Tetanic stimulations

Fatigue during intermittent tetanic stimulation is caused by three mechanisms (a) decreased maximum Ca activated tension, (b) decreased sensitivity of the contractile proteins, and (c) decreased Ca release from the SR. 

Lindinger, M.I. Heigenhauser, G.J.F. (1988). Ion fluxes during tetanic stimulation in isolated perfused rat hindlimb. Am. J. Physiol. 254, R117-R126. 

A supra-maximal stimulus applied as a series of square waves of 0.2 ms duration at a frequency of 50 Hz for a duration of 5 s is tetanic stimulation. 

The double-burst stimulation pattern is a newer mode of electrical nerve stimulation developed with the goal of allowing for manual detection of residual neuromuscular blockade when it is not possible to record the responses to single-twitch, TOF, or tetanic stimulation. In this pattern, three nerve stimuli are delivered at 50 Hz followed by a 700 ms rest period and then, by two or three additional stimuli at 50 Hz. It is easier to detect fade in the responses to double-burst stimulation than to TOF stimulation. The absence of fade in response to double-burst stimulation implies that clinically significant residual neuromuscular blockade does not exist. 

We already indicated that intravenous injection of ethanol blocked the LTP induced by tetanic stimulation [18]. However, when saffron crude extracts were injected intracerebroventricularly, the blocking effect of ethanol on the LTP decreased dose-dependently [19]. Moreover, crocin prevents the ethanol-induced impairment of memory acquisition in ST and SD tests [20], From these results it is easily suggested that crocin antagonized the blocking effect of ethanol on the induction of LTP. 

In the control experiments, strong tetanic stimulation induced robust LTP. Ethanol (30% 10-15 ml/kg) did not show any significant effect on the baseline synaptic responses, but suppressed the induction of LTP following strong tetanic stimulation in a concentration-dependent manner... 

The effect of crocin on the LTP-suppressing effect of ethanol was investigated (Fig. (4)). The potentiation induced by strong tetanic stimulation in the presence of 20 mg/kg crocin and 30% of ethanol (15 ml/kg) was significantly larger than that in the presence of 30% of ethanol (15 ml/kg) alone, indicating that crocin clearly attenuates the action of ethanol [21]. 

F1g.(4). Effects of ethanol and crocin on LTP induced by strong tetanic stimulation in the CA1 region of rat hippocampal slices. 

The inset in A is a representative evoked potential recorded from the CA1 pyramidal cell layer. Calibration hards vertical 2 mV, horizontal 10 msec. The population spike amplitude was defined as an average of the amplitude from the first positive peak 1 to the succeeding negative peak 2 and the amplitude from die negative peak 2 to the second positive peak 3. A Time-course of potentiation induced by strong tetanic stimulation in the control slices (O, n=23) and in the slices treated with 30% of ethanol (IS ml/kg) (, n=27 ) and in the slices treated with 30% of ethanol (IS ml/kg) and 20 mg/kg crocin ( A, n-7). (1) and (2) indicated 30% ethanol of IS ml/kg and 10 ml/kg, respectively. Ethanol or crocin was added in the perfusing ACSF from 15 or 20 min, respectively, before tetanic stimulation. The ordinate indicates the population spike amplitude expressed as a percentage of the baseline values immediately before tetanic stimulation. 

B Summary ofthe effects of ethanol and crocin on the induction of LTP. The magnitude ofLTP was evaluated with die population spike amplitude 30 min after tetanic stimulation. The numbers of observations in each group are shown in parentheses. All data are represented as the mean SEM. p<0.01 vs. control, p<0.05 vs. 30% of ethanol (IS ml/kg) alone. Duncan s multiple range test. 

The LTP-suppressing action of ethanol is reduced by the presence of crocin in rat hippocampal slices in in vitro experiment. Crocin alone does not affect the baseline responses or the potentiation induced by weak tetanic stimulation. It becomes evident that crocin attenuates the action of ethanol within the hippocampus supporting in vivo experiments as... 

Hippocampal slices (400-500 frm) were quickly prepared from male Wistar rats (8- to 9-weeks-old) and maintained in a chamber at 35 °C, where they were continuously perfused with artificial cerebrospinal fluid as described in our previous paper [11]. A bipolar tungsten electrode was placed in the stratum radiatum to stimulate Schaffer collateral and commissural afferents. The evoked potential was extracellularly recorded from the pyramidal cell layer of the CA1 subfield with a glass capillary microelectrode. A single test stimulation (0.05 msec duration) was applied at intervals of 30 sec. Drugs were delivered by perfusion. To induce potentiation of the evoked potentials, tetanic stimulation was applied at the same intensity through the same stimulating electrode as used for the test stimulation. The magnitude of LTP was evaluated by the population spike amplitude 30 min after tetanic stimulation. 

A Time-course of potentiation of population spike amplitude induced by application of tetanic stimulation (30 pulses at 60 Hz). Saline (, n=9) or ethanol (10%, A, n=5 20%, ... 

Monitoring the effect of muscle relaxants during surgery (and recovery following the use of cholinesterase inhibitors) typically involves the use of a device that produces transdermal electrical stimulation of one of the peripheral nerves to the hand and recording of the evoked contractions (twitches Figure 27-6). The motor responses to different patterns of peripheral nerve stimulation are measured. The three most commonly used patterns of include (1) single-twitch stimulation, (2) train-of-four (TOF) stimulation, and (3) tetanic stimulation. Two newer modalities are also available to monitor neuromuscular transmission double-burst stimulation and posttetanic count. 

As shown, tetanizing stimulation of the sciatic nerve produced contraction of the gastroneumius muscle and reflex increase in BP and respiration. Occlusion of the carotid artery causes increased BP and HR. Pressure on the ocular muscles decreases BP and respiration. Due to their transitory nature, many other reflexes can be used. 

Anderson, R.J. (1987). Effect of diisopropylfluorophosphate and soman on rat skeletal muscle contracture during tetanic stimulation. J. Toxicol. Environ. Health 22 491-6. 

The problem of accumulation may be marked in intensive care situations, where D-tubocurarine is used to maintain long-term paralysis (42). These patients may also have impaired renal and hepatic function, with protein and electrolyte imbalance. The timing of repeat injections of D-tubocurarine (and, indeed, all relaxant drugs) in such cases should be guided by monitoring of neuromuscular function (by response to single twitch, train-of-four, or tetanic stimulation, which is more sensitive but painful), or clinically by observing the return of muscle tone. 

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