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W2040 Responses of Nucleus Tractus Solitarius Neurons to CCK-8s, Vanilloid and Purinergic Agonists
AGA Abstracts
gastric =6) met inclusion criteria and yielded tabulated coordinates from 14 contrasts for RD, 11 contrasts for GD and 9 contrasts for ED. A total of 416 foci were used for the ALE analysis 128 RD, 109 ED, and 179 GD. Compared to ED, RD produced greater consistent activity in the rostral aspects of the dorsal anterior cingulate cortex (ACC), right ventrolateral prefrontal cortex (vlPFC) [Brodman Area (BA) 44], and FC (BA 10) and less consistent activity was observe in primary and secondary motor cortices (precentral gyrus [BA 4, BA 6]) and the medial and superior frontal gyrus (BA 8, BA 6). ED and RD activated different regions of the Mid-insula (INS), while only RD was associated with activation of the anterior (a) INS. In comparison to RD, during GD greater consistent activations were observed in the cerebellum, MCC, and bilateral thalamus. During RD compared to GD, more consistent activations were observed in the rostral ACC, aINS, Mid-INS, FC (BA 10), and inferior parietal cortex (BA 40). Different regions of activation in the inferior frontal gyrus (BA 47) were observed during gastric and rectal distension. Conclusion: Convergent and unique patterns of activation were observed with distensions of the 3 different GI tract regions. Greater consistent activity was observed in anterior aspects of the homeostatic afferent (rACC, aINS) and frontal modulatory (FC) regions with RD in comparison to GD and ED. Gastric distention produced greater thalamus and Mid ACC activation than GD and RD. ED showed greater consistent activation in motor cortex (BA 6, BA8) and mid-INS. Both GD and RD were characterized by greater consistent cerebellar activity. These differences may be related in part to different patterns of innervation between the 3 regions.
W2039 Brain Imaging of the Motion Sickness Induced Nausea with a Novel Stimulation Paradigm, An FMRI Study Braden Kuo, Clarissa Foy, Sara Neuman, Whitney Michalek, Yong Zhang, Lauren LaCount, Kyungmo Park, Jieun Kim, Jeungchan Lee, Di Z. Ye, Vitaly Napadow
W2037 Assessment of Cortico-Limbic Activation Following Colorectal Distension in the Rat; Influence of Genetics and Early Life Stress Sinead M. Gibney, Romain D. Gosselin, Timothy G. Dinan, John F. Cryan
Background: Nausea, a common and unpleasant GI-associated sensation, has never been evaluated with functional MRI (fMRI). Similar to pain, nausea also elicits autonomic response and may be modulated by specific brain networks. Aim: To interrogate the neural correlates of nausea using fMRI. Methods: The nauseagenic stimulus was a standardized visual presentation of alternating black (1.2cm, 6.9° viewing angle) and white stripes (1.85cm, 10.6° viewing angle) with left-to-right linear motion 62.5 °/sec. This stimulus was projected with a 150° field of view, incorporating a specialized 23-channel head coil to allowing unimpeded visual stimulation. BOLD T2*-weighted fMRI was performed with a 1.5T Siemens Avanto with concurrent autonomic monitoring. FMRI data were analyzed using a parametric approach driven by subject button-box response to estimate the brain correlates of nausea. Subjects were trained to recognize and rate VAS nausea levels on a scale of 1-4, with 4 corresponding to 75% of the worst nausea experienced, triggering the end of linear motion stimulation. We first defined ON blocks which began at nausea level transitions (0 to 1, 1 to 2, and 2 to 3). Block duration was chosen to be 1 minute. Data at single subject level were analyzed with a general linear model (GLM), which contained regressors for each of the transition blocks, as well as a regressor capturing the entire stripes presentation as a regressor of no interest. Data from the single subject level (transition block regressor parameter estimates and their variance) were transformed to MNI-space and passed up to a group level random effects model which included contrast coding for nauseagenic transition periods weighted by linearly increasing nausea intensity. Results: 13 female subjects (mean age 30 yr) completed both mock scan training and fMRI imaging sessions. The average time of visual stimulation was 13.1 ± 6 min. 10/13 subjects reached a level 4. No vomiting occurred during the study for any subject. VAS nausea level transitions with increasing intensity were correlated with brain activation in the orbito-frontal, anterior cingulate (ACC), and dorsolateral prefrontal cortices, as well as the nucleus accumbens (NA) and caudate. Conversely brain deactivations occurred in the dorsolateral prefrontal cortex and cerebellum. Conclusions: Nausea induces affective and autonomic dysregulation by modulating limbic (e.g. ACC) brain regions as well reward circuitry (e.g. NA). Our novel fMRI paradigm was successful in characterizing the neural correlates of nausea and can serve as a model to evaluate the neurobiology of nausea with pathology, as well as the impacts of potential interventions.
Background & Aims: The underlying cause of irritable bowel syndrome (IBS) has been difficult to establish, but evidence suggests that genetic and environmental factors can affect the clinical course of this disorder in humans. The pattern of altered physiological responses to visceral stressors reported in IBS patients is comparable to those seen in the maternally separated (MS) rat model and the genetically selected Wistar Kyoto (WKY) rat strain, suggesting that they may be attractive models in which to study the brain-gut axis dysregulation seen in IBS. Many studies using animal models of IBS exclusively assess the pseudoaffective responses to noxious visceral stimulation, such as the visceromotor response. However, as IBS symptoms can be subjective human experiences, many human studies also assess abnormal activity in brain regions involved in the processing of visceral pain. This suggests that a comparison of brain regions activated in response to noxious visceral stimulation is necessary for the generation of animal models of IBS. Methods: Male rats were exposed to colonic rectal distension and abdominal contractions were counted. Several corticolimbic structures were analysed for the presence of c-fos+ immunoreactivity including the prelimbic (PrL), infralimbic (IL), rostral anterior cingulate (rACC) and caudal anterior cingulate cortices (cACC), and the amygdala (AMY). The immediate early gene c-fos is rapidly expressed in several brain regions in response to various stressors and is therefore a reliable indicator of activated cell populations in the central nervous system. C-fos+ cells were visualised using an avidin-biotin complex immunoperoxidase method, and counted bilaterally for each brain region analysed. Results: When compared to relevant controls, WKY and MS rats displayed increased visceral hypersensitivity to CRD. In all groups, exposure to CRD induced cellular activation in the PrL, IL, rACC, cACC and the AMY. However, in the PrL, IL, rACC and AMY, an interaction between stress and strain was found suggesting that in these brain regions the WKY and MS rats have a more pronounced cellular response to CRD compared to their relevant controls. No interaction between stress and strain was found in the caudal anterior cingulate cortex in either group. Conclusions: Our data confirm a comparable corticolimbic response to visceral pain in two preclinical models of IBS as seen in IBS patients. This supports the use of these rats as models of this disorder. The identification of this neuronal activation pattern may provide further insight into the neurochemical pathways through which therapeutic strategies for IBS could be derived.
W2040 Responses of Nucleus Tractus Solitarius Neurons to CCK-8s, Vanilloid and Purinergic Agonists ShuXia Wan, Vander Baptista, R. Alberto Travagli
W2038 Novel Test of Bi-Directional Assessment of Brain-Anorectal Axis in Healthy Humans Kasaya Tantiphlachiva, Jessica A. Paulson, Jose Maria Remes Troche, Ashok Attaluri, Konrad S. Schulze, Shaheen Hamdy, Satish S. Rao
The subnucleus centralis of the nucleus tractus solitarius (cNTS) receives sensory inputs from subdiaphragmatic viscera through afferent vagal fibers and is involved in vago-vagal circuits controlling gastrointestinal motility. Recent reports by Andresen's group indicate that vagal sensory fibers inputs to NTS neurons can be distinguished based on their response to vanilloid agonists (active on vagal C-fibers only) or to purinergic agonists (active on Adelta fibers only). Our previous In Vitro studies suggested that exogenously applied sulfated cholecystokinin (CCK-8s) increases the excitability of cNTS neurons by increasing the release of glutamate from vagal afferent fibers. Since it has been suggested that CCK-8s exerts its gastrointestinal-related effects via activation of C-fibers only, the aim of this study was to test whether vanilloid and CCK-8s sensitive fibers impinging on the cNTS neurons were distinguishable from fibers responsive to purinergic agonists Whole cell patch clamp recordings made from cNTS neurons were conducted to record the response of spontaneous excitatory postsynaptic glutamate currents (sEPSC) to perfusion with capsaicin (CAP), αβ-met-ATP (ATP) and/or CCK-8s. When applied alone ATP (N=15), CAP (N=30) and CCK8s (N=40) increased the frequency of sEPSC (P<0.05) in 37, 75 and 43 % of cNTS neurons, respectively. Approximately 30% of cNTS neurons were responsive to both CCK-8s and ATP, to CCK-8s and CAP, or to ATP and CAP while 32% of the neurons were responsive to all three agonists. Interestingly, we observed that all neurons responding to ATP or CCK8s were also responsive to CAP. Perivagal treatment with CAP, which is suggested to induce a selective degeneration of C-fibers, decreased by 45% the number of cNTS neurons responding to ATP, CAP or CCK-8s. Our data suggest that 1) cNTS responding to ATP also respond to CAP, suggesting that the distingishing C- vs A-delta fibers based on their selective response to either ATP or CAP cannot be applied to cNTS neurons; 2) based on the response to ATP, CAP and CCK-8s, perivagal CAP treatment may induce a non-selective degeneration of both C- and A-delta vagal fibers impinging on cNTS neurons.
INTRODUCTION: Brain-gut interactions play an important role in the pathophysiology of functional gastrointestinal disorders. Although fMRI, MEG, PET are useful, these tests only assess afferent pathways and are not practical for routine use. Hence, there remains a need for simple non-invasive tests for assessing bi-directional function of brain-gut axis. AIMS: To develop a comprehensive series of tests assessing afferent anorectal-brain function using cortical evoked potentials (CEP), and efferent brain-anorectal function using motor evoked potentials (MEP) in healthy subjects, and to generate normative data. METHODS: In 24 healthy subjects (M/F 7/17, age 20-57 years), CEP were assessed by electrical stimulation of anus and rectum at 10 and 1 cm from anal margin with a probe containing 2 pairs of bipolar steel ring electrodes, each 2 cm apart and a neurophysiology recording system (Cadwell Sierra). Anal and Rectal MEP were subsequently recorded by the same probe following transcranial magnetic stimulation (TMS) with a 9-cm circular coil (Cadwell), located over the left and right paramedian motor cortex. Stimulation intensity was between 60-90% of 2.2 Tesla. The anorectal sensory thresholds for first sensation and pain (mA) during electrical stimulation, anal and rectal latencies [P1, N1, P2, N2 (msec)] and amplitudes [P1-N1, P2-N2 (μV)] for CEP responses and anal and rectal latencies and amplitudes for MEP, and for each side were analyzed. Test duration was 2 hours. RESULTS: Electrosensory thresholds (Mean ± 95% CI) for first sensation and pain were 19±4 and 45±9 mA in rectum and 9± 3 and 36±7 mA in anus. Table shows mean (95%CI) latencies and amplitudes of CEP and MEP responses. CONCLUSIONS: We designed a comprehensive neurophysiologic test for bi-directional assessment of cortico-anorectal function in humans and have provided normative data. The test is safe, less expensive and holds promise for novel insights regarding neurovisceral mechanisms, the pathophysiology of brain-gut interactions and assessment of therapeutic interventions. Acknowledgement: NIH Grant R01 DK057100.
AGA Abstracts
A-778
gastric =6) met inclusion criteria and yielded tabulated coordinates from 14 contrasts for RD, 11 contrasts for GD and 9 contrasts for ED. A total of 416 foci were used for the ALE analysis 128 RD, 109 ED, and 179 GD. Compared to ED, RD produced greater consistent activity in the rostral aspects of the dorsal anterior cingulate cortex (ACC), right ventrolateral prefrontal cortex (vlPFC) [Brodman Area (BA) 44], and FC (BA 10) and less consistent activity was observe in primary and secondary motor cortices (precentral gyrus [BA 4, BA 6]) and the medial and superior frontal gyrus (BA 8, BA 6). ED and RD activated different regions of the Mid-insula (INS), while only RD was associated with activation of the anterior (a) INS. In comparison to RD, during GD greater consistent activations were observed in the cerebellum, MCC, and bilateral thalamus. During RD compared to GD, more consistent activations were observed in the rostral ACC, aINS, Mid-INS, FC (BA 10), and inferior parietal cortex (BA 40). Different regions of activation in the inferior frontal gyrus (BA 47) were observed during gastric and rectal distension. Conclusion: Convergent and unique patterns of activation were observed with distensions of the 3 different GI tract regions. Greater consistent activity was observed in anterior aspects of the homeostatic afferent (rACC, aINS) and frontal modulatory (FC) regions with RD in comparison to GD and ED. Gastric distention produced greater thalamus and Mid ACC activation than GD and RD. ED showed greater consistent activation in motor cortex (BA 6, BA8) and mid-INS. Both GD and RD were characterized by greater consistent cerebellar activity. These differences may be related in part to different patterns of innervation between the 3 regions.
W2039 Brain Imaging of the Motion Sickness Induced Nausea with a Novel Stimulation Paradigm, An FMRI Study Braden Kuo, Clarissa Foy, Sara Neuman, Whitney Michalek, Yong Zhang, Lauren LaCount, Kyungmo Park, Jieun Kim, Jeungchan Lee, Di Z. Ye, Vitaly Napadow
W2037 Assessment of Cortico-Limbic Activation Following Colorectal Distension in the Rat; Influence of Genetics and Early Life Stress Sinead M. Gibney, Romain D. Gosselin, Timothy G. Dinan, John F. Cryan
Background: Nausea, a common and unpleasant GI-associated sensation, has never been evaluated with functional MRI (fMRI). Similar to pain, nausea also elicits autonomic response and may be modulated by specific brain networks. Aim: To interrogate the neural correlates of nausea using fMRI. Methods: The nauseagenic stimulus was a standardized visual presentation of alternating black (1.2cm, 6.9° viewing angle) and white stripes (1.85cm, 10.6° viewing angle) with left-to-right linear motion 62.5 °/sec. This stimulus was projected with a 150° field of view, incorporating a specialized 23-channel head coil to allowing unimpeded visual stimulation. BOLD T2*-weighted fMRI was performed with a 1.5T Siemens Avanto with concurrent autonomic monitoring. FMRI data were analyzed using a parametric approach driven by subject button-box response to estimate the brain correlates of nausea. Subjects were trained to recognize and rate VAS nausea levels on a scale of 1-4, with 4 corresponding to 75% of the worst nausea experienced, triggering the end of linear motion stimulation. We first defined ON blocks which began at nausea level transitions (0 to 1, 1 to 2, and 2 to 3). Block duration was chosen to be 1 minute. Data at single subject level were analyzed with a general linear model (GLM), which contained regressors for each of the transition blocks, as well as a regressor capturing the entire stripes presentation as a regressor of no interest. Data from the single subject level (transition block regressor parameter estimates and their variance) were transformed to MNI-space and passed up to a group level random effects model which included contrast coding for nauseagenic transition periods weighted by linearly increasing nausea intensity. Results: 13 female subjects (mean age 30 yr) completed both mock scan training and fMRI imaging sessions. The average time of visual stimulation was 13.1 ± 6 min. 10/13 subjects reached a level 4. No vomiting occurred during the study for any subject. VAS nausea level transitions with increasing intensity were correlated with brain activation in the orbito-frontal, anterior cingulate (ACC), and dorsolateral prefrontal cortices, as well as the nucleus accumbens (NA) and caudate. Conversely brain deactivations occurred in the dorsolateral prefrontal cortex and cerebellum. Conclusions: Nausea induces affective and autonomic dysregulation by modulating limbic (e.g. ACC) brain regions as well reward circuitry (e.g. NA). Our novel fMRI paradigm was successful in characterizing the neural correlates of nausea and can serve as a model to evaluate the neurobiology of nausea with pathology, as well as the impacts of potential interventions.
Background & Aims: The underlying cause of irritable bowel syndrome (IBS) has been difficult to establish, but evidence suggests that genetic and environmental factors can affect the clinical course of this disorder in humans. The pattern of altered physiological responses to visceral stressors reported in IBS patients is comparable to those seen in the maternally separated (MS) rat model and the genetically selected Wistar Kyoto (WKY) rat strain, suggesting that they may be attractive models in which to study the brain-gut axis dysregulation seen in IBS. Many studies using animal models of IBS exclusively assess the pseudoaffective responses to noxious visceral stimulation, such as the visceromotor response. However, as IBS symptoms can be subjective human experiences, many human studies also assess abnormal activity in brain regions involved in the processing of visceral pain. This suggests that a comparison of brain regions activated in response to noxious visceral stimulation is necessary for the generation of animal models of IBS. Methods: Male rats were exposed to colonic rectal distension and abdominal contractions were counted. Several corticolimbic structures were analysed for the presence of c-fos+ immunoreactivity including the prelimbic (PrL), infralimbic (IL), rostral anterior cingulate (rACC) and caudal anterior cingulate cortices (cACC), and the amygdala (AMY). The immediate early gene c-fos is rapidly expressed in several brain regions in response to various stressors and is therefore a reliable indicator of activated cell populations in the central nervous system. C-fos+ cells were visualised using an avidin-biotin complex immunoperoxidase method, and counted bilaterally for each brain region analysed. Results: When compared to relevant controls, WKY and MS rats displayed increased visceral hypersensitivity to CRD. In all groups, exposure to CRD induced cellular activation in the PrL, IL, rACC, cACC and the AMY. However, in the PrL, IL, rACC and AMY, an interaction between stress and strain was found suggesting that in these brain regions the WKY and MS rats have a more pronounced cellular response to CRD compared to their relevant controls. No interaction between stress and strain was found in the caudal anterior cingulate cortex in either group. Conclusions: Our data confirm a comparable corticolimbic response to visceral pain in two preclinical models of IBS as seen in IBS patients. This supports the use of these rats as models of this disorder. The identification of this neuronal activation pattern may provide further insight into the neurochemical pathways through which therapeutic strategies for IBS could be derived.
W2040 Responses of Nucleus Tractus Solitarius Neurons to CCK-8s, Vanilloid and Purinergic Agonists ShuXia Wan, Vander Baptista, R. Alberto Travagli
W2038 Novel Test of Bi-Directional Assessment of Brain-Anorectal Axis in Healthy Humans Kasaya Tantiphlachiva, Jessica A. Paulson, Jose Maria Remes Troche, Ashok Attaluri, Konrad S. Schulze, Shaheen Hamdy, Satish S. Rao
The subnucleus centralis of the nucleus tractus solitarius (cNTS) receives sensory inputs from subdiaphragmatic viscera through afferent vagal fibers and is involved in vago-vagal circuits controlling gastrointestinal motility. Recent reports by Andresen's group indicate that vagal sensory fibers inputs to NTS neurons can be distinguished based on their response to vanilloid agonists (active on vagal C-fibers only) or to purinergic agonists (active on Adelta fibers only). Our previous In Vitro studies suggested that exogenously applied sulfated cholecystokinin (CCK-8s) increases the excitability of cNTS neurons by increasing the release of glutamate from vagal afferent fibers. Since it has been suggested that CCK-8s exerts its gastrointestinal-related effects via activation of C-fibers only, the aim of this study was to test whether vanilloid and CCK-8s sensitive fibers impinging on the cNTS neurons were distinguishable from fibers responsive to purinergic agonists Whole cell patch clamp recordings made from cNTS neurons were conducted to record the response of spontaneous excitatory postsynaptic glutamate currents (sEPSC) to perfusion with capsaicin (CAP), αβ-met-ATP (ATP) and/or CCK-8s. When applied alone ATP (N=15), CAP (N=30) and CCK8s (N=40) increased the frequency of sEPSC (P<0.05) in 37, 75 and 43 % of cNTS neurons, respectively. Approximately 30% of cNTS neurons were responsive to both CCK-8s and ATP, to CCK-8s and CAP, or to ATP and CAP while 32% of the neurons were responsive to all three agonists. Interestingly, we observed that all neurons responding to ATP or CCK8s were also responsive to CAP. Perivagal treatment with CAP, which is suggested to induce a selective degeneration of C-fibers, decreased by 45% the number of cNTS neurons responding to ATP, CAP or CCK-8s. Our data suggest that 1) cNTS responding to ATP also respond to CAP, suggesting that the distingishing C- vs A-delta fibers based on their selective response to either ATP or CAP cannot be applied to cNTS neurons; 2) based on the response to ATP, CAP and CCK-8s, perivagal CAP treatment may induce a non-selective degeneration of both C- and A-delta vagal fibers impinging on cNTS neurons.
INTRODUCTION: Brain-gut interactions play an important role in the pathophysiology of functional gastrointestinal disorders. Although fMRI, MEG, PET are useful, these tests only assess afferent pathways and are not practical for routine use. Hence, there remains a need for simple non-invasive tests for assessing bi-directional function of brain-gut axis. AIMS: To develop a comprehensive series of tests assessing afferent anorectal-brain function using cortical evoked potentials (CEP), and efferent brain-anorectal function using motor evoked potentials (MEP) in healthy subjects, and to generate normative data. METHODS: In 24 healthy subjects (M/F 7/17, age 20-57 years), CEP were assessed by electrical stimulation of anus and rectum at 10 and 1 cm from anal margin with a probe containing 2 pairs of bipolar steel ring electrodes, each 2 cm apart and a neurophysiology recording system (Cadwell Sierra). Anal and Rectal MEP were subsequently recorded by the same probe following transcranial magnetic stimulation (TMS) with a 9-cm circular coil (Cadwell), located over the left and right paramedian motor cortex. Stimulation intensity was between 60-90% of 2.2 Tesla. The anorectal sensory thresholds for first sensation and pain (mA) during electrical stimulation, anal and rectal latencies [P1, N1, P2, N2 (msec)] and amplitudes [P1-N1, P2-N2 (μV)] for CEP responses and anal and rectal latencies and amplitudes for MEP, and for each side were analyzed. Test duration was 2 hours. RESULTS: Electrosensory thresholds (Mean ± 95% CI) for first sensation and pain were 19±4 and 45±9 mA in rectum and 9± 3 and 36±7 mA in anus. Table shows mean (95%CI) latencies and amplitudes of CEP and MEP responses. CONCLUSIONS: We designed a comprehensive neurophysiologic test for bi-directional assessment of cortico-anorectal function in humans and have provided normative data. The test is safe, less expensive and holds promise for novel insights regarding neurovisceral mechanisms, the pathophysiology of brain-gut interactions and assessment of therapeutic interventions. Acknowledgement: NIH Grant R01 DK057100.
AGA Abstracts
A-778