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Tonic Contractions (tonic + contraction)
Selected AbstractsCorrective movements in response to displacements in visual feedback are more effective during periods of 13,35 Hz oscillatory synchrony in the human corticospinal systemEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006Alexandros G. Androulidakis Abstract Oscillatory synchronization in the beta (,20 Hz) band is a common feature of human motor control, manifest at cortical and muscular levels during tonic contraction. Here we test the hypothesis that the influence of visual feedback on performance in a positional hold task is increased during bursts of beta-band synchrony in the corticospinal motor system. Healthy subjects were instructed to extend their forefinger while receiving high-gain visual feedback of finger position on a PC screen. Small step displacements of the feedback signal were triggered either by bursts of beta oscillations in scalp electroencephalogram or randomly with respect to cortical beta activity, and the resulting positional corrections expressed as a percentage of the step displacement. Corrective responses to beta and randomly triggered step changes in visual feedback were 41.7 ± 4.9 and 31.5 ± 6.8%, respectively (P < 0.05). A marked increase in the coherence in the beta band was also found between muscle activity and cortical activity during the beta-triggered condition. The results suggest that phasic elevations of beta activity in the corticospinal motor system are associated with an increase in the gain of the motor response to visual feedback during a tonic hold task. Beta activity may index a motor state in which processing relevant to the control of positional hold tasks is promoted, with behavioural consequences. [source] Long-lasting contractile action and the inhibitory action of cupric ions on ileal longitudinal muscleAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 4 2004K. Miyazaki Summary 1 Cupric ions (Cu2+), at concentrations above 0.03 mm, induced a progressive increase in the tonic contraction of guinea-pig ileal longitudinal muscle. Maximal contraction of 0.1 mm Cu2+ attained a level above that of the 60-mm K+ -induced tonic response, within 20 min of application. The tension induced by Cu2+ persisted for more than several hours. Tetrodotoxin (3 × 10,6 m) had no effect on the contraction induced by 0.1 mm Cu2+. 2 After incubation in a Ca2+ -free medium, the ileal response to 0.1 mm Cu2+ was lost. Nifedipine, a L-type Ca2+ channel blocker, dose-dependently inhibited contractions induced by Cu2+. 3 As the duration of the first application of 0.1 mm Cu2+ increased above 30 min, after washing with normal medium, the contractile response to a second application of 0.1 mm Cu2+ decreased gradually. After 150 min of the first application of 0.1 mm Cu2+, a second application of Cu2+ could not evoke any contraction. 4 After the application of 0.1 mm Cu2+ for 150 min, when muscles were washed with a medium containing 1 mm EDTA, the response to 0.1 mm Cu2+ returned to a greater extent in the normal Ca2+ medium. 5 In conclusion, Cu2+ (0.1 mm) induced a maximal ileal tension above that of the K-induced tonic response within 20 min. The ileal contraction to Cu2+ persisted for more than several hours and depended on extracellular Ca2+ concentrations. It is possible that a part of Cu2+, bound to a EDTA-inaccessible site, also has a tension inhibitory effect. [source] Effect of caffeine on response of rabbit isolated corpus cavernosum to high K+ solution, noradrenaline and transmural electrical stimulationCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2004Adebowale Adebiyi Summary 1.,Caffeine has wide-ranging activities on smooth muscles, including contractile and relaxant effects. The aim of the present study was to examine the activity of caffeine on rabbit corpus cavernosum (RCC). 2.,The effects of caffeine (0.5,4.0 mmol/L) on the response of RCC to high K+ solution, noradrenaline (NA) and transmural electrical stimulation (EFS) were studied in a tissue bath system. 3.,Caffeine did not contract the RCC. However, 0.5,4.0 mmol/L caffeine caused concentration-dependent relaxation of tension development in high-K+ (120 mmol/L) solution in contrast with the solvent control. At 4.0 mmol/L caffeine, high-K+ solution-induced tone of the RCC was reduced by 73.4 ± 7.3%. Caffeine (0.5,4.0 mmol/L) also concentration-dependently relaxed NA (12.5 µmol/L)-induced tonic contraction of the RCC. At 4.0 mmol/L caffeine, NA-induced tone of the RCC was reduced by 41.1 ± 7.0%. Incubation of RCC in 2.0 mmol/L caffeine for 30 min prior to EFS (1,40 Hz) caused a marked rightward shift in the frequency,response curve. 4.,The results of the present study suggest that caffeine exhibits relaxant activity on rabbit cavernosal smooth muscle and the mechanism of this activity possibly involves inhibition of Ca2+ signalling. [source] Chalcones as potent antiplatelet agents and calcium channel blockersDRUG DEVELOPMENT RESEARCH, Issue 1 2001Chun-Nan Lin Abstract In an effort to continually develop potent antiplatelet agents with vasorelaxing and antiinflammatory actions, a novel series of antiinflammatory chalcones was continually screened to evaluate their antiplatelet and vasorelaxing effects. Their structure,activity relationships and mode of action were discussed and characterized. A novel series of antiinflammatory chalcones was studied on antiplatelet effect in rabbit washed platelets and human platelet-rich plasma (PRP) and vasorelaxing effect in rat thoracic aorta. Arachidonic acid-induced platelet aggregation was potently inhibited by almost all the chalcone derivatives and 13,15 also had a potent inhibitory effect on cyclooxygenase. The selective chalcones 12,16 tested in human PRP significantly inhibited secondary aggregation induced by adrenaline. In rat thoracic aorta, most of chalcones at high concentration significantly depressed the contractions induced by Ca2+ (1.9 mM) in high K+ (80 mM) medium and the phasic and tonic contractions caused by norepinephrine (3 ,M). In the rat thoracic aorta, the phenylephrine- and high K+ -induced 45Ca2+ influx were both inhibited by a selective chalcone derivative, 14. These results indicate that the antiplatelet actions of chalcones are mainly mediated through the suppression of cyclooxygenase activity and reduced thromboxane formation and their inhibitory effects on the contractile response caused by high K+ and norepinephrine in rat thoracic aorta are mainly due to inhibition of Ca2+ influx through both voltage-dependent and receptor-operated Ca2+ channels. Drug Dev. Res. 53:9,14, 2001. © 2001 Wiley-Liss, Inc. [source] The spectrum of benign myoclonus of early infancy: Clinical and neurophysiologic features in 102 patientsEPILEPSIA, Issue 5 2009Roberto H. Caraballo Summary Purpose:, To redefine benign myoclonus of early infancy (BMEI) through analysis of clinical and neurophysiologic features in 102 patients with the aim to widen the spectrum of the syndrome, including a number of different clinical expressions of transient nonepileptic paroxysmal movements occurring in normal infants. Methods:, We recruited patients from one center in Argentina and two in Italy, including infants with normal neurologic and psychomotor development presenting with brief paroxysmal abnormal movements. Children with motor phenomena occurring only during sleep were excluded. Patients with abnormal interictal or ictal electroencephalography (EEG) findings were also excluded. The follow-up ranged from 2,40 years. Results:, One hundred and two infants (60 male) met the inclusion criteria. Age at onset ranged from 1,12 months, with a median age of 6.2 months. The following nonepileptic paroxysmal motor phenomena were recognized: (1) myoclonus, (2) spasms and brief tonic contractions, (3) shuddering, (4) atonia or negative myoclonus, (5) more than one type of motor phenomenon. In the majority of cases the episodes occurred only while awake and repeated several times a day. In 45 (44.1%) of the 102 cases contractions appeared in clusters. Conclusions:, Based on the analysis of clinical and EMG features in this large series of infants, we postulate that the spectrum of the syndrome is wider than initially suspected, and that the different transient motor manifestations and their correlation with different EMG patterns will allow recognition of this definitely benign condition comprising a variety of episodic motor phenomena in normal babies. [source] Effect of in vivo and in vitro ethanol on adrenergic and purinergic responses of the bisected rat vas deferens to low and high frequency pulsesAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 4 2001C. Boselli 1 This study investigates the effect of acute in vivo and in vitro ethanol administration on the contractions evoked electrically and by exogenous noradrenaline and ,,,-methylene-ATP in the rat bisected vas deferens. 2 In vivo ethanol treatment (3 g kg,1, i.p.) significantly potentiated the early purinergic (phase I) and the delayed adrenergic (phase II) phases evoked by single-pulse stimulation of the epididymal portion of the rat vas deferens, leaving unaffected both phases in the prostatic portion. In vitro 50 mM ethanol significantly depressed phase I leaving unaffected phase II in both portions from untreated rats. In vitro ethanol significantly depressed phase I in the epididymal portion from in vivo ethanol treated animals and potentiated phase II in both portions. 3 In vivo ethanol treatment (3.0 g kg,1, i.p.) selectively impaired the response to noradrenaline only in the prostatic portion of rat vas deferens while it was devoid of any action on ,,,-methylene-ATP contractions. Ethanol 50 mMin vitro was devoid of any action on the response to exogenous noradrenaline and ,,,-methylene-ATP in both tissues. 4 In vivo ethanol treatment slightly but significantly increased the phasic response in the epididymal portion to trains of stimuli (2,30 Hz). In vitro 50 mM ethanol was ineffective against the phasic and tonic contractions elicited by the tetanus in both portions. 5 It is concluded that ethanol treatment affects purinergic and adrenergic pathways of transmission possibly leading to a disruption of physiological contractions necessary to seminal emission. [source] Functional antagonism between nitric oxide and ATP in the motor responses of guinea-pig ileumAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 3 2000Chr. Ivancheva 1 The interaction of nitric oxide and ATP in the non-adrenergic, non-cholinergic (NANC) motor responses and the presence of NADPH-diaphorase and quinacrine-positive myenteric neurones were studied on guinea-pig ileum using mechanographic, histochemical and quinacrine-fluorescence techniques. In the presence of phentolamine, propranolol and atropine, the non-precontracted longitudinally oriented organ bath preparations responded to sodium nitroprusside (1,100 ,m) or ATP (5,50 ,m) with tetrodotoxin (0.1 ,m)-resistant relaxation or contraction, respectively. The effects of ATP were suramin (50 ,m)- and apamin (5 ,m)-sensitive. 2 The NANC motor responses elicited by electrical stimulation (0.8 ms, 1,20 Hz, 20 s) consisted of tetrodotoxin-sensitive relaxation phase followed by a phase of twitch-like and tonic contractions. 3 NG-nitro-L-arginine (L-NNA, 0.1,0.5 mm) inhibited or abolished the relaxation phase. L-arginine (0.5 mm), but not D-arginine (0.5 mm), restored the relaxation phase in L-NNA-pretreated preparations. The relaxation phase increased after ATP-induced desensitization of purinoceptors and in the presence of suramin (50 ,m) but was abolished by apamin (5 ,m). 4 The phase of contractions was enhanced by L-NNA (0.1,0.5 mm) and restored by L-arginine (0.5 mm). The twitch-like and tonic contractions were decreased during ATP-induced purinoceptor desensitization and in the presence of suramin (50 ,m). Apamin (5 ,m) inhibited the tonic contractions. 5 The desensitization of purinoceptors by ATP did not change the L-NNA-induced inhibition of the relaxation phase but decreased the L-NNA-increased phase of contractions. L-NNA reduced the relaxation phase and increased the phase of contractions during purinoceptor desensitization. 6 We conclude that in the longitudinal muscle layer of the guinea-pig ileum, nitric oxide mediates the relaxation phase while ATP contributes via smooth muscle P2 purinoceptors to the phase of contractions suggesting a postjunctional functional antagonism between nitric oxide and ATP. The presence of NADPH-diaphorase- and quinacrine-positive neuronal cells and processes running to the muscle cells confirms a physiological role of nitric oxide and ATP in the ileal neurotransmission. [source] Contraction kinetics of isolated human myometrium during menstrual cycle and pregnancyBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 1 2000Mikhail Tchirikov Objective To investigate the interaction between actin and myosin in the myometrium by studying the contraction kinetics of isolated samples of human myometrium. Design Experimental and observational cross-sectional study. Setting Eppendorf University Hospital, Hamburg. Samples Myometrium samples were taken from women in the follicular phase (n= 6) or luteal phase (n= 6) of the menstrual cycle and during pregnancy at term (n= 25). Methods The frequency, extent and rate of force development were determined in spontaneously active myometrial preparations. From a resting force of 2 mN, sustained tonic contractions were induced by K+ -depolarisation (124 mM), or by protein kinase C activation (19.9 ,M indolactam). The steady force was reversibly interrupted by rapid length changes (100 Hz sinus vibrations lasting 1 s, 5% of muscle length). Extent (steady plateau), as well as rate of force increase after cessation of vibrations, were derived from bi-exponential functions fitted to the time course of force recovery. Results Frequency of spontaneous contractions was higher in the follicular phase [mean (SD) 18.3 contractions/hour (1.0)] than in the luteal phase [13.4 contractions/hour (8.1)] or in pregnancy at term [8.8 contractions/hour (7.6)]. During indolactam treatment, steady force in pregnancy at term was significantly increased [8.8 mN (4.0)], compared with the follicular phase [3.7 mN (0.9)]. Force recovery was distinctly slower in pregnancy at term during indolactam treatment [time constant 99.2 s (57.9); P < 0.005] than during K+ -depolarisation [time constant 29.1 s (5.9)], whereas in the follicular phase the rate of force recovery was faster with indolactam [16.8 s (7.1)] than with K+ depolarisation [24.4 s (5.9); P < 0.005]. Conclusions The responses of human myometrium to contraction stimuli differ according to the reproductive state. Membrane depolarisation causes similar responses in all myometrial strips. In contrast, near term stimulation of protein kinase C generates a large tonic force and slow contraction kinetics, whereas early in the menstrual cycle contraction kinetics are fast. [source] Effects of ovariectomy and oestrogen replacement on the function and expression of Rho-kinase in rat bladder smooth muscleBJU INTERNATIONAL, Issue 5 2006Sung K. Hong OBJECTIVE To investigate the effects of ovariectomy and oestrogen replacement on the function and expression of Rho-kinase in rat bladder smooth muscle, as the actual effects of oestrogen deprivation on bladder smooth muscle are unclear. MATERIALS AND METHODS Female Sprague,Dawley rats were placed into one of three groups: sham-operated, bilateral ovariectomy-only, and bilateral ovariectomy plus oestrogen replacement groups. In the last group, oestrogen was replaced by weekly injection of ,-estradiol 17-cypionate (250 µg/kg subcutaneously for 6 weeks) beginning at 1 week after ovariectomy, whereas the other groups received vehicle-only injections for 6 weeks. After treatment, the bladder was removed for muscle strip studies to evaluate the effects of Y-27632, a specific inhibitor of Rho-kinase, on baseline tension and carbachol-induced tonic contractions. Also, the protein expression of RhoA and Rho-kinase isoenzymes was assessed by Western blot analysis. RESULTS Of the three groups, incubation with 10 µm Y-27632 resulted in the largest decrease in baseline tension of strips from the bilateral ovariectomy-only group, but this was not statistically significant (P > 0.05). For carbachol-induced tonic contractions, strips from the bilateral ovariectomy-only group were attenuated the most among the three groups after adding Y-27632 (P < 0.05). However, there were no significant differences in the levels of RhoA and the two Rho-kinase isoenzymes in bladder tissues from the three groups. CONCLUSION Our data show that oestrogen might inhibit the function of Rho-kinase in bladder smooth muscle, while having no significant effect on its expression. This finding might help to explain the greater incidence of urinary tract symptoms suggestive of overactive bladder after the menopause in women. [source] Sympathectomy reveals ,1A - and ,1D -adrenoceptor components to contractions to noradrenaline in rat vas deferensBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2004Linda Cleary We have previously demonstrated that contractions of rat vas deferens to exogenous noradrenaline involve predominantly ,1A -adrenoceptors, but that contractions to endogenous noradrenaline involve predominantly ,1D -adrenoceptors. In this study, we have examined the effects of sympathectomy on the subtypes of ,1 -adrenoceptor in rat vas deferens in radioligand binding and functional studies. In vehicle-treated tissues, antagonist displacement of [3H]prazosin binding to ,1 -adrenoceptors was consistent with a single population of ,1 -adrenoceptors. Binding affinities for a range of ,1 -adrenoceptor antagonists were expressed as pKi values and correlated with known affinities for ,1 -adrenoceptor subtypes. The correlation was significant only with ,1A -adrenoceptors. In tissues from rats sympathectomised with 6-hydroxy-dopamine (2 × 100 mg kg,1 i.p.), binding affinity for the ,1D -adrenoceptor antagonist BMY 7378 fitted best with a two-site model. In functional studies, the potency of noradrenaline at producing total (phasic plus tonic) but not tonic contractions was increased in tissues from sympathectomised rats. Results obtained from sympathectomised rats suggest that phasic contractions are mainly ,1D -adrenoceptor mediated, whereas tonic contractions are mainly ,1A -adrenoceptor mediated, based on the effects of BMY 7378 and the ,1A -adrenoceptor antagonist RS 100329. It is concluded that the predominant ,1 -adrenoceptor in vehicle-treated rat vas deferens is the ,1A -adrenoceptor, both in terms of ligand binding and contractions to exogenous agonists. The ,1D -adrenoceptor is only detectable by ligand binding following chemical sympathectomy, but is involved in noradrenaline-evoked contractions, particularly phasic contractions, of rat vas deferens. British Journal of Pharmacology (2004) 143, 745,752. doi:10.1038/sj.bjp.0705987 [source] | ||||||||||