Peptidergic nerves in the colon of patients with ulcerative colitis

BACKGROUND/AIMS: The cause of impaired motility, such as diarrhea and toxic megacolon, in patients with ulcerative colitis is unknown. Neuropeptides have recently been shown to be a neurotransmitter in the non-adrenergic non-cholinergic inhibitory and excitatory nerves in the human gut. To clarify the physiological significance of vasoactive intestinal polypeptide, substance P and neurotensin in the colon of patients with ulcerative colitis, we investigated the enteric nerve responses on lesional and normal bowel segments derived from patients with ulcerative colitis and patients who underwent colon resection for colonic cancers. METHODOLOGY: Twenty-four specimens were obtained from the lesional colon of 6 patients with ulcerative colitis (4 male, 2 female; ages 14-51 years, mean: 40.3 years). The patients with ulcerative colitis had chronic disease (4 with moderate disease, 2 with severe disease). Seventy-two specimens were obtained from the normal colon of 10 patients with colonic cancer (8 men and 2 women; ages 40-56 years, mean: 51.2 years). A mechanographic technique was used to evaluate in vitro muscle responses to these peptides of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers. RESULTS: (1) Peptidergic nerves such as vasoactive intestinal polypeptide, substance P, and neurotensin nerves were found to act on both normal colon and ulcerative colitis colon; (2) the colon with ulcerative colitis was more strongly innervated by vasoactive intestinal polypeptide nerves than the normal colon; (3) Substance P and neurotensin nerves act more weakly in the UC colon that the normal colon. CONCLUSIONS: These findings suggest that peptidergic nerves play an important role in the impaired motility observed in patients with UC.     

Are there any functional differences of nitric oxide between the transitional segment in Hirschsprung's disease and the diseased colon in hypoganglionosis?

BACKGROUND/AIMS: In histological studies, there are no significant differences between the transitional segment (TS) of Hirschsprung's disease (HD) and the diseased segment in patients with hypoganglionosis (Hypo). In contrast, there are no reports whether or not TS show impaired motility like Hypo. Nitric oxide (NO) has recently been shown to be a neurotransmitter in the non-adrenergic noncholinergic (NANC) inhibitory nerves in the human gut. To clarify the significance of NO in TS and Hypo, enteric nervous responses in colonic tissue obtained from TS and Hypo were investigated. METHODOLOGY: This study investigated responses of the enteric nervous system including NANC inhibitory nerves in colonic tissue obtained from TS in 10 patients with HD (8 boys and 2 girls, aged from 6 months to 2 years) and diseased colon in 6 patients with Hypo (6 boys, aged from 6 months to 2 years). Normal colons obtained from patients with HD and Hypo (n = 16) were used as controls. Mechanography was used to evaluate in vitro colonic responses to electrical field stimulation (EFS) of adrenergic and cholinergic nerves before and after treatments with various autonomic nerve blockers, N(G)-monomethyl-L-arginine (L-NMMA), and L-arginine. RESULTS: Non-adrenergic non-cholinergic (NANC) inhibitory nerves were found to act on the normal colon and to a lesser extent both in the TS and Hypo. In addition, there were no significant differences between the TS and Hypo. Nitric oxide (NO) mediates the relaxation reaction of the NANC inhibitory nerve in the normal colon and to a lesser extent both in the TS and Hypo. In addition, there were no significant difference between the TS and Hypo. CONCLUSIONS: Diminution of NO mediation of NANC inhibitory nerves may be largely related to the impaired motility observed in patients with TS and diseased colon of Hypo.     

Regulation of the peptidergic nerves (substance P and vasoactive intestinal peptide) in the colon of women patients with slow transit constipation: an in vitro study

BACKGROUND/AIMS: In histological studies, there is evidence to suggest a diminution of the peptidergic nerves such as vasoactive intestinal peptide (VIP) and substance P (SP) in the enteric nervous system in the colon of patients with slow transit constipation (STC). To clarify the pathophysiological significance of peptidergic nerves in the colon of patients with STC, we investigated the enteric nerve responses on pathological and normal bowel segments derived from patients with STC and patients who underwent colon resection for colon cancers, respectively. METHODOLOGY: Twenty-eight preparations were taken from the pathological sigmoid colon of 16 women with STC (aged 40-58 years, average 48.8 years). Forty-eight preparations were taken from the normal sigmoid colon of 20 women with colonic cancer (aged 40-55 years, average 49.6 years). A mechanographic technique was used to evaluate in vitro muscle responses to VIP and SP of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers. RESULTS: Responses mediated by non-adrenergic non-cholinergic (NANC) inhibitory nerves were found in the normal colon, but were more frequently in the colon with STC than in the normal colon (p < 0.01). Responses mediated by excitatory nerves such as cholinergic nerves were more dominant in the normal colon than in the STC colon. At 1 x 10(-8), 1 x 10(-7), 1 x 10(-6) g/mL, VIP and SP in both the normal and STC colonic muscle strips produced a concentration-dependent relaxation to VIP and contraction to SP. In addition, the relaxation reaction to VIP in the colon with STC was also weaker than in the normal colon (p < 0.01). The contraction reaction to SP in the colon with STC was weaker than in the normal colon (p < 0.01). VIP acts through neural mechanisms, whereas SP may act both through nerves and also directly on both the normal and STC muscle strips. CONCLUSIONS: Responses mediated by NANC inhibitory nerves were significantly increased in the colon with STC compared with the normal colon. A decrease of responses to peptidergic nerves such as SP and VIP may also play an important role in the impaired motility observed in the colon of patients with STC. These results indicate that the disturbances in the neural component of the enteric nervous system in the colon of women patients with STC may initiate or contribute to the functional changes.     

Regulation of the enteric nervous system in the internal anal sphincter in Hirschsprung's disease

BACKGROUND/AIMS: The cause of impaired motility of the aganglionic internal anal sphincter (IAS) in Hirschsprung's disease (HD) is unknown. To clarify the physiological significance of non-adrenergic non-cholinergic (NANC) excitatory and inhibitory nerves in the IAS of HD, we investigated the enteric nerve responses on lesional and normal IAS in patients with HD and in patients who had undergone rectal amputation for low rectal cancer. METHODOLOGY: Twelve preparations were taken from the lesional IAS of 7 patients with HD (5 boys and 2 girls aged between 6 months and 1.5 years with a mean age of 8 months). Twenty preparations were taken from the normal IAS of 10 patients with low rectal cancer (6 men and 2 women, aged between 48 and 72 years with a mean age of 54.6 years). A mechanographic technique was used to evaluate in vitro muscle responses to the electrical field stimulation (EFS) of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers. RESULTS: Cholinergic nerves are mainly involved in the regulation of enteric nerve responses to EFS in the normal IAS. The aganglionic IAS of patients with HD was more strongly innervated by cholinergic nerves than the normal IAS (p < 0.05). NANC excitatory and inhibitory nerves were found to act on the normal IAS, but had no effect on it in aganglionosis. CONCLUSIONS: These findings suggest that NANC excitatory and inhibitory nerves play an important role in the impaired motility observed in the IAS in HD.     

Regulation of the enteric nervous system in the colon of patients with slow transit constipation

BACKGROUND/AIMS: The cause of impaired motility in patients with slow transit constipation is unknown. To clarify the physiological significance of cholinergic, adrenergic, non-adrenergic non-cholinergic inhibitory nerves in the colon of patients with slow transit constipation, we investigated the enteric nerve responses on lesional and normal bowel segments derived from patients with slow transit constipation and patients who underwent colon resection for colonic cancers. METHODOLOGY: Twenty preparations were taken from the lesional colon of 6 patients with slow transit constipation (2 men and 4 women, aged 23 to 68 years, with a mean age of 44.0 years). Thirty-six preparations were taken from the normal colon of 12 patients with colonic cancer (6 men and 6 women, aged 40 to 60 years, with a mean age of 52.2 years). A mechanographic technique was used to evaluate in vitro muscle responses to acetylcholine, adrenalin, electrical field stimulation of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers. RESULTS: The contraction reaction to acetylcholine in the colon with slow transit constipation was significantly weaker than in the normal colon (P < 0.01). The relaxation reaction to adrenalin in the colon with slow transit constipation was stronger than in the normal colon. The colon with slow transit constipation was more strongly innervated by non-adrenergic non-cholinergic inhibitory nerves than the normal colon, significantly (P < 0.05). CONCLUSIONS: These findings suggest that a decrease of cholinergic nerve and an increase of non-adrenergic non-cholinergic inhibitory nerve play an important role in the impaired motility observed in the colon of patients with slow transit constipation.     

Physiological studies on nitric oxide in the right sided colon of patients with diverticular disease

BACKGROUND/AIMS: Previously, we reported that non-adrenergic non-cholinergic (NANC) inhibitory nerves are decreased in the left-sided colon of patients with diverticular disease, contributing to their intraluminal high pressure by segmentation (1). It is established that nitric oxide (NO) is released by stimulation of NANC inhibitory nerves. Among Oriental people, including the Japanese, right-sided diverticular disease has predominated more frequently than among Western people. In order to evaluate the function of NO in the right-sided colon of patients with diverticular disease, we examined the enteric nerve responses in colonic materials from patients with this disease, using the right-sided normal colon as a control. METHODOLOGY: Colonic tissue specimens were obtained from 8 patients with diverticular disease of the right-sided colon, and normal segments of the right-sided colon were obtained from 11 patients with localized diseases. A mechanograph was used to evaluate in vitro colonic responses to electrical field stimulation (EFS) of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers, N(G)-nitro-L-arginine (L-NNA), and L-arginine. RESULTS: 1) Cholinergic nerves were more dominant in the diverticular colon than in the normal colon (p<0.01). 2) NANC inhibitory nerves were found to act on the normal colon and to a lesser extent in the diverticular colon (p<0.05). 3) NO mediates the relaxation reaction of NANC inhibitory nerves in the normal colon and to a lesser extent in the diverticular colon. CONCLUSIONS: The intrinsic intestinal innervation contains excitatory and inhibitory nerves and the former, especially cholinergic nerves, are dominant in the right-sided colon with diverticula. In addition, reduction of the action of NANC inhibitory nerves by substances such as NO may be largely related to the tight intraluminal pressure by colonic segmentation observed in the right-sided colon with diverticula.     

Role of nitric oxide in the left-sided colon of patients with diverticular disease

BACKGROUND/AIMS: Non-adrenergic non-cholinergic inhibitory nerves are the most important nerves in the enteric nervous system of the human gut. Recently, it has been established that nitric oxide is released by stimulation of non-adrenergic non-cholinergic inhibitory nerves. Therefore, in order to evaluate the function of nitric oxide in the left-sided colon of patients with diverticular disease, we examined the enteric nerve responses in colonic tissues from patients with this disease, and also used the left-sided normal colon as a control. METHODOLOGY: Colonic tissue specimens (the diverticular bearing segments) were obtained from 9 patients with diverticular disease of the left-sided colon, and normal segments of the left-sided colon were obtained from 16 patients with ascending colon cancer. A mechanograph was used to evaluate in vitro colonic responses to electrical field stimulation of adrenergic and cholinergic nerve before and after treatments with various autonomic nerve blockers, NG-nitro-L-arginine, and L-arginine. RESULTS: 1) The diverticular colon was more strongly innervated by cholinergic nerves than the normal colon (P < 0.01); 2) Non-adrenergic non-cholinergic inhibitory nerves were found to act on the normal colon and to a lesser extent in the diverticular colon (P < 0.05). 3) Nitric oxide mediates the relaxation reaction of non-adrenergic non-cholinergic inhibitory nerves in the normal colon and to a lesser extent in the diverticular colon. CONCLUSIONS: These findings suggest that the intrinsic intestinal innervation contains excitatory and inhibitory nerves and that the former, especially cholinergic nerves, are dominant in the left-sided colon with diverticula. In addition, diminution of action of non-adrenergic non-cholinergic inhibitory nerves by substances such as nitric oxide may be largely related to the high intraluminal pressure by colonic segmentation observed in the left-sided colon with diverticula.     

The effects of neurotensin in the colon of patients with slow transit constipation

BACKGROUND/AIMS: The cause of dysmotility in the colon of patients with slow transit constipation (STC) is still unknown. Neurotensin (NT) has recently been shown to be a neurotransmitter in the non-adrenergic non-cholinergic (NANC) excitatory nerves of the human alimentary tract. To clarify the physiological significance of NT in the colon of patients with STC, we examined the enteric nerve responses in lesional and normal bowel segments derived from patients with STC and patients who underwent colon resection for colonic cancers. METHODOLOGY: Twenty-eight preparations were taken from colonic lesions in 10 patients with slow transit constipation (2 men and 8 women, aged 23 to 70 years, mean 46.3 years). Forty-six preparations were taken from the normal colons of 16 patients with colonic cancer (8 men and 8 women, aged 40 to 66 years, mean 50.1 years). A mechanographic technique was used to evaluate in vitro muscle responses to electrical field stimulation (EFS) before and after treatment with various autonomic nerve blockers and NT. RESULTS: After blocking both the adrenergic and cholinergic nerves (Experiment 1), NT showed contraction reaction on both normal and STC colons in a concentration-dependent manner. The contraction reactions to NT in the normal colon were more dominant than those in the STC colon. There were significant differences between the frequency of contraction reactions to NT in normal colon strips and those in STC colon strips (P < 0.001). Following addition of tetrodotoxin (Experiment II), all muscle strips of normal and STC colons demonstrated contraction responses by NT. The effects of NT in the normal and STC colon muscle strips were essentially the same as in experiment 1, although the extent of contraction was somewhat diminished. CONCLUSIONS: Those results suggested that NT acts both via NANC excitatory nerves and also directly on the colonic smooth muscle. A decrease of NT mediates NANC excitatory nerves and plays an important role in the dysmotility observed in the colons of patients with STC.     

Are there any functional differences of the enteric nervous system between the right-sided diverticular colon and the left-sided diverticular colon? An in vitro study

Purpose

To evaluate functional differences of the enteric nervous system (ENS) in patients between right-side colonic diverticula (RCD) and left-sided colonic diverticula (LCD), the author compared the ENS responses between RCD and LCD.

Methods

Ten specimens were obtained from 10 patients with RCD, and 16 specimens were taken from 16 LCD. As a control, twenty-two specimens of right-sided normal colon (RNC) were obtained from 22 colonic cancers. Twenty-four specimens of left sided normal colon (LNC) were obtained from 24 colonic cancers. A mechanography was used to evaluate in vitro muscle responses to electrical field stimulation (EFS) before and after treatment with various autonomic nerve blockers.

Results

Before blockade of the adrenergic and cholinergic nerves, the incidences of contraction via cholinergic nerve in the colons with diverticula were significantly greater than those in the normal colons (right-sided colon; p?=?0.0022, left-sided colon; p?<?0.0001). There were no significant differences between RNC and LNC (p?=?0.3606), and between RCD and LCD (p?=?0.7684). After the blockade of adrenergic and cholinergic nerves, the incidence of relaxation via non-adrenergic non-cholinergic inhibitory (NANC) nerve in the normal colons was significantly greater than that in the diverticular colons (right-sided colon; p?=?0.0435, left-sided colon; p?=?0.0034). There were no significant differences between RNC and LNC (p?=?0.2909) and between RCD and LCD (p?=?0.9464).

Conclusion

Cholinergic nerves were dominant in bilateral diverticular colon compared with bilateral normal colon. NANC inhibitory nerves were dominant in bilateral normal colon compared with bilateral diverticular colon. There were also no functional differences of the ENS between RCD and LCD.     

The role of interleukin-1 beta (IL-1beta) in the normal human colon in vitro

BACKGROUND/AIMS: The possibility that interleukin-1 beta (IL-1beta) is a neuromodulator of the non-adrenergic non-cholinergic (NANC) inhibitory nerves which may be mediated by nitric oxide (NO) was recently reported from animal experiments. To clarify the physiological significance of the relationship between IL-1beta and NO in the normal human colon, enteric nervous responses to IL-1beta in the normal colon muscle strips were investigated. METHODOLOGY: Normal colon muscle strips derived from patients who underwent colon resection for left-sided colon cancers (14 cases) were used. The subjects consisted of 8 men and 6 women, aged from 44 to 65 years with a mean age of 56.8 years. A mechanographic technique was used to evaluate in vitro colon muscle responses to IL-1beta of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers and N(G)-nitro-L-arginine (L-NNA). RESULTS: IL-1beta concentration dependently caused a relaxation reaction before and after the blockade of the adrenergic and cholinergic nerves. The frequency of relaxation responses after blocking the adrenergic and cholinergic nerves was higher than that before blocking, but there was no significant difference between them. Both tetrodotoxin and L-NNA inhibited the relaxation reaction in response to IL-1beta in the human colon. CONCLUSIONS: These findings suggest that IL-1beta plays an important role in regulating relaxation of the normal human colon via nitregic nerves, and that NO plays a role as a neurotransmitter in the NANC inhibitory nerves.     

The role of nitric oxide (NO) in the human pyloric sphincter

BACKGROUND/AIMS: Nitric oxide (NO) has recently been shown to be a neurotransmitter in non-adrenergic non-cholinergic (NANC) inhibitory nerves in the gastrointestinal tract. To clarify the role of NO in the human pyloric sphincter, enteric nerve responses in pyloric tissue specimens obtained from patients with gastric cancer were investigated. METHODOLOGY: Fresh specimens of normal pylorus obtained from 18 patients with gastric cancer were used. The subjects consisted of 12 men and 6 women, aged from 45-74 years (average: 60.1 years). A mechanograph was used to evaluate in vitro pyloric sphincter muscle responses to electrical field stimulation (EFS) of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers, and N(G)-nitro-L-arginine (L-NNA) and L-arginine. RESULTS: Cholinergic nerves were mainly involved in the regulation of enteric nerve responses to EFS in the basal condition of the study, and NANC inhibitory nerves acted on human pylorus. L-NNA concentration dependently inhibited the relaxation in response to EFS in the human pylorus, and this inhibitory effect in the pylorus was reversed by L-arginine. CONCLUSIONS: These findings suggest that the cholinergic/adrenergic and NANC inhibitory nerves play important roles in regulating contraction and relaxation of the human pylorus, and that NO plays an important role as a neurotransmitter in NANC inhibitory nerves of the human pylorus.     

The role of nitric oxide (NO) in the human internal anal sphincter

Purpose. Nitric oxide (NO) has recently been shown to be a neurotransmitter in nonadrenergic noncholinergic (NANC) inhibitory nerves in the human gut. To clarify the physiological significance of NO in the human internal anal sphincter (IAS), we investigated enteric nervous responses in normal IAS muscle strips above the dentate line, obtained from patients with rectal cancer. Methods. Normal IAS muscle strips above the dentate line, obtained from ten patients who underwent rectal amputation for low rectal cancers were used. The subjects consisted of eight men and two women, aged from 46–72 years (mean age, 54.2 years). A mechanographic technique was used to evaluate in-vitro IAS muscle responses to electrical field stimulation (EFS) of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers, N^G-nitro-l-arginine (l-NNA) and l-arginine. Results. Excitatory nerves were mainly involved in the regulation of enteric nerve responses to EFS in the baseline condition of the study, and NANC inhibitory nerves acted on the normal IAS. l-NNA concentration-dependently inhibited the relaxation in response to EFS in the human IAS, and this inhibitory effect in the IAS was reversed by l-arginine. Conclusions. These findings suggest that NANC inhibitory nerves play important roles in regulating relaxation of the human IAS, and that NO plays an important role as a neurotransmitter in NANC inhibitory nerves of the human IAS. Received: September 7, 2000 / Accepted: January 12, 2001     

Pathophysiological role of the cholinergic and adrenergic nerves in patients with allied disorders of Hirschsprung's disease (intestinal neuronal dysplasia and hypoganglionosis)--an in vitro experiment

BACKGROUND/AIMS: There are no reports about the pathophysiological roles of cholinergic and adrenergic nerves in the intestines of patients with allied disorders of Hirschsprung's disease (HD) such as intestinal neural dysplasia (IND) and hypoganglionosis (Hypo). To clarify the significance of the cholinergic and adrenergic nerves in Hypo and IND, we investigated enteric nerve responses to acetylcholine (Ach) and noradrenaline (NA) in colonic tissues obtained from patients with these diseases. METHODOLOGY: Colonic tissue specimens were obtained from 8 patients with HD (aganglionosis; 4 boys and 4 girls, aged 6 months to 3 years), 4 patients with Hypo (4 boys, aged 9 months to 3 years and 5 months), and 3 patients with IND (3 boys, aged 6 months to 3 years). Colon specimens from 8 patients without constipation (5 boys and 3 girls, aged 4 to 12 years) were used as controls. A mechanograph was used to evaluate in vitro colonic responses to electrical field stimulation (EFS), Ach, and NA. RESULTS: All muscle strips showed responses to EFS. Tetrodotoxin almost abolished the EFS responses in all the muscle strips. According to these results, we ascertained that the enteric nervous system was present in all muscle strips. 1) Ach showed a contraction reaction. The frequency of the contraction reaction in normal colon was highest, followed by those in IND colon, Hypo colon, and HD colon in decreasing order. In addition, significant differences were noted between the frequency of the contraction reaction in normal colon and those in IND colon, Hypo colon and HD colon (p < 0.01, p < 0.001, p < 0.0001, respectively). 2) NA showed a relaxation reaction. The frequency of relaxation reaction in normal colon was highest, followed by those in IND colon and Hypo colon in decreasing order. HD colon showed no response. In addition, significant differences were noted between the frequency of the relaxation reaction in normal colon and those in IND colon, Hypo colon and HD colon (p < 0.05, p < 0.001, p < 0.0001, respectively). There was also a significant difference between IND colon and HD colon (p < 0.05). CONCLUSIONS: The diminution of action of cholinergic and adrenergic nerves may be largely related to the impaired motility observed in IND, Hypo, and HD.     

Role of Nitric Oxide in the Colon of Patients With Slow-Transit Constipation

PURPOSE: The cause of dysmotility in patients with slow-transit constipation is unknown. Nitric oxide has recently been shown to be a neurotransmitter in the nonadrenergic, noncholinergic inhibitory nerves of the human gut. To clarify the physiologic significance of nitric oxide in the colon of patients with slow-transit constipation, we investigated the enteric nerve responses in lesional and normal bowel segments derived from patients with slow-transit constipation and patients who underwent colon resection for colonic cancers. METHODS: Twenty-six preparations were taken from colonic lesions in eight patients with slow-transit constipation (2 men; age, 23 to 69 (mean, 44.8) years). Forty-two preparations were taken from the normal colons of 14 patients with colonic cancer (8 men; age, 40 to 66 (mean, 52.4) years). A mechanographic technique was used to evaluate in vitro muscle responses to electric field stimulation before and after treatment with various autonomic nerve blockers, NG-nitro-L-arginine, and L-arginine. RESULTS: The colons of patients with slow-transit constipation were more strongly innervated by nonadrenergic, noncholinergic inhibitory nerves than were normal colons (P <0.05). Nitric oxide was found to act on both normal and slow-transit constipation colons. The colons of patients with slow-transit constipation were more strongly innervated by nitric oxide nerves than were normal colons (P < 0.01). Responses to electric field stimulation were the same in each case among the normal colons and were also the same in each case among the slow-transit constipation colons. CONCLUSION: These findings suggest that an increase of nitric oxide mediates nonadrenergic, noncholinergic inhibitory nerves and plays an important role in the dysmotility observed in the colons of patients with slow-transit constipation.     

Relationship between nitric oxide and non-adrenergic non-cholinergic inhibitory nerves in human lower esophageal sphincter

Nitric oxide (NO) has recently been shown to be a neurotransmitter in the non-adrenergic non-cholinergic (NANC) inhibitory nerves in the gastrointestinal tract. To clarify the the role of NO in the human lower esophageal sphincter (LES), enteric nerve responses in lower esophageal tissue specimens obtained from patients with esophageal cancer (n=7) and patients with gastric cancer (n=6) were investigated. A mechanographic technique was used to evaluate in vitro LES muscle responses to electrical field stimulation (EFS) of adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers, including N^G-nitro-L-arginine (L-NNA) and L-arginine. Findings were: (1) Cholinergic nerves were those mainly involved in the regulation of enteric nerve responses to EFS in the steady state, and NANC inhibitory nerves acted on the LES; (2) L-NNA concentration-dependently inhibited the relaxation in response to EFS in the LES; and (3) this inhibitory effect in the LES was reversed by L-arginine. These findings suggest that cholinergic and NANC inhibitory nerves play important roles in regulating contraction and relaxation of the human LES, and that NO plays an important role as a neurotransmitter in NANC inhibitory nerves of the human LES.     

Regulation of enteric nervous system in the proximal and distal parts of the normal human pyloric sphincter--in vitro study

BACKGROUND/AIMS: The structure of the pyloric sphincter (PS) muscle has recently been shown to divide into two parts (proximal and distal parts). To clarify the functional differences in the human PS between proximal and distal parts, we investigated the enteric nerve responses in normal proximal and distal PS specimens. METHODOLOGY: Normal PS specimens derived from 20 patients with early gastric cancer (13 men and 7 women aged from 50 to 64 years, average 58.2 years) were used. These PS muscles were divided into 2 parts [1/2 oral site of PS; proximal part (PPS; n=26), 1/2 anal site of PS; distal part (DPS; n=24)]. A mechanographic technique was used to evaluate in vitro muscle strip responses to electrical field stimulation (EFS) before and after treatment with various autonomic nerve blockers. RESULTS: Findings were: (1) Response to EFS before blockade of the adrenergic and cholinergic nerves: Excitatory responses (contraction reaction) via cholinergic nerves in the PPS were regulated more predominantly than in the DPS. Inhibitory responses (relaxation reaction) via adrenergic nerves in the DPS were regulated more predominantly than in the PPS. (2) Response to EFS after blockade of the adrenergic and cholinergic nerves: Excitatory responses (contraction reaction) via non-adrenergic non-cholinergic (NANC) excitatory nerves in the PPS were regulated significantly more than in the DPS (P = 0.0439). Inhibitory responses (relaxation reaction) via NANC inhibitory nerves in the DPS were also regulated significantly more than in the PPS (P = 0.0439). (3) EFS response in the pylorus was blocked by tetrodotoxin. CONCLUSIONS: There are differences between the PPS and DPS in the regulation of the enteric nervous system. Contraction reaction via excitatory nerves, especially cholinergic nerves, was mainly involved in the regulation of enteric nerve responses to EFS in the PPS. Relaxation reaction via inhibitory nerves, especially NANC inhibitory nerves, was mainly involved in the regulation of enteric nerve responses to EFS in the DPS.     

Physiological studies on neurotensin in rat small bowel isografts

BACKGROUND/AIMS: The cause of dysmotility in the small intestine of patients with small bowel transplantation (SBT) is still unknown. It is established that neurotensin (NT) is released by stimulation of non-adrenergic non-cholinergic (NANC) excitatory nerves. It is considered that the ileum is more important than the jejunum in regard to digestive functions. In order to evaluate the intestinal function of rat ileal isografts, this study examined the enteric nerve responses to electrical field stimulation (EFS) and NT in the isografted rat ileum, using the normal ileum as a control. METHODOLOGY: Orthotopic entire small bowel transplantation (SBT) with portocaval drainage was performed from Lewis rats to Lewis rats. Grafted tissue specimens were obtained 130 days after SBT (n = 8). As controls, normal segments of the ileum were obtained from untransplanted Lewis rats (n = 20). A mechanograph was used to evaluate in vitro ileal responses to electrical field stimulation (EFS) of the adrenergic and cholinergic nerve before and after treatments with various autonomic nerve blockers and NT. RESULTS: All ileal muscle strips used in the present studies responded to EFS before and after the blockade of both the adrenergic and cholinergic nerves. The intrinsic innervation contains both excitatory (cholinergic and NANC excitatory nerves) and inhibitory nerves (adrenergic and NANC inhibitory nerves) in the normal and isografted ileum of LEW rats. Excitatory nerves, especially NANC excitatory nerves, were more dominant in the isografted ileum than in the normal ileum (P < 0.001). NANC inhibitory nerves were found to act on the normal ileum and to a greater extent in the isografted ileum (P < 0.05). NT mediates the contraction reaction of NANC excitatory nerve in the normal ileum and to a greater extent in the isografted ileum (P < 0.05). CONCLUSIONS: Contraction reactions of NT were observed in both the normal and isografted ileum, but were increased in the isografted ileum. The increase of the NT in mediating NANC excitatory nerves and decrease of the NANC inhibitory nerves may be largely related to the peristaltic abnormalities seen in the isografted LEW rat ileum.     

Idiopathic chronic constipation is associated with decreased colonic vasoactive intestinal peptide

To investigate the reported association between idiopathic chronic constipation and morphologic abnormalities of enteric nerves, we measured the concentrations of six neuropeptides, vasoactive intestinal peptide, peptide histidine-methionine, substance P, methionine5-enkephalin, neuropeptide Y, and the bombesinlike intestinal peptides, in descending colon from 4 patients with idiopathic chronic constipation. Decreased concentrations of vasoactive intestinal peptide (707 +/- 112 ng/g wet tissue) and peptide histidine-methionine (543 +/- 58 ng/g) were found in the muscularis externa obtained from constipated patients compared with normal concentrations (40 patients) of vasoactive intestinal peptide (1199 +/- 47 ng/g) and peptide histidine-methionine (815 +/- 45 ng/g). Vasoactive intestinal peptide was identified by immunocytochemistry in nerve fibers within the circular smooth muscle layer of descending colon obtained from 6 control patients, but not in nerve fibers within the circular smooth muscle of descending colon obtained from 3 patients with idiopathic chronic constipation. By contrast, the distribution of immunoreactive met5-enkephalin was similar in normal descending colon and in descending colon obtained from patients with idiopathic chronic constipation. Decreased colonic concentrations of vasoactive intestinal peptide (a candidate nonadrenergic, noncholinergic inhibitory neurotransmitter) may be associated with diminution of inhibitory innervation of colonic circular smooth muscle in some patients with idiopathic chronic constipation.     

Impaired capsaicin and neurokinin-evoked colonic motility in inflammatory bowel disease

BACKGROUND: Inflammatory bowel disease (IBD) is associated with altered sensory and motor function in the human colon. The aim of the present study was to compare neuromuscular function in normal and IBD-affected colon in vitro, with emphasis on inhibitory enteric nerves, sensory neuropeptides and stimulation of axon collaterals. METHODS: Strips of longitudinal and circular muscle were prepared following colectomy from six patients with intestinal carcinoma (mean age 64.2 +/- 4.8 years) and six patients with IBD (Crohn's disease, n = 3; ulcerative colitis, n = 3: mean age 35.8 +/- 5.7 years). Responses were measured to electrical field stimulation, potassium chloride, 1,1-dimethyl-4-phenylpiperazinium iodide, isoprenaline, calcitonin gene-related peptide (CGRP), capsaicin and neurokinin (NK)-1 and -2 receptor subtype-specific agonists, alone or after muscle precontraction. RESULTS: The NK-1 and CGRP receptor-mediated relaxation was reduced in the circular (by 44%, P < 0.05) and longitudinal (by 61%, P < 0.05) muscle from IBD-affected colon, respectively. Maximal NK-2 receptor-mediated contraction was also significantly decreased in both longitudinal (71%, P < 0.001) and circular (51%, P < 0.01) muscle. Capsaicin evoked relaxation in precontracted colonic longitudinal and circular muscle; this was significantly diminished in the IBD-affected colon (by 63%, P < 0.001 and 76%, P < 0.01, respectively). Responses evoked by stimulation of enteric inhibitory nerves were not significantly altered. CONCLUSIONS: Colonic muscle strips from patients with IBD exhibited impaired CGRP and NK-1 receptor-mediated relaxation and NK-2 receptor-mediated contraction. Capsaicin-activated relaxation of colonic smooth muscle is deficient in IBD-affected colon. These results suggest a discrete effect of IBD on sensory-motor coupling and tachykinin-mediated effects on colonic motility.     

The Aging Colon: The Role of Enteric Neurodegeneration in Constipation

Constipation is a common problem in the elderly, and abnormalities in the neural innervation of the colon play a significant role in abnormalities in colonic motility leading to delayed colonic transit. The scope of this review encompasses the latest advances to enhance our understanding of the aging colon with emphasis on enteric neurodegeneration, considered a likely cause for the development of constipation in the aging gut in animal models. Neural innervation of the colon and the effects of aging on intrinsic and extrinsic nerves innervating the colonic smooth muscle is discussed. Evidence supporting the concept that neurologic disorders, such as Parkinson’s disease, not only affect the brain but also cause neurodegeneration within the enteric nervous system leading to colonic dysmotility is presented. Further research is needed to investigate the influence of aging on the gastrointestinal tract and to develop novel approaches to therapy directed at protecting the enteric nervous system from neurodegeneration.