Physiological studies on vasoactive intestinal peptide in rat small bowel isografts

BACKGROUND: Vasoactive intestinal peptide (VIP) is released by stimulation of nonadrenergic noncholinergic (NANC) inhibitory nerves. In order to evaluate the function of VIP in jejunal isografts, we examined the enteric nerve responses in isografted rat jejunum compared with normal jejunum. METHODS: 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 jejunum were obtained from nontransplanted Lewis rats (n = 20). A mechanograph was used to evaluate in vitro jejunal responses to electrical field stimulation (EFS) of the adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers and VIP. RESULTS: The isografted jejunum was more strongly innervated by excitatory nerves, especially NANC excitatory nerves, than the normal jejunum (P <.05). VIP mediated relaxation reactions of NANC inhibitory nerves in the normal but to a lesser extent in the isografted jejunum (P <.05). CONCLUSIONS: The increased NANC excitatory nerves and the decreased effects of VIP in mediating NANC inhibitory nerves may largely relate to the peristaltic abnormalities seen in the isografted LEW rat jejunum.     

Physiologic Studies on Nitric Oxide in Rat Small Bowel Isografts

The enteric nervous system (ENS), especially the nonadrenergic noncholinergic (NANC) inhibitory nerves, is an important factor in intestinal peristalsis. Recently, it was established that nitric oxide (NO) is released after stimulation of NANC inhibitory nerves. Inhibitory nerves such as NANC inhibitory nerves in the ENS are more easily damaged than excitatory nerves by reperfusion or ischemic injuries during small bowel transplantation (SBT). To evaluate the effects of reperfusion and ischemic injuries to the ENS in the transplanted small bowel, we examined the ENS responses, including the effects of NO in the isografted rat jejunum, using the nontransplanted jejunum as a control. To avoid potentially confounding immune phenomena, we used syngeneic Lewis (LEW) rats. Orthotopic entire SBT with portocaval drainage was performed from LEW rats to LEW rats. Isografted muscle strips were obtained from 8 LEW rats 130 days after SBT (n = 24). As controls, normal muscle strips of the jejunum were obtained from 20 nontransplanted LEW rats (n = 60). A mechanograph was used to evaluate in vitro jejunal responses to electrical field stimulation of the adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers, N ^g -nitro-l-arginine (L-NNA), and l-arginine. The results indicated that excitatory nerves, especially NANC excitatory nerves, were more dominant in the isografted jejunum than in the normal jejunum (p < 0.01). NANC inhibitory nerves were found to act on the normal jejunum and to a lesser extent on the isografted jejunum (p < 0.05). NO mediates the relaxation reaction of NANC inhibitory nerves in the normal jejunum and to a lesser extent in the isografted jejunum. These results indicated that the intrinsic intestinal innervation contains excitatory and inhibitory nerves and that the former, especially NANC excitatory nerves, are more dominant in the isografted jejunum than in the normal jejunum. In addition, reduction of the action of NANC inhibitory nerves such as that by NO may be largely related to impaired motility in the isografted jejunum. Thus over a long period of time (more than 130 days after SBT) transplanted small bowel dysmotility may be influenced by reperfusion or ischemic injury to the ENS (especially NANC inhibitory nerves) via NO in the transplanted jejunum after syngeneic SBT.     

Role of the peptidergic nerves in Hirschsprung's disease and hypoganglionosis

The purpose of this study is to examine the role of peptidergic nerves (VIP, Substance P, Neurotensin) in Hirschsprung's disease (aganglionosis) and hypoganglionosis in relation to the normoganlionic state of the colon using a mechanographic technique in vitro. The following results were obtained. 1) Normoganglionic muscle strips demonstrated the presence of intact non-adrenergic inhibitory nerve. The activities of such nerves, however, were reduced in hypoganglionic muscle strips, and were absent in aganglionic muscle strips. 2) Peptidergic nerve activities by VIP, substance P, and Neurotensin were present in normoganglionic muscle strips, while they were reduced in hypoganglionic muscle strips, and absent in aganglionic muscle strips. 3) VIP may act as a neurotransmitter-neuromodulator of non-adrenergic inhibitory nerve, while SP and Neurotensin may act as that of non-cholinergic excitatory nerve with some direct effect on the intestinal muscle.     

Long-Term Effects of Extrinsic Denervation on VIP and Substance P Innervation in Circular Muscle of Rat Jejunum

Intestinal denervation contributes to enteric motor dysfunction after small bowel transplantation (SBT). Our aim was to determine long-term effects of extrinsic denervation on function of nonadrenergic, noncholinergic innervation with substance P and vasoactive intestinal polypeptide (VIP). Contractile activity of jejunal circular muscle strips from six age-matched, naive control rats (NC) and eight rats 1 year after syngeneic SBT was studied in tissue chambers. Spontaneous contractile activity did not differ between groups. Exogenous VIP inhibited contractile activity dose-dependently to a comparable degree in both groups. The VIP antagonist ([d-p-Cl-Phe⁶,Leu¹⁷]-VIP) and the nitric oxide synthase inhibitor l-N^G-nitro-arginine did not affect VIP-induced inhibition but increased contractile activity during electrical field stimulation (EFS) in both groups. Exogenous substance P increased contractile activity dose-dependently, greater in NC than SBT. The substance P antagonist ([d-Pro²,d-Trp^7,9]-substance P) inhibited effects of exogenous substance P and decreased the excitatory EFS response. Immunohistofluorescence showed tyrosine hydroxylase staining after SBT indicating sympathetic reinnervation. In jejunal circular muscle after chronic denervation, response to exogenous substance P, but not VIP, is decreased, whereas endogenous release of both neurotransmitters is preserved. Alterations in balance of excitatory and inhibitory pathways occur despite extrinsic reinnervation and might contribute to enteric motor dysfunction after SBT. Parts of this work were presented at the annual meeting of the Society for Surgery of the Alimentary Tract in Washington, DC, on May 21, 2007 and published in abstract form in Gastroenterology 2007;132:A890.     

Role of nitric oxide in the internal anal sphincter of Hirschsprung's disease

It is not clear what contribution the internal anal sphincter (IAS) makes to the impaired motility observed in patients with Hirschsprung's disease (HD). Nitric oxide (NO) has recently been shown to be a neurotransmitter in the nonadrenergic noncholinergic (NANC) inhibitory nerves in the human gut. To clarify the physiologic significance of NO in the IAS of HD (aganglionosis), we investigated the enteric nerve responses on lesional (aganglionic) and normal IAS muscle strips above the dentate line. Lesional and normal IAS muscle strips above the dentate line were derived from patients with HD (10 cases) and patients who underwent rectal amputation for low rectal cancer (12 cases). 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, N(G)-L-nitroarginine, and L-arginine. The following results were obtained: (1) Cholinergic nerves are mainly involved in the regulation of enteric nerve responses to EFS in the normal IAS. (2) The aganglionic IAS of patients with HD was more strongly innervated by cholinergic nerves than the normal IAS (p < 0.05). (3) NANC inhibitory nerves were found to act on the normal IAS but had no effect on the enteric nerves in patients with aganglionosis. (4) NO was found to act on normal IAS, but no effect was observed in the aganglionic IAS. These findings suggest that innervation of the cholinergic nerves and a loss of NO mediation of NANC inhibitory nerves play an important role in the impaired motility observed in the IAS with HD.     

Inhibition by nitric oxide and nonadrenergic, noncholinergic (NANC) nerves is preserved in a canine model of extrinsic denervation: implications for small bowel transplantation

BACKGROUND: Small bowel transplantation (SBT) is complicated by changes in graft motility, especially in the early postoperative period. This dysmotility may be related in part to the extrinsic denervation necessitated by the procedure, but specific neurotransmitter response to SBT is incompletely understood. The aim of this study was to evaluate the role of nitric oxide and nonadrenergic, noncholinergic (NANC) enteric neural input in the nonimmunologic etiology of the dysmotility seen after SBT. METHODS: A technique of jejunoileal extrinsic denervation (without disruption of mesenteric vascular supply) was used as a model of canine jejunoileal autotransplantation to avoid potential confounding factors such as ischemia-reperfusion and postallotransplant immunologic effects. Longitudinal smooth muscle strips from ileum and jejunum were studied with in vitro tissue chamber methodology at 0, 2, and 8 weeks after this experimental model to explore early and late effects of denervation. Effects of exogenous nitric oxide (NO) and electric field stimulation (EFS), which releases native, endogenous enteric neurotransmitters) were evaluated in neurally intact control dogs and those undergoing extrinsic denervation. RESULTS: Exogenous NO caused a dose-dependent inhibition of spontaneous contractile activity and in some muscle strips a decrease in basal tone in both groups of dogs. These effects were unchanged by neural blockade with tetrodotoxin and preserved after extrinsic denervation. EFS produced inhibition of spontaneous contractile activity in ileum and a complex, inconsistent response in jejunum. The response to EFS in both ileum and jejunum was unchanged after extrinsic denervation. CONCLUSIONS: Nitric oxide inhibits contractile activity in canine longitudinal muscle of small bowel. Motility changes seen after this large animal model of extrinsic denervation are not caused by changes in NO or NANC neural function. The variability observed between different segments of intestine is important to consider in the context of SBT.     

Role of VIP and substance P in NANC innervation in the longitudinal smooth muscle of the rat jejunum - influence of extrinsic denervation

BACKGROUND: This study was designed to determine changes in nonadrenergic, noncholinergic (NANC) neurotransmission mediated by Vasoactive Intestinal Polypeptide (VIP) and Substance P after small bowel transplantation (SBT). MATERIALS AND METHODS: Six groups of rats (n > or = 6 per group) were studied: na?ve controls (NC); 1 wk after anesthesia/sham celiotomy (SC-1); 1 or 8 wk after jejunal and ileal transection/reanastomosis (TA-1, TA-8), or syngeneic, orthotopic SBT (SBT-1, SBT-8). Jejunal longitudinal muscle strips were studied under NANC-conditions for spontaneous contractile activity, response to exogenous VIP and Substance P, and electrical field stimulation (EFS). RESULTS: Spontaneous activity did not differ between the six groups. VIP inhibited contractile activity in all groups 1 wk postoperatively (P < 0.05), which was prevented by the NO synthase inhibitor L-N(G)-nitro arginine (L-NNA). In contrast, VIP had no effect in the other groups. Precontraction with Substance P exposed an inhibitory effect of VIP in all groups (P < 0.05 each). Substance P increased contractile activity in all groups, but to a lesser extent in SBT-8 compared with NC, TA-8, and SBT-1 (P < 0.05). The inhibitory effect of EFS at 6 Hz was prevented by L-NNA in NC and TA-8; addition of the VIP antagonist ([D-p-Cl-Phe(6), Leu(17)]-VIP) increased contractile activity in NC, but not in TA-8 and SBT-8. The Substance P antagonist ([D-Pro(2), D-Trp(7,9)]-Substance P) decreased contractile activity during EFS at 50 Hz in NC and SBT-8. CONCLUSIONS: SBT decreased response to exogenous Substance P, although release of endogenous Substance P (EFS) is preserved. Changes in VIP signaling are acute and reversible and not caused by effects of SBT.     

Small bowel transplantation: Effects on function of nonadrenergic, noncholinergic nerves

Previous work from our laboratory showed that spontaneous contractile activity of jejunal smooth muscle increases after small bowel transplantation. Our aim was to determine whether small bowel transplantation alters the function of nonadrenergic, noncholinergic (NANC) nerves. Seven groups of rats, (n ≥7 in each group) were studied as follows: 1 week after sham celiotomy and 1 week and 8 weeks after 45 minutes of ischemia/ reperfusion (IR1 and IR8), jejunal and ileal transection and reanastomosis (TR1 and TR8), or orthotopic small bowel transplantation (TX1 and TX8). Contractility of jejunal circular muscle strips was studied in vitro. Spontaneous contractile activity increased in the IR1, TR1, and TX1 and TX1 and TX8 groups (P<0.01). Under NANC conditions, spontaneous activity increased in TR1 and in both TX1 and TX8 (P<0.01) despite the lack of an increase in the frequency of contraction in TX1. Electrical field stimulation inhibited contractile activity at low frequencies, but under NANC conditions this inhibition persisted at higher frequencies. The calculated equieffective frequency (F₁₀₀) that produced a response equal to baseline contractile activity was similar in all groups, but under NANC conditions was greater in TX1 (P<0.025). Functional alterations of NANC nerves are partly responsible for the increase in spontaneous activity in rat jejunal circular muscle strips after a limited ischemia/reperfusion injury, after selective disruption of enteric neural continuity (transection/reanastomosis), and after small bowel transplantation. These findings may provide important insight into graft dysfunction after small bowel transplantation in humans. Supported by United States Public Health Service grant DK 39337 from the National Institutes of Health and by the Mayo Foundation.     

The role of motilin and cisapride in the enteric nervous system of the lower esophageal sphincter in humans

To assess the pharmacophysiological significance of the enteric nervous system and the responses of the human lower esophageal sphincter (LES) to motilin and cisapride, the mechanical responses of esophgeal tissues from six patients with esophageal cancer and seven patients with gastric cancer were investigated. Circular muscle reactions were recorded to evaluate the in vitro esophageal responses to electrical field stimulation (EFS), motilin, and cisapride, evoking the adrenergic and cholinergic nerves before and after treatment with various autonomic nerve blockers. The findings of this study revealed that: cholinergic nerves are mainly involved in the regulation of enteric nerves in the steady state, while nonadrenergic non-cholinergic (NANC) inhibitory nerves also exist; motilin may act both via nerves and also directly on the LES smooth muscle; and cisapride releases acetylcholine from the end of the postganglionic fiber of the cholinergic nerve in human LES thereby inducing contraction of the LES. These results suggest that cholinergic and NANC inhibitory nerves play an important role in human LES, and that motilin and cisapride is clinically useful for improving the impaired LES of patients with gastroesophageal reflux. Part of this work was presented at the 15th Annual Conference of Gut Hormones held on July 21, 1994, in Shizuoka, Japan.     

An in vitro pharmacological study of the human trigone--a site of non-adrenergic, non-cholinergic neurotransmission

Muscle strips from the human detrusor and trigone were studied in vitro. The detrusor muscle contracted strongly to both cholinergic receptor stimulation with carbachol and to electrical field stimulation. There was no evidence of atropine resistance in the detrusor strips. The superficial trigone responded maximally to alpha-adrenergic receptor stimulation but also produced a significant cholinergic response. Intramural nerve stimulation in the presence of both atropine and phentolamine produced a residual non-adrenergic, non-cholinergic (NANC) response of 40% of its maximum at 5 Hz. Electrical stimulation, particularly at the lower frequencies of stimulation, produced relaxation responses in 40% of the superficial trigonal muscle strips. These relaxations were not blocked by atropine, phentolamine or propranolol, but were abolished by tetrodotoxin. The possible role of the cholinergic "input" to the superficial trigone and the importance of the NANC excitatory and inhibitory innervation in preventing vesico-ureteric reflux and and in aiding bladder neck opening is discussed.     

Role of the Enteric Nervous System in the Elongated Sigmoid Colon of Patients With Sigmoid Volvulus

To clarify the physiologic function of the enteric nervous system (ENS) in the elongated sigmoid colon (ESC) of patients with sigmoid volvulus (SV), we examined the enteric nerve responses in lesional and normal longitudinal muscle strips (LMS) derived from patients with ESC and patients who underwent colon resection for colonic cancers. Thirty preparations of LMS were taken from the lesional sigmoid colons of 10 ESC patients with SV (8 men and 2 women, aged 53 to 80 years, mean 66.2 years). Forty preparations of LMS were taken from the normal sigmoid colons (NSC) of 20 patients with colonic cancer (12 men and 8 women, aged 55 to 76 years, mean 62.3 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. Response to EFS before blockade of the adrenergic and cholinergic nerves was as follows: NSC and ESC significantly demonstrated relaxation reaction rather than contraction reaction (P = 0.0253, P < 0.0001, respectively). ESC showed relaxation reaction more than NSC (P = 0.1138). Response to EFS after blockade of the adrenergic and cholinergic nerves was as follows: NSC and ESC significantly demonstrated relaxation reaction via nonadrenergic noncholinergic (NANC) inhibitory nerves rather than contraction reaction via NANC excitatory nerves (P < 0.0001, P < 0.0001, respectively). ESC with SV significantly showed relaxation reaction more than NSC (P = 0.0092). An increased response of relaxation mediated NANC inhibitory nerves may play a role in impaired motility in the ESC of patients with SV.Key words: Sigmoid volvulus, Elongated sigmoid colon, Enteric nervous system, Nonadrenergic noncholinergic inhibitory nerve, PathophysiologyThe elongated sigmoid colon (ESC) is considered as a cause of chronic constipation.¹⁻⁴ The ESC frequently suffer from sigmoid volvulus (SV).^3,4 In general, ESC in patients with SV is characterized by impaired motility and is associated with changes in the structure of the enteric nervous system (ENS), based on histologic studies.⁵⁻⁸ However, there are some reports that ENS in the colon of ESC with SV is normal.^9,10 Histopathologic findings in the colon of ESC with SV are still inconclusive.It is well known that enteric nerves including the nonadrenergic noncholinergic (NANC) excitatory and NANC inhibitory nerves play important roles in the regulation of gut motility.^8,11 Recent studies have suggested that NANC inhibitory nerves act more dominantly than NANC excitatory nerves in the regulation of enteric nerves in the normal colon.^11,12 Mitolo-Chieppa et al¹² reported that the ENS is very important for peristalsis of human large intestine and impaired ENS function was found in the colon of patients with slow transit constipation. However, the function of the ENS in the ESC of patients with SV is still unclear. It seems reasonable to infer that physiologic studies of the ENS in the ESC of patients with SV may help to clarify the pathophysiology of impaired motility in patients with ESC.The ENS attaches to the longitudinal muscle and not circular muscle.¹³ In this study, then, we examined the responses of electrical field stimulation (EFS) on both lesional and normal colonic longitudinal muscle strips (LMS) derived from ESC patients with SV and patients who underwent colon resection for colonic cancers by mechanogram.     

Contractile activity of circular smooth muscle in rats one year after small bowel transplantation: differing adaptive response of the jejunum and ileum to denervation

The aim of the present study was to determine the long-term effects of isogeneic small bowel transplantation (SBT) on jejunal and ileal circular smooth muscle contractile activity in the rat. Transmural strips of circular muscle were prepared from proximal jejunum and distal ileum of 1-year-old control rats and rats 1 year after SBT (SBT-1Y) to measure isometric force. Spontaneous contractile activity and the doseresponses to bethanechol and norepinephrine were studied Electrical field stimulation (EFS) at varying frequencies (1 to 20 Hz) was evaluated under adrenergic and chohnergic blockade to investigate inhibitory nerves Spontaneous activity both in the jejunum and ileum in SBT-1Y rats was not different compared to control rats Sensitivity to bethanechol did not differ between control and SBT-1Y rats in the jejunum or ileum Sensitivity to norepinephrine, however, was significantly mcreased after SBT in the ileum but not in the jejunum During EFS, inhibition was seen at low frequencies, and contractions were induced at high frequencies in all groups The degree of inhibition did not differ between control and SBT-1Y rats in the jejunum, however, it tended to be mcreased in the ileum after SBT The long-term adaptive response of smooth muscle to the extrinsic denervation accompanying SBT differs between the jejunum and the ileum Supported by grant DK 39337 from the National Institutes of Health, United States Public Health Service (M G S.), and by Ethicon Corporation, the Mayo Foundation, and the First Department of Surgery, Tohoku University School of Medicine Presented at the annual meeting of the American Gastroenterological Association, San Francisco, Calif, 1996, and the Thirty-Eighth Annual Meeting of The Society for Surgery of the Alimentary Tract, Washington, D C, May 11–14, 1997 Abstracts of this work were published in Gastroenterobgy 110 A758, 1996, and Gastroenterology 112 A824, 1997     

Role of Nitric Oxide in the Colon of Patients with Ulcerative Colitis

n = 6) and patients who underwent colon resection for colonic cancers ( n = 10). A mechanographic technique was used to evaluate in vitro 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. The results showed that (1) NANC inhibitory nerves were found to act on both normal colon and UC colon; (2) the colon with UC was more strongly innervated by NANC inhibitory nerves than the normal colon; (3) l-NNA concentration-dependently inhibited the relaxation in response to EFS in the colon of both normal and UC colon; and (4) this inhibitory effect in the colon of both normal and UC patients was reversed by l-arginine; (5) NO acts more strongly in the UC colon than the normal colon. These findings suggest that NANC inhibitory nerves play an important role in the impaired motility observed in patients with UC and that NO plays an important role as a neurotransmitter in NANC inhibitory nerves of human colon.     

Influence of the length of the small bowel graft on the severity of graft versus host disease

The influence of the length and origin of a small bowel graft on graft versus host disease (GVHD) was studied in 33 (Lewis x brown Norway) F1 hybrids transplanted with different types of Lewis small bowel grafts. Recipients of an entire small bowel graft (N = 9), a jejunal graft (N = 6), or an ileal graft (N = 6) displayed a similar acute lethal GVHD, with 100% mortality rate and equivalent survival time (15 +/- 0.7, 16.8 +/- 0.9, and 16 +/- 0.6 days, respectively) (P greater than 0.01). On the other hand, 80% of the recipients of a segmental jejunal graft (N = 10) recovered from a transitory form of GVHD and regained weight similarly to the isografted rats (N = 4). It was concluded that the entire small bowel, jejunum, and ileum can provoke an equivalent GVHD after transplantation, whereas a segment of jejunum decreases the intensity of GVHD, probably by reducing the amount of transplanted lymphoid tissue.     

NK2 tachykinin receptors mediate contraction of the pig intravesical ureter: tachykinin-induced enhancement of non-adrenergic non-cholinergic excitatory neurotransmission

The current study was designed to characterize the functionally active tachykinin receptors involved in tachykinin-elicited contractions in the pig intravesical ureter, and to investigate the possible modulation exerted by the natural tachykinins substance P (SP) and neurokinin A (NKA) on the non-adrenergic non-cholinergic (NANC) excitatory ureteral neurotransmission. In pig intravesical ureteral strips pretreated with phosphoramidon (10(-5) mol/L) to block the endopeptidase activities, isometric force recordings showed that SP, NKA, and the NK2 receptor selective agonist [beta-Ala(8)]-NKA (4-10), all three induced contractions, with the following potency order: NKA > [beta-Ala(8) ]-NKA (4-10) > SP. [Sar(9), Met(O(2))(11)]-SP and senktide, selective agonists of the NK1 and NK3 receptors, respectively, failed to modify the ureteral tone. Urothelium removal and incubation with tetrodotoxin (10(-6) mol/L), phentolamine (10(-7) mol/L), propranolol (3 x 10(-6) mol/L), atropine (10(-7) mol/L) and indomethacin (3 x 10(-6) mol/L), did not alter the contraction induced by a submaximal (10(-7) mol/L) dose of [beta-Ala(8)]-NKA (4-10). MEN 10,376 (10(-8)-10(-7) mol/L), a NK2 receptor antagonist, reduced the contraction to 3 x 10(-8) mol/L NKA. GR 82334 (10(-6) -10(-5) mol/L) and SR 142801 (10(-8)-10(-7) mol/L), selective antagonists of the NK1 and NK3 receptors, respectively, did not modify that contraction. In pig intravesical ureteral strips in NANC conditions, SP and NKA induced a potentiation of the contractions to electrical field stimulation (EFS) and to exogenous ATP. The results suggest that the tachykinins evoke a direct contraction of pig intravesical ureteral strips through NK2 receptors located in the smooth muscle. SP and NKA exert an enhancement of the NANC excitatory neurotransmission of the pig intravesical ureter.     

Mechanism mediating nitric oxide-induced inhibition in human jejunal longitudinal smooth muscle

BACKGROUND: Enteric neurotransmission is a complex process involving multiple neurotransmitters, including nitric oxide (NO). Our aim was to evaluate the role and mechanism(s) of action of NO in normal human jejunal longitudinal smooth muscle. METHODS: Transmural strips of normal human jejunum obtained from subjects undergoing gastric bypass were studied in organ chambers. Effects of exogenous NO (7 x 10(-6) mol/L to 7 x 10(-5) mol/L) and electrical field stimulation (nonspecific release of endogenous neurotransmitters) on spontaneous contractile activity and on precontracted muscle strips (substance P, 10(-5) mol/L) were evaluated in the presence and absence of the competitive NO synthase inhibitor N(G)-amino-L-arginine (L-NNA, 10(-3) mol/L) and the specific soluble guanylyl cyclase inhibitor 1H-[1,2,4]-oxadiazaolo-[4,3-a]-quinoxalin-1-one (ODQ, 10(-5) mol/L and 10(-4) mol/L). RESULTS: Exogenous NO dose-dependently inhibited spontaneous contractility and relaxed precontracted smooth muscle strips. The effects of NO were markedly attenuated or completely inhibited in the presence of ODQ. Electric field stimulation under nonadrenergic, noncholinergic conditions also inhibited spontaneous contractility and relaxed precontracted smooth muscle strips; both of these effects were attenuated, but not completely inhibited, in the presence of both ODQ and L-NNA. CONCLUSIONS: NO is an endogenous inhibitory neurotransmitter in human jejunal longitudinal smooth muscle, acting at least in part via a mechanism mediated by guanylyl cyclase. Other (non-nitrergic) nonadrenergic, noncholinergic inhibitory neurotransmitters are likely active in this portion of the human gut.     

Responses of muscle strips from the internal anal sphincter in Hirschsprung's disease to drugs and electrical field stimulation

Responses of isolated muscle strips from the rat and the dog internal anal sphincter (IAS) to drugs and electrical field stimulation (EFS) were investigated in vitro for the purpose of clarifying a manner of neural control of IAS. Also, responses of muscle strips from IAS of the patients with Hirschsprung's disease were compared with those of muscle strips from human control IAS. Muscle strips from the dog and human IAS as normal control showed contractions to norepinephrine (NE), which were abolished in the presence of phentolamine and relaxations to isoproterenol. EFS (less than 1 msec) induced relaxations of the muscle strips. These responses to EFS were not affected by either one of phentolamine, propranolol and atropine but were inhibited by tetrodotoxin. Muscle strips from IAS in Hirschsprung's disease contracted to both NE and EFS, the responses of which were abolished in the presence of phentolamine. But no relaxation to EFS of muscle strips from IAS in Hirschsprung's disease was observed. These findings revealed that normal IAS is pharmacologically innervated by alpha-adrenergic excitatory nerve, beta-adrenergic inhibitory nerve and non-adrenergic, non-cholinergic inhibitory nerve and suggested that IAS in Hirschsprung's disease is also affected by alpha-adrenergic excitatory nerve but inhibitory neural control is absent.     

脾气虚证大鼠小肠兴奋性肠神经的形态学变化

目的：观察脾气虚证大鼠小肠兴奋性神经乙酰胆碱神经和P物质神经的形态学变化。方法：清洁级成年Wistar大鼠40只,随机分为2组,脾气虚组用体质筛选、苦寒泻下和耗气破气相结合方法。建立大鼠模型,取存活大鼠上段小肠制作肠肌层全厚标本,利用免疫荧光方法标记乙酰胆碱神经和P物质神经兴奋性神经纤维,用激光扫描共聚焦显微镜检测、分析。结果：与对照组相比,脾气虚组大鼠小肠P物质、乙酰胆碱神经纤维数量明显减少（P＜0.05）,荧光强度值明显降低（P＜0.05）,神经结构紊乱,相互间的连接不连续,完整的网络状结构被破坏。结论：脾气虚时大鼠小肠运动功能障碍的发生可能与兴奋性神经纤维的减少密切相关。     

Differential adrenergic response to extrinsic denervation in canine longitudinal jejunal and ileal smooth muscle

Early postoperative complications after small bowel transplantation (SBT) are likely mediated, at least in part, by dysmotility caused by the obligate disruption of extrinsic and enteric nerves in the graft. Adrenergic hypersensitivity of gut smooth muscle has been observed in some (but not all) segments of intestine in various experimental models of SBT, highlighting regional and species variability in response to denervation. Little is known about changes in canine longitudinal muscle after extrinsic denervation. Six dogs each underwent either complete extrinsic denervation of the jejunoileum or a control operation (transection and reanastomosis of the proximal jejunum and distal ileum). In vitro contractile response of longitudinal muscle strips to norepinephrine was evaluated at the time of the operation, and 2 weeks and 8 weeks later. After extrinsic denervation, the jejunal response to norepinephrine was preserved at all time points; however, the ileum displayed a decreased sensitivity to norepinephrine, an effect unmasked after intramural neural blockade with tetrodotoxin. These data support a potential for neurally mediated dysmotility after SBT and reinforce the differences in responses to extrinsic denervation between species, as well as differences within different regions and between anatomic segments of small intestine in the same species. Presented in part at the Ross Residents and Fellows Research Conference and the Forty-Second Annual Meeting of The Society for Surgery of the Alimentary Tract, Atlanta, Georgia, May 20–23, 2001 (poster presentation); and published as an abstract in Gastroenterology 120:A351, 2001. Supported by grants from the National Institutes of Health (NIH DK39337 and NIH DK07198) and the Mayo Foundation.