodegeneration in the ENS and contribute to gastrointestinal symptoms in people with neurodegenerative disorders.

Acetylene compound isolated from Atractylodes japonica stimulates the contractility of rat distal colon via inhibiting the nitrergic-purinergic relaxation

AIM OF THE STUDY

Our previous research has showed that rhizome of Atractylodes japonica Koidz (Compositae) exhibits an increase in the spontaneous contractility of distal colon in rats. The aims of this study are to identify the phytochemical(s), which stimulate(s) the colonic contractility, contained in Atractylodes japonica and to evaluate the pharmacological mechanism responsible for the colonic muscle contraction.

MATERIALS AND METHODS

Based on the stimulatory activity-guided fractionation on the isometric contraction of rat distal colonic strips, atractylodiol (ATD) and diacetyl-atractylodiol (DATD) were isolated from the CHCl(3) fractions of Atractylodes japonica.

RESULTS

ATD and DATD dose-dependently increased both tension and amplitude of distal colon longitudinal muscle (DCLM), but they stimulated only amplitude in the distal colon circular muscle. The ED(50) values of ATD and DATD to stimulate the amplitude of DCLM were revealed as 9.1×10(-9)M and 1.8×10(-8)M, respectively. l-NAME (0.1mM) significantly increased the ADT (1μM)-induced contraction of DCLM, whereas SNAP (0.1mM) markedly reduced the stimulatory effects of ATD on DCLM contractility. The combined effects of SNAP and atropine (0.5μM) on the ATD-induced contraction of DCLM were similar to the inhibitory effects of SNAP alone. Suramin (0.1mM) significantly enhanced the increase of ATD-induced DCLM contraction, whereas ADPβS (0.1mM) markedly abolished the stimulatory effects of ATD on the spontaneous contractility of DCLM.

CONCLUSIONS

The present results demonstrate that acetylene compounds, ATD and DATD, are the effective phytochemical of Atractylodes japonica to stimulate the motility of distal colon in rats, and ATD possibly enhances the spontaneous contractility of distal colon through inhibiting the mechanism of nitrergic-purinergic relaxation.

[Serotonin- and nitroxidergic neurons of rat medulla oblongata]

The purpose of the present work was topochemical mapping of serotonin- and nitroxidergic neurons in medulla oblongata of 12 Wistar rats in eight nuclei envolved in so-called "bulbar vasomotor to the center". It was found that a portion of serotoninergic neurons lying in a projection of the investigated nuclei, was equal, on the average, to 12-15%, and those in the nuclei of posterior raphe group increased up to 31-43%. Nitroxidergic neurons were distributed more uniformly, and their portion in different nuclei varied from 19 to 49%. 2-6% of neurons were located between the nuclei, and between the nuclei and conducting pathways; these cells presumably carry out integration functions in hemodynamics regulation.

Nitric oxide-mediated blood flow regulation as affected by smoking and nicotine

Cigarette smoking is a major risk factor for atherosclerosis, cerebral and coronary vascular diseases, hypertension, and diabetes mellitus. Chronic smoking impairs endothelial function by decreasing the formation of nitric oxide and increasing the degradation of nitric oxide via generation of oxygen free radicals. Nitric oxide liberated from efferent nitrergic nerves is also involved in vasodilatation, increased regional blood flow, and hypotension that are impaired through nitric oxide sequestering by smoking-induced factors. Influence of smoking on nitric oxide-induced blood flow regulation is not necessarily the same in all organs and tissues. However, human studies are limited mainly to the forearm blood flow measurement that assesses endothelial function under basal and stimulated conditions and also determination of penile tumescence and erection in response to endothelial and neuronal nitric oxide. Therefore, information about blood flow regulation in other organs, such as the brain and placenta, has been provided mainly from studies on experimental animals. Nicotine, a major constituent of cigarette smoke, acutely dilates cerebral arteries and arterioles through nitric oxide liberated from nitrergic neurons, but chronically interferes with endothelial function in various vasculatures, both being noted in studies on experimental animals. Cigarette smoke constituents other than nicotine also have some vascular actions. Not only active but also passive smoking is undoubtedly harmful for both the smokers themselves and their neighbors, who should bear in mind that they can face serious diseases in the future, which may result in lengthy hospitalization, and a shortened lifespan.

Effects of estrous cycle and xenoestrogens expositions on mice nitric oxide producing system

Nitric oxide (NO)-containing neurons are widely distributed within the central nervous system, including regions involved in the control of reproduction and sexual behavior. Nitrergic neurons may co-localize with gonadal hormone receptors and gonadal hormones may influence neuronal NO synthase expression in adulthood as well as during development. In rodents, the female, in physiological conditions, is exposed to short-term changes of gonadal hormones levels (estrous cycle). Our studies, performed in mouse hypothalamic and limbic systems, reveal that the expression of neuronal NO synthase may vary according to the rapid variations of hormonal levels that take place during the estrous cycle. This is in accordance with the hypothesis that gonadal hormone activation of NO-cGMP pathway is important for mating behavior. NO-producing system appears particularly sensitive to alterations of endocrine balance during development, as demonstrated by our experiments utilizing perinatal exposure to bisphenol A, an endocrine disrupting chemical. In fact, significant effects were detected in adulthood in the medial preoptic nucleus and in the ventromedial subdivision of the bed nucleus of the stria terminalis. Therefore, alteration of the neuronal NO synthase expression may be one of the causes of the important behavioral alterations observed in bisphenol-exposed animals.

Spatial pattern analysis of nitrergic neurons in the myenteric plexus of the duodenum of different mammalian species

Nitrergic myenteric neurons are especially susceptible to the development of neuropathy in functional gastrointestinal disorders. Investigations of the similarities and dissimilarities in the organization of nitrergic neurons in the various mammalian species are therefore important in an effort to determine the extent to which the results obtained in different animal models can be generalized. In the present work, the density and the spatial organization of the nitrergic neurons in the myenteric plexus of the duodenum were investigated in 7 mammalian species. After nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry, the Plexus Pattern Analysis software (PPAs) was applied to count the nuclei of nitrergic neurons, calculate the proportions of the areas covered by the plexus and perform randomization analysis. All 7 species exhibited a large population of nitrergic myenteric neurons, with densities in the range 12-56 cells/mm 2 . The distribution patterns of these neurons differed markedly in the different species, however, the rat was the only species in which the nitrergic neurons appeared to be randomly distributed. The PPAs in conjunction with NADPH-d histochemistry proved to be a simple and fast tool with which to reveal similarities and dissimilarities in the spatial arrangement of the nitrergic neurons in the different species.

The role of nitric oxide in the electrical field stimulation-induced contractions of sphincter of oddi and gallbladder strips in Guinea pigs

The aim of this study was to investigate the modulatory role of nitric oxide (NO) in the electrical field stimulation (EFS)-induced contractions of isolated sphincter of Oddi (SO) and gallbladder strips from guinea pigs. EFS was used to activate the intrinsic nerves in SO and gallbladder strips. EFS produced frequency-dependent biphasic contractile responses in the SO strips. A smaller contraction, "on response", occurred during EFS, which was followed by a bigger contraction, "off response". Both responses were completely and irreversibly abolished by tetrodotoxin (TTX) (10(-6) M). Atropine (10(-6) M) inhibited the "on response", but not the "off response". EFS produced frequency-dependent monophasic contractile responses in gallbladder strips, which were completely and irreversibly abolished by TTX (10(-6) M) and atropine (10(-6) M). A nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine (10(-4) M and 3 x 10(-4) M, in SO and gallbladder strips, respectively), significantly increased all EFS-induced contractions of SO and gallbladder strips. L-Arginine, but not D-arginine reversed the effect induced by the NOS inhibitor, at all frequencies, in both strips. These results suggested that NO released from nitrergic nerve endings might play a regulatory role in the cholinergic neurotransmission of guinea pig SO and gallbladder strips. The "off response" in he SO preparations might be a rebound increase that was modulated by the nonadrenergic, noncholinergic inhibitory mediator NO.

ORL-1 receptor mediates the action of nociceptin on ascending myenteric reflex pathways in rats

BACKGROUND AND AIMS

Nociceptin is the endogenous agonist of the "orphan" opioid receptor-1 (ORL-1). We investigated whether activation of the ORL-1 receptor influences smooth muscle contractility and enteric neurotransmission within ascending myenteric reflex pathways of rats.

METHODS

Reverse transcriptase polymerase chain reaction was performed to evaluate the presence of ORL-1 receptors. The ascending part of the ascending myenteric reflex in rats was studied in ileal segments using a 3-chambered organ bath. Intracellular recordings were performed to evaluate pharmacologic effects on excitatory and inhibitory junction potentials (EJP; IJP). Single- and double-labeling immunohistochemistry was used to examine the distribution of ORL-1 within the intestinal wall.

RESULTS

ORL-1 expression and immunoreactivity was found in the large majority of myenteric neurons. In addition to the cholinergic myenteric neurons, all nitrergic myenteric neurons expressed the ORL-1 receptor. Nociceptin significantly reduced cholinergic twitch contractions, an effect that was reversed by the ORL-1 receptor antagonist [Nphe(1)]nociceptin(1-13)NH(2). Neither nociceptin nor [Nphe(1)]nociceptin(1-13)NH(2) had a direct influence on smooth muscle contractility. Nociceptin significantly reduced ascending myenteric reflex contractions and prolonged the latency from stimulation to contraction. Both effects were antagonized by [Nphe(1)]nociceptin(1-13)NH(2). Intracellular recordings demonstrated that nociceptin reduces the cholinergically mediated EJP and the nitrergic phase of IJP in a concentration-dependent manner, effects that were reversible in presence of [Nphe(1)]nociceptin(1-13)NH(2).

CONCLUSIONS

We conclude that activation of ORL-1 receptors on myenteric neurons reduce excitatory and inhibitory neurotransmission within the gastrointestinal tract. This is accompanied by a reduction of the small intestinal peristaltic reflex response. These effects might be used pharmacologically.

Interaction between glutamatergic and nitrergic mechanisms mediating cardiovascular responses to l-glutamate injection in the diagonal band of Broca in anesthetized rats

In a previous study, we reported depressor and bradycardiac responses after L-glutamate (L-glu) microinjection into the diagonal band of Broca (dbB) in anesthetized rats. Here, we report the glutamatergic-receptor subtype mediating the cardiovascular effects evoked by L-glu injection into the dbB and the involvement of local nitric oxide (NO) mechanisms as well as peripheral effectors. Microinjections of 100 nL of L-glu (1, 27, 81, 130 or 200 nmol) into the dbB of urethane-anesthetized rats caused short-lasting depressor and bradycardiac responses. Responses were dose-related, with an ED(50) of approximately 81 nmol. This dose was used in later experiments. The cardiovascular responses to L-glu in the dbB were abolished by local pretreatment (100 nL) with the selective N-methyl-D-aspartic acid (NMDA) receptor antagonist LY235959 (4 nmol) but were not affected by pretreatment with the selective non-NMDA receptor antagonist NBQX (4 nmol). Responses to L-glu in the dbB were blocked by local pretreatment with the selective neuronal NO-synthase (nNOS) inhibitor N(omega)-propyl-L-arginine (NPLA, 0.04 nmol); the NO scavenger carboxy-PTIO (C-PTIO, 1 nmol) or the guanylate cyclase inhibitor ODQ (1 nmol). These results suggest that the microinjection of L-glu into the dbB of urethane-anesthetized rats causes dose-related depressor and bradycardiac responses through the NMDA receptor-NO-guanylate cyclase pathway.

Modulation of stress consequences by hippocampal monoaminergic, glutamatergic and nitrergic neurotransmitter systems

Several findings relate the hippocampal formation to the behavioural consequences of stress. It contains a high concentration of corticoid receptors and undergoes plastic modifications, including decreased neurogenesis and cellular remodelling, following stress exposure. Various major neurotransmitter systems in the hippocampus are involved in these effects. Serotonin (5-HT) seems to exert a protective role in the hippocampus and attenuates the behavioural consequences of stress by activating 5-HT1A receptors in this structure. These effects may mediate the therapeutic actions of several antidepressants. The role of noradrenaline is less clear and possibly depends on the specific hippocampal region (dorsal vs. ventral). The deleterious modifications induced in the hippocampus by stress might involve a decrease in neurotrophic factors such as brain derived neurotrophic factor (BDNF) following glutamate N-methyl-D-aspartate (NMDA) receptor activation. In addition to glutamate, nitric oxide (NO) could also be related to these effects. Systemic and intra-hippocampal administration of nitric oxide synthase (NOS) inhibitors attenuates stress-induced behavioural consequences. The challenge for the future will be to integrate results related to these different neurotransmitter systems in a unifying theory about the role of the hippocampus in mood regulation, depressive disorder and antidepressant effects.

Androgen and estrogen receptor-mediated mechanisms of testosterone action in male rat pelvic autonomic ganglia

Although male reproductive function is primarily androgen dependent, many studies suggest that estrogens have direct actions on the male reproductive organs. Pelvic autonomic neurons provide the motor control of the internal reproductive organs and the penis and various properties of these neurons are affected by endogenous androgens. However, the possible role of estrogens at this site has not been examined. Here we have investigated the significance of estrogens produced by aromatization of testosterone (T) in the physiological actions of androgens on adult male rat pelvic ganglion neurons. Reverse transcriptase polymerase chain reaction (RT-PCR) studies showed that aromatase and both estrogen receptors (ERalpha and ERbeta) are expressed in these ganglia. Western blotting also showed that aromatase is expressed in male pelvic ganglia. Using immunohistochemical visualization, ERalpha was predominantly expressed by nitric oxide synthase (NOS)-positive parasympathetic pelvic ganglion neurons. In vivo studies showed that the decrease in pelvic ganglion soma size caused by gonadectomy could be prevented by administration of T or dihydrotestosterone (DHT), but not 17beta-estradiol (E2), showing that this maintenance action of testosterone is mediated entirely by androgenic mechanisms. However, in vitro studies of cultured pelvic ganglion neurons revealed that T, DHT and E each stimulated the growth of longer and more complex neurites in both noradrenergic and cholinergic NOS-expressing neurons. The effects of T were attenuated by either androgen or estrogen receptor antagonists, or by inhibition of aromatase. Together these studies demonstrate that estrogens are likely to be synthesized in the male pelvic ganglia, produced from T by local aromatase. The effects of androgens on axonal growth are likely to be at least partly mediated by estrogenic mechanisms, which may be important for understanding disease-, aging- and injury-induced plasticity in this part of the nervous system.

Immunohistochemical localisation of cholinergic muscarinic receptor subtype 1 (M1r) in the guinea pig and human enteric nervous system

Little is known regarding the location of cholinergic muscarinic receptor 1 (M1r) in the ENS, even though physiological data suggest that M1rs are central to cholinergic neurotransmission. This study localised M1rs in the ENS of the guinea pig ileum and human colon using fluorescence immunohistochemistry and RT-PCR in human colon. Double labelling using antibodies against neurochemical markers was used to identify neuron subytpes bearing M1r. M1r immunoreactivity (IR) was present on neurons in the myenteric and submucosal ganglia. The two antibodies gave similar M1r-IR patterns and M1r-IR was abolished upon antibody preabsorption. M1r-IR was present on cholinergic and nNOS-IR nerve cell bodies in both guinea pig and human myenteric neurons. Presynaptic M1r-IR was present on NOS-IR and VAChT-IR nerve fibres in the circular muscle in the human colon. In the submucosal ganglia, M1r-IR was present on a population of neurons that contained cChAT-IR, but did not contain NPY-IR or calretinin-IR. M1r-IR was present on endothelial cells of blood vessels in the submucosal plexus. The localisation of M1r-IR in the guinea pig and human ENS shown in this study agrees with physiological studies. M1r-IR in cholinergic and nitrergic neurons and nerve fibres indicate that M1rs have a role in both cholinergic and nitrergic transmission. M1r-IR present in submucosal neurons suggests a role in mediating acetylcholine's effect on submucosal sensory and secretomotor/vasodilator neurons. M1r-IR present on blood vessel endothelial cells suggests that M1rs may also mediate acetylcholine's direct effect on vasoactivation.

Morphine leads to contraction of the ileal circular muscle via inhibition of the nitrergic pathway in mice

Morphine inhibits small intestinal transit in mice, although few mu-opioid receptors are present in the ileum. The present study focused on the action of morphine in the isolated mouse ileum to reveal the mechanism by which morphine inhibits mouse small intestinal transit. In the isolated circular muscle, morphine caused tonic contraction. This contraction was potently inhibited by naloxone and the mu-opioid receptor antagonist cyprodime. Moreover, the response was almost completely inhibited by tetrodotoxin and N(G)-nitro-L-arginine, but only moderately inhibited by atropine and indomethacin. In the isolated longitudinal muscle, morphine caused no or only slight contractions. Furthermore, electrically induced contraction was dose-dependently depressed by morphine, an effect that was not reversed by naloxone. These findings indicate that 1) morphine-induced circular muscle contraction occurs in the mouse ileum, 2) the contraction occurs through mu-opioid receptors mainly by inhibiting the release of nitric oxide from nitrergic nerves, although cholinergic nerves are at least partly involved in this contractile mechanism, and 3) inhibition of descending relaxation of peristalsis by morphine may slow small intestinal transit.

Pacemaker activity and inhibitory neurotransmission in the colon of Ws/Ws mutant rats

The aim of this study was to characterize the pacemaker activity and inhibitory neurotransmission in the colon of Ws/Ws mutant rats, which harbor a mutation in the c-kit gene that affects development of interstitial cells of Cajal (ICC). In Ws/Ws rats, the density of KIT-positive cells was markedly reduced. Wild-type, but not Ws/Ws, rats showed low- and high-frequency cyclic depolarization that were associated with highly regular myogenic motor patterns at the same frequencies. In Ws/Ws rats, irregular patterns of action potentials triggered irregular muscle contractions occurring within a bandwidth of 10-20 cycles/min. Spontaneous activity of nitrergic nerves caused sustained inhibition of muscle activity in both wild-type (+/+) and Ws/Ws rats. Electrical field stimulation of enteric nerves, after blockade of cholinergic and adrenergic activity, elicited inhibition of mechanical activity and biphasic inhibitory junction potentials both in wild-type and Ws/Ws rats. Apamin-sensitive, likely purinergic, inhibitory innervation was not affected by loss of ICC. Variable presence of nitrergic innervation likely reflects the presence of direct nitrergic innervation to smooth muscle cells as well as indirect innervation via ICC. In summary, loss of ICC markedly affects pacemaker and motor activities of the rat colon. Inhibitory innervation is largely maintained but nitrergic innervation is reduced possibly related to the loss of ICC-mediated relaxation.

Effect of nitroxyl on the hamster retinal nitridergic pathway

There is a growing body of evidence on the role of nitric oxide (NO) in retinal physiology. Recently, interest has developed in the functional role of an alternative redox form of NO, namely nitroxyl (HNO/NO(-)), because it is formed by a number of diverse biochemical reactions. The aim of the present report was to comparatively analyze the effect of HNO and NO on the retinal nitridergic pathway in the golden hamster. For this purpose, sodium trioxodinitrate (Angeli's salt) and diethylammonium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA/NO) were used as HNO and NO releasers, respectively. Angeli's salt and DEA/NO significantly decreased nitric oxide synthase activity. In addition, Angeli's salt (but not DEA/NO) significantly decreased l-arginine uptake. DEA/NO significantly increased cGMP accumulation at low micromolar concentrations, while Angeli's salt affected this parameter with a threshold concentration of 200muM. Although Angeli's salt and DEA/NO significantly diminished reduced glutathione and protein thiol levels in a similar way, DEA/NO was significantly more effective than AS in increasing S-nitrosothiol levels. None of these compounds increased retinal lipid peroxidation. These results suggest that HNO could regulate the hamster retinal nitridergic pathway by acting through a mechanism that only partly overlaps with that involved in NO response.

Unique distribution of interstitial cells of Cajal in the feline pylorus

The feline gastrointestinal (GI) tract is an important model for GI physiology but no immunohistochemical assessment of interstitial cells of Cajal (ICC) has been performed because of the lack of suitable antibodies. The aim of the present study was to investigate the various types of ICC and associated nerve structures in the pyloric sphincter region, by using immunohistochemistry and electron microscopy to complement functional studies. In the sphincter, ICC associated with Auerbach's plexus (ICC-AP) were markedly decreased within a region of 6-8 mm in length, thereby forming an interruption in this network of ICC-AP, which is otherwise continuous from corpus to distal ileum. In contrast, intramuscular ICC (ICC-IM) were abundant within the pylorus, especially at the inner edge of the circular muscle adjacent to the submucosa. Similar distribution patterns of nerves positive for vesicular acetylcholine transporter (VAChT), nitric oxide synthase (NOS) and substance P (SP) were encountered. Quantification showed a significantly higher number of ICC-IM and the various types of nerves in the pylorus compared with the circular muscle layers in the adjacent antrum and duodenum. Electron-microscopic studies demonstrated that ICC-IM were closely associated with enteric nerves through synapse-like junctions and with smooth muscle cells through gap junctions. Thus, for the first time, immunohistochemical studies have been successful in documenting the unique distribution of ICC in the feline pylorus. A lack of ICC-AP guarantees the distinct properties of antral and duodenal pacemaker activities. ICC-IM are associated with enteric nerves, which are concentrated in the inner portion of the circular muscle layer, being part of a unique innervation pattern of the sphincter.

Postnatal androgen deprivation dissociates the development of smooth muscle innervation from functional neurotransmission in mouse vas deferens

The pelvic autonomic nervous system is a target for circulating androgens in adults, with androgen exposure or deprivation affecting the structure and function of urogenital tract innervation. However, the critical period for androgen exposure to initially establish pelvic autonomic neuromuscular transmission has not been determined. We have examined the sympathetic innervation of the vas deferens in hypogonadal (hpg) mice that are deprived of androgens after birth but undergo normal prenatal sexual differentiation and remain androgen responsive throughout life. In vasa deferentia from hpg mice, purinergic excitatory junction potentials and contractions could not be elicited by electrical stimulation and P2X(1) purinoceptors could not be demonstrated by immunofluorescence. Moreover, a novel inhibitory nitrergic transmission developed. Administering testosterone to adult hpg mice restored purinergic excitatory transmission and P2X(1) purinoceptor immunofluorescence, and nitrergic inhibitory transmission was lost. Despite the deficit in excitatory neurotransmission in hpg mice, their vasa deferentia were innervated by numerous noradrenergic axons and pelvic ganglia appeared normal. In addition, noradrenergic contractions could be elicited by electrical stimulation. This study has revealed that postnatal androgen exposure has a profound effect on the development of excitatory transmission in vas deferens smooth muscle, primarily by a postjunctional action, but is not essential for development of the structural innervation of this organ. Our results also indicate that there is no postnatal critical period for androgen exposure to establish neuroeffector transmission and that postnatal androgen exposure can be delayed until adulthood, with little consequence for establishment of normal sympathetic neurotransmission.

Nitric oxide-mediated nonadrenergic noncholinergic relaxation of piglet pulmonary arteries decreases with postnatal age

Nonadrenergic noncholinergic (NANC) vasodilator mechanisms may contribute to the maintenance of adult pulmonary and systemic vascular tone. However, their actions in the neonatal circulation have not been studied. We aimed to investigate NANC vasorelaxation in neonatal and 2-week-old piglet pulmonary and mesenteric arteries and to examine the potential role of nitric oxide (NO) in this phenomenon. Responses to electric field stimulation (EFS, 50V, 0.25-32 Hz) were investigated in pulmonary and mesenteric artery rings (external diameter 150-200 microm) precontracted with the thromboxane A2 mimetic U46619, in the presence of guanethidine (10 microM) and atropine (10 microM). Under these conditions, EFS resulted in a frequency dependent relaxation of newborn pulmonary (maximal relaxation of 53+/-9.1%), mesenteric (68.8.2+/-7.1%) and 2-wk-old mesenteric (46 6.3%) arteries but this relaxation was significantly reduced (4.5+/-2.2%) in 2-week-old pulmonary arteries. In neonatal pulmonary arteries, the neurotoxin tetrodotoxin (0.3 muM), the NO synthase inhibitor L-NAME (0.1 mM), and the guanylyl cyclase inhibitor ODQ (10 microM) abolished EFS-induced relaxations, suggesting that NANC relaxation of porcine neonatal pulmonary arteries is mediated by NO, which is probably neuronal in origin. However, The expression in pulmonary arteries of the neuronal NO synthase (nNOS), as determined by Western-blot analysis, increased with postnatal age whereas the expression of the endothelial NOS (eNOS) did not change. In conclusion, NANC relaxation is present in neonatal pulmonary and mesenteric arteries and it is, at least partially, mediated through NO. NANC relaxation of porcine pulmonary and mesenteric arteries decreases with postnatal maturation.

Relationships between neurons expressing neuronal nitric oxide synthase, degree of microglia activation and animal survival. A study in the rat cortex after transient ischemia

The focal ischemia obtained in an animal model of middle cerebral artery occlusion (MCAo) causes the "core" of damage in the striatum and the "penumbra" of damage in the fronto-parietal cortex. The latter is mainly functionally affected and shows changes in nNOS and iNOS expression during the acute phase of ischemia. With the aim to study possible relationships between these changes and the affection entity during the animal recovery, we investigated from 24 up to 144 h after reperfusion the expression and content of these two NOS isoforms in the neurons and microglia and the degree of microglia reactivity in the fronto-parietal cortices of rats undertaken to transient MCAo. Evaluation of motor-sensory performances and survival allowed dividing the animals into two groups. Immunohistochemistry, western blot and quantitative analysis demonstrated, both in the ischemic and contralateral cortex of the rats with longer survival, wellness and significantly increased number of the nNOS-IR neurons at 24 h and moderately activated microglia up to 144 h. In the rats not recovering, injured and significantly decreased nNOS-IR neurons, intensely activated microglia and appearance of iNOS-IR were seen at all time points. In conclusion, since the recovery occurs when nNOS-IR neurons are greatly increased, we presume nNOS protect the tissue likely controlling the passage from the state of reactive to that of activated microglia. Moreover, the morphological signs of wellness and the two-fold increase in number of the nNOS-IR neurons appear to be characteristic of the "penumbra" area and could explain why this region is mainly functionally affected.

The effect of age on colocalization of acetylcholinesterase and nicotinamide adenine dinucleotide phosphate diaphorase staining in enteric neurons in an experimental model

PURPOSE

Cholinergic and nitrergic neurons form 2 main subpopulations of the myenteric neurons, and they have been the targets of detailed morphological investigations in bowel motility disorders. However, little is known regarding the colocalization of neurotransmitters within the same enteric neurons. The aim of this study was to determine the histochemical colocalization of cholinergic and nitrergic neurons in the porcine distal large bowel myenteric plexus from fetal to adulthood.

METHODS

Distal large bowel specimens were taken from 6 randomly selected age groups (3 animals in each group) from midway of gestation to adulthood. The myenteric plexus was exposed using whole-mount technique. After nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) staining, cells per ganglion were counted. Then the specimens were stained with acetylcholinesterase (AChE), and the cells that were stained with individual enzymes and with both enzymes were counted.

RESULTS

Colocalization of AChE and NADPH-d was seen in all age groups, and it was highest during the mid part of gestation (30%) and decreased steadily thereafter into adulthood (8%). The individual number of NADPH-d- and AChE-positive neurons per ganglion remained constant till 4 weeks of age and significantly increased thereafter into adulthood.

CONCLUSION

The use of double-labeling histochemical technique shows for the first time the colocalization of cholinergic and nitrergic activity in a large population of enteric neurons in the late fetal and newborn period. Age-related loss of cholinergic and nitrergic colocalization in the myenteric plexus is most likely a maturational process.

Nitrergic modulation of gastrointestinal function during early endotoxemia

After bacterial infection, the host reacts by signalling to the central nervous system where a cascade of physiologic, neuroendocrine and behavioural processes is orchestrated, collectively termed the acute phase response. Endotoxemia following Gram-negative bacterial infection induces a wide array of effects, including fever, loss of appetite and changes in gastrointestinal function that attempt to eliminate the challenge and restore homeostasis. Systemic administration of low doses of endotoxin (5-40 microg/kg) to rats is associated with changes in gastrointestinal motor function, inhibition of gastric acid secretion and increase in the gastric mucosal resistance to damage. These changes are rapid in onset (observed within one hour), not related to vascular dysfunction, and appear to be mediated by mechanisms that involve the peripheral and the central nervous system. Nitric oxide (NO) plays a central role in the physiology of the gastrointestinal tract and its response to illness. Accumulated evidence supports an increase of NO synthesis in the brainstem, as well as in the gastric myenteric plexus thirty minutes after endotoxin administration. Such a synthesis is due to constitutive nitric oxide synthase (NOS) and occurs before the induction of NOS takes place. In this review we provide experimental evidence supporting the hypothesis that activation of a physiologic mechanism, mediated by the autonomic and the central nervous systems as well as constitutive NOS isoforms, is involved in acute changes of gastrointestinal function during early endotoxemia.

Cholinesterase inhibitor blockade and its prevention by statins of sympathetic alpha7-nAChR-mediated cerebral nitrergic neurogenic vasodilation

Cholinesterase inhibitors (ChEIs) have been used to treat Alzheimer's disease (AD). The efficacy of these drugs, however, is less than satisfactory. The possibility that ChEIs may have effects unrelated to ChE activity, such as negatively modulate neuronal nicotinic acetylcholine receptors (nAChRs) was evaluated. Since alpha7-nAChRs on cerebral perivascular sympathetic neurons mediate cerebral parasympathetic-nitrergic vasodilation, effects of physostigmine, neostigmine, and galantamine on alpha7-nAChR-mediated dilation in isolated porcine basilar arterial rings denuded of endothelium was examined using in vitro tissue bath technique. The results indicated that these ChEIs blocked vasodilation induced by choline (0.3 mmol/L), nicotine (0.1 mmol/L), and transmural nerve stimulation (TNS). The ChEI inhibition of dilation induced by TNS but not by choline or nicotine was prevented by atropine (0.1 micromol/L) pretreatment. Furthermore, using confocal microscopy, significant calcium influx induced by choline and nicotine in cultured porcine superior cervical ganglion (SCG) cells was attenuated by ChEIs. In alpha7-nAChR-expressed Xenopus oocytes, nicotine-induced inward currents were attenuated by alpha-bungarotoxin and ChEIs. Moreover, ChEI inhibition of nicotine- and choline-induced dilation was prevented by pretreatment with mevastatin and lovastatin (10 micromol/L), which did not affect ChEI inhibition of TNS-induced relaxation. These findings suggest that ChEIs inhibit the alpha7-nAChRs located on postganglionic sympathetic nerve terminals of SCG origin, causing a decreased release of nitric oxide in the neighboring nitrergic nerves and cerebral vasodilation. Inhibition of alpha7-nAChRs leading to a potential cerebral hypoperfusion may contribute to the limitation of ChEIs and question the validity of using a ChEI alone in treating AD. The efficacy of ChEIs may be improved by concurrent use of statins.

Nitric oxide synthase-containing neurons in the amygdaloid nuclear complex of the rat

The nitric oxide-producing neurons in the rat amygdala (Am) were studied, using reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry. Almost all nuclei of the Am contained NADPHd-positive neurons and fibers, but the somatodendritic morphology and the intensity of staining of different subpopulations varied. The strongly stained neurons displayed labeling of the perikaryon and the dendritic tree with Golgi impregnation-like quality, whilst the dendrites of the lightly stained neurons were less successfully followed. Many strongly positive neurons were located in the external capsule and within the intraamygdaloid fiber bundles. A large number of small, strongly stained cells was present in the amygdalostriatal transition area. In the Am proper, a condensation of deeply stained cells occurred in the lateral amygdaloid nucleus. In the basolateral nucleus, the strongly NADPHd-positive neurons were few, and were located mainly along the lateral border of the nucleus. These cells clearly differed from the large, pyramidal, and efferent cells. The basomedial nucleus contained numerous positive cells but most of them were only lightly labeled. A moderate number of strongly stained neurons appeared in the medial division of the central nucleus, and a larger accumulation of strongly positive cells was present in the lateral and the capsular divisions. The medial amygdaloid nucleus contained numerous moderately stained neurons and displayed the strongest diffuse neuropil staining in Am. In the nucleus of the lateral olfactory tract, the first layer contained only NADPHd-stained axons, in the second layer, there were numerous moderately stained cells, and in the third layer, a few but deeply stained neurons. From the cortical nuclei, the most appreciable number of stained neurons was seen in the anterior cortical nucleus. The anterior amygdaloid area contained numerous NADPHd-positive neurons; in its dorsal part the majority of cells were only moderately stained, whereas in the ventral part the neurons were very strongly stained. The intercalated amygdaloid nucleus lacked NADPHd-positive neurons but an appreciable plexus of fine, tortuous axons was present. In the intra-amygdaloid part of the bed nucleus of the stria terminalis (st) some lightly stained cells were seen but along the entire course of st strongly stained neurons were observed. Some Am nuclei, and especially the central lateral nucleus and the intercalated nucleus, display considerable species differences when compared with the primate Am. The age-related changes of the nitrergic Am neurons, as well as their involvement in neurodegenerative diseases is discussed.

Acute restraint increases NADPH-diaphorase staining in distinct subregions of the rat dorsal raphe nucleus: implications for raphe serotonergic and nitrergic transmission

The brainstem dorsal raphe nucleus (DRN) maintains a rough topographic cell ordering with respect to biological function. This study examined the influence of acute restraint on nitric oxide (NO) synthase (NOS) neurons in distinct DRN subregions. NADPH diaphorase staining (NOS index) intensity was higher in the DRN dorsomedial, ventromedial and lateral wings subregions of restrained vs. control rats. The mean number of cells was not significantly different between both groups of animals. The restrained-induced NADPH-diaphorase activity was significantly higher in the rostral ventromedial and caudal lateral wings than the corresponding caudal and rostral subregions but no significant difference was observed between rostral and caudal dorsomedial subregions. These observations suggest that restraint stress differentially activates NO-producing neurons in distinct DRN subregions.

Alteration of nitrergic neuromuscular transmission as a result of acute experimental colitis in rat

Nitric oxide (NO) is a non-adrenergic, non-cholinergic neurotransmitter found in the enteric nervous system that plays a role in a variety of enteropathies, including inflammatory bowel disease. Alteration of nitrergic neurons has been reported to be dependent on the manner by which inflammation is caused. However, this observed alteration has not been reported with acetic acid-induced colitis. Therefore, the purpose of the current study was to investigate changes in nitrergic neuromuscular transmission in experimental colitis in a rat model. Distal colitis was induced by intracolonic administration of 4 % acetic acid in the rat. Animals were sacrificed at 4 h and 48 h postacetic acid treatment. Myeloperoxidase activity was significantly increased in the acetic acid-treated groups. However, the response to 60 mM KCl was not significantly different in the three groups studied. The amplitude of phasic contractions was increased by Nomega-nitro-L-arginine methyl ester (L-NAME) in the normal control group, but not in the acetic acid-treated groups. Spontaneous contractions disappeared during electrical field stimulation (EFS) in normal group. However, for the colitis groups, these contractions initially disappeared, and then reappeared during EFS. Moreover, the observed disappearance was diminished by L-NAME; this suggests that these responses were NO-mediated. In addition, the number of NADPH-diaphorase positive nerve cell bodies, in the myenteric plexus, was not altered in the distal colon; whereas the area of NADPH-diaphorase positive fibers, in the circular muscle layer, was decreased in the acetic acidtreated groups. These results suggest that NO-mediated inhibitory neural input, to the circular muscle, was decreased in the acetic acid-treated groups.

Intramuscular interstitial cells of Cajal associated with mast cells survive nitrergic nerves in achalasia

Achalasia is dominated by injury to inhibitory nerves. As intramuscular interstitial cells of Cajal (ICC-IM) are proposed to form functional units with nitrergic nerves, their fate in achalasia may be critically important. We studied the relationship between loss of nitrergic nerves and injury to ICC-IM in patients with achalasia and determined associations between ICC-IM and mast cells (MC), using quantitative immunohistochemistry and electron microscopy. Loss of neuronal nitric oxide synthase (nNOS) immunoreactivity was completed within 3 years of acquiring achalasia. Thereafter, progressive ultrastructural injury to remaining nerve structures was evident. Within the first 2 years, the number of ICC-IM did not decline although ultrastructural injury was already present. Thereafter, loss of ICC-IM occurred unrelated to duration of disease. Damage to ICC-IM appeared unrelated to nerve injury. A significant MC infiltration was observed in the musculature; the number of MC was positively related to the persistent number of ICC-IM. Mast cell formed close contacts with ICC-IM and piecemeal-degranulation occurred towards ICC-IM. In conclusion, injury to ICC-IM in achalasia is variable, but not related to duration of disease and injury to nitrergic nerves. MC are prominent and form close functional contact with ICC-IM which may be responsible for their relatively long survival.

Neurochemically defined cell columns in the nucleus prepositus hypoglossi of the cat and monkey

Many studies have shown that the nucleus prepositus hypoglossi (PH) participates with the vestibular nuclear complex, the cerebellum and the oculomotor nuclei in the control of eye movements. We have looked at the neurochemical organization of PH in the cat and monkey using a recently developed antibody, 8B3, that recognizes a chondroitin sulfate proteoglycan. In the cat, immunoreactivity to 8B3 labels a set of cells in PH. On frontal sections, these cells form a cluster that is seen over the entire anterior-posterior (A-P) extent of PH, but the number of cells in the cluster changes with A-P level. Earlier studies have identified an A-P cell column in PH of the cat whose neurons synthesize nitric oxide. We have used both single- and double-label protocols to investigate the relation between the two cell groups. Single-label studies show spatial overlap but that the cells immunoreactive to nitric oxide synthase (nNOS) are more numerous than cells immunoreactive to 8B3. Double-label studies show that all cells immunoreactive to 8B3 were also immunoreactive to nNOS, but, as suggested by the single-label data, there are many nNOS-immunoreactive cells not immunoreactive to 8B3. Populations of 8B3 and nNOS-immunoreactive cells are also found in PH of squirrel and macaque monkeys. The results suggest that nNOS-immunoreactive cells in PH may consist of two functionally different populations.

Localization of putative nitrergic neurons in peripheral chemosensory areas and the central nervous system of Aplysia californica

The distribution of putative nitric oxide synthase (NOS)-containing cells in the opisthobranch mollusc Aplysia californica was studied by using NADPH-diaphorase (NADPH-d) histochemistry in the CNS and peripheral organs. Chemosensory areas (the mouth area, rhinophores, and tentacles) express the most intense staining, primarily in the form of peripheral highly packed neuropil regions with a glomerular appearance as well as in epithelial sensory-like cells. These epithelial NADPH-d-reactive cells were small and had multiple apical ciliated processes exposed to the environment. NADPH-d processes were also found in the salivary glands, but there was no or very little staining in the buccal mass and foot musculature. In the CNS, most NADPH-d reactivity was associated with the neuropil of the cerebral ganglia, with the highest density of glomeruli-like NADPH-d-reactive neurites in the areas of the termini and around F and C clusters. A few NADPH-d-reactive neurons were also found in other central ganglia, including paired neurons in the buccal, pedal, and pleural ganglia and a few asymmetrical neurons in the abdominal ganglion. The distribution patterns of NADPH-d-reactive neurons did not overlap with other known neurotransmitter systems. The highly selective NADPH-d labeling revealed here suggests the presence of NOS in sensory areas both in the CNS and the peripheral organs of Aplysia and implies a role for NO as a modulator of chemosensory processing.

Calbindin is predominantly expressed in nitrergic neurons in rat esophagus

We used immunohistochemistry to investigate the colocalization pattern of calbindin D28k (Calb) with nitric oxide and acetylcholine in myenteric neurons in the rat esophagus and compared it to that in the ileum or distal colon. The proportion of Calb-immunoreactive (IR) neurons to the total neurons in the esophagus (8%) was lower than that in the ileum (38%) or distal colon (27%). A majority (84%) of the esophageal Calb-IR neurons were uniaxonal neurons. On the other hand, 88% and 66% of Calb-IR neurons in the ileum and distal colon, respectively, had Dogiel type II morphology, while most of the others were Dogiel type I neurons. Double immunolabeling indicated that most (87%) of the esophageal Calb-IR neurons were nitric oxide synthase (NOS) positive and a minority (21%) were choline acetyltransferase (ChAT) positive. Most (93% and 89%, respectively) of the Calb-IR neurons in the ileum and distal colon showed ChAT immunoreactivity and only a small number exhibited NOS immunoreactivity in the ileum and distal colon. In the esophagus, some of Calb-IR nerve endings surrounding the myenteric neurons were NOS positive, but no Calb immunoreactivity was found on the motor endplates of the striated muscles. Therefore, the present study revealed that most of the Calb-IR neurons in the esophagus are nitrergic, and it suggested that the Calb-IR neurons might be primarily involved in interneuronal roles in the esophageal nervous system.

Modelling release of nitric oxide in a slice of rat's brain: describing stimulated functional hyperemia with diffusion-reaction equations

The physicochemical process of nitric oxide (NO degrees ) release from an active neuron is modelled based on the results obtained experimentally in independent series of experiments reported elsewhere in which the NO degrees release elicited by patch-clamping a single neuron (stellate neuron from cerebellum area) is monitored by an ultramicroelectrode introduced into a slice of living rat's brain. This process is believed to be central to brain behaviour by coupling neuronal activity with the blood supply to active areas of the living brain through precise control of NO degrees -mediated dilatation of blood capillary vessels. This work, based on the conformal mapping approach initially proposed in a previous work, aims to model the overall physicochemical and diffusional processes giving rise to the release of NO degrees by a neuron and during its collection at an electrode sensor. Fitting simulated currents to experimental ones published previously yields indeed the gross kinetic information which represents the overall neuron activation and defines the instant value of the concentration of NO degrees at the neuron surface. This allows reconstructing the NO degrees fluxes around the neuron body as they would have been in the absence of the electrode sensor. This permits one to appreciate how far NO degrees is released by the neuron at concentrations which greatly exceed their basal values. The success of this procedure is exemplified using a set of three experimental data reported elsewhere.

Kainic acid and nitrergic neurons in immature hippocampus

Using histochemical analysis the effect of intraperitoneal administration of kainic acid on hippocampal neurons was studied. 18-day-old male rats of the Wistar strain received kainic acid (10mg/kg) in one dose. Two days later, the 20-day-old animals were transcardially perfused with 4% paraformaldehyde under deep thiopental anaesthesia. Cryostat sections were stained to identify NADPH-diaphorase positive neurons that were then quantified in the CA1 and CA3 areas of the hippocampus, in the dorsal and ventral blades of the dentate gyrus and in the hilus of the dentate gyrus. Combination of the Fluoro-Jade B and bis-benzimide (Hoechst 33342) was used in the same areas, to identify possible neurodegeneration. After the kainic acid administration the number of NADPH-d positive neurons was lower in CA1 and CA3 areas of the hippocampus and in the hilus of the dentate gyrus, compared to the control group which we consider as baseline. Fluoro-Jade B staining detected a moderate density of neurodegeneration after KA administration in CA3 and CA1 areas of the hippocampus and the hilus of the dentate gyrus.

Memory consolidation of Pavlovian fear conditioning requires nitric oxide signaling in the lateral amygdala

Nitric oxide (NO) has been widely implicated in synaptic plasticity and memory formation. In studies of long-term potentiation (LTP), NO is thought to serve as a 'retrograde messenger' that contributes to presynaptic aspects of LTP expression. In this study, we examined the role of NO signaling in Pavlovian fear conditioning. We first show that neuronal nitric oxide synthase is localized in the lateral nucleus of the amygdala (LA), a critical site of plasticity in fear conditioning. We next show that NO signaling is required for LTP at thalamic inputs to the LA and for the long-term consolidation of auditory fear conditioning. Collectively, the findings suggest that NO signaling is an important component of memory formation of auditory fear conditioning, possibly as a retrograde signal that participates in presynaptic aspects of plasticity in the LA.