Prostaglandin-targeting agents and spectral heart rate variability in experimental partial bladder outlet obstruction in rats.

The purpose of this study was to determine the activity of the autonomic nervous system (ANS), using spectral analysis of the heart rate variability (HRV) in the model of partial bladder outlet obstruction (PBOO) in rats treated with selected non-steroidal anti-inflammatory drugs (NSAID): piroxicam (PRX) or meloxicam (MLX), and following administration of PGF2a prostaglandin analogue (Enzaprost F5). Neither the use of PGF2a analogue nor of MLX, caused significant changes in the HRV spectrum (except for HRV spectrum total power reduction with MLX). The use of PRX caused reduction of the total power and powers of all components of the HRV spectrum (except for VLF). Moreover, increased nLF and reduced nHF were observed. The obtained results suggest that the total prostaglandin synthesis block with a non-selective cyclooxygenase inhibitor (PRX) results in reduced ANS total activity, with decreased parasympathetic activity and a relative sympathetic predominance. The preferential cyclooxygenase-2 block (MLX) caused reduction of the total ANS activity as well, however with no clear disproportion of any part of the ANS. Therefore, prostaglandin synthesis inhibition and associated decrease of parasympathetic activity may constitute an additional and favourable feature of NSAID pharmacodynamics in the treatment of BPH.

Exogenous melatonin abolishes mechanical allodynia but not thermal hyperalgesia in neuropathic pain. The role of the opioid system and benzodiazepine-gabaergic mechanism.

Melatonin (MT) is a neurohormone synthesized and secreted by the pineal gland. MT plays an important role in the regulation of physiological and neuroendocrine functions. The purpose of this study was to assess the overall effect of melatonin on neuropathic pain, the type of melatonin receptor involved, and potential role of the opioid system and GABA(A) receptors. The experiments were conducted by using the animal neuropathic pain model (CCI). The rats with CCI showed the characteristic for the mechanical allodynia and thermal hyperalgesia signs that were calculated by using the von Frey's and Hargreaves' tests. The conducted studies measured the effects of intraperitoneal administration of naloxone (opioid antagonist), prazosin (MT3 antagonist), luzindole (MT1/MT2 receptor antagonist), picrotoxin (GABA(A) antagonist) and flumazenil (benzodiazepine antagonist) on the antinociceptive effects caused by melatonin. Melatonin caused the increase in the pain threshold of the mechanical allodynia and the slight increase in the threshold of the thermal hyperalgesia. The pre-treatment with naloxone completely abolished the antinociceptive effects of melatonin in von Frey's test, but not thermal sensation in the Hargreaves's test. Prazosin did not have any effects, while administration of luzindole significantly suppressed the antinociceptive effect of melatonin. The antiallodynic effect of MT was also abolished by flumazenil and picrotoxin. Melatonin influences the mechanical allodynia but not thermal hyperalgesia via activation of opioid system and benzodiazepine-GABAergic pathway. Antinociceptive effects of melatonin are mostly related to the MT1/MT2 receptors interaction.

The role of sensory C-fibers in response of vagal afferent stimulation by gastric distension in rats with experimental chronic gastric ulcer.

There is growing evidence that gastric vagal afferent input may contribute to the altered sensations associated with gastrointestinal disorders. The aim of our study was to evaluate gastric vagal afferents (VA) activity in rats with experimental gastric ulcer and ulcer healing. The study was carried out on rats with gastric ulcer (GU), including, a group with perivagal capsaicin pretreatment (CAP), a group with capsaicin administration in gastric ulcer (CAP+GU) animals and control rats. In all rats electrical VA activity was recorded and analysed. In GU rats recordings were carried out in chronic ulcer and ulcer healing. In GU and CAP+GU groups gastric balloon distensions with vagal recording was performed on 3(rd) day after ulcer induction. Usually, experimental GU healed spontaneously within 2 weeks. Three days after acetic acid application when GU fully develop, the frequency of the basal VA activity was almost 3-times higher than in the control intact rats and remained elevayed until 4(th) week after ulcer induction. VA response to gastric distension increased concomitantly with increased balloon volume in both GU and control animals, but it was several times higher in GU rats. Perivagal capsaicin application decreased the frequency of spontaneous VA activity and decreased the response of VA to gastric distension. In CAP+GU, spontaneous activity as well as the response to gastric distension were higher than in CAP rats. Our study shows that GU induced inflammatory changes increase sensitivity of gastric VA. Capsaicin-sensitive vagal afferent fibers may play some role in this phenomenon. Peripheral sensitization of VA persists even when gastric ulcer is completely healed.

The vagal afferents discharge and myoelectrical activity in the gastric hyperalgesia model in rats.

A long term exposure of the gastric mucosa to inflammatory factors is suspected to alter the normal stomach motility. The consequence of it is an abnormal sensomotor response to food causing dyspeptic symptoms. Our study aimed to investigate the vagal afferents activity and the gastro-duodenal slow wave response to the mild gastric mucosa inflammation in rats. The gastric mucosal inflammation was induced by addition iodoacetamide to drinking water for 5 days. The gastro-duodenal slow wave, vagal nerve recordings and the gastric mucosa examination were performed on 6th day. The iodoacetamide irritated gastric mucosa presented the minimal inflammatory infiltration with mast cells. The vagal afferent activity was significantly increased after iodoacetamide treatment from 0.3 +/- 0.1 to 1.9 +/- 0.58 Hz, (p<0.05). The gastric slow wave accurate frequencies extracted from the fast Fourier transform spectra accelerated from 0.08 +/- 0.01 to 0.1 +/- 0.02 Hz (p<0.05). The duodenal frequencies remained unchanged (from 0.64 +/- 0.02 to 0.59 +/- 0.1 Hz). These results suggest that mild gastric mucosa irritation sensitizes vagal afferents and alters gastric but not duodenal pacemaker activity which may contribute to dyspeptic sensations.

Effect of subdiaphragmatic vagotomy and cholinergic agents in the hypothalamic-pituitary-adrenal axis activity.

In the present study, we examined whether the vagus nerve is involved in mediating the stimulation of hypothalamic-pituitary-adrenal (HPA) axis by cholinergic muscarinic and nicotinic agonists, carbachol and nicotine. The site of HPA axis muscarinic stimulation was determined using peripheral (i.p.) and intracerebroventricular (i.c.v.) administration of carbachol, atropine sulphate (AtrS) and atropine hydrobromide (AtrBr). The i.p. carbachol-(0.5 mg/kg)-induced corticosterone response was significantly reduced by i.p. pretreatment with AtrBr (0.1 mg/kg), but was not diminished by i.c.v. AtrS (0.1 mug). The increase in corticosterone secretion induced by i.c.v. carbachol (2 microg) was totally abolished by i.c.v. pretreatment with AtrS (0.1 microg) but was not altered by i.p. AtrBr. Subdiaphragmatic vagotomy performed 2 weeks earlier substantially decreased the i.p. carbachol (0.2 mg/kg)-induced ACTH response and markedly augmented ACTH and corticosterone response to a higher dose of carbachol (0.5 mg/kg) in comparison with the responses in sham operated rats. Vagotomy abolished the stimulatory effect of i.p. nicotine in a low dose (1 mg/kg) on ACTH and corticosterone secretion; the ACTH response to higher dose (2.5 mg/kg) was considerably reduced, while corticosterone response remained unaffected. These results suggest that carbachol given i.c.v. evokes considerable corticosterone response by stimulation of central cholinergic muscarinic receptors. A major part of the i.p. carbachol-induced corticosterone secretion results from peripheral cholinergic muscarinic receptor stimulation. Subdiaphragmatic vagotomy moderately intensified the carbachol-induced ACTH and corticosterone secretion. Vagotomy significantly reduced the nicotine-induced ACTH secretion, possibly by the involvement of vagal afferents. The nicotine-induced corticosterone secretion is not exclusively regulated by circulating ACTH but by various intra-adrenal regulatory components.

Effect of long-term vagal stimulation on food intake and body weight during diet induced obesity in rats.

Regulation of food intake and body weight is accomplished by several mechanisms. CNS receives information from periphery and modifies food intake mainly by vagal nerves that provide the major neuroanatomical link between gastrointestinal sites stimulated during food intake and CNS sites that control feeding behavior and metabolism. Gastric mechanoreceptors and jejunal chemoreceptors activated by food or vagal nerve stimulation (VNS), which mimic the physiological input, suppress feeding within short-term regulation. Our research was aimed on determination the role of electrical VNS in long-term control of food intake and body weight in diet induced obesity fed rats. Food intake, body weight and epididymal fat pad were assessed in male Wistar rats divided into three groups (controls vs. VNS). Rats were implanted with microchip and kept during the whole study (100 days) on diet induced obesity. Vagal nerve was stimulated by electrical rectangular pulses duration 10 ms, amplitude 200 mV, frequency 0.05 Hz generated by microchip. In control group surgery produced no significant changes in meal size and body weight gain as compared to intact group. In contrast, significantly decreased epididymal fat pad weight, decreased meal size with effect on decreased weight gain was observed in VNS rats. Data support theory that VNS can increase vagal afferent signal conduct to CNS and mimics the satiety signals leading to reduce food intake and body weight gain.

Melatonin and serotonin effects on gastrointestinal motility.

The gastrointestinal tract represents the most important extra pineal source of melatonin. Presence of melatonin (M) suggests that this hormone is somehow involved in digestive pathophysiology. Release of GI melatonin from serotonin-rich enterochromaffin EC cells of the GI mucosa suggest close antagonistic relationship with serotonin (S) and seem to be related to periodicity of food intake. Food deprivation resulted in an increase of tissue and plasma concentrations of M. Its also act as an autocrine and paracrine hormone affecting not only epithelium and immune system but also smooth muscle of the digestive tract. Low doses M improve gastrointestinal transit and affect MMC. M reinforce MMCs cyclic pattern but inhibits spiking bowel activity. Pharmacological doses of M delay gastric emptying via mechanisms that involve CCK2 and 5HT3 receptors. M released in response to lipid infusion exerts a modulatory influence that decreases the inhibitory effects of the ileal brake on gastric emptying. On isolated bowel S induces dose dependent increase in tone and reduction in amplitude of contraction which is affected by M. M reduced the tone but not amplitude or frequency of contraction. M is a promising therapeutic agent for IBS with activities independent of its effects on sleep, anxiety or depression. Since of its unique properties M could be considered for prevention or treatment of colorectal cancer, ulcerative colitis, gastric ulcers and irritable bowel syndrome.

Peripheral mechanisms of intestinal dysmotility in rats with salsolinol induced experimental Parkinson's disease.

Gastrointestinal dysmotility in Parkinson's disease (PD) has been attributed in part to peripheral neurotoxine action. Our purpose was the evaluation of the salsolinol effect on intramuscular interstitial cells of Cajal (ICC), duodenal myoelectrical activity (DMA) and vagal afferent activity (VAA) in rats with experimental PD. Twenty rats were divided into 2 equal groups. Experimental PD was produced in one group by 3 weeks of the intraperitoneal salsolinol injections (50 mg/kg/day), whereas the 2-nd group served as control. DMA and VAA were recorded in both groups during fasting and stepwise--gastric distension (GD) of 10 ml. Subsequently fragments of duodenum were removed and intramuscular ICC were assessed as c-Kit antigen percentage in the duodenal muscular zone. Analyses of the fasting DMA and VAA recordings didn't reveal differences between the compared groups. During GD increase of DMA dominant frequency (p=0.04) and VAA frequency (p<0.01) was observed in the controls whereas in the salsolinol group both parameters remained unchanged. Image analysis of duodenum revealed decreased c-Kit expression in the salsolinol-injected animals (p=0.05). The results of our study may suggest the direct effect of salsolinol on both ICC and neuronal pathways of gastro-duodenal reflexes.

Peripheral mechanisms of intestinal dysmotility in the morphine tolerant and dependent rats.

Changes of intestinal motility and transit produced by tolerance to and dependence upon morphine have been partly attributed to peripheral mechanisms. We evaluated the effect of chronic peripheral morphine administration and peripheral mu-receptor blockade on vagal afferent activity (VAA) and c-Kit positive intramuscular cells of Cajal (ICCs). Ten rats were subjected to chronic subcutaneous morphine infusion for 72 h with subsequent VAA recording. Potential frequency was evaluated within recordings before and after mu receptor blockade by (D)-Phe -Cys -Tyr -(D)-Trp -Orn -Thr -Phe -Thr (CTOP) i.p. injections. Afterwards the rats were sacrificed and intramuscular c-Kit antigen expression was assessed by image analysis within removed fragments of duodenum and ascending colon. An equal group of rats served as a control for VAA and c-Kit expression. Analysis of VAA revealed similar frequencies of potentials in morphine tolerant / dependent rats before CTOP and in the controls. CTOP increased potential frequency in the morphine group which effect was visible mostly within the first 20 minutes (p=0.01). The morphine infused animals presented also higher c-Kit expression in both the duodenum (p<0.001) and the ascending colon (p<0.001) in comparison to the control group. Results of our study may indicate the involvement of both the intestinal wall and the long vago-vagal reflexes in tolerance to and dependence upon opioids.

Encoding meal in integrated vagal afferent discharge.

Vagal afferents are integral part of the negative feedback loop induced by constitution and size of food stomach and jejunum. Aim of this study was to assess vagal discharge in response to food and gastric distension in rats. Electrophysiological recordings of vagal afferents in fasted (n=32), fed rats (n=20) and during gastric balloon distension (n=12) were performed. After 60 minutes of fasted nerve recording tube feeding was done. Fasted rats also underwent gastric distension via oesophagus. Vagal afferents discharges were analysed with dual time-amplitude window discriminator. Total vagal afferent discharge in fasted and fed rats revealed 0.3 +/- 0.12 vs 0.56 +/- 0.22 Hz (p<0.05). We observed two distinct discharge patterns: high amplitude low frequency (HALF) and low amplitude high frequency (LAHF). HALF spikes were observed more frequent in fasted than in fed rats (0.05 +/- 0.02 vs. 0.03 +/- 0.016 Hz (p<0.05). Conversely LAHF spikes in fed rats predominated over their occurrence in fasted rats: 0.52 +/- 0.2 vs. 0.25 +/- 0.12 Hz (p<0.05). Left vagal afferents discharge rises with gastric distension of 6, 8 and 10 ml and were: 0.46 +/- 0.22 Hz, 0.65 +/- 0.31 Hz, 0.86 +/- 0.33 Hz (p<0.05) respectively. Similar discharge showed right vagal afferents: 0.41 +/- 0.08 Hz, 0.51 +/- 0.13 Hz and 0.77 +/- 0.27 Hz (p<0.05) for 6, 8 and 10 ml of distension, respectively. We conclude that interdigestive information from gastrointestinal tract is encoded in high amplitude low frequency of spikes pattern in the vagus nerves.

Capasaicin induced deafferentation enhances the effect of electrical vagal nerve stimulation on food intake and body mass.

Study was based on hypothesis that electrical stimulation (ES) with parameters obtained from analysis of vagal afferent discharge fed state may fake brain with satiety state. We evaluated effect of denervation of vagal capsaicin-sensitive afferents on food intake and body weight in rats with ES of vagal nerves using microchip (MC). Group A was scheduled to MC implantation, B to sham operation only, C to MC implantation and capsaicin vagal deafferentation, and D to capsaicin denervation only. ES lasted 24 days. MC parameters were 0.05 Hz, 0.1s, 0.55 V. ES of left vagus significantly reduced total food intake as well as the mean daily intake in groups A and C in comparison to control and D group (ANOVA, F=18.55, p=0.0038). Body weight was lower in group A (3462 g) and C (2727 g) then in control (3814 g) and D (3568 g) (F=25.68, p=0.00068). Leptin decreased in C (165 pg/mL) in comparison to A (625 pg/mL), B (677 pg/mL), and D (612 pg/mL) (p<0,05), mainly due to ES (F=7.27, p=0.019). Glucose was decreased in A (F=5.55, p=0.036) - by 11% and by 16% in C group. Proper vagal neuromodulation results in central and peripheral effects causing food intake and body weight downregulation.

[Interstitial cells of Cajal and their pacemaker function]. / Komórki Cajala i ich funkcja rozrusznikowa.

Interstitial cells of Cajal are known more than 100 years. These cells are proved now as slow wave pacesetters. Ultrastructure and physiologic pacemaker's activity is well described by many authors. Dysfunction of these cells is associated with different pathological states in gastrointestinal tract. Strong relationships between GI motility diseases and qualitative and quantitative changes of ICC are observed. Nowadays most of the gastroenterologists agree that evaluation of these cells should become routine diagnostic procedure. We gave a short review of recent achievements and ideas on interstitial cells of Cajal function in gastroenterology.

[Effect of chemical sympathectomy on myoelectric activity of the small bowel]. / Wplyw sympatektomi chemicznej na aktywnosc mioelektryczna jelit.

UNLABELLED: Central and peripheral noradrenergic system modulates myoelectric activity of the small bowel. Aim of this study was to evaluate the role of peripheral noradrenergic system in modulation of slow waves activity. Recordings of slow waves were performed on 20 conscious rats chronically fitted with 2 unipolar electrodes. After controls recording the animals were injected i.p. with 6-hydroxydopamine (6-OHDA--Sigma H8523) and the recording were performed on daily basis through the period of one month. RESULTS: The increase of frequency slow waves during the first week after 6-OHDA from 0.61 (+/- 0.11) to 0.71 (+/- 0.03), (p. < 0.05), and amplitude from 14468 +/- 11196 to 19128 +/- 5282 (microV)2 (p > 0.05) were observed. Variability in control recording was higher (SD +/- 0.11) than after 6-OHDA (SD 0.03). Next day diarrhoea after 6-OHDA occurred, persisted despite return normal myoelectric activity. Slow waves frequency gradually returns to control value after the fourth week. CONCLUSION: Peripheral noradrenergic system has a significant effect on the frequency and variability of slow wave and minor role on its amplitude but no on diarrhoea pattern.

[The role of leptin in metabolic regulation]. / Rola leptyny w regulacji metabolizmu.

Leptin discovery--the hormone derived from adipose tissue became a challenging event in understanding food intake and energy balance regulation. Leptin serum level correlates with fat stores and reacts according to changes in energy balance. Although leptin is thought of as a factor preventing obesity, in most of the cases obesity develops in association with increase in serum leptin level which indicates leptin resistance. It may be possible that the primary role of leptin is to mediate the signal for the switch between the starved and fed state. There is a lot of evidence that leptin has systemic effects apart from those related to energy homeostasis, including regulation of neuroendocrine, immune and reproductive function.

Effects of continuous microchip (MC) vagal neuromodulation on gastrointestinal function in rats.

Afferent fibers from gastrointestinal tract outnumber efferents ten times in vagal nerves. Modifying the afferent input makes possible to change discharge of vagal efferents affecting gastrointestinal functions in process known as neuromodulation (NM). Lately it has been used in the treatment of pain and hyperactive neurogenic bladder in urology. MC induced NM may therefore provide a concurrent to pharmacology tool, in treatment of gastrointestinal disorders. The aim of this study was to investigate the effects of long term neuromodulation procedure with use of MC on gastric motility, secretion and weight control in conscious rats. Experiments were performed on 30 Wistar male rats (250-350 g) divided in two groups: sham operated and microsurgically implanted with MC on left vagal nerve below diaphragm. Following stimulation parameters were used: frequency of 0.5-30 Hz, amplitude of 0.55 V, impulse duration of 10 ms in monophasic fashion. In both groups food intake and body weight were measured through the period of 2 weeks after recovery period. Then gastric fistula was implanted in gastric antrum and fasted gastric motility recorded with use of PowerLab system (Australia). Gastric emptying and secretion were also tested with use of phenol red and automatic titration methods. On the daily basis glucose level with standard test and leptin after MC implantation were measured. Recording of vagal activity in fasted rats showed burst of action potentials about 5 +/- 2.5 in period of 5000 sec, each burst with spike frequency up to 35 Hz. Food (5 ml of Intralipid--intragastrically) almost doubled amount of bursts to 12 +/- 5 in period of 5000 sec with increase in frequency at spike up to 50 Hz. MC induced vagal activity showed continuous spike activity similar to fed pattern. MC induced NM decreases daily food intake by 6% (33.6 +/- 4.8 vs control 35.5 +/- 4.8 g, p < 0.01). Body weight gain in rats before MC implantation decreased by 20% within 2 weeks after recovery (34.8 +/- 9.08 vs control 23.56 +/- 4.15 g). Fasting control glucose level also decreased of 5.5% (93.15 +/- 9.3 vs control 98.5 +/- 11.2 mg%, p < 0.05). Frequency of gastric contractions did not change significantly in MC versus control but amplitude of contractions increased of about 66.7% (2.0 +/- 0.8 vs 1.17 +/- 0.52) at the dominant frequency 0.08 Hz range and about 71.5% (1.17 +/- 0.35 vs 0.68 +/- 0.47, p < 0.05) at the frequency 0.12 Hz. in FFT analysis PowerLab (chart v = 4.01). BAO decreased by 29.25% without H+ concentration changes (0.2 +/- 0.14 vs 0.14 +/- 0.12 mmol/30 min, p < 0.05) but MAO did not change in MC rats (0.37 +/- 0.25 vs 0.42 +/- 0.28 mmol/30 min, p 0.05). Gastric emptying of isotonic solution increased by 10% (90.46 +/- 5.34 vs 80.39 +/- 9.95) percent of marker passing to duodenum/5 min, p < 0.0001). Our results suggest that MC induced NM affect brain-gut axis via influencing metabolic and gastric function and decreases body weight.

The role of vagal efferents in regulation of gastric emptying and motility in rats.

UNLABELLED: Nonpharmacologic regulation of gastrointestinal motility may become competitive to actually applied methods in the nearest future. The Aim of this study was to evaluate effect of vagal stimulation on gastric motility and emptying. Experiments were performed on 30 male Wistar rats in vivo. Electrodes (120 um O Cr/Mo Microfil Industries) were placed on right vagal trunk below diaphragm without affecting its integrity. The fistula was implanted in gastric antrum. Stimulation parameters were: 0.3 V; 0.5 Hz, impulse duration--10 msec, time stimulation--5 min. Gastric pressure (balloon, Synectics pressure transducer, Sweden) and gastric emptying (red phenol method) were measured subsequently during and between stimulations. RESULTS: Stimulation significantly decreased amplitude of gastric contractions about 14% (52.7 +/- +/- 24.5 vs control 66.8 +/- 15.0; p < 0.05) and increased liquid gastric emptying from isotonic solution about 10% (87.35 +/- 4.75 vs control 75.31 +/- 11.24; p < 0.001), hypertonic liquid about 15% (49.05 +/- 12.16 vs control 34.1 +/- 13.68; p < 0.001) and hypotonic liquid about 7% (83.05 +/- 8.8 vs control 76.29 +/- 11.88). The frequency of gastric contractions did not change significantly in Fast Fourier Analysis of the period of stimulations and in control group. CCK concentrations were not significantly different between stimulated and control group (0.3 +/- 0.08 vs control 0.27 +/- 0.06 pmol/L). L-NAME infusion abolished completely acceleration of gastric emptying of isotonic solution (50.38 +/- 12.66 vc control 87.82 +/- 5.49; p < 0.05), hypertonic solution (32.17 +/- 15.09 vs control 51.65 +/- 10.74; p < 0.05) and hypotonic solution (60.42 +/- 12.05 vs control 82.67 +/- 8.06; p < 0.05) during electrical stimulation. DISCUSSION: In this experiment efferent stimulation of abdominal vagal nerve release neuromediators from afferent and efferent fibers. The main regulator seems to be nitric oxide. These results indicate the effective vagal nerve stimulation affects gastric motility and emptying. It is likely that observed effects reflect integrated response with activating vago-vagal reflexes and neurohumoral factors.