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Reflex Circuit (reflex + circuit)

Distribution by Scientific Domains

Life Sciences	71%
Medical Sciences	28%

Selected Abstracts

Prostaglandin I2 sensory input into the enteric nervous system during distension-induced colonic chloride secretion in rat colon

ACTA PHYSIOLOGICA, Issue 3 2010
J. D. Schulzke
Abstract Aim:, Intestinal pressure differences or experimental distension induce ion secretion via the enteric nervous system, the sensorial origin of which is only poorly understood. This study aimed to investigate sensorial inputs and the role of afferent and interneurones in mechanically activated submucosal secretory reflex circuits. Methods:, Distension-induced rheogenic chloride secretion was measured as increase in short-circuit current 10 min after distension (,ISC10; distension parameters ± 100 ,L, 2 Hz, 20 s) in partially stripped rat distal colon in the Ussing-chamber in vitro. PGE2 and PGI2 were measured by radioimmunoassay. Results:, ,ISC10 was 2.0 ± 0.2 ,mol h,1 cm,2 and could be attenuated by lobeline, mecamylamine and dimethylphenylpiperazine, indicating an influence of nicotinergic interneurones. Additionally, a contribution of afferent neurones was indicated from the short-term potentiation of ,ISC10 by capsaicin (1 ,m). As evidence for its initial event, indomethacin (1 ,m) inhibited distension-induced secretion and the release of PGI2 was directly detected after distension. Furthermore, serotoninergic mediation was confirmed by granisetron (100 ,m) which was functionally localized distally to PGI2 in this reflex circuit, as granisetron inhibited an iloprost-induced ISC, while indomethacin did not affect serotonin-activated ion secretion. Conclusions:, Distension-induced active electrogenic chloride secretion in rat colon is mediated by a neuronal reflex circuit which includes afferent neurones and nicotinergic interneurones. It is initiated by distension-induced PGI2 release from subepithelial cells triggering this reflex via serotoninergic 5-HT3 receptor transmission. Functionally, this mechanism may help to protect against intestinal stasis but could also contribute to luminal fluid loss, e.g. during intestinal obstruction. [source]

Improved organotypic cell culture model for analysis of the neuronal circuit involved in the monosynaptic stretch reflex

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2006
Björn Dagberg
Abstract Knowledge regarding neuronal circuit formation is central for the understanding of the vast network making up the brain. It is therefore necessary to find novel ways to analyze the mechanisms involved in well-defined neural circuits. We present an improved in vitro model of the monosynaptic stretch reflex circuit, based on primary organotypic cell cultures. By using limb tissue as a source of muscle fibers instead of circumspinal tissue we could make the in vitro system more in vivo like in the sense that it focuses on the stretch reflex involving limb muscles. Furthermore, our analyses showed that this procedure allows muscle fibers to follow the normal developmental pattern. Particularly interesting was the finding of slow tonic myosin heavy chain expressing muscle fibers, a developmental marker for muscle spindles, in the cultures showing that this system has the potential to contain the complete reflex circuits. © 2006 Wiley-Liss, Inc. [source]

Neuromodulatory Processes of the Brain,Gut Axis

NEUROMODULATION, Issue 4 2008
Alexandru Gaman MD
ABSTRACT Brain,gut axis represents a complex reflex circuit that integrates the communication between cortex and the digestive system. Disturbances of the neuromodulatory processes in the brain,gut axis generate functional digestive disorders mainly centered on the pain symptoms and motility disorders. This article reviews structural and pathophysiologic aspects of the brain,gut axis and explains how the neuromodulatory interventions currently used in order to treat gastrointestinal conditions related to the brain,gut axis disturbances. The neuromodulation can be realized by pharmacologic targeting mainly receptors in the periphery or using electrical stimulation applied at different levels of the nervous system or directly in the muscular layers of the bowels resulting in modulation of the digestive system activity. The efficacy of the methods using electrostimulation is dependent on the parameters of the physical system used: amplitude, frequency, burst time of the electrical current, and also the positioning of the electrodes. While pharmacologic interventions are largely used at the moment, neuromodulatory interventions involving electrical stimulation showed clinical efficacy in research trials and have promise. [source]

Prostaglandin I2 sensory input into the enteric nervous system during distension-induced colonic chloride secretion in rat colon

Electrical activation of the orbicularis oculi muscle does not increase the effectiveness of botulinum toxin type A in patients with blepharospasm

EUROPEAN JOURNAL OF NEUROLOGY, Issue 3 2010
A. Conte
Background:, Our primary aim in this study was to determine whether electrically induced activation of the injected muscle increases effectiveness of botulinum type A toxin (BonT-A) in patients with blepharospasm (BPS). The second aim was to assess the safety of BonT-A by investigating whether BonT-A injection alters the excitability of blink reflex circuits in the brainstem. Methods:, Twenty-three patients with BPS received BonT-A (Botox) injected bilaterally into the orbicularis oculi muscle at a standard dose. In 18 patients, electrically induced muscle activation of the orbicularis oculi muscle on one side was performed for 60 min (4 Hz frequency) in a single session, immediately after BonT-A injection and in five patients for 60 min once a day for five consecutive days. The severity of BPS was assessed clinically with the BPS score. Compound muscle action potential (cMAPs) from the orbicularis oculi muscles were measured bilaterally. The blink reflex recovery cycle was studied at interstimulus intervals of 250 and 500 ms. Participants underwent clinical and neurophysiological assessment before BonT-A injection (T0) and 2 weeks thereafter (T1). Results:, Compound muscle action potential amplitude significantly decreased at T1 but did not differ between stimulated and non-stimulated orbicularis oculi in the two groups. BonT-A injection left the blink reflex recovery cycle tested on the stimulated and non-stimulated sides unchanged. Conclusions:, In patients with BPS, the electrically induced muscle activation neither increases the effectiveness of BonT-A nor produces larger electrophysiological peripheral effects. The lack of BonT-A-induced changes in the blink reflex recovery cycle provides evidence that BonT-A therapy is safe in patients with BPS. [source]

Morphologies and projections of defined classes of neurons in the submucosa of the guinea-pig small intestine

THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2003
John B. Furness
Abstract Four types of neurons have previously been identified by neurochemical markers in the submucosal ganglia of the guinea-pig small intestine, and functional roles have been ascribed to each type. However, morphological differences among the classes have not been determined, and there is only partial information about their projections within the submucosa. In the present work, we used intracellular microelectrodes to fill neurons of each type with biocytin, which was then converted to a permanent dye, so that the shapes of the neurons could be determined and their projections within the submucosa could be followed. Cell bodies of noncholinergic secretomotor/ vasodilator neurons had Dogiel type I morphology. These neurons, which are vasoactive intestinal peptide immunoreactive, had single axons that ran through many ganglia without providing terminals around other neurons. Cholinergic secretomotor neurons with neuropeptide Y immunoreactivity had Stach type IV morphology, and cholinergic secretomotor/vasodilator neurons had stellate cell bodies. The axons of these two types ran short distances in the plexus and did not innervate other submucosal neurons. Neurons of the fourth type, intrinsic primary afferent neurons, had cell bodies with Dogiel type II morphology and their processes supplied networks of varicose processes around other nerve cells. It is concluded that each functionally defined type of submucosal neuron has a characteristic morphology and that intrinsic primary afferent neurons synapse with secretomotor neurons to form monosynaptic secretomotor reflex circuits. Anat Rec Part A 272A:475,483, 2003. © 2003 Wiley-Liss, Inc. [source]