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Reflex Activation (reflex + activation)
Selected AbstractsEffects of amphetamine on salivary secretionEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2009Bengt Götrick Amphetamine induces xerogenic effects, but its mechanism of action and xerogenic potency are unknown. In the current in vivo study on the rat parotid gland, the effects of amphetamine on reflex-evoked and acetylcholine-evoked salivation were examined in the absence and presence of adrenergic and dopaminergic antagonists. Under anaesthesia, amphetamine increased the secretion of salivary fluid and the amount of protein therein in response to acetylcholine. Phentolamine abolished the increase in salivary flow and had no effect on the salivary protein concentration, whereas propranolol only reduced the salivary protein concentration. Reflex activation of the secretion evoked a well-maintained level of secretion that was reduced by amphetamine [50% inhibitory dose (ID50) 1.9 ± 0.1 mg kg,1 intravenously); the salivary protein concentration was increased in the presence of amphetamine. Phentolamine and haloperidol reduced the amphetamine-inhibitory effect on the reflex-evoked fluid response, whereas propranolol had no effect on the fluid response. The xerogenic effect of amphetamine is mainly exerted by central mechanisms involving ,-adrenoceptors, while, indirectly, amphetamine causes secretion of protein by inducing the release of noradrenaline from glandular nerve terminals. [source] The interaction of central command and the exercise pressor reflex in mediating baroreflex resetting during exercise in humansEXPERIMENTAL PHYSIOLOGY, Issue 1 2006Kevin M. Gallagher Central command and the exercise pressor reflex can independently reset the carotid baroreflex (CBR) during exercise. The present investigation assessed the interactive relationship between these two neural mechanisms in mediating baroreflex resetting during exercise. Six men performed static leg exercise at 20% maximal voluntary contraction under four conditions: control, no perturbation; neuromuscular blockade (NMB) induced by administration of the neuromuscular blocking agent Norcuron (central command activation); MAST, application of medical antishock trousers inflated to 100 mmHg (exercise pressor reflex activation); and Combo, NMB plus MAST (concomitant central command and exercise pressor reflex activation). With regard to CBR control of heart rate (HR), both NMB and Combo conditions resulted in a further resetting of the carotid,cardiac stimulus,response curve compared to control conditions, suggesting that CBR,HR resetting is predominately mediated by central command. In contrast, it appears that CBR control of blood pressure can be mediated by signals from either central command or the exercise pressor reflex, since both NMB and MAST conditions equally augmented the resetting of the carotid,vasomotor stimulus,response curve. With regard to the regulation of both HR and blood pressure, the extent of CBR resetting was greater during the Combo condition than during overactivation of either central command or the exercise pressor reflex alone. Therefore, we suggest that central command and the exercise pressor reflex interact such that signals from one input facilitate signals from the other, resulting in an enhanced resetting of the baroreflex during exercise. [source] Hypertonia in childhood secondary dystonia due to cerebral palsy is associated with reflex muscle activation,MOVEMENT DISORDERS, Issue 7 2009Johan van Doornik PhD Abstract It is often assumed that co-contraction of antagonist muscles is responsible for increased resistance to passive movement in hypertonic dystonia. Although co-contraction may certainly contribute to hypertonia in some patients, the role of reflex activation has never been investigated. We measured joint torque and surface electromyographic activity during passive flexion and extension movements of the elbow in 8 children with hypertonic arm dystonia due to dyskinetic cerebral palsy. In all cases, we found significant phasic electromyographic activity in the lengthening muscle, consistent with reflex activity. By correlating activation with position or velocity of the limb, we determined that some children exhibit position-dependent activation, some exhibit velocity-dependent activation, and some exhibit a mixed pattern of activation. We conclude that involuntary or reflex muscle activation in response to stretch may be a significant contributor to increased tone in hypertonic dystonia, and we conjecture that this activation may be more important than co-contraction for determining the resistance to passive movement. © 2009 Movement Disorder Society [source] Voiding reflex in chronic spinal cord injured cats induced by stimulating and blocking pudendal nerves,,NEUROUROLOGY AND URODYNAMICS, Issue 6 2007Changfeng Tai Abstract Aims To induce efficient voiding in chronic spinal cord injured (SCI) cats. Methods Voiding reflexes induced by bladder distension or by electrical stimulation and block of pudendal nerves were investigated in chronic SCI cats under ,-chloralose anesthesia. Results The voiding efficiency in chronic SCI cats induced by bladder distension was very poor compared to that in spinal intact cats (7.3,±,0.9% vs. 93.6,±,2.0%, P,<,0.05). In chronic SCI cats continuous stimulation of the pudendal nerve on one side at 20 Hz induced large amplitude bladder contractions, but failed to induce voiding. However, continuous pudendal nerve stimulation (20 Hz) combined with high-frequency (10 kHz) distal blockade of the ipsilateral pudendal nerve elicited efficient (73.2,±,10.7%) voiding. Blocking the pudendal nerves bilaterally produced voiding efficiency (82.5,±,4.8%) comparable to the efficiency during voidings induced by bladder distension in spinal intact cats, indicating that the external urethral sphincter (EUS) contraction was caused not only by direct activation of the pudendal efferent fibers, but also by spinal reflex activation of the EUS through the contralateral pudendal nerve. The maximal bladder pressure and average flow rate induced by stimulation and bilateral pudendal nerve block in chronic SCI cats were also comparable to those in spinal intact cats. Conclusions This study shows that after the spinal cord is chronically isolated from the pontine micturition center, bladder distension evokes a transient, inefficient voiding reflex, whereas stimulation of somatic afferent fibers evokes a strong, long duration, spinal bladder reflex that elicits efficient voiding when combined with blockade of somatic efferent fibers in the pudendal nerves. Neurourol. Urodynam. 26:879,886, 2007. © 2007 Wiley-Liss, Inc. [source] The ProSealTM laryngeal mask airway in childrenPEDIATRIC ANESTHESIA, Issue 3 2005M. LOPEZ-GIL MD Summary Background :,The ProSealTM (PLMA) is a new laryngeal mask device with a modified cuff to improve the seal and a drain tube to provide access to the gastrointestinal tract. We assessed the performance of the size 2 (which has no dorsal cuff) and size 3 (which has a dorsal cuff) in terms of insertion success, efficacy of seal, tidal volume, gas exchange, fiberoptic position, gastric tube placement and frequency of problems. Methods :,Eighty children undergoing minor surgery were studied (n = 40, size 2 PLMA, weight 10,25 kg; n = 40, size 3 PLMA, weight >25,50 kg). Induction was with remifentanil and propofol. Insertion was with the introducer tool and by experienced users. Maintenance was with propofol or sevoflurane and pressure controlled ventilation. Results :,The first-time and overall insertion success rate was 84 and 100%, respectively. Oropharyngeal leak pressure was 31 ± 5 cmH2O. There were no gastric or drain tube air leaks. Tidal volume and gas exchange was adequate in all patients, other than two brief episodes of hypoxia because of airway reflex activation. The vocal cords and epiglottis were visible in 99 and 80%, respectively, via the airway tube. The first-time and overall insertion success rate for gastric tube insertion was 87 and 100%, respectively. During maintenance, the PLMA was removed in one patient with airway reflex activation and another required epinephrine for bronchospasm. There were no differences in performance between the sizes 2 and 3 PLMA. Conclusion :,The PLMA is an effective airway device in children and isolates the glottis from the esophagus when correctly positioned. Despite the lack of a dorsal cuff, the performance of the size 2 was similar to the size 3 PLMA in the age groups tested. [source] REFLEXLY EVOKED COACTIVATION OF CARDIAC VAGAL AND SYMPATHETIC MOTOR OUTFLOWS: OBSERVATIONS AND FUNCTIONAL IMPLICATIONSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 12 2006Julian FR Paton SUMMARY 1The purpose of the present review is to highlight the pattern of activity in the parasympathetic and sympathetic nerves innervating the heart during their reflex activation. 2We describe the well-known reciprocal control of cardiac vagal and sympathetic activity during the baroreceptor reflex, but point out that this appears to be the exception rather than the rule and that many other reflexes reviewed herein (e.g. peripheral chemoreceptor, nociceptor, diving response and oculocardiac) involve simultaneous coactivation of both autonomic limbs. 3The heart rate response during simultaneous activation of cardiac autonomic outflows is unpredictable because it does not simply reflect the summation of opposing influences. Indeed, it can result in bradycardia (peripheral chemoreceptor, diving and corneal), tachycardia (nociceptor) and, in some circumstances, can predispose to malignant arrhythmias. 4We propose that this cardiac autonomic coactivation may allow greater cardiac output during bradycardia (increased ventricular filling time and stronger contraction) than activation of the sympathetic limb alone. This may be important when pumping blood into a constricted vascular tree, such as is the case during the peripheral chemoreceptor reflex and the diving response. [source] DIFFERENTIAL NEURAL CONTROL OF GLOMERULAR ULTRAFILTRATIONCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2004Kate M Denton Summary 1.,The renal nerves constrict the renal vasculature, causing decreases in renal blood flow (RBF) and glomerular filtration rate (GFR). Whether renal haemodynamics are influenced by changes in renal nerve activity within the physiological range is a matter of debate. 2.,We have identified two morphologically distinct populations of nerves within the kidney, which are differentially distributed to the renal afferent and efferent arterioles. Type I nerves almost exclusively innervate the afferent arteriole whereas type II nerves are distributed equally on the afferent and efferent arterioles. We have also demonstrated that type II nerves are immunoreactive for neuropeptide Y, whereas type I nerves are not. 3.,This led us to hypothesize that, in the kidney, distinct populations of nerves innervate specific effector tissues and that these nerves may be selectively activated, setting the basis for the differential neural control of GFR. In physiological studies, we demonstrated that differential changes in glomerular capillary pressure occurred in response to graded reflex activation of the renal nerves, compatible with our hypothesis. 4.,Thus, sympathetic outflow may be capable of selectively increasing or decreasing glomerular capillary pressure and, hence, GFR by differentially activating separate populations of renal nerves. This has important implications for our understanding of the neural control of body fluid balance in health and disease. [source] Renin Inhibitors in Chronic Heart Failure: The Aliskiren Observation of Heart Failure Treatment Study in ContextCLINICAL CARDIOLOGY, Issue 9 2010FESC, FRACP, Henry Krum PhD Renin-angiotensin aldosterone system (RAAS) activation is a key neurohormonal contributor to the progression of chronic heart failure. Strategies that block this activation have consistently demonstrated major beneficial impacts on morbidity and mortality in this setting. Direct renin inhibitors (DRIs) present a novel opportunity to block at an additional or alternative step in this pathway, that being conversion of angiotensinogen to angiotensin I. Theoretical benefits of blocking at the level of renin include: inhibition of the reflex activation of plasma renin activity induced by conventional downstream RAAS blockers. Minimization of angiotensin II and/or aldosterone escape and blocking upstream at the rate-limiting step of angiotensin I production. Preclinical and early-phase clinical studies have largely supported this hypothesis. In the Aliskiren Observation of Heart Failure Treatment study, patients with systolic chronic heart failure receiving background angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers and ,-blockers benefited from aliskiren in reduction vs placebo of plasma levels of brain natriuretic peptide, the primary efficacy endpoint of that study. Large-scale outcome trials are, however, required to definitively determine the benefits of a DRI strategy additional to, or as an alternative to, conventional approaches such as ACE inhibitors in the systolic chronic heart failure setting. Copyright © 2010 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose. [source] | ||||||||||