Integration of vagal afferent responses to gastric loads and cholecystokinin in rats

1991 ◽  
Vol 261 (1) ◽  
pp. R64-R69 ◽  
Author(s):  
G. J. Schwartz ◽  
P. R. McHugh ◽  
T. H. Moran
Keyword(s):  
Discharge Rate ◽  
Celiac Artery ◽  
Gastric Volume ◽  
Afferent Activity ◽  
Rapid Adaptation ◽  
Discharge Rates ◽  
Group I ◽  
Afferent Fibers ◽  
Vagal Afferent ◽  
Contrast Group

The neurophysiological responses to 2-ml intragastric saline loads and 100-pmol celiac artery infusions of cholecystokinin (CCK) were obtained from 20 vagal afferent fibers in 14 rats. Two groups of fibers were identified. Discharge rates of group I fibers (n = 16) were significantly increased by gastric loading, adapted slowly to maintained gastric volume, and were inhibited by load withdrawal. CCK elicited a significant increase in the discharge rate of these group I fibers. Prior exposure to CCK nearly doubled the response of these fibers to a subsequent gastric load. In contrast, group II fibers (n = 4) increased firing rate only during infusion of a gastric load and showed rapid adaptation and no response to CCK. CCK failed to alter subsequent responses to gastric loads in these fibers. These results 1) demonstrate an integration of signals elicited by exogenous CCK and gastric loads at the level of vagal afferent fibers and 2) imply that aspects of CCK's inhibition of food intake may derive from CCK's ability to mimic and amplify vagal afferent activity provoked by meal-related gastric events.

Cholecystokinin and satiety: effect of hypothalamic obesity and gastric bubble insertion

1992 ◽  
Vol 262 (2) ◽  
pp. R241-R244
Author(s):  
M. G. Boosalis ◽  
N. Gemayel ◽  
A. Lee ◽  
G. A. Bray ◽  
L. Laine ◽  
...  
Keyword(s):  
Gastric Volume ◽  
Time Dependent ◽  
Dependent Manner ◽  
Hypothalamic Obesity ◽  
Double Blind ◽  
Afferent Fibers ◽  
Hypothalamic Injury ◽  
Obese Subjects ◽  
Vagal Afferent ◽  
Gastric Bubble

Cholecystokinin (CCK) is a gut peptide whose proposed effect on satiety is thought to be related to gastric volume and to be signaled through vagal afferent fibers to the medial hypothalamus. To test these hypotheses we infused CCK C-terminal octapeptide (CCK-8) or saline in a random double-blind fashion in three groups of subjects: 17 obese subjects, 6 of whom subsequently received a gastric bubble, and 5 obese subjects whose obesity was due to hypothalamic injury. The number of sandwich canapes eaten after saline or CCK-8 infusion was recorded during three consecutive 10-min eating periods. Each subject served as his/her own control. The prior infusion of CCK-8 significantly decreased the consumption of sandwich canapes in the first eating period in both the control obese subjects and the subjects with obesity due to hypothalamic injury. Insertion of a gastric bubble did not enhance the satiety effect of CCK-8. These studies support the hypothesis that CCK produces satiety in a time-dependent manner that is not enhanced after the insertion of a gastric bubble but is operative in obese subjects with hypothalamic injury.

Apolipoprotein A-IV stimulates duodenal vagal afferent activity to inhibit gastric motility via a CCK1 pathway

2004 ◽  
Vol 287 (2) ◽  
pp. R354-R359 ◽  
Author(s):  
J. Glatzle ◽  
N. Darcel ◽  
A. J. Rechs ◽  
T. J. Kalogeris ◽  
P. Tso ◽  
...  
Keyword(s):  
Gastric Motility ◽  
Feedback Inhibition ◽  
Lipid Absorption ◽  
Nerve Terminals ◽  
Afferent Activity ◽  
Apolipoprotein A ◽  
Afferent Fibers ◽  
Vagal Afferent ◽  
Upper Gastrointestinal

Apolipoprotein A-IV (apo A-IV), a peptide expressed by enterocytes in the mammalian small intestine and released in response to long-chain triglyceride absorption, may be involved in the regulation of gastric acid secretion and gastric motility. The specific aim of the present study was to determine the pathway involved in mediating inhibition of gastric motility produced by apo A-IV. Gastric motility was measured manometrically in response to injections of either recombinant purified apo A-IV (200 μg) or apo A-I, the structurally similar intestinal apolipoprotein not regulated by triglyceride absorption, close to the upper gastrointestinal tract in urethane-anesthetized rats. Injection of apo A-IV significantly inhibited gastric motility compared with apo A-I or vehicle injections. The response to exogenous apo A-IV injections was significantly reduced by 77 and 55%, respectively, in rats treated with the CCK1 receptor blocker devazepide or after functional vagal deafferentation by perineural capsaicin treatment. In electrophysiological experiments, isolated proximal duodenal vagal afferent fibers were recorded in vitro in response to close-arterial injection of vehicle, apo A-IV (200 μg), or CCK (10 pmol). Apo A-IV stimulated the discharge of duodenal vagal afferent fibers, significantly increasing the discharge in 4/7 CCK-responsive units, and the response was abolished by CCK1 receptor blockade with devazepide. These data suggest that apo A-IV released from the intestinal mucosa during lipid absorption stimulates the release of endogenous CCK that activates CCK1 receptors on vagal afferent nerve terminals initiating feedback inhibition of gastric motility.

Gastric loads and cholecystokinin synergistically stimulate rat gastric vagal afferents

1993 ◽  
Vol 265 (4) ◽  
pp. R872-R876 ◽  
Author(s):  
G. J. Schwartz ◽  
P. R. McHugh ◽  
T. H. Moran
Keyword(s):  
Food Intake ◽  
Vagal Afferents ◽  
Sufficient Information ◽  
Afferent Activity ◽  
Combined Load ◽  
Synergistic Inhibition ◽  
Afferent Fibers ◽  
Inhibit Food Intake ◽  
Vagal Afferent ◽  
Afferent Response

Both gastric preloads and exogenous cholecystokinin (CCK) administration inhibit food intake, and combinations of preloads and CCK suppress feeding to a greater degree than either stimulus delivered alone. A role for the vagus nerve in mediating CCK's inhibition of food intake has been proposed, and gastric vagal afferent fibers respond to both gastric loads and local CCK infusions. To examine whether combined load and CCK stimuli may synergistically augment gastric neural afferent activity at the level of the peripheral vagus, we have examined the gastric vagal afferent responses (n = 8) to a range of gastric saline loads (1, 2, and 3 ml) and exogenous close celiac arterial CCK (10 and 100 pmol) when administered alone or in combination. Gastric loads ineffective in eliciting a significant increase in vagal afferent activity when administered alone became effective when combined with doses of CCK that were subthreshold for the production of a vagal afferent response. Gastric loads that alone were effective in producing a significant vagal afferent response yielded an even greater response when administered in combination with both subthreshold and suprathreshold doses of CCK. These data demonstrate that, in rats, signals produced by combined gastric load and exogenous CCK administration are integrated peripherally and interact synergistically. These results suggest that signals arising from the vagus may provide sufficient information for the synergistic inhibition of food intake produced by combinations of gastric loads and exogenous CCK.

The ENT emergency clinic: does senior input matter?

2012 ◽  
Vol 127 (1) ◽  
pp. 15-19 ◽  
Author(s):  
A Mirza ◽  
L McClelland ◽  
M Daniel ◽  
N Jones
Keyword(s):  
Quality Of Care ◽  
Discharge Rate ◽  
Surrogate Marker ◽  
Operating Theatre ◽  
Number Of Children ◽  
Discharge Rates ◽  
Time Period ◽  
Number Of Patients

AbstractBackground:Many ENT conditions can be treated in the emergency clinic on an ambulatory basis. Our clinic traditionally had been run by foundation year two and specialty trainee doctors (period one). However, with perceived increasing inexperience, a dedicated registrar was assigned to support the clinic (period two). This study compared admission and discharge rates for periods one and two to assess if greater registrar input affected discharge rate; an increase in discharge rate was used as a surrogate marker of efficiency.Method:Data was collected prospectively for patients seen in the ENT emergency clinic between 1 August 2009 and 31 July 2011. Time period one included data from patients seen between 1 August 2009 and 31 July 2010, and time period two included data collected between 1 August 2010 and 31 July 2011.Results:The introduction of greater registrar support increased the number of patients that were discharged, and led to a reduction in the number of children requiring the operating theatre.Conclusion:The findings, which were determined using clinic outcomes as markers of the quality of care, highlighted the benefits of increasing senior input within the ENT emergency clinic.

Inhibition of cardiac vagal component of baroreflex by group III and IV afferents

1991 ◽  
Vol 260 (3) ◽  
pp. H730-H734 ◽  
Author(s):  
P. N. McWilliam ◽  
T. Yang
Keyword(s):  
Peroneal Nerve ◽  
Baroreceptor Reflex ◽  
Interval Prolongation ◽  
Group Iii ◽  
Control Value ◽  
Pressure Elevation ◽  
Group I ◽  
Afferent Fibers ◽  
The Difference ◽  
The Right

The action of electrically evoked activity in somatic afferent fibers on the sensitivity of the baroreceptor reflex was examined in decerebrate cats. The sensitivity of the reflex was expressed as the difference between the maximum prolongation of R-R interval in response to carotid sinus pressure elevation and the mean of 10 R-R intervals immediately before pressure elevation. The control value of R-R interval prolongation was 192 +/- 50 ms. Stimulation (10 Hz) of group I and II fibers of the right peroneal nerve (evoked volleys recorded from the sciatic nerve) had no effect on R-R interval prolongation (171 +/- 45 ms). Recruitment of group III fibers (10 Hz) conducting at 23.6 +/- 0.65 m/s reduced the prolongation of R-R interval to 52 +/- 14 ms. Recruitment of group IV fibers (10 Hz) conducting less than 2.5 m/s further reduced the prolongation of R-R interval to 1.0 +/- 8.0 ms. It is concluded that the inhibition of the cardiac vagal component of the baroreceptor reflex produced by electrical stimulation of the peroneal nerve is mediated by afferent fibers of groups III and IV.

Jejunal or portal vein infusions of lipids increase hepatic vagal afferent activity

Neuroreport ◽  
2001 ◽  
Vol 12 (14) ◽  
pp. 3101-3105 ◽  
Author(s):  
Alan Randich ◽  
D. Seth Spraggins ◽  
James E. Cox ◽  
Stephen T. Meller ◽  
Gary R. Kelm
Keyword(s):  
Portal Vein ◽  
Afferent Activity ◽  
Vagal Afferent

New analytical solution for the study of hydraulic interaction between Alpine tunnels and groundwater

2003 ◽  
Vol 174 (5) ◽  
pp. 441-448 ◽  
Author(s):  
Jean-Christophe Maréchal ◽  
Pierre Perrochet
Keyword(s):  
Analytical Solution ◽  
Surface Waters ◽  
Discharge Rate ◽  
Water Discharge ◽  
Rate Condition ◽  
Type Curves ◽  
Discharge Rates ◽  
The Alps ◽  
Surface Monitoring ◽  
Tunnel Discharge

Abstract The present paper addresses two major problems encountered during tunnel drilling and related to the hydraulic interaction with surrounding groundwater bodies. The first one is the prediction of water discharge into the tunnel, as a function of the geometric and hydrogeological data. The second problem is related to the assessment of the draining effects on surface waters (springs, lakes, wetlands). Surface monitoring campaigns are costly and evaluating their duration is a sensitive question. Both problems are tightly related and depend on aquifer dynamics. It is shown that in a geological context with steeply dipping structures, nearly vertical, inducing series of aquifers and aquicludes such as in the Alps, the drainage of the aquifer by the tunnel can be modelled by the analytical solution of Jacob and Lohman [1952] for artesian wells. First developed for horizontal, confined unsteady flow towards a vertical well with constant drawdown, it is adapted here to a horizontal tunnel by a rotation of π/2. The main difference between this solution and more classical Theis’ solutions is that a constant drawdown condition replaces the constant discharge rate condition. Hence, a relation is obtained for the time-dependent discharge rate Q(t) detected at the tunnel after drilling, as a function of aquifer transmissivity (T), storage coefficient (S), initial drawdown (so) and tunnel radius (ro). This analytical solution is compared to a finite-elements model simulating a draining tunnel in a simplified 2D vertical cross-section. The comparisons show that the decay of the tunnel discharge can be divided into two periods. During the first period, radial drawdown develops around the tunnel and there is excellent match between analytical and numerical results. Tunnel discharge results from the decompression of rock and water (storage effects) as a response to the sudden initial drawdown at the tunnel location. During the second period, the drawdown cone reaches the aquifer limits (lateral and upper) and numerical discharge rates decrease faster than analytical rates because of hydraulic heads decline at the aquifer limits. In the Alps, such trends were observed for the discharge rates into the Simplon and Mont-Blanc tunnels, and the analytical solution of Jacob and Lohman [1952] was applied to the first discharge period to evaluate aquifer transmissivity and storage coefficients. As indicated by the simulations, and corroborated by field observations, the analytical solution is only valid during a first period after tunnel opening, the duration of which scaling with the inverse of the aquifer diffusivity (T/S). In the second part of the paper, dimensionless type-curves are presented to enable rapid evaluation of the time where a given drawdown is observed at a given distance from the tunnel. Accounting for tunnel geometry (radius and depth) and aquifer parametres (T and S), these curves could for instance help in practice to determine when surface waters would start to be affected by a draining tunnel underneath. Although neglecting the boundary effects discussed in the first part of the paper, these type-curves demonstrate the great inertia of mountain aquifers, and could be used to adjust the duration of surface monitoring campaigns according to the specific tunnel/aquifer settings.

Pain-induced changes in motor unit discharge depend on recruitment threshold and contraction speed

2021 ◽  
Author(s):  
Eduardo Martinez-Valdes ◽  
Francesco Negro ◽  
Michail Arvanitidis ◽  
Dario Farina ◽  
Deborah Falla
Keyword(s):  
Discharge Rate ◽  
Tibialis Anterior Muscle ◽  
Maximum Voluntary Contraction ◽  
Motor Units ◽  
Inhibitory Effect ◽  
Voluntary Contraction ◽  
Recruitment Threshold ◽  
Contraction Speed ◽  
Discharge Rates ◽  
Hypertonic Saline Injection

At high forces, the discharge rates of lower and higher threshold motor units (MU) are influenced in a different way by muscle pain. These differential effects may be particularly important for performing contractions at different speeds since the proportion of lower and higher threshold MUs recruited varies with contraction velocity. We investigated whether MU discharge and recruitment strategies are differentially affected by pain depending on their recruitment threshold (RT), across a range of contraction speeds. Participants performed ankle dorsiflexion sinusoidal-isometric contractions at two frequencies (0.25Hz and 1Hz) and two modulation amplitudes [5% and 10% of the maximum voluntary contraction (MVC)] with a mean target torque of 20%MVC. High-density surface electromyography recordings from the tibialis anterior muscle were decomposed and the same MUs were tracked across painful (hypertonic saline injection) and non-painful conditions. Torque variability, mean discharge rate (MDR), DR variability (DRvar), RT and the delay between the cumulative spike train and the resultant torque output (neuromechanical delay, NMD) were assessed. The average RT was greater at faster contraction velocities (p=0.01) but was not affected by pain. At the fastest contraction speed, torque variability and DRvar were reduced (p<0.05) and MDR was maintained. Conversely, MDR decreased and DRvar and NMD increased significantly during pain at slow contraction speeds (p<0.05). These results show that reductions in contraction amplitude and increased recruitment of higher threshold MUs at fast contraction speeds appears to compensate for the inhibitory effect of nociceptive inputs on lower threshold MUs, allowing the exertion of fast submaximal contractions during pain.

Binaural processing of sound pressure level in the inferior colliculus

1987 ◽  
Vol 57 (4) ◽  
pp. 1130-1147 ◽  
Author(s):  
M. N. Semple ◽  
L. M. Kitzes
Keyword(s):  
Inferior Colliculus ◽  
Sound Pressure ◽  
Spatial Information ◽  
Discharge Rate ◽  
Excitatory Input ◽  
Central Nucleus ◽  
Intensity Difference ◽  
Inhibitory Input ◽  
Directional Information ◽  
Discharge Rates

The central auditory system could encode information about the location of a high-frequency sound source by comparing the sound pressure levels at the ears. Two potential computations are the interaural intensity difference (IID) and the average binaural intensity (ABI). In this study of the central nucleus of the inferior colliculus (ICC) of the anesthetized gerbil, we demonstrate that responses of 85% of the 97 single units in our sample were jointly influenced by IID and ABI. For a given ABI, discharge rate of most units is a sigmoidal function of IID, and peak rates occur at IIDs favoring the contralateral ear. Most commonly, successive increments of ABI cause successive shifts of the IID functions toward IIDs favoring the ipsilateral ear. Neurons displaying this behavior include many that would conventionally be classified EI (receiving predominantly excitatory input arising from one ear and inhibitory input from the other), many that would be classified EE (receiving predominantly excitatory input arising from each ear), and all that are responsive only to contralateral stimulation. The IID sensitivity of a very few EI neurons is unaffected by ABI, except near threshold. Such units could provide directional information that is independent of source intensity. A few EE neurons are very sensitive to ABI, but are minimally sensitive to IID. Nevertheless, our data indicate that responses of most EE units in ICC are strongly dominated by excitation of contralateral origin. For some units, discharge rate is nonmonotonically related to IID and is maximal when the stimuli at the two ears are of comparable sound pressure. This preference for zero IID is common for all binaural levels. Many EI neurons respond nonmonotonically to ABI. Discharge rates are greater for IIDs representative of contralateral space and are maximal at a single best ABI. For a subset of these neurons, the influence arising from the ipsilateral ear is comprised of a mixture of excitation and inhibition. As a consequence, discharge rates are nonmonotonically related not only to ABI but also to IID. This dual nonmonotonicity creates a clear focus of peak response at a particular ABI/IID combination. Because of their mixed monaural influences, such units would be ascribed to different classes of the conventional (EE/EI) binaural classification scheme depending on the binaural level presented. Several response classes were identified in this study, and each might contribute differently to the encoding of spatial information.(ABSTRACT TRUNCATED AT 400 WORDS)

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