All Publications

  • Adult enteric nervous system in health is maintained by a dynamic balance between neuronal apoptosis and neurogenesis PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Kulkarni, S., Micci, M., Leser, J., Shin, C., Tang, S., Fu, Y., Liu, L., Li, Q., Saha, M., Li, C., Enikolopov, G., Becker, L., Rakhilin, N., Anderson, M., Shen, X., Dong, X., Butte, M. J., Song, H., Southard-Smith, E. M., Kapur, R. P., Bogunovic, M., Pasricha, P. J. 2017; 114 (18): E3709-E3718


    According to current dogma, there is little or no ongoing neurogenesis in the fully developed adult enteric nervous system. This lack of neurogenesis leaves unanswered the question of how enteric neuronal populations are maintained in adult guts, given previous reports of ongoing neuronal death. Here, we confirm that despite ongoing neuronal cell loss because of apoptosis in the myenteric ganglia of the adult small intestine, total myenteric neuronal numbers remain constant. This observed neuronal homeostasis is maintained by new neurons formed in vivo from dividing precursor cells that are located within myenteric ganglia and express both Nestin and p75NTR, but not the pan-glial marker Sox10. Mutation of the phosphatase and tensin homolog gene in this pool of adult precursors leads to an increase in enteric neuronal number, resulting in ganglioneuromatosis, modeling the corresponding disorder in humans. Taken together, our results show significant turnover and neurogenesis of adult enteric neurons and provide a paradigm for understanding the enteric nervous system in health and disease.

    View details for DOI 10.1073/pnas.1619406114

    View details for Web of Science ID 000400358000016

    View details for PubMedID 28420791

  • Substance P is essential for maintaining gut muscle contractility: a novel role for coneurotransmission revealed by botulinum toxin AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY Li, C., Micci, M., Murthy, K. S., Pasricha, P. J. 2014; 306 (10): G839-G848


    Substance P (SP) is commonly coexpressed with ACh in enteric motor neurons, and, according to the classical paradigm, both these neurotransmitters excite smooth muscle via parallel pathways. We hypothesized that, in addition, SP was responsible for maintaining the muscular responsiveness to ACh. We tested this hypothesis by using botulinum toxin (BoNT/A), a known blocker of vesicular release of neurotransmitters including ACh and neuropeptides. BoNT/A was injected into rat pyloric sphincter in different doses; as control we used boiled BoNT/A. At the desired time point, pylorus was dissected out and pyloric contractility was measured ex vivo in an organ bath and by measuring phosphorylation of myosin light chain 20 (MLC20). BoNT/A (10 IU) significantly reduced the response of pyloric muscle to exogenous ACh, an effect that was accompanied by reduced MLC20 phosphorylation in the muscle. Both effects were reversed by exogenous SP. CP-96345, a NK1 receptor antagonist, blocked the ability of exogenous SP to reverse the cholinergic hyporesponsiveness as well as the reduction in MLC20 phosphorylation induced by BoNT/A. In conclusion, we have identified a novel role for SP as a coneurotransmitter that appears to be important for the maintenance of muscular responsiveness to the principal excitatory neurotransmitter, ACh. These results also provide new insight into the effects of botulinum toxin on the enteric nervous system and gastrointestinal smooth muscle.

    View details for DOI 10.1152/ajpgi.00436.2012

    View details for Web of Science ID 000336844200004

    View details for PubMedID 24699329

    View details for PubMedCentralID PMC4347745

  • Anatomical and functional characterization of a duodeno-pancreatic neural reflex that can induce acute pancreatitis AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY Li, C., Zhu, Y., Shenoy, M., Pai, R., Liu, L., Pasricha, P. J. 2013; 304 (5): G490-G500


    Neural cross talk between visceral organs may play a role in mediating inflammation and pain remote from the site of the insult. We hypothesized such a cross talk exists between the duodenum and pancreas, and further it induces pancreatitis in response to intraduodenal toxins. A dichotomous spinal innervation serving both the duodenum and pancreas was examined, and splanchnic nerve responses to mechanical stimulation of these organs were detected. This pathway was then excited on the duodenal side by exposure to ethanol followed by luminal mustard oil to activate transient receptor potential subfamily A, member 1 (TRPA1). Ninety minutes later, pancreatic inflammation was examined. Ablation of duodenal afferents by resiniferatoxin (RTX) or blocking TRPA1 by Chembridge (CHEM)-5861528 was used to further investigate the duodeno-pancreatic neural reflex via TRPA1. ~40% of dorsal root ganglia (DRG) from the spinal cord originated from both duodenum and pancreas via dichotomous peripheral branches; ~50% splanchnic nerve single units responded to mechanical stimulation of both organs. Ethanol sensitized TRPA1 currents in cultured DRG neurons. Pancreatic edema and myeloperoxidase activity significantly increased after intraduodenal ethanol followed by mustard oil (but not capsaicin) but significantly decreased after ablation of duodenal afferents by using RTX or blocking TRPA1 by CHEM-5861528. We found the existence of a neural cross talk between the duodenum and pancreas that can promote acute pancreatitis in response to intraduodenal chemicals. It also proves a previously unexamined mechanism by which alcohol can induce pancreatitis, which is novel both in terms of the site (duodenum), process (neurogenic), and receptor (TRPA1).

    View details for DOI 10.1152/ajpgi.00012.2012

    View details for Web of Science ID 000315678800004

    View details for PubMedID 23306082

    View details for PubMedCentralID PMC3602681

  • Effect of progesterone on colonic motility and fecal output in mice with diarrhea NEUROGASTROENTEROLOGY AND MOTILITY Li, C. P., Ling, C., Biancani, P., Behar, J. 2012; 24 (4)


    Patients with diarrhea and slow transit constipation (STC) have high 5-HT levels. In STC, the high 5-HT levels have been difficult to explain, as 5-HT stimulates peristalsis. Over expression of progesterone (P4) receptors in epithelial and muscle cells of the colon may reconcile this contradiction because P4 decreases SERT and increases 5-HT levels, but their effects are rendered ineffective because of the impaired muscle contraction.? We examined whether P4 treatment could reduce the stool output in two mouse diarrheal models because of higher 5-HT levels, the SERT knock-out (KO), and the fluoxetine-treated mice.? Contractility of colon circular muscle strips from wild mice was studied. Fecal water and dry fecal output were measured daily over a 4-day period in wild and SERT-KO mice and in fluoxetine-treated mice treated with IM saline or P4. 5-HT levels were measured using ELISA.? Progesterone blocked the spontaneous and stimulated phasic contractions. Fecal water output measured in two consecutive 4-day periods was not different in wild and SERT-KO mice. The fecal output in the SERT-KO mice was higher than in wild mice. P4 treatment reduced the 4-day fecal output in both groups compared with saline treatment. Oral fluoxetine treatment increased 5-HT levels in wild mice and increased the 4-day fecal output compared with oral saline. P4 treatment caused a decrease in the fecal output in both groups.? Progesterone decreased the contractility of circular muscle strips, and reduced the fecal output in two diarrheal models, the SERT-KO and fluoxetine-treated mice.

    View details for DOI 10.1111/j.1365-2982.2011.01875.x

    View details for Web of Science ID 000301530300017

    View details for PubMedID 22284724

  • Systemic administration of anti-NGF increases A-type potassium currents and decreases pancreatic nociceptor excitability in a rat model of chronic pancreatitis AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY Zhu, Y., Mehta, K., Li, C., Xu, G., Liu, L., Colak, T., Shenoy, M., Pasricha, P. J. 2012; 302 (1): G176-G181


    We have previously shown that pancreatic sensory neurons in rats with chronic pancreatitis (CP) display increased excitability associated with a decrease in transient inactivating potassium currents (I(A)), thus accounting in part for the hyperalgesia associated with this condition. Because of its well known role in somatic hyperalgesia, we hypothesized a role for the nerve growth factor (NGF) in driving these changes. CP was induced by intraductal injection of trinitrobenzene sulfonic acid (TNBS) in rats. After 3 wk, anti-NGF antibody or control serum was injected intra-peritoneally daily for 1 wk. This protocol was repeated in another set of experiments in control rats (receiving intraductal PBS instead of TNBS). Pancreatic nociceptors labeled with the dye Dil were identified, and patch-clamp recordings were made from acutely dissociated DRG neurons. Sensory neurons from anti-NGF-treated rats displayed a lower resting membrane potential, increased rheobase, decreased burst discharges in response to stimulatory current, and decreased input resistance compared with those treated with control serum. Under voltage-clamp condition, neuronal I(A) density was increased in anti-NGF-treated rats compared with rats treated with control serum. However, anti-NGF treatment had no effect on electrophysiological parameters in neurons from control rats. The expression of Kv-associated channel or ancillary genes Kv1.4, 4.1, 4.2, 4.3, and DPP6, DPP10, and KCHIPs 1-4 in pancreas-specific nociceptors was examined by laser-capture microdissection and real-time PCR quantification of mRNA levels. No significant differences were seen among those. These findings emphasize a key role for NGF in maintaining neuronal excitability in CP specifically via downregulation of I(A) by as yet unknown mechanisms.

    View details for DOI 10.1152/ajpgi.00053.2011

    View details for Web of Science ID 000298640200018

    View details for PubMedID 22038828

    View details for PubMedCentralID PMC3345962

  • Nerve Growth Factor Modulates TRPV1 Expression and Function and Mediates Pain in Chronic Pancreatitis GASTROENTEROLOGY Zhu, Y., Colak, T., Shenoy, M., Liu, L., Pai, R., Li, C., Mehta, K., Pasricha, P. J. 2011; 141 (1): 370-377


    The pathogenesis of pain in chronic pancreatitis (CP) is poorly understood and treatment remains difficult. We hypothesized that nerve growth factor (NGF) plays a key role in this process via its effects on the transient receptor potential vanilloid 1, TRPV1.CP was induced by intraductal injection of trinitrobenzene sulfonic acid in rats. After 3 weeks, anti-NGF antibody or control serum was administered daily for 1 week. Pancreatic hyperalgesia was assessed by nocifensive behavioral response to electrical stimulation of the pancreas as well as by referred somatic pain assessed by von Frey filament testing. TRPV1 currents in pancreatic sensory neurons were examined by patch-clamp. The expression and function of TRPV1 in pancreas-specific nociceptors was examined by immunostaining and quantification of messenger RNA levels.Blockade of NGF significantly attenuated pancreatic hyperalgesia and referred somatic pain compared with controls. It also decreased TRPV1 current density and open probability and reduced the proportion of pancreatic sensory neurons that expressed TRPV1 as well as levels of TRPV1 in these neurons.These findings emphasize a key role for NGF in pancreatic pain and highlight the role it plays in the modulation of TRPV1 expression and activity in CP.

    View details for DOI 10.1053/j.gastro.2011.03.046

    View details for Web of Science ID 000292299700058

    View details for PubMedID 21473865

  • Long pulse gastric electrical stimulation induces regeneration of myenteric plexus synaptic vesicles in diabetic rats NEUROGASTROENTEROLOGY AND MOTILITY Li, C., Liu, S., Guan, Y., Qian, W., Du, F., Hou, X. 2010; 22 (4): 453-?


    Gastric electrical stimulation (GES) may improve delayed gastric emptying in diabetic gastroparesis, but whether enteric nervous system (ENS) is directly involved in its mechanism of improvement in gastric motility is unclear. The aims were to investigate the correlation between the changes in ENS and effects of long pulse GES on them in diabetic rats induced by streptozotocin (STZ).Electron microscopy, immunohistochemistry, RT-PCR and western blot were used to evaluate changes of myenteric plexus neurons and synaptic vesicles in different stages of the diabetic rats. The effects of GES were detected by same methods after pacing wires were implanted and then diabetes was induced and followed by long pulse GES.Since 6 weeks after STZ injection, the nerve fibres were incompact and synaptic vesicles in myenteric neurons reduced. Furthermore, the myenteric neurons showed severe damage such as partial depletion of the axon, swelling of mitochondria and seriously decreased synaptic vesicles in 12 weeks after STZ injection. The synaptophysin and PGP9.5-positive area and expressions of synaptophysin mRNA and protein decreased with the duration of diabetes. Long pulse GES could induce increase of myenteric neuronal synaptic vesicles, synaptophysin and PGP9.5-positive area and in myenteric plexus. The synaptophysin mRNA and protein expression rose after GES, whatever GES beginning early or late, short-term or long-term.The longer duration of diabetes, the more significant damages to myenteric neurons and synaptic vesicles of diabetic rats; long pulse GES could induce regeneration of myenteric plexus synaptic vesicles, thereby reform gastric motility.

    View details for DOI 10.1111/j.1365-2982.2009.01420.x

    View details for Web of Science ID 000275339700014

    View details for PubMedID 19886913

  • Effect of Four Medications Associated with Gastrointestinal Motility on Oddi Sphincter in the Rabbit PANCREATOLOGY Li, C., Qian, W., Hou, X. 2009; 9 (5): 615-620


    Modulatory drugs of gastrointestinal (GI) motility are a possibility for use to relieve the main clinical presentation of sphincter of Oddi (SO) dysfunctions which are not easily distinguished from those occurring in high prevalence functional GI disorders. The aim of this study was to investigate the effects of GI motility modulators including pinaverium, domperidone, trimebutine, and tegaserod on the contractile activity of SO stimulated by carbachol in the rabbit.The contraction responses precontracted by carbachol (0.1 microM) of in vitro rabbit SO rings were evaluated before and after the addition of a series concentration (10(-13) to 10(-3)M) of pinaverium, domperidone, trimebutine, and tegaserod.Pinaverium induced a concentration-dependent relaxation of isolated SO rings (10(-13) vs. 10(-7) vs. 10(-3)M = 16.6 +/- 4.8 vs. 47.1 +/- 5.5 vs. 81.2 +/- 6.2%, p < 0.001 by ANOVA) precontracted with carbachol (0.1 microM). Tegaserod did not significantly effect (10(-13) vs. 10(-7) vs. 10(-3)M = 2.3 +/- 2.2 vs. 6.7+/- 2.1 vs. 10.1 +/- 2.3%, p > 0.05 by ANOVA) SO motility, but domperidone seemed to stimulate SO contractions (10(-12) vs. 10(-7) vs. 10(-3)M = -2.2 +/- 1.5 vs. -13.9 +/- 2.0 vs. -21.0 +/- 2.7%, p < 0.05 by ANOVA). At low doses (10(-13) to 10(-7)M), trimebutine stimulated SO contraction (-8.7 +/- 1.4 vs. -9.3 +/- 2.0%); however, high doses (10(-6) to 10(-3)M) of trimebutine inhibited SO motility (-5.9 +/- 1.7 vs. 14.5 +/- 2.0%, p < 0.05 by ANOVA).Pinaverium totally inhibits contractions induced by carbachol and tegaserod has no effect on carbachol-induced contractions. Domperidone stimulates contractions induced by carbachol. Trimebutine could either stimulate or inhibit SO contractions depending on its dosage.

    View details for DOI 10.1159/000212095

    View details for Web of Science ID 000274592500010

    View details for PubMedID 19657216